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Join Date: Jan 2005
Location: North Delta, BC (96Av x 116St)
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The purpose of this FAQ is to provide a fundamental introduction to all aspects of OTA, as well as to introduced readers to the amazing depth and variety of great information in the Digital Home OTA Forum discussion threads. You are currently reading Post #1 of the OTA FAQ, which is followed by over twenty more FAQ posts that cover various distinct areas of OTA knowledge.* What does OTA mean?
It stands for Over The Air television reception, as has been available free-of-charge in Canada since the early 1950s using antennas for reception. OTA is not to be confused with FTA, which is a form of satellite TV reception using entirely different gear.* Why are we switching from analogue to digital TV?
Analogue TV (also known as NTSC) is the original television standard in North America and it has served well for many decades but is prone to many different kinds of interference that can make viewing troublesome for consumers. The newer digital standard called ATSC (also known as DTV, for "Digital Television") eliminates almost all of that interference, as illustrated in this split-screen video made by recneps77:
In an ongoing poll of DHC OTA users, the great majority have paid less than $500 Canadian for all the OTA gear they required. Less than 1% paid more than $1,000. Some have canceled some or all of their satellite or cable programming, so their OTA equipment will pay for itself in savings over time. There are no direct costs or fees to the consumer for OTA programming.* Are there OTA stations in my area?
The OTA Forum has a sub-forum called Reception Results which features a thread for every section of Canada. Read through the thread for your own area and if necessary the surrounding area(s) to see what DHCers have already reported. A vast amount of experience and trial & error has gone into those threads, so please read through yours from the beginning. See Post #10 in this OTA FAQ to learn how to use a variety of online tools for best aiming of your OTA antenna for the stations in your area.* Will I get stations from more than one city?
TV antennas need to be pointed at the broadcast antenna, so if the cities are fairly well lined up in one direction, aim an antenna and enjoy. If you are fairly evenly between two locations there are antennas that receive front and back simultaneously. If the cities are wide apart, mount the antenna on a rotor. You can program the rotor's remote control to turn the antenna into proper position, which will usually take less than 30 seconds. Some DHCers have used 2 or more antennas aimed in different directions rather than a rotor. See Post #16 in this FAQ for info on how to combine 2 or more antennas.* What if the stations are far away?
TV signals typically start to drop off in strength as they travel about 120 to 180 km outwards from the broadcast antenna, so reception in those deep fringe and deepest fringe areas requires special antennas, gear, and installation techniques as you reach or exceed the higher distances. Expert help is available to you by discussing your situation in the Reception Results thread for your area.* Will my TV get the Digital OTA stations?
Check to see that it has an ATSC Tuner. Many, if not most, older TVs have NTSC-only tuners, which will not receive DTV stations. For those NTSC-only TVs a consumer can use a converter box to feed ATSC signals to them in the lower-grade NTSC format. See Post #17 in this FAQ for more detail on ATSC tuners found in set top boxes, HDTVs, and other equipment.* Okay, which antenna do I need?
The DHC OTA Forum contains detailed threads about different OTA antenna brands and models. See also Post #3 in this FAQ for antenna buying tips, and also be sure to download the Antenna Decision Chart (PDF). You will likely need to do some reading in the OTA Forum to understand the rankings and other criteria in the chart. Keep in mind that just because a competing-brand antenna looks a lot like a leading brand antenna does not mean that it performs the same - there can be significant performance differences. Stick to our advice on brand and model recommendations and you will not go wrong! If its not on the chart, don't buy it. Also see Post #3 in this FAQ for essential Antenna buying and planning tips.* I'm pretty handy with tools. Can I build my own antenna?
Absolutely yes, and in Post #11 of this FAQ you'll find info on best plans, techniques, materials, and other great info for Do It Yourselfers, including how to use computer modeling software for antenna design. The DHC OTA Forum is the one and only home of the Gray-Hoverman and Stealth Hawk do-it-yourself antenna projects, which have created powerful home built super antennas for OTA TV reception that routinely outperform most commercial antenna models.* Some new antennas look the same as my grandfather's old one! Aren't they old fashioned?
No, TV antenna technology is essentially the same as it has been for several decades because the laws of electromagnetism and physics apply equally now as they did then. Today some manufacturers are finding clever ways to cram antennas into small form factors, but unfortunately due to those laws of nature the antenna's performance drops the more they try that. Manufacturers now have modern materials to work with so the construction of their products seems to be more durable, but antennas have often lasted more than 20 years. Since TV antennas have been around so long, there is already a large body of real world knowledge about antenna designs and capabilities. See Post #5 in this FAQ for an explanation of how TV antennas actually work.* Which other OTA equipment will I need?
There may be conditions affecting your reception that require specific equipment, such as preamps, attenuators, distribution amplifiers, splitters, combiners, a tower, etc. If you try such equipment without proper knowledge or guidance you could damage your TV and other equipment. The OTA Forum is the right place to ask the experts. See Post #14 in this FAQ for further info.* Aren't Satellite and Cable TV better than OTA TV?
For specialty channels and pay-per-view movies and events, Satellite or Cable TV are needed because such channels as TSN and Discovery HD are not broadcast OTA. However, if you want regular, local programming, OTA is free of charge or fee to the consumer. The only cost you will pay is for the gear itself and any taxes on it.* Does Digital OTA TV have an On Screen Guide?
If you have an ATSC tuner in your TV and live in a suitable area, what's the harm in hooking up an antenna and seeing OTA for yourself? Even so, suit yourself and respect the decisions of others. You can discuss these issues in the Pros & Cons of Going OTA thread.
- With a top quality OTA receiver and antenna gear, the improvement in picture and audio quality over Cable TV or Satellite can be spectacular, especially in HDTV, as many DHCers attest. This is not conjecture; the improvement is readily visible and audible on good systems, especially when seen in split-screen mode.
- Some consumers will want to have the best of both: keeping their Sattelite or Cable TV subscriptions and watching their favourite programming OTA.
- Some will find no reason to use OTA because they find the quality of their TV reception by other means is satisfactory to them.
- Some will find that using OTA is not possible due to certain local situations, and so will rely on either Satellite (if they can aim a dish correctly from their location) or Cable TV if it is available
- Some will find going 100% OTA to be the most worthwhile solution, while watching first run movies and specials via Internet providers like Netflix, Hulu, and Qriocity, or by DVD/BluRay rental from video stores.
- If you are planning a move to another city, Cable TV set top boxes from one Cable company almost always do not work with the systems of different Cable companies; Satellite gear can be moved anywhere that the dish can be aimed succesfully, and OTA gear works fine as long as stations are available.
- Some CATV subscribers have had their FM radio service dropped by their providers. With an OTA VHF/FM antenna there are not only analogue FM radio stations available but also many HD Radio stations in border areas carrying digital audio that rivals CDs for quality.
Yes, the ATSC standard incorporates a data standard called PSIP, which contains program, channel, time, and other data for the ATSC tuner to display. There are also several Third Party program guides available, such as TVGOS, TitanTV, Schedules Direct, and others. See this thread about OTA On-Screen & Third Party Electronic Program Guides.* Why is everything here named in letters that I don't understand?
Here in the OTA forum we sometimes use the term DX, which some say means "Dial Crossing". DXing has been a hobby of enthusiasts going back to the early days of radio and now of television. DXers enjoy scanning broadcast frequencies in search of unusual or long distance signals, such as during odd weather conditions. Thus, DXers are very knowledgeable about high quality equipment and the techniques needed. Many TV DXers are also ham radio enthusiasts.* Isn't all this OTA stuff illegal, like satellite piracy?
