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Niagara: Best DIY OMNI?

8K views 36 replies 9 participants last post by  audioguy_on_ca 
#1 ·
I looking for an answer about what I can focus in/need to learn up on. I'm within 60-70 miles of just about all the major broadcaster's TS and want them all reliably, so I can cut the cable, buy a bigger pipe to the net and DL/stream what I can't get OTA.

Here's my TVFool:http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d46aec0e383d10f

SBGH? DBGH? wire mesh? colinear rods? NARODs?
 
#2 ·
Try the Stealth Hawk first, it has a pseudo omni pattern, like a bunch of flower petals in all directions, modest gain. If that doesn't work out out try a SBGH without any reflectors. It will have two main lobes, 180 degrees apart, more gain than SH, but not as much as SBGH with reflectors. They are both equally simple to build.
 
#4 ·
It would help to see your TV Fool - in any case - to know the directions and approximate strengths of the channels you would like to receive.

And to see what channels you have exactly - VHF lo ? any VHF Hi any? which ones?

That might help give some more specific advice for the type of DIY antenna you could try.

I had good luck in Ottawa with a simple bi-directional UHF / VHF combo loop mounted outside above the chimney (high/clear outside mount is the key here) - the main local stations were more or less from two main towers in almost opposite directions. The pattern of this type of antenna is pretty broad / wide in two directions, so it is almost like omnidirectional - and it picked up all the local VHF hi and UHF channels in Ottawa, with moderate strength, without a pre-amp, down 60 ft of coax cable (but you could add a pre-amp possibly, like if you want to split the signal to feed several receivers) ... and it even picked up one VHF lo channel when it was still there (Global on rf 6 - but now moved to 14 in Ottawa).

That antenna I mention is the 23 inch BIL - 23" Bowtie in Loop, which I made of 3/8" soft copper tube from a tube coil.

There's pictures of it in my Photo Album, in some threads (Loops Thread) and you can see it also with performance graphs in Holl_Ands website.
[ 23" BIL - 23" Bowtie in Loop - was developed and modelled by a few Forum Members - Wildwillie and Holl_ands I believe. ]

But if some of your signals are weaker ... you'll likely need a little better antenna than just a 23" combo loop. (ex- as mentioned by others, reflectorless, 4 bay with larger whiskers for some VHF hi like the 9.5x9 or a reflectorless GH with NA rods for some VHF hi reception if needed.

... we should see your TV Fool - will help the experts here to give you some more specific advice.
 
#5 ·
To get 2-Edge Network Stations (CBS, ABC, NBC, MyN), you're going to need a LOT more Gain than an "Omni" Antenna. A Bi-Directional Antenna pointed towards 126-141 degrees will ALSO point it's Reverse Beam towards 306-321, which will be more than adequate for your stronger LOS stations at 346 degrees, if the Beamwidth is 40-degrees or more (piece of cake).

High Gain Antennas that provide this capability include fol. DIY and Commercial 4-Bay Bowties with NO Reflector....and the first few DIY models also provide very usable Hi-VHF Raw Gain for Ch9 (but iffy on Ch7 & Ch13):
http://imageevent.com/holl_ands/multibay/4bay

Although they provide very wide Beamwidths, I wouldn't recommend any of the fol. Loop Antennas due to their much lower Gain....most of them are only "1-Bay" designs....and the "2-Bay" DIY Hourglass-Loop (NO Reflector) only provides 5-6 dBi Gain....very iffy for those 2-Edge Network Stations:
http://imageevent.com/holl_ands/loops

BTW: If you want to receive Ch6, you might want to try a very simple DIY Lo-VHF Hourglass-Loop and combine with main Antenna using a Lo/Hi-VHF Combiner (aka HLSJ). This one is Optimized for Ch6:
http://imageevent.com/holl_ands/loops/lovhfhourglassloopnorefl
While this one is Optimized to ALSO include the FM Band, with some loss of Gain on Ch6:
http://imageevent.com/holl_ands/loops/lovhffmhourglassloop
Note that wire size is NOT Critical in the Hourglass-Loop....even on Lo-VHF Freqs....so feel free to use as small as AWG12 or as large as 1/2-inch Copper Tubing.
 
