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Old 2013-07-13, 12:47 PM   #3571
roger1818
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Quote:
Originally Posted by gculley View Post
I considered the lower gain preamp, but then that would be the same as throwing in an attenuator post-preamp which actually solved the issue but cost me my weakest stations.
It isn't the same thing. If the pre-amp is overloading, the damage to the signals has been done and an attenuator won't clean them up. However, if it isn't the pre-amp that is overloading, an attenuator may help.
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Old 2013-07-13, 01:15 PM   #3572
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Lowest 4G-LTE Cell Tower TRANSMIT Bands for AT&T are 734-746 MHz and Verizon are 746-757 MHz. Bear in mind that when I prepared the following, 716-728 MHz occupancy was changing (hopefully it's for RECEIVE???):
http://www.digitalhome.ca/forum/show....php?p=1389931

I only know of one website that will identify the exact locations of Cell Towers broadcasting in the "700 MHz Band" [formerly Ch52-69]. Perhaps other users know a better way to sort out the INFREQUENT locations of the 4G-LTE Towers from the higher frequency towers that must have much closer separations:
http://www.antennasearch.com
Enter your location and DOWNLOAD the Antenna File. Go to far RIGHT side of spread sheet and look for 700 MHz Band frequencies.....it's a needle in haystack problem. Since the search distance is only 4-miles, you'll only see nearby 4G-LTE towers....mine are more than 7 miles away so I needed to enter a street address close to where I suspected the towers to be (antenna "farms" on mountain tops) to finally see them. I was surprised to see that Qualcom was no longer transmitting MEDIAFLO from their FIRST ever location in San Diego....only 2 miles away....and no one had taken over their transmit facilities....so no more overload desensitization issues for me....

4G-LTE towers are only a potential problem when very close to your location. A Signal Level Meter measurement can also be useful to see how strong a signal is actually present on the Preamp's input....esp if trying a filter to reduce the signal strength.

Note that the LOWEST 4G-LTE frequencies, 704-716 MHz, are used by AT&T's Cell PHONES....which means that YOUR FAMILY might be the worse source of EMI on TV signals in your home.....fortunately, you will probably see this if it's an issue and can take various protective measures if it's a problem.....
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Old 2013-07-15, 11:40 AM   #3573
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Thanks for all the help guys, it's amazing how much there is to consider out there!

I erected my antenna over the weekend after fixing a bent mast from an icestorm last spring. I wish I'd checked for new posts here before I did so that I could experiment with an additional FM trap.

For my new antenna configuration, I created a 3-element yagi, cut for ch. 10, to be able to separate hi-vhf from uhf stations at the preamp. This allowed me to remove the insertion loss of my Ch. 13 notch filter from my UHF channels. I mounted the yagi about 18 inches above my CM4228HD (I know, that's a bit close but I had to factor in other constraints) and ran it throught the notch filter. The CM7777 is set to "separate" the VHF and UHF frequencies and, of course, I left the built-in FM trap in.

Interestingly enough, the yagi performs a little better than my hacked CM4228HD for hi-vhf (approximately 2 db better). I played around with the positioning of the antenna and found that I was able to fix my multipath issue by pointing virtually straight at our local CKCO tower. No attenuator was needed this time.

I believe that my more rigorous tweaking of antenna position made the difference, where when I did this for the CM4228HD it was more of a course sweep of the rotator that I did to see if antenna position would help. Live and learn!

I'm able to receive CJMT (UHF Ch. 40) at about -5.5NM pretty reliably, but it's as weak as I can go. It's signal quality is almost always 13% lower than its signal strength, so perhaps I needed an additional FM trap. I'll give that a try the next time I take the antenna down. I don't think that adding one would help post pre-amp as the concern is with pre-amp overload.
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Old 2013-07-20, 07:35 PM   #3574
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Default RCA TVPRAMP1R Amplifier

Has anyone found Noise Figure (NF), FM trap attenuation and overload (max. input signal strength) specifications for the RCA TVPRAMP1R amplifier?

This looks like one of the few remaining switchable dual VHF/UHF input, mast mounted, pre-amps. with a switchable FM trap. It is available through Walmart for $21.95, Office Depot for $22.99 and Solid Signal for $27.99 plus shipping ($4.95).