NO! OTA television reception is the original form of television broadcasting and is 100% legal as always. See Post #13 in this FAQ for further information about the legality of OTA.* Is all this great OTA info free?
This web site, www.digitalhome.ca, is a private business. It cannot survive on bread alone. Please register as a member at our site, at no cost to you.Please proceed to Post #2 in the OTA FAQ
While we are happy to share our information here with other members and with guest viewers, this site asserts and respects copyright laws and we take a very dim view of plagiarism of our material. Please report sites that misuse our contents.
Advertisers are very welcome to contact the owner, and here's what consumers can do: whenever you contact any OTA-related company, station, network, supplier, vendor, installer, technician, marketing person, representative, or other corporate person, be sure to tell them about this site and that their advertising support here would be most welcome. Here's an example:Also, please consider selecting one of our Paid Membership options. Please help us keep this web site going strong. Help us to help you.Quote:
Listing a bunch of stations is easy but not very realistic or helpful to readers because reception conditions are very local, even between houses on the same street if one is up high and the other is quite a ways downhill. The approach at this web site is to provide information that is extremely local to a person's location. We use Reception Results threads for every part of Canada rather than general lists that usually are not satisfactory. Over about five years we have accumulated Reception Results from people living all across Canada, so now the general expectation of what a person can receive has become clear for most major centres and populated areas. Unfortunately in some areas on the fringe of reception from DTV stations we just don't have very many user experiences to rely on. With time this will change, and we are grateful for the pioneers out there.Will I be able to just "set and forget" my OTA gear? If I need to change it can I get help with keeping my OTA system at its best?
Five years ago we had almost no knowledge, experience, or factual information on how DTV reception in various parts of Canada would be. DTV was still very new so even the stations themselves were changing and improving all along, so that what a person found out one day would be different a week later. As of the middle of 2009 we are still fairly early on in the Canadian DTV conversion process, with about 30 operational DTV stations spread across several major cities. Canadians in border areas get a wide variety of U.S. DTV stations but the status of those stations has been changing frequently due to the June, 2009 U.S. DTV conversion.
Yes to both questions, but in all honesty TV stations change over time, and we do our best to keep our readers up to date. With members who are station employees and in other broadcasting positions we often get the news before anyone else does. Your OTA system may or may not need optimizing in the future to deal with changing situations, and here is a good example of a "power OTA user" and his evolving system:Quote:Originally Posted by Biggy
Antennas are designed along well known electromagnetic principles that predate HD, SD, DTV, etc. by almost a half century. Any vendor that claims that a particular antenna model is "better for HD" etc. etc. is full of it. Don't pay attention to that misleading sales & marketing nonsense. The original Channel Master 4228, for instance, is one of the highest rated UHF antennas out there today for all analogue and digital reception, yet its design is about 30 years old! Channel Master has replaced it with the 4228HD, which may mislead people into believing that it is better for HD when in fact independent research proves that it is weaker than the original that it replaced.Is there a warning list of OTA stuff that I should never buy?
Avoid the hype... just the facts, ma'am.
In some central urban areas, such as atop a high rise in downtown Toronto, a set of cheap Canadian Tire rabbit ears might do the job if you just want the local digital and analogue stations, but in other urban areas, rural locales, and deep fringe areas there are a lot of things to consider before purchasing a TV antenna.
Keep in mind that TV antenna technology is essentially the same as it has been for several decades since the laws of electromagnetism and physics apply equally then as now, so this means we are fortunate that there is a body of real world knowledge and evidence about antenna designs and capabilities if you know whom to ask. There are enough real world examples out there for the experts to give you the best advice and save you a lot of trouble. Advice can be found here in the OTA Forum for those difficult situations or possibly pricey decisions. Don't be timid about asking newbie questions.
So, avoid impulse buys based on advertising claims (especially about reception range!) and ignore any claims of an antenna being "Digital Ready" or "HD Compatible" because those terms mean nothing. Never, never buy an antenna because it "looks great" on top of your TV. Getting the best reception is what its all about.Essential buying and planning tips for OTA antennas:
- All OTA antennas are "digital ready" and "HDTV ready" (ignore those marketing words)
- TV antennas of every kind just pick up signals whether they are broadcast in digital or analogue form
- in theory reception of equal strength analogue signals versus digital signals (all other things being equal too) would therefore be exactly the same
- in the real world many issues unrelated to the antenna can make such signals differ, as discussed in this OTA FAQ
- the antenna itself handles both types equally
- Mount antennas outdoors and as high as possible, free from obstructions
- Attic or indoor mounting can present reception problems due to signal losses so they should be a last option
- Most DTV stations are in the UHF band but some are in VHF
- VHF and UHF antennas are different in size and shape because they receive different frequency bands
- VHF has 2 bands:
- VHF-LO contains channels 2 through 6 (54 to 88 Megahertz) requiring a huge antenna
- VHF-HI contains channels 7 through 13 (174 to 216 MHz) requiring a large antenna
- FM Radio (88 to 108 MHz) is in between VHF-LO and VHF HI so most VHF TV antennas are also excellent FM Radio antennas, referred to as VHF/FM and capable of also receiving HD Radio (Hybrid Digital) FM stations in CD audio quality from U.S. border areas
- UHF band contains channels 14 through 69 (470 to 806 MHz) requiring a relatively small antenna
- Combo antennas feature a UHF and a VHF on one spar
- For consumers a Combo offers good performance with simpler installation and less room on the mast
- Pros and OTA hobbyists prefer the performance of separate UHF and VHF/FM antennas rather than a Combo
- Satellite Dishes cannot be used to receive OTA signals because they operate on totally different frequencies
Yes, there is a humourous thread called Wacky, Tacky OTA Gear (What NOT To Buy!) that is well worth reading to help you avoid wasting your money on junk and OTA gear NOT to buy. Avoid gimmic antennas such as the ill-conceived Terk 55, the fraudulent Xium Air, or the ones that promise to turn your household AC wiring or aluminum eaves troughs into a TV antenna. Additionally, the OTA Clone & Coat Hanger Antennas - Avoid Most Of Them thread warns of cheap "clone" antennas that may look like high performance models but are usually poor performers.Can I just go to my local consumer electronics store for OTA stuff?
If you are unsure about a product, the OTA Forum has many threads that deal with specific items and/or brands in which you can read or offer advice. A fool and his money are soon parted.
Yes, some of those stores have some OTA equipment and OTA-savvy knowledgeable staff, but in Canada it generally seems that retail salespeople do not tend to be well briefed on Digital OTA. You can read through the Popularizing OTA HDTV In Canada thread to get a better understanding of the OTA popular awareness situation. For this reason we recommend dedicated, knowledgeable OTA vendors for your parts, sales, service, and installations.Is it okay to use an old antenna?
Oxidation may be a problem on many old antennas if it is causing welded or soldered joints to fail. If your antenna is still solidly constructed you are fine to clean it with steel wool. I would use something like an SOS or Jet pad for that. Clean the feed points too (where the balun is connected) and replace the old wingnuts or screws with new ones.Can I put up my own antenna?