#6 ·
SBGH? DBGH? wire mesh? colinear rods? NARODs?
I looked at your report and I am guessing you are 2 miles south of my location in St Catharines.

You are 32.1 and I am 30.3 miles from CFTO.
You are 47.0 and I am 48.2 miles from WGRZ.

I use a CM 4228 aimed at WGRZ and I scan all channels but no WBBZ RF 7.
All Hamilton and Toronto channels come in on the back and sides on the 4228.

Don't worry about RF 6 - it is now RF 17 CIII and it is rock solid.

FYI
 
#8 ·
wow

dsspredator - local knowledge (I'm N of Scott and E of Vine, south of Realty Park) is most welcome. Many thanks! but days like this are made for building your own antennae methinks...

holl_ands - I'm guessing you're at least an engineer who understands the math and physics. maybe an EE. maybe an EE with specialty in RF systems. regardless, my next question for you: how much gain is "adequate" and fairly easily attainable to get those 2Edge stations? (I understand bi-directional and lobes and arrays, bitstream, yada yada - check my nickname. I deal with dB on a daily basis. my transducers are microphones and loudspeakers, so feel free to get a bit more technical if you care to reply)

nikiml - you sound pretty confident. I'm going to dive in!
 
#9 ·
nikiml - you sound pretty confident.
Who? me? Never!

But if Toronto channels come from the back of CM 4228 they should come through GH0 and the Buffalo ones don't seem much weaker.
But holl_ands is right and you need more gain in some directions, it all depends on what you want to get. I would think the GH0 will get you down to MyN.

My point was only that if you are building reflectorless GH, then the GH0n has added flexibility(in VHF-hi) that you may use.
 
#10 ·
[QUOTEMany thanks! but days like this are made for building your own antennae methinks...

][/QUOTE]
Only if you got a warm place. Its gonna get cold Friday, even here. :(

nikiml - you sound pretty confident. I'm going to dive in!
Its kind of like a no brainer, but you wont know for sure until you've done it. :p
 
#12 ·
OK - silly me, seen the TV fool now.

So if I understand the discussion correctly so far, there are no VHF lo channels, 6 Global there went to 17.

And the only VHF hi is 9 .

But looks like there are many LOS channels from all different directions. Some off at 90 degrees too. Not just front and back, but also to the side.

So some sort of good TRUE Omni-directional antenna for all the locals LOS would be good, I think, in this case. As the OP, original poster originally asked about. "Omni"

UFO Omni ?
[ not one of those expensive ufo "smart antenna" / micro antenna - just one of those simple standard fixed ufo antennas]

This is Not a DIY antenna - but I have good luck with an old simple manufactured, residential UFO type antenna.
[ not the greatest for vhf lo, but mine picks up 6 analog really well anyway, and you have no real vhf lo there. ]

I get 6, 7, 11 local and UHF's too.

It's a quick simple easy inexpensive solution, easy to install, and has a lot of built in features that help get Omni reception quickly and easily.

Best results - put up outside, above the roof obviously. Chimney mount.

Example:

Mine is an old 21" diameter. And I think the larger diameter ones are better.

Mine is Similar to a TDP - model 5MS921
(Tandy Distribution Products - read: Radio Shack / The Source)

Mine is Similar to:
Antenna Craft Omni-State 5MS921
21" HDTV VHF UHF antenna
"20 db built in amplifier" [ pre-amp built in ! ]
"FM Trap" [ built in - helps for TV to reject local powerful FM signals ]
"Operates on 120 VAC with supplied adaptor" [ the power injector inside near the set ]
12 V DC power injector
"20 mile range" [ mine outside, on the tower is picking up much further than that - LOS. Watertown PBS, and Belleville TVO from Kingston - solid. ]


Now really ... I think that's quite a package for easy Omni reception.
Very cost effective with a lot included and easy to install.

That sort of antenna should *NOT* cost like 100 or 200 dollars.

I'm guessing maybe 40 or 50 dollars.

I'm sure Winegard or CM-channel master, or Antenna Craft have those simple UFO's still - like for RV's.


For DX - long distance reception, that is a different story - ya - different / separate setup - You will likely need a high gain directional antenna with good low noise pre-amp, probably with a rotor to point it around in different directions.