Manufacturer (for RCA?): VOXX International
RCA says :”Outperforms old preamps made for analog & Preserves signal purity with Extremely Low Noise (ELN) circuitry” but doesn’t specify an actual NF.

Other specs. listed include:
Separate or combined inputs for UHF/VHF
Switchable FM trap reduces interference from FM frequencies
VHF gain: 16dB
UHF gain: 22dB

Last edited by Pete Higgins; 2013-07-20 at 09:16 PM. Reason: Add Title
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Old 2013-07-20, 09:47 PM   #3575
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Channel Master & Winegard are the ONLY manufacturers who provide MEANINGFUL, ADVERTISED Overload Specs for their production products.....hopefully verified on the production line via random sample tests....

Sounds unlikely, but Newegg sez that BravoView (who???) makes the RCA TVPRAMP1R. Perhaps they'll respond to an email query:
http://www.newegg.com/Product/Produc...9SIA25V0PZ2245

However, I found that it's found under the RCA brand as one of the many AudioVoxx "manufactured" products (e.g. imported under license):
http://www.rcaaudiovideo.com/antennas
http://www.voxxintl.com
There is a link to the User's Manual (no specs of any kind), FAQ (no help) and an email query that you could try to obtain an answer (highly unlikely....if they bothered to have the overseas manufacturer meet a specific Noise Figure spec, they would probably require that it be proven via sample tests, preferably by an independent laboratory, it would ALREADY be in their literature to justify the extra cost)....it is SO MUCH EASIER to simply hope most customers doesn't know to even LOOK for a Noise Figure spec.....and save a boatload of money in the process.... Doesn't necessarily mean it's a poor product...simply means it's a product with UNKNOWN performance.
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Old 2013-07-20, 10:49 PM   #3576
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Default Re: RCA TVPRAMP1R Amplifier

Thanks holl_ands,

Office Depot lists VOXX International as the manufacturer.

Wikipedia says: “Voxx International, formerly Audiovox Corporation, is an American consumer electronics company founded in 1965 and headquartered in Hauppauge, New York. The company specializes in three areas: OEM and after-market automotive electronics, consumer electronics accessories, and consumer and commercial audio equipment. Voxx International's domestic brands include: Acoustic Research, Advent, Code Alarm, Invision, Jensen, Klipsch, Prestige, RCA, and Terk, among others. It's international brands include: Hirschmann, Heco, Incaar, Oehlbach, Mac Audio, Magnat, Audiovox Germany, and Schwaiger, among others. In addition the company licenses the Energizer brand."

I sent the following information request to RCA/Audiovox; #130720-000063 "What are the Noise Figure (NF), FM trap attenuation and overload (max. input signal level) specifications for the RCA TVPRAMP1R amplifier?"

If I get a reply, I'll share it.
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Old 2013-07-22, 07:30 AM   #3577
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Quote:
Channel Master & Winegard are the ONLY manufacturers who provide MEANINGFUL, ADVERTISED Overload Specs for their production products.....
Perhaps that was so in the past, but it would appear that CM no longer provides ANY overload data for their new (2012) pre-amps while WG has converted to conventional engineering specifications of OIP3 and P1dB for their new Boost pre-amplifiers. FWIW, from the several CM and WG pre-amps I and our engineer have both tested (different test equipment, same samples), I've found the claimed noise figures to be substantially higher than the claimed values, so I really don't have much confidence in their claimed overload characteristics, either.

Pete,

I did test an RCA this past winter, I'll have to see if I can dig up my notes. BTW, RCA's webpage for the pre-amp gives "Intermodulation: Avg>60dB" as a specification. I have no clue what they're trying to say there, so, if they get back to you, please share. As I recall, the RCA amp posted respectable NF and IMD numbers, even better than some well known well known competitor's long-time products. The only real knock I could come up with was its total lack of shielding (same problem as Winegard's AP and HDP products) and relatively flimsy construction.
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Old 2013-07-22, 01:05 PM   #3578
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Modern Plastics have built-in electromagnetic shielding as part of the "mix"...no need to use expensive metal anymore.