As for reception, oxidation will reduce the antenna's effectiveness but it would happen over a long time from when it was new, not suddenly. If you were to take a perfectly new version of the same antenna and compare it side-by-side with your older one you might see some difference in the resulting signal strength, but not at a worrisome level. I have an old-timer 4-bay bowtie reflector on my roof that was almost white with oxidation but I did not hesitate to use it after a cleanup and it works beautifully.
Absolutely, and Post #21 of this FAQ gives a variety of useful tips and links to discussion threads about important antenna installation topics. For those who do not wish to put up their own antenna and OTA gear, experienced, professional installers can be found in almost any part of Canada and the United States.An Overview of Various Antenna Types
As you read through your printed-out Antenna Chart, here is further info on the most highly regarded consumer antennas. If you cannot locate one for purchase, try to find the next highest one rated on the Antenna Chart:
- VHF/FM-Only: does not receive UHF stations but receives locally available VHF TV Channels 2 through 13 and FM Radio stations
- VHF-HI-Only: receives locally available VHF-HI TV Channels 7 through 13
- VHF/FM/UHF: is called a "Combo" and is capable of receiving all locally available TV channels and FM Radio stations
- VHF/FM/UHF Deepest Fringe: It is best to leave this category to pros or experienced OTA hobbyists. Mount 2 UHF antennas in stacked configuration (see Post #16 in this FAQ) with a VHF/FM, feeding them into a high-gain all channel preamp atop a minimum 20 foot tower or similar elevation with unimpeded signal from the target. A heavy duty rotor and/or mount is advised due to the weight and wind load. NOTE: A Deepest Fringe setup is NOT suitable for closer use because its great reception power can overload and/or damage amps, TVs, and receivers if proper safeguards are not in place.
- Metro/Suburban, Condo, RV, or Apartment:
- Outdoor antenna products like the costly Winegard Square Shooter, the Super Delhi, the pricey Antennas Direct Lacrosse, or the Channel Master 3010A-Stealth antennas have been introduced to be esthetically suitable (smaller) although they are often no match beyond the near fringe range for mainstream antenna gear.
- UFO-style omnidirectional antennas like the Antennacraft 5MS921 Omni-State, Winegard MetroStar, or Channel Master SmartTenna are useful on Recreational Vehicles and boats, but are prone to suffer from multipath signal interference more than standard antennas. In Canada the one and only location in which I would consider a UFO antenna as a viable alternative to a standard antenna is in the central and northern part of the Niagara Peninsula in Ontario since the Toronto, Hamilton, and Buffalo stations surround the area and are relatively equal in signal strength.
- Clip-on satellite dish OTA antennas rarely offer anything but extremely local performance so should be avoided.
- Indoor Antennas: See Post #6 in this FAQ
- UHF-Only: See the section immediately below.
UHF-Only AntennasHere's what the antenna pros have found over the years about each type of UHF antenna, in very brief form. Today's consumer-grade UHF antennas, needed for receiving the great majority of DTV stations OTA in Canada, are divided into two basic designs:
Both have their relative strengths and purposes. The three main antenna manufacturers in the Canadian consumer marketplace (Delhi, Channel Master, and Winegard) make variations on those designs. There were Parabolic models available to consumers many years ago, but that category is now exclusively used by professionals, such as in CATV Head End scenarios or in research.
- Corner Reflector Yagi (pronounced yoggy)
- Bowtie Reflector
Corner Reflector YagisIf you have a clear, direct, unobstructed, line-of-sight aim from your antenna mast to the transmitting antenna and it is within about 80km of it, consider purchasing a corner reflector yagi like a Delhi CYD1470, Channel Master 4248, Televes DAT-75, Winegard PR-9032, or Antennas Direct 91XG (the best of this breed). It is very easy to aim because you can point it like a rifle at the broadcasting site and lock it into place. On a rotor swinging around to several different azimuths it loses out to the other type of antenna because it is so directional (biased in one specific direction) with a fairly narrow receiving aperture and relatively small side lobes, therefore can be quite picky to aim. This is actually a positive feature of the Corner Reflector Yagi because in known areas of signal crowding its great side-rear rejection qualities are needed. Some users do well with long distance reception using a preamp and a fixed mount. Some users do fine with a Yagi on a rotor, but in almost all such rotating situations it is bettered by the other antenna type.Bowtie ReflectorsIf some obstructions such as large trees lay between your antenna, or the broadcast site is more than about 80 km away, or if the stations are at several different azimuths and you want to put an antenna up on a rotor, you require a bowtie reflector such as a Winegard PR-8800, Terrestrial Digital DB-8, or the original Channel Master 4228 (the best of this breed). It's reflector mesh is great at gathering UHF signals that tend to scatter over long distances. Its receiving aperture is very wide and its side lobes are relatively large, meaning that on a rotor it will generally tend to get a digital lock on a DTV station before the Yagis above will. Having said that, it is also fine in suburban situations and in fixed positions for all-purpose situations. Each bowtie (x-shaped signal receptor) is known as a bay, and the greater the range to the station, the greater the number of bays should be. Four-bay versions exist for suburban to fringe use, such as the Delhi 4BT-1483, the Winegard PR-4400, and the new Channel Master 4221HD (the best of this breed). Some bowtie antennas such as the Delhi SL-4BT are sold without reflectors, giving a figure-eight reception pattern to those who are located in between desired stations. The chief difference between a CM4228 and a CM4221HD is that the CM4228 is more directional and provides about 3dB more gain, while the CM4221 has a wider reception pattern.Money Is No Object
UPDATE Oct. 31, 2008: Channel Master has stopped making antennas in the USA and moved manufacturing duties to China. They have substantially changed (through outsourcing) all their antenna designs in the process.
UPDATE Jan. 27, 2009: OTA gear suppliers in Canada have run out of stock of the original-style Channel Master 4221s and 4228s. Additionally, testing reveals that the new CM4228HD antennas are weaker in performance than the original CM4228 models. It is advised that if an original CM4228 cannot be purchased, the reader should consider purchasing the next best model shown on the Antenna Chart.
UPDATE Mar. 16, 2009: Ken Nist, of HDTVPrimer.com, has published an easy hardware hack that corrects a significant flaw in the design of the new CM4228HD antenna, improving its performance significantly. Read about it in this thread.
UPDATE May 1, 2009: A thread discusses hardware hacks that consumers can make to improve the performance of their CM4221HD antenna.If you must, and absolutely MUST, have the ultimate in UHF antenna performance, you can buy precision cut single channel or log periodic antennas from professional-grade manufacturers such as Wade or Blonder Tongue, or you can contact Wade about their colossal CATV head end parabolic models. If you think you need one of these bad boys (especially the dual dish model) parked up on your roof, go see a psychiatrist but definitely check your local bylaws and ordinances before you drain thousands of $$$ from your bank account!