True Omni - DIY antennas are:
Bi-conical or Discone - but no, they are low gain and vertical polarization I think. No good - TV is horizontal polarized. Guys with scanners use this sort of antenna - to pick up signals from all directions / unknown/moving directions and vertically polarized - like mobile radio transmissions.

FM almost Omni, horizontally polarized - is the standard crossed folded dipoles connected together. [ but Holl_ands mentioned the FM cross has a null in one direction ]

Most other DIY antennas mentioned here, like the standard reflectorless GH, whisker antennas like M4, or loops, are mostly bi-directional and will have nulls at 90 degrees and 270 degrees.

I do see people putting up those simple UFO antennas on old towers for LOCAL Omni reception.

I have one too - giving good service - and since amplified, able to split 3 ways and feed 3 TV's - no problem. It's a quick solution - even if not DIY.

But buy a good quality one. with a warrantee - if you decide to do that.

If it does not work out for you, or is crap - then you can return it, try another, or try something else.
 
#13 ·
I'm still thinking build, and I'm gonna go omni until I know what direction I'm NOT getting stuff from with that...one of the cool perks of being in this location is that from the "North" is where Toronto beams in From, and from the "South" is where the 'merican networks beam in from. I'm looking across the street at my neighbour's chimney and see he has commercial antennae pointed in each of those directions, and he says he gets 30+ channels. I'd love to show him up with ONE that gets as many or more, just as a point of pride. Even a properly aimed bidirectional antenna will catch what I'm looking for I'll bet.
 
#14 ·
Crossed GH, no reflector for omni? Combined? Connected together?
[ in other words 2 GH's but mounted/aimed fixed at 90 degrees from each other and combined ? And possibly a "mild" / medium to low power pre-amping like 10-15 db, to avoid any local signal "overloading" ]

Crossed 4 Bay Whisker (no reflector) antennas ? Similar idea?

Just a couple quick high level concept / ideas.

I have seen similar things done.

Example: A guy just puts up 2 M4's, combines them, and points them in different directions to get multi-direction reception - but with better gain than other types of Omni antennas.

But for best results, and least problems, point the 2nd antenna exactly in the NULL of the first antenna - in theory will give you a pretty good Omni coverage ???.

Best of luck... if you're trying to show up/do better than your neighbor ... you'll likely need something like that.

Something really interesting could get developed here that will be very useful for a lot of people ... I think.

Will have to computer model it to be sure.
 
#15 ·
Yes, I'm a retired Communications System Engineer with BS/MS degrees in Physics (Electronics) and Computer/Information Systems (Statistical Communications and Coding). Among many other subjects, I've worked on Propagation Predictions and development/test of various Signal Modulations, Error Detection & Correction Codes, Diversity Combiners, Adaptive Equalizers and Adaptive Antenna Arrays.

=====================================================
How to Calculate whether an Antenna is "Adequate":

"Click Here" at bottom of TVFool Report to see fol. definition for Net Margin, NM (dB):

NM(dB) - This is the predicted Noise Margin (NM) of each channel "in the air" at your location, specified in dB. You must add/subtract any gains/losses you get from your antenna, building penetration, amps, cables, splitters, and other factors present in your situation. Hypothetically speaking, you need to end up with an NM value above 0 in order to pick up a station.

However, this is based on the STATISTICAL Longley-Rice Propagaton Model, presuming F(50,90) Reliability Statistics, which means 50 percent of users under the "same" conditions will experience a 90 percent long term reliability. In other words the signal is going to drop out for many minutes...or hours per year and in the short term expect to see a bunch of error streaks and screen freezes:
http://www.tvantenna.tv/papers/paper1999.asp
http://hraunfoss.fcc.gov/edocs_public/attachmatch/FCC-05-199A3.pdf

For Long Term Reliability, I recommend a NM of AT LEAST 10 dB for LOS stations and as much as 20 dB for 1-Edge and 2-Edge stations since they are very prone to Multipath Fading. In Microwave Link Budgets, this is called the "Fade Margin", typically targeted to be about 20 dB.

Also note that TVFool's Longley-Rice model also doesn't account for Man-Made (mostly Impulse) Noise (add up to another 10-20+ dB for Ch6 thru Ch2 respectively, depending on your local environment), Clutter Loss (although crude corrections are included in FCC OET-69), Tree Loss and Indoor Loss.