Manufacturer - U.S.A - Consumer antennas - wide product line
Manufacturer - U.S.A - Consumer antennas
Manufacturing and Marketing -U.S.A. - wide product line of it's own and rebranded antennas
http://www.antennacraft.net/ and sold in stores by:
Channel Master (original pre-2008 stock only - see International section below for post-2008 info)
- The Source: Canadian retail electronics chain - rebranded Antennacraft and international antennas
http://www.thesourcecc.com (see Home > TV & Home Entertainment > Antennas > Outdoor Antennas on web page)
- Radio Shack: U.S. retail electronics chain - rebranded Antennacraft and international antennas
http://www.radioshack.com (see Home Entertainment -> Accessories -> Antennas on web page)
Manufacturer - USA - Consumer antennas - wide product line
Gemini/Philips AccessoriesQuote:Originally Posted by videobruce
Manufacturing and Marketing - U.S.A. - sells own and rebranded antennas through stores - range of different types including gimmick antennas - some rebranded as Magnavox, some as Zenith
Manufacturing and Marketing - U.S.A. - sells own and rebranded antennas through stores - range of different types - still living down bad reputation from certain gimmick antenna products - have teamed with Winegard to improve Terk's product quality
Manufacturer - Canada - made by Wade Antenna and includes Delhi and former Jerrold consumer brands - after 2010 has left the consumer antenna business - was leader in consumer VHF/FM and VHF/FM/UHF Combination antennas
Wade's professional division (TACO), along with Blonder Tongue, cater to the highest end of the professional OTA market, in which CATV Head End installations and Research are the main usage. Products like precision cut single channel yagis, log periodic antennas, and giant parabolic reflectors are therefore built to exacting standards and in fact are often not useful to average consumers wanting basic UHF/VHF/FM antennas due to their specific designs for only certain uses. It is possible to find useful consumer-grade antennas from them, but they'll be very expensive. Each manufacturer offers a wide range of professional grade OTA antennas, amps, and related OTA gear.
Wade Antenna (TACO brand & former Lindsay products)
Manufacturer - Canada
Manufacturer - U.S.A.
Manufacturer - Germany
Keep in mind that due to smaller broadcast areas across Europe and Asia, the antenna manufacturers give less emphasis to the kind of fringe and deep fringe conditions that we take for granted in North America, but more emphasis on side and rear signal rejection due to greater competing station density over there. Certain UHF antennas from Europe and Asia are unusable here due to some frequency differences. VHF antennas from Europe are not suitable for Canada, usually due to polarity differences.
Channel Master (post-2008 stock only)
Manufacturer - China - Consumer antennas
Blake - UK
Manufacturer - consumer antennas - solid construction and build quality
Televes - Spain
Manufacturer - consumer antennas - products are very distinctively designed and coloured - UHF corner reflector yagis
Kathrein-Scala - Germany
Manufacturer - consumer antennas - rare in Canada - highly regarded in Europe
Triax - Denmark
Manufacturer - consumer antennas - rare in Canada
Hopefully this will not leave you glassy-eyed or confused, so you can skip this part if you like and go right to the next post in the OTA Knowledge Base & FAQ.Why do some stations broadcast in the VHF band while others are in the UHF band?
- TV signals travel in waves between the transmitter and your antenna(s), with the transmitter's waves causing the receiving antenna(s) to resonate in the same pattern
- this is like having several tuning forks in a room close together - if you strike one (the transmitter) the identical tuning fork (the receiver) will resonate the same, just quieter
- the harder you strike the transmitting fork the louder it will be and the louder the receiver fork will resonate or the farther the receiver fork can be to still resonate
- the other bigger and smaller tuning forks will remain silent through it all and show no resonance because the transmitter waves do not affect them, no matter how powerful the transmission
- TV signals are separated from eachother by their frequency, expressed in multiples of 1 Hertz. At a frequency of 1Hz a wave is replaced every second, which is why 1 Hertz used to be called 1 cps (cycle-per-second) in many parts of the world
- the range of all frequencies is called the frequency spectrum
- contiguous frequencies are grouped together on the spectrum in bands, such as the VHF or UHF TV bands or the FM Radio band (for a detalied list see the table in Post #20 of this FAQ)
- the VHF and UHF TV bands are divided into channels (VHF-LO = Channels 2 through 6, VHF-HI = Channels 7 through 13, and UHF = Channels 14 through 69)
- the FM Radio band does not have channels - stations are assigned frequencies expressed in MegaHertz from 88.1 MHz to 107.9 MHz
- TV antennas are commonly constructed for only a single band (UHF-only, VHF-LO, or VHF-HI)
- a broadband TV antenna is one that is designed to pick up all channels in every TV band, sometimes with the FM Radio band too
- the opposite of a broadband antenna is a channel cut model, which is optimized for just one specified channel
- the lower the channel number on your TV, the lower the channel's frequency
- the lower the channel's frequency, the longer its wavelength (frequency goes down while wavelength goes up, and frequency goes up while wavelength goes down)
- the longer the channel's wavelength, the wider the receiving antenna's element must be to capture each wave
- Channel 2 has a frequency of as low as 54 Megahertz with a wavelength of 5.55 metres (18.22 feet)
- Channel 69 has a frequency of as high as 806 Megahertz with a wavelength of .37 metres (1.22 feet)
- this is why VHF antennas are so much bigger than UHF ones
- when TV stations wish to build an OTA transmitter they must calculate the power required to cover their desired geographical area
- this area is called their contour
- transmitter design is a highly technical feat of engineering and is overseen in Canada by federal government authorities (Industry Canada handles the technical details and issues, while the CRTC handles licensing details and issues)
- the power that a TV station is authorized to transmit with is called their Effective Radiated Power (ERP)
- thus, for example, under normal circumstances a TV in Fredericton cannot get an OTA station in Moncton because the ERP of the Moncton station is only sufficient to cover a locally specified contour
Usually a station's assigned channel is a matter of it being available in a given area so that it will not interfere with another station on the same channel in a different area. VHF channels were the original ones, but over the decades channels in the UHF band were assigned by Industry Canada (and the FCC in the U.S.A.) as demand for channels by broadcasters increased.How does a bowtie reflector antenna work?
Broadcasters prefer the VHF-HI band due to the laws of physics and electromagnetism. VHF channels require much less transmitter power to cover the exact same area as UHF channels. For example, to cover a certain area, the higher the channel number, the more power it would take. Conversely, the lower the channel, the less power it would take to cover that same area.
Another factor is that VHF-HI signals tend to travel (propogate) better over a given area than UHF signals. Unfortunately in the case of VHF-LO channels the signals tend to suffer interference worse than VHF-HI and UHF channels. During the transition to digital TV across North America, the use of VHF-LO channels is being phased out and the frequencies reassigned to other uses than television.
What does a reflector on an antenna do?Quote:Originally Posted by ZozoQuote:Originally Posted by Rop
Reflector meshes or rods cause an antenna to be "directional" by causing signal strength from behind to be lessened while simultaneously causing the gain at the front of the antenna to increase by the same amount. The reception pattern thus becomes very forward-biased, which is rated as its Front-to-Back ratio (FB). The higher the FB, the more directional the antenna is.
On the other hand, a reflectorless antenna has a figure-eight reception pattern with an equal FB.
The Zenith ZHDTV1Z Silver Sensor indoor antenna is considered the benchmark design for indoor UHF ATSC antennas.Rabbit Ears
Other manufacturers build clones under their own brand names, such as Terk, Philips, Samsung, and others. Its distinctive flying-vee style is instantly recognizable. Consumers will find occasional differences in some ZSS clone brands, such as a single, non-sectional element cover and/or the addition of extendable rabbit-ear elements for added VHF reception and/or an integrated signal amplifier.
Generally a consumer can feel comfortable that a ZSS clone will perform almost identically to the original ZSS.The following discussion thread deals specifically with ZSS and ZSS-clone antennas:Quote:Originally Posted by hoosierdxer
Antennas Mounted In AtticsIf your intended stations are all on VHF and you will not be getting any UHF stations, a set of good old fashioned rabbit ears is okay for your situation since you cannot use an outdoor antenna. Just remember that conventional rabbit ears are not suitable for UHF reception. Don't spend a lot of money on rabbit ears - the cheapest basic unamplified ones from Zellers or WalMart are fine - don't read the claims on the boxes when you are shopping!Quote:
You will need to put the aerials completely flat horizontally from the centre stand, not upwards or in a Vee. The lower the channel number, the more you need to extend them outwards. The higher the channel, the more you need to push them in. Practice makes perfect.
Further, you will need to rotate the rabbit ears to get the intended stations, depending on which direction the signals are coming from. The aerials have to be at a right angle to the direction of the signals.
If this doesn't work out for you, try an amplified set of rabbit ears, but keep in mind that amplifying indoor TV signals actually amplifies ambient signal noise too so your results will vary.
Analogue TV reception with attic-mounted antennas has traditionally been haphazard and unsatisfactory for most people due to problems with ghosting and other interference caused by reflection of signals off of metal hardware such as sheet metal flashing, electrical boxes, aluminum siding, etc.
Digital television had similar problems in attics during the first few generations of ATSC tuner, but the situation has been greatly improved with the Generation 5 and newer chipsets now on the market. The problems have not disappeared... they've just been addressed a bit better electronically.
Having said that, of course an indoor and/or attic antenna is generally no match for a proper outdoor antenna in almost any situation, so an attic mount should always be considered last after exhausting all outdoor antenna mounting possibilities.
This illustration gives an overview of the Digital OTA broadcast process from a TV station's cameraman all the way to a typical full OTA home installation with outdoor antenna (skipping tons of technical detail, of course!):
Maybe, maybe not, (See Post #2 in the OTA Forum Knowledge Base & FAQ) but the best way to find out is to read through the Reception Results thread for your area to see how others have done.
Follow these step-by-step Instructions:Using the Rabbit Ears site:
- use Google Maps Canada to zoom in to your location and get your exact Latitude and Longitude map coordinates
- enter your exact map coordinates at the TVFool site and wait for your results page to load
- your coordinates and location will be kept secret - it will not show up to anyone else on your completed report
- NOTE: Canadians are advised to NOT use their proper street address, city, province, or postal code due to inaccuracies - hopefully this will be resolved soon
- after it loads, copy-and-paste the URL of your personal TVFool report to a file or clipboard for future reference
- read through the Reception Results thread for your area to see how others have done, in case there are local reception issues
- if you require assistance analyzing your TVFool results just post the URL you saved above into a post at this site
Using SJM's site:The contributors to Rabbit Ears are mostly folks from one of the big U.S. online OTA forums.Quote:Originally Posted by 99gecko
Using the FCC's Online Mapping Engine:Quote:Originally Posted by sjm
You can go to the FCC's OTA maps site and punch in your Canadian postal code to see if any U.S. stations will reach your area. When it shows the stations you can click on one to see a direct line from your location to it: http://www.fcc.gov/mb/engineering/maps/Using Google Earth and/or Google Maps:
Using the Antennapoint site:That's a great starting point. With most ATSC tuners you should have a signal strength or signal quality meter that will let you take the final setup step of "peaking" your antenna for its specific best performance. Make sure to do that with all the expected channels in that direction so that you can come up with the best compromise among them. I've seen signal strength change with even just a tiny twist of the mast, so taking this step is definitely worth it.Quote:Originally Posted by Mingy
One more thing: if you're using 2 or more antennas don't be surprised if your common logic about aiming goes awry as their reception lobes superimpose and interact. You might discover like some other DHCers have that some really weird effects happen, with resulting aiming that is counter-intuitive. It doesn't always turn out too radical, but ya never know...
I've done a Google Earth mashup of all present and future Vancouver, Victoria, Bellingham, and Seattle/Tacoma OTA TV stations as per the Industry Canada and FCC databases. It is really cool to zoom in on the Mt. Seymour antenna farm or the multi-tower installations in Seattle and Tacoma.Quote:Originally Posted by bimmer
I might do some other Canadian areas, but if someone follows my format as a template and does a mashup of their own area of Canada, please post a link to your mashup file here and we'll see if we can get a good collection going. Note that this is not done with Google Maps, it is done with Google Earth.
- If you don't have Google Earth, you can download it for free for Windows, OS X, and Linux from here: http://earth.google.com/
- Download my mashup file (Save To Disk): http://www.user.dccnet.com/jonleblan...SeaTac-OTA.kmz
- Start Google Earth and make sure you have it installed and properly running
- In the File Menu select Open and select the downloaded file to begin.
- If you have any difficulties with Google Earth you can read through their help page here: http://earth.google.com/support/?hl=en
Here is a screen capture of it from a fairly high altitude:
Here's one for the folks in Winnipeg, S. MB, and SE SK (don't expect these stations to necessarily be available without Deepest Fringe gear in many places outside of Winnipeg):Quote:Originally Posted by roger1818
OTA Stations in the Sault Ste. Marie Ontario and Michigan area:
OTA Stations In Calgary, Alberta (created by DHC members gsjacobs and csclgry)
Antennapoint provides a quick set of aiming points for U.S. DTV stations nearest you:Using the Earth Tools site:
Using the Touratel site:Quote:Originally Posted by Ahuntsicguy
There are topological maps online here:Determining Your Magnetic Declination in Canada:
Don't trust compass bearings until you've factored in the magnetic declination for your location:
Very High Performance, may be complex to build, may require some shop skills:What NOT To Build:
Good Performance, less complex to build, suitable for hobbyists and inexperienced:
- Introduction to the Gray-Hoverman TV Antenna (UHF, some variants have VHF-HI capability)
- Bow Tie TV Antenna Designs (mclapp's M4 featured) (UHF, some variants have VHF-HI capability)
- 400-A "Finclone" - Huge & Powerful (a real chore to build, great VHF and UHF capability)
- Delhi 5y & 10y Channel Cut VHF Yagis - Saved From Oblivion For DIYers (VHF-LO or VHF-HI capability on specific channels)
- The "Hentenna" Compact TV Antenna for OTA
- The Bi-Quad Indoor TV Antenna (suitable for highrise buildings)
- UHF Loops - simple bi-directional antennas (See Post #109)
Before wasting your time or ours on an antenna that you saw in a video or found on a website please read these threads:Antenna Research & Development:
For those of you wanting to take part in leading edge technical design, computer modeling, building, research and development of antennas at our site:Tips & Tricks For Antenna Construction:
See these threads for invaluable tips and tricks on how to build the very best DIY antennas:
TV broadcasting in Canada has been done Over The Air since the 1950s. Cable and Satellite came along later as supersets of that. OTA is 100% legal and always has been.Quote:Originally Posted by magnet
Quote:Originally Posted by vmpv
In a perfect OTA world, a consumer would just connect a small antenna to their HDTV and proceed to pick up all the wonderful DTV programming available in their area. In reality there may be cases in which the OTA gear needs to be of a certain quality and performance capability to bring in distant or dispersed signals. Boosting the antenna's output is often the answer, so preamplifiers and signal amplifiers are commonly available for OTA users to accomplish that task.Key Concepts:
Not all OTA amplifiers are alike. Each type of amplifier has a separate role to play, so they should not be confused with each other. The amount of energy coming off of an OTA antenna is quite small compared to the energy coming out of a cable TV connection or a VCR, as an example. With the amount of energy from an antenna being so small, we need the amplification to deliver as pure a signal as possible. Unfortunately all amplifiers add "noise", which is the enemy of good reception.