And finally, TVFool (as well as many other models) rely on the SRTM-3 or SRTM-1 topographical data base, which (at best) can only resolve terrain to about 100+ ft, which means it doesn't KNOW that my house is located at the bottom of a 60-ft high hill in my backyard and hence generates overly optimistic predictions for stations in that direction.

Hence, I like to see as much information as possible from posters....and TRY to make CONSERVATIVE recommendations....and SOME people are going to be on ONE side or ANOTHER on that 50 percent distribution curve and will perform significantly better.....or worse than the "nominal" prediction.

Fade Margin (dB) = Corrected NM (dB) =
NM (dB) + Antenna Gain (dBd=dBi-2.15) - Cascaded Noise Figure (dB)

Since SCALAR (not dB) Loss AFTER the Preamp is REDUCED by the amount of SCALAR Gain in the Preamp, you need to use fol. on-line Spread Sheet Calculator [aka System Noise Figure]:
https://docs.google.com/spreadsheet/ccc?key=0Ap6QeEL-E_5VcGhzUk5aTkNwS3FnYnFLQ0g2aEZtTHc&hl=en#gid=0

Or, if using a Preamp, add assumed Balun Loss (and Balun-to-Preamp Cable Loss) to "Signal Loss" in fol. Chart for specific Preamp models:
http://www.digitalhome.ca/forum/showthread.php?p=888368

I also prepared fol. Spread Sheet Calculator to compare alternative Preamps to NO Preamp case:
http://photos.imageevent.com/holl_ands/files/ota/System Noise Figure - holl_ands.xls
Additional files that may be of interest can be found in my signature link below.
 
#16 ·
Right...
In my audio world, when 2 bidirectional transducers (microphones) at right angles at their null points are utilized, the resultant array is named after the Bell Labs Engineer who apparently came up with the concept in the 30s to capture a stereo field. Conveniently, the result is perfectly mono-compatible, and the resultant signal gain is 3-6dB. I'm betting the maths/physics hold true here in the RF world as well. Now I'm just looking for the right preamp...
maybe this one http://www.digitalhome.ca/forum/showthread.php?t=142375
 
#17 ·
WooHOOOO! Jackpot! Cool beans, holl_ands...pleased to meet you! You're JUST the person I've been looking for. Underpromise and overdeliver - a REAL Engineer.

Lucky for me and people in this geographical area, we're blessed to be in close proximity (within 40-60mi) to fairly large network TS's lashing the ether with MW of RF energy. An Antenna with a gain of ~10dB with a preamp of similar power will put the first few 2Edge stations on myTVFool up into the 30-40dB NM range...and that's just above the halfway point on that (by your standards, which I respect) flawed list.

Thank you, kind sir, for all the resources and knowledge you've provided.
 
#18 ·
Yes, check out Holl_Ands website. He may have already modelled and documented some different variations of Omni antennas.

Careful - what works with sound (an air compression wave), might not work with RF waves. EM / RF waves are not so intuitive.

That's why we always say " you would have to computer model that to be sure "

But ya ... the concept you mention is similar .

And if you understand all the audio stuff and graphs and characteristics - you will surely understand what is there on Holl_ands website.

Careful also with your choice of pre-amp - if you decide to try one.
The best ones for this purpose have a low noise rating, and perhaps a switchable FM trap - to knock down high power, nearby local FM transmissions. Looks like you have no VHF lo channels, so in theory you could have some sort of high pass filter and reject anything below ch 7.
( some use a HLSJ ? for this purpose? maybe? a high low system join device and connect through the high side to select only VHF hi, and reject VHF lo, and maybe FM too ... not sure if the high side rejects FM too, but I think so. )

Many run into trouble overloading the pre-amp, with a high gain antenna, and nearby powerful local TV signals.


AUDIO stuff - working with sound - is also very interesting and COMPLEX.
( I've read a little on it ... very interesting )

I bet the Home Theatre guys and Audio Philes here on the Forum would be VERY interested to hear from you . Browse around.

Some guys are into HD Radio - digital FM - and antennas and receivers to try and receive that from the U.S. (very few stations in Canada yet.)

So welcome to the Forum ...