A preamp is therefore specially designed to boost that OTA signal but with only a very little bit of noise added. By contrast, a signal amp, distribution amp or drop amp is fundamentally noisier, because the incoming cable TV signal is strong enough to get around the noise problems. Amplifier designers have a lot more leeway with the design of them versus preamps, so they are not as "clean". When looking at the specifications of any TV amplifier it is important to look first at it's "noise figure" (expressed in dB) instead of it's advertised boost.In some cases the signal from the antenna might be too strong, so there are ways to lower that signal while keeping the quality of the signal high.Quote:Originally Posted by goforit
OTA Amplifiers - A Quick Introduction
- Amplification = Boosting or increasing the OTA signal
- Attenuation = Reducing or lowering the OTA Signal
- Noise = unwanted "junk" added to the OTA signal that can sometimes prevent tuners from acquiring a digital lock on a DTV station
OTA Preamps - a Pleasure To Compare
- input = antenna signal
- Output = very clean, boosted antenna signal
- Signal amplifier:
- input = any unamplified OTA signal
- Output = one boosted OTA signal but usually more noisy than a preamplifier
- Distribution amplifier:
- input = any unamplified OTA signal
- Output = 2 or more with boosted signal but usually more noisy than a preamplifier
- Drop amplifier: same as Signal amplifier but is really for CATV use due to extended frequency range past OTA frequencies
Preamps are used for taking in your antenna's signal as close as possible up the mast nearest the antenna and amplifying it in very specific ways to allow the signal to travel strongly down a cable to your tuner. Don't assume that any old TV/CATV amplifier will do, it has to be a specifically designed antenna preamp.Professonal Signal Amplifiers, Drop Amplifiers, and Distribution Amplifiers - Reliable and Known Performance
In many cases an antenna gives strong enough signal power on its own to drive the tuner so a preamp would not be necessary. In most cases, a weak signal in a fringe or deep fringe area can be dramatically improved with a preamp. In other cases, a mixture of near and far stations can cause preamp problems. For example, someone in downtown Toronto should ask before using one because of their proximity to the CN Tower's already strong signals. There are always ways around those problems using filters, blockers, attenuators, traps, etc.Not all preamps are alike, even from the same manufacturer. Some have higher amounts of added "noise", others lower. Noise is the enemy of TV tuners, so the lower the better. Some provide low amounts of "gain" (boost), others are for very high gain. Don't assume that the preamp with the highest gain figure is necessarily the best for all conditions. Bad idea.Quote:Originally Posted by roger1818
Due to the very critical role that OTA Preamps play, the manufacturers almost always provide reliable specifications for those products. People have been using Preamps for decades, so their Gain, Noise, Loss, and other properties are well known. It is possible to make direct comparisons between them, so in our case we have the charts and tables in the OTA Forum that clear up any questions. When a new type of Preamp like the models from Kitztech and Research Comms come along that clearly outperforms the others, that's big news and you'll read about it here!
If a preamplifier is not sufficient to provide a strong enough signal to all your TVs, FM radio tuners, PVRs, and other receivers below the antenna, it is time to put in an amplifier below the preamplifier. Having said that, there are times and places in which a very high gain/low noise preamplifier can do the job itself, but seldom the other way around. A signal amplifier is not therefore a lesser thing than a preamplifier; it has 2 benefits: some models can be purchased with several outputs, some with adjustable input and outputs, and in all signal amplifiers are generally capable of handling high power input signals and spreading them evenly across one or more outputs. Other more specialized signal amplifiers allow blending of such things as the OTA signal with CATV, Satellite, etc.The Sorry State of Common, Store-Bought Signal Amplifiers
High performance Signal Amplifiers, Drop Amplifiers, and Distribution Amplifiers (especially for MATV systems) are offered for sale by well known and reputable companies like Blonder Tongue, Tin Lee, and others, and from the big antenna manufacturers like Winegard and PCT (the new Channel Master) too. The specs are published, the performance attributes are well known, and the results are predictable. These are the preferred choice of OTA professionals and hobbyists, and they understandably carry a price tag that may seem out of reach for some consumers.
Now contrast that with the sorry state of Signal and Drop amplifiers that are sold blister-packed, far and wide, in consumer electronics and department stores. Apart from their Raw Gain figures, none of the critical specifications such as Noise, Return Loss, and others are listed on the packaging nor even on the web sites of the companies shown on the labels. Indeed, it is often impossible to tell whether any company electronics engineer would exist to answer questions about those specs. Most likely the amp was imported and relabeled for our marketplace. So, while it might be tempting to simply add "12.5dB of boost" to your OTA system as the packaging material might say, you might also be adding unacceptable noise and/or other properties that cripple reception.Attenuators
I completely understand that some of you are hoping for a comparison chart or objective test evaluation of commonly available signal amps discussed above, and I would absolutely welcome any such test results posted here by someone with electronics testing experience, but at some point the consumer has to acknowledge that the entire category of them is suspect. As with any product, some people have good luck with them, but I personally have avoided them since the 1980s when the better ones started to disappear from the marketplace.
If your chosen amplifier's output is too high, causing trouble with TV reception, it is possible to either adjust a distribution amp's output level downwards on some models or put an attenuator downstream of the amp. Attenuators are for purposely lowering the signal strength in a cable run in order to prevent such symptoms as signal overload, in which a TV or FM Radio tuner cannot cope with too strong a signal. Its not good to try to fill a balloon with a fire hose...FiltersYou can get them in a wide variety of attenuation levels from a good antenna store, but I also found them in 6db strength (only) at The Source for a low price, where they are sold under the Nexxtech brand. They look like simple F-type coax couplers, but a little bit longer. They are handy to have around if you are trying out a new preamp/amp. Adjustable attenuators are also avaliable but are more expensive. Reasonably priced adjustable attenuators can be found on the Antennas Direct website.
Important note: If you have a preamp and you are putting the attenuator in its direct path you need to make sure that your attenuator does not block DC current from the preamp's power supply or the preamp will not have power to operate.
Sometimes there are cases in which we might wish to raise or lower the signal on an entire band, such as when joining two antennas to use the UHF band from both of them but using only the VHF band from one of them. Perhaps we might wish to just raise or lower the signal on specific channels in relation to the other channels, rather than on all of them. For this we use filters. Filters cannot amplify; they only attenuate.
- Filters work the same on the VHF, UHF, and FM Radio bands.
- If we're filtering an entire band the device is known as either a Band Pass or a Band Stop filter.
- Band Stop filters are often named as Traps for the affected band, such as an FM Trap filter on a preamp.
- Some filter devices have variable filtering levels for stopping/trapping certain channels or likewise passing them.
- If we're filtering just certain channels instead of entire bands the device is known as a Notch filter (they get the name "Notch" from the diagram of their operation).
- Some notch filters block or pass just one channel, while some do several at once.
- Some notch filters allow you to select the channels yourself, while others have to be purchased with the filtered channels preconfigured.
- a Stop or Trap, which allows all channels through except for the one(s) that you want blocked (you'd ask for a "Channel 12 stop filter" or a "Channel 12 trap")Code:Allowing all, but stopping/trapping 4, 7, and 9: 2 3 4 5 6 7 8 9 10 11 12 13 ______ ______ ___ ___________ [-] [-] [-] ...
- a Pass, which stops/traps all channels except for the one(s) you want allowed (you'd ask for a "Channel 33 pass filter")Code:Stopping/Trapping all, but allowing 2, 5, 8, and 12: 2 3 4 5 6 7 8 9 10 11 12 13 ]-[______]-[______]-[_________]-[__ ...
This is a feature of the ATSC standard for use during the analogue-to-digital transition that allows broadcast stations to telecast on a newly assigned DTV channel but "trick" the receiver at your home into displaying a channel number that corresponds to the original analogue channel or any other unused channel they please.
For a fictional example:
An analogue station called CKZZ on channel 8 spent 39 years in a market and has branded itself heavily on its channel number. Their DTV assignment is channel 43 so they must move all their programming over to 43.1, but now they face a big advertising job and the loss of almost 4 decades of "Channel 8" market branding. Using PSIP Channel Remapping, CKZZ-DT begins telecasting on 43.1 but sets its PSIP data to display 8.1 on home receivers. Their "Channel 8" identity is thus saved. After the transition period is done (2009 in the U.S., 2011 in Canada) and the analogue Channel 8 transmitter is permanently shut down, CKZZ-DT's owners make the strategic decision to physically broadcast on 8.1 and leave 43.1 behind for Industry Canada and the CRTC to reassign to any other TV station they choose. Effect on the consumer? The home receiver picks up the change and adapts accordingly with no consumer effort needed. Once again, their "Channel 8" identity is thus saved. Everyone is happy.DT stations will be allowed to reoccupy/replace their original old VHF analogue channel slots as long as they are in the high band (7 through 13) because VHF-low is being reassigned away from TV. In the example I gave, CKZZ analogue channel 8 goes dark one day, CKZZ-DT digital channel 43.1 (that remaps to 8.1) then shuts down momentarily, then comes back up genuinely on 8.1 and no longer on 43.1, which the authorities are now free to reassign to any other station that wants channel 43.1.Quote:Originally Posted by Yaamon
It is much, much more energy-efficient ($$$) to broadcast in the VHF-HI band than in the UHF band to cover the same area, so this is a desirable move for some stations to make. Others will decide to just stay where they are with their new assignments.
You can check the FCC database to see which stations in the U.S. near the Canadian border have elected to go back to VHF-HI and which have elected to stay in UHF. As always, the situation up here in Canada is murky at best.
This is why I will always keep an excellent VHF-HI antenna around...
There ought to be rules against that, but unfortunately as a Canadian there isn't much you can do to ask the U.S. station(s) or the FCC to take action.Quote:Originally Posted by Nester5000
Absolutely, but ideally the antennas must be identical. Stacking identical antennas (such as two DB-8s) is relatively easy, and ganging different types of antenna that use the same band (such as a CM4221HD UHF with a 91XG UHF) can be quite difficult, while combining a VHF with a UHF is routinely done and works very well.Ganging & Combining Antennas: A Walk Through
What is the difference between Ganging and Stacking two antennas?
What are the basic rules of stacking and ganging antennas?
- "Ganging" is the combining of 2 or more antennas' outputs together into one coax or twinlead cable to provide signal to one or more TVs, including with physically separate, individually aimed antennas.The electronics term ganging is really just a re-use of the English word for:In electronics I can have 2 resistors side by side on a circuit board but if they are involved in different circuits they are not ganged. If they are part of the same circuit and the current flows through both of them as part of the same task they are "ganged".Quote:Originally Posted by wiktionary
- "Stacking" is the specific vertical ganging of 2 identical antennas faced in the exact same direction for long distance, deepest fringe reception. The goal of stacking is not to make 2 antennas into 1, but rather to get both of the antennas working as a team. For example, to stack 2 CM4221HDs, just mount one above the other in the exact same aim with their respective bowties spaced uniformly. By experimentation we can vary this spacing of the upper and lower antennas to find the best performance. Research shows that the 2 antennas can actually work against each other if spaced incorrectly. Stacking is a way of increasing the gain usually by about 2 or 3 dB over just the single antenna because the receiving patterns of the antennas join into one, and their focus is sharpened more to the horizontal than the vertical plane.
- "Horizontal Stacking" is the same as above but with the antennas mounted side-by-side and aimed at the exact same azimuth, joined by equal lengths of coax or twinlead cable. Horizontal ganging is what Channel Master did perfectly in the 1980s with their original CM4228 antenna (ganging 2 original CM4221s side-by-side) and we can see this still in practice with such models as the CM4228HD and the Antennas Direct DB8. Unlike with pancakes, OTA terminology allows two objects to be "stacked" side-by-side.
- For stacking or ganging of co-mounted antennas aimed at the exact same azimuth (joined as a team) the coax/twinlead lengths must be exactly equal
- For ganged antennas that are not stacked, proper antenna separation (see below) is vitally important
- For ganging of antennas aimed at substantially different azimuths the leads can be of different lengths
- For ganging of antennas in which the aiming points are less than 20░ apart I still cut them identically
- stacking or ganging non-identical antennas requires a great deal of trial-and-error for inconclusive benefit
- stacking or ganging three or more antennas is best left to extremely dedicated experimenters
- stacking or ganging indoor antennas with outdoor antennas is usually futile or extremely disappointing
- no matter which method you choose, be prepared to test, test, test!
In a case where we have UHF stations in two relatively fixed directions that are between about 20 to 160 degrees apart we might be able to avoid using a rotor by ganging two antennas, but we will have some work to do. First, it is highly advised that the antennas be identical. It is possible to gang different brands or types of UHF antenna, but for the newcomer it can be overly complicated and difficult to accomplish.Stacking Identical Bowtie Reflector Antennas: A Walk Through
For this article we will assume that Antenna A and Antenna B are identical CM4221HDs and that the path from each to their respective target stations is clear.
When we gang two antennas it is essential to use one of these two methods to connect them, with more detailed information provided later in this article:
At this point, regardless of which option we choose, we might face a very basic electronic problem. We'll need to make sure that the two antennas are in phase so that their signals complement eachother instead of cancelling eachother out. We won't be able to tell if there is a phase problem until we hook up a TV or signal meter, so lets assume we're all hooked up and ready to test.
- connecting their feed points with 300 ohm twinlead (as short as possible) into a single balun, which then feeds into your preamp. If your antennas are subject to local interference use shielded, foam-filled 300 ohm twinlead.
- connecting their feed points directly to individual baluns, which then feed over coaxial cable into a joining device to create a single coax lead going into your preamp. A high frequency, high quality 2-to-1 splitter will suffice as a joining device. Such splitters can be found in many electronics and satellite stores, but avoid the cheapie ones. The balun-to-splitter cable can be RG59 coax, but I personally use RG6 for everything just because it means buying one less coil of coax.
Now we face another very basic electronic problem. Ganged antennas cannot be too close together or their fields will interact in undesirable ways, so in the case of a CM4221HD we should leave at least 25 inches of space between them (see explanation later in this article). Remember that this minimum distance does not apply to stacking, just ganging.
At this point we need to take our best guess as to the aim of the two antennas, but don't worry yet about getting it right. We just need to have some signal showing up on the screen or on the meter. If there is little or no good signal after connecting the downleads of Antenna A and Antenna B through the splitter, disconnect the balun wires off of Antenna B, switch the two wires around, reconnect them to that antenna, check for signal, and we'll find that the signals are now in phase and are working properly together.
Next, we will have the actual aiming task to perform. The term for getting one antenna's aim perfect is called peaking. The most natural expectation is that we would disconnect Antenna A from the splitter and peak Antenna B perfectly for its intended station(s), then do the opposite to peak Antenna A for its own. Nope! If only it were that easy!