P.S.
when 2 bidirectional transducers (microphones) at right angles
I also have read where they place one transducer further back in a large room / recording space / hall - and that gives the recording like a natural delay / echo - ambience ... something like that.

Similar to a trick they do with an antenna sometimes - to try and help null out an interfering signal from the back.
(phase cancellation, time and distance signal / wave must travel. And with RF stuff, the time and distance the signal travels through the transmission line, ex. the coax cable, can be used in various ways as well. Very interesting stuff - all of it ! )
 
#19 ·
M4 4-Bay with 90-degree Twist between Upper and Lower 2-Bays was discussed here:
http://www.digitalhome.ca/forum/showthread.php?p=1939242
Raw Gain in "best" direction was very low on lower channels, with an Irregular Azimuthal Pattern....although SWR was MUCH better than similar Hoverman Type 1 "Omni" with a Twist per Doyt Hoverman's Patent, discussed in preceding posts.

So it's important in a two-antenna solution to provide adequate physical separation to minimize coupling between them.....probably 4-feet or more as was found to be the case for Vertically Stacked Antennas.....something that only happens with Electromagnetic waves.....not in microphones.
 
#20 ·
Welcome here, audioguy_on_ca, I have family right nearby you and dsspredator (near Niagara & Linwell). Be sure to pour through the following thread for everything you need to know about OTA in St. Catharines:

ON - Niagara Peninsula - OTA thread: http://www.digitalhome.ca/forum/showthread.php?t=36534

This present thread here in the Antenna R&D forum is perfect for your DIY needs, and the experts here are amazing, but when you're wondering how your neighbours have been doing you'll see everything like preamps, antennas, etc. etc. in the Niagara thread going back almost 10 years. You'll do great. :)
 
#21 · (Edited by Moderator)
Thanks to nikiml for the pattern option on his web page: I understand polar plots.

A crossed GH design is looking like it will suit me best - but not with 0 degrees of one element aimed at the spike of Toronto broadcasters on my TVFool; turned 30 or so degrees west of that, so that when the elements combine, all of the signals on the report fall within at least one of the 4 lobes of the array. I'm sure that will get me very close to (and in most cases, well above) the >20dB NM holl_ands mentions (for the channels I'm interested in) at the array, and I'll bet I won't need to amplify.
 
#22 ·
Wait a second!

(sorry for reviving this thread, but I had to drop this project as work picked up)

nikiml - am I understanding the size of your GH0 design to be roughly 3' x 2' ish? that's way smaller than I expected...I guess I just realized lengths are in millimeters.

now...what happens if we play with bending the elements I guess they're referred to in more than the single plane, turning this into a 3D design? can the antenna be compacted? Will it perform as well? Are these questions for the people in the fractal design threads? :eek:
 
#23 ·
now...what happens if we play with bending the elements I guess they're referred to in more than the single plane, turning this into a 3D design?
It is a 3D design.

The displayed dimension info is in relation to the coordinate system drawn in the center. The coordinate systems also defines the orientation of the antenna by the following convention: +X is towards the transmitter, Y is horizontally broadside and Z is up.
http://clients.teksavvy.com/~nickm/help.html
 
#24 ·
It is a 3D design.
I probably deserve that.

seriously, though; if i keep with the 2x and 3x multiples of 45 degree bends at the corners of the GH double diamond, will I enhance gain or directionality or both in any way or just wind up with a difficult to construct 3D antenna? (Perhaps the question to ask is: if i condense the length of an antenna into a smaller space am I making it more or less effective, and where is the trade-off happening, gain or directionality?)
 
#25 ·
if i condense the length of an antenna into a smaller space
We all know that small is beautiful but not in the case of a TV antenna unless you've got the transmitters very close to you.

You could go smaller if you'd have UHF-HI channels ONLY, like RF40 to 51 to deal with.
.
 
#26 ·
if i condense the length of an antenna into a smaller space am I making it more or less effective
Nikimls models are very optimizied. If you mess with the dimensions, you are sure to get poorer results. He also hasn't optimized any fractal designs yet.

You can look at my modeling results fractalizing the original reflectorless uhf-only SBGH here in post #15:
http://www.digitalhome.ca/forum/showthread.php?t=95684&highlight=fractal
 
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