Unfortunately there may be some further aiming to do. The problem is that antennas have a specific beam pattern of reception that has areas of strong and weak signal. For example, see this illustration of the CM4228's beam pattern (from the HDTV Primer site):Now imagine if our two antennas, perfectly peaked individually for their own targets, share an overlap that causes a strong area (a peak) to overlap a very weak area (a null), and we can see that our reception will suffer. Of course the worst scenario would be if the two antennas shared nulls in the exact direction of some of our desired stations.
So, as we can see, a compromise is often required, and this best-of-both-worlds solution can take a fair amount of time and effort to locate exactly. Don't be discouraged. Many people have found aiming solutions that provide them with suitably strong reception from both directions of aim.
And here's an experimental alternative to using a coax splitter when stacking identical antennas, but the problem is that the "rated" 300ohm impedence of each antenna (as broadband antennas their real world impedence is variable depending on the frequency of each channel) will combine to result in only 150ohms, which will cause a typical 4:1 balun to yield only 37.5ohm impedence on the coax downlead on some channels. This means that some channels may be weaker than the coax splitter technique while some may be stronger.
- stack your antennas one above the other so that all of their bowties are equally, evenly spaced
- combine their output with exactly equal lengths of RG6 into a reversed high quality splitter
- run a single coax downlead from the reversed splitter
- test by watching a signal meter on your TV or with a signal tester
- if the reception is great your antennas are in phase and you can solder, twist, or crimp the twinlead ends to the balun and cover it with roofing tar or heavy duty electrical tape
- if the antennas are out of phase your reception will be horrible
- fix that by simply switching the two conductors on just one of the baluns
- test again, slightly moving the lower antenna apart from the upper one to watch for improvements, and when you find the best solution go ahead and permanently attach all the connectors
- get about 8 to 10 feet of 300ohm twinlead (the old fashioned stuff)
- connect both antennas with it, leaving about 2 inches of extra length
- measure the length of that twinlead connection as exactly as possible
- mark the exact middle of the length
- cut and strip the 300ohm twinlead at that middle point
- temporarily attach the balun to those twinlead ends (as the unison point of the output from both antennas)
- connect your coax downlead to the balun
- test by watching a signal meter on your TV or with a signal tester
- if the reception is great your antennas are in phase and you can solder, twist, or crimp the twinlead ends to the balun and cover it with roofing tar or heavy duty electrical tape
- if the antennas are out of phase your reception will be horrible
- fix that by simply switching the two conductors on just one of the twin leads
- test again, and it should be fine to permanently attach all the connectors
Yes, it would work exactly the same, so just be careful about testing if the antennas are in phase before you permanently connect them and the balun together. Also check the information below on correctly spacing your two Delhi 10Y13s.Note to all about 300ohm twinlead
300ohm twinlead is usually fine for just about any ganging or stacking into a single balun, but if you are in an area that already is known to test badly for interference you should use shielded, foam filled 300ohm twinlead for more protection.What if I want to use more than one antenna but don't want to combine them in any way?
If you want to use two or more antennas independently of each other, such as one for each apartment in a subdivided home, you will need to reduce or eliminate effects of the antennas caused by their proximity to each other. This issue is called Antenna Spacing. The antenna spacings given here have always served well but holl_ands has been doing some terrific research using computer modeling and can discuss it over in the Stacking, Ganging, Combining TV Antennas thread. The spacings here in the OTA FAQ are tried-and-true examples, while the results that holl_ands is getting are for people needing to get every last ounce of signal regardless of the complexity of putting up a longer/higher mast (wind and snow load, weight on a rotor, etc.) so please keep that in mind. To use the tried-and-true spacings listed here, first read Post #5 in the OTA Knowledge Base & FAQ, then this:Can I use separate UHF and VHF antennas together?
- Same-band antennas should be spaced apart at least one full wavelength (λ) of the lowest channel they can receive
- use full wave spacing, but if not possible use half-wave (as a last resort try quarter-wave spacing)
- VHF-LO (includes VHF/FM, VHF/FM/UHF Combo): channel 2 λ = 18.22 feet (5.55 metres) apart, but 1/2 can be done
- VHF-HI (7-13) antennas: channel 7 λ = 5.65 feet (1.72 metres) apart, but 1/2 can be done
- FM Radio antennas: 88MHz λ = 11.18 feet (3.41 metres) apart, but 1/2 can be done
- UHF antennas: channel 14 λ = 25.12 inches (.64 metres)
- Channel-cut (single-channel-specific) antennas: using Post #19 in the OTA FAQ you can find the required channel's wavelength to determine the best full wave or 1/2 wave spacing
- Different-band antennas also need to be spaced properly:
- VHF-LO with a VHF-HI: channel 7 λ = 5.65 feet (1.72 metres) apart, but 1/2 can be done
- VHF-LO with an FM Radio: 88MHz λ = 11.18 feet (3.41 metres) apart, but 1/2 can be done
- Either a VHF-LO, FM Radio, or VHF-HI with a UHF: channel 14 λ = 25.12 inches (.64 metres)
Yes, if a single Combo antenna is not suitable for your needs you can easily combine the output of a UHF and VHF antenna in several ways, with some being better than others depending on the situation at hand (that means you might have to do some testing):For a wide ranging discussion of the topics in this post please read through the Stacking, Ganging, Combining TV Antennas thread in the main OTA Forum.
- combine their balun output up on the mast into a UHF VHF Separator/Joiner, such as a
- Pico Macom UVSJ
- Winegard CC 7870 2-Way Antenna Joiner Coupler
- Antennas Direct EU385-CF UHF / VHF Antenna Combiner
- if each antenna has its own preamp do as above except combine from the signal output of the preamps' power injectors into the Separator/Joiner
- combine their balun output up on the mast into a reversed high quality, low loss splitter for a single coax downlead
- combine their balun output up on the mast into a VHF/UHF preamp (only if amplification is suitable)
- join their feed lines together with 300ohm twinlead cut half way between them, where you attach a balun and downlead
- run their separate coax downleads into an A-B switch at your TV (not convenient for PVRs that cannot operate the A-B switch as needed)The thing about Channel 13 and the other VHF Hi channels is that a good VHF antenna will give about 10 to 15dB of unamplified gain on those channels to give a solid lock, so I don't think you should try to use your CM4221 for Channel 13 when it cannot deliver much at that frequency in the first place. Boosting it a lot could simultaneously cause big problems with the UHF channels.Quote:Originally Posted by keeneye
Since you only want one VHF Hi channel, my advice is that you look at either (best to worst):
- a precision-cut single channel antenna for Channel 13 up with your CM4221
- separate VHF/FM antenna up with your CM4221 (nice to have FM Radio stations, particularly if they are HD Radio)
- a good Combo to replace your CM4221 (convenience of just one antenna up there)
- replace the CM4221 with a CM4228, which has decent VHF Hi reception (see next point and apply to CM4228 if needed)
- CM4228 into an all-band preamplifier (might be too strong on the UHFs - you'd have to test)
- (not guaranteeing this will work) stay with your CM4221 but put in a splitter from the balun, with:
- one lead going into a UHF-only filter to TV
- the other lead going into a strong VHF-only Preamplifier to TV
|antenna , atsc , chart , faq , hdtv , knowledge base , ntsc , ota , stampeder|
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