I think I've mentioned this before. In Europe (and elsewhere), Preamp Max Output is usually stipulated in accordance with DIN 45004B (Unequal THREE Carrier Test in dBuV units with Intermod Products at -60 dB) or DIN 45004K:
http://www.powercommunications.com.a...erSettings.pdf
http://www.antech.ro/pdf/Norme_tv.pdf [See pg4 and test CONVERSION tables on pg5-7]

Sometimes European manufacturers explicitly cite the standard and sometimes it's IMPLIED:
http://www.fringeelectronics.co.uk/PDF/Masthead.pdf

PS: Finally found my earlier post re DIN45004:
http://www.digitalhome.ca/forum/show...04#post1377858
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Old 2013-07-22, 02:02 PM   #3579
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Default Re: RCA TVPRAMP1R Amplifier

ADTech & holl_ands,

Thanks for the replies.

ADTech, I think your notes on a presumably “store bought” sample would be more meaningful than manufactures published specs., although I think it is important to know what they claim and how close production samples achieve. Been in meetings where marketing wanted to round up on the good specs and round down on the bad ones? I recently bought a good 8-Bay to play with, who’s published specs. "severly challenge" the laws of physics.

holl_ands, yet again, you’re a treasure trove of good information. Just wish I was smart enough to digest & retain it all. Don’t stop, I’m picking up a lot. Thanks.

To my delight, I had an email from RCA (Audiovox Customer Service) waiting when I booted up this morning. It said:

Dear Pete,
The TVPRAMP1R is spec at: 16dB gain with a 2dB noise figure and 22dB gain with a 3dB noise figure.

Thank you for using Audiovox Electronics

Ed.
Customer Service
"

I wrote back:

Ed,

Thanks for your timely reply.

I live 3.5 miles from a real channel 26 UHF station (294.86 deg. @ -15.6 dBm) and a 99.9 MHz FM station (~294 deg. @ -13.4 dBm) and have to point almost exactly through them (292 deg.) to get the Los Angeles, CA stations 52 miles away (-85.6 to -112.9 dBm). Here is my TV Fool report: http://www.tvfool.com/?option=com_wr...1dda169109ca5c

One amplifier will be used with an Antennas Direct 91XG UHF Yagi antenna & an Antennacraft Y10 7-13 10 element high VHF Yagi. The other will be used with an 8-Bay Bow Tie & a Winegard YA1713 10 element high VHF Yagi. I currently have Antennas Direct 20 dB FM Band filters and Channel Plus NF-471 55 dB channel 26 notch filters available to help protect the amps. from overload.

If available, the amount of onboard FM attenuation and the maximum input signal level(s) before 1 dB gain compression starts would be extremely helpful for me to reengineer my system.

Thanks in advance.

If Ed is able to send any more information I’ll post it.
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Old 2013-07-22, 04:56 PM   #3580
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Quote:
Modern Plastics have built-in electromagnetic shielding as part of the "mix"...no need to use expensive metal anymore.
I've yet to examine a plastic-encased pre-amp with such plastic. If those plastics are in actual usage, it isn't by the manufacturers of any of the amps that I've tested so far. The noise figure data from the plastic-cased amps I've tested make it painfully obvious that the plastic is in no way inhibiting ingress of undesired signals as I get the same results with the covers off as on. For example, I just ran my RCA sample across the 8970A and I'm getting noise figure spikes to 10+ dB in the FM band and spikes in the UHF band to as much as 4 dB on frequencies that our St Louis stations run on. If our office and my desk were in a much stronger location (I cannot pick up local UHF signals reliably at my desk except by "extraordinary" means). There are also spikes that occur in the 4G LTE band, notably between roughly 730 and 750 MHz.

Quote:
DIN 45004B (Unequal THREE Carrier Test in dBuV units with Intermod Products at -60 dB) or DIN 45004K:
Although DIN 45004B was superseded back in the 90's, it does indeed still see current usage in the ROW. Its successor standard, 50083-3/5, is also seen quite frequently in specification sheets from the ROW. As a matter of observation, we recently received some specification sheets for candidate amps from Taiwan that included DIN45004B power level specs.

I had a third RF generator for a week or so last month, so I was able to do some lab work with several amps and was able to do some comparison testing with the two-tone IMD measurements I've been making. I will say the the single 45004B number is extremely easy to comprehend instead of working backwards from an TOI/OIP3 number. However, given the proper conversions, it's not difficult to translate from one to any of the others. For example, the indicated chart on pages 294-295 of the Alcad technical annex referenced shows that DIN45004B - 3 dB = EN 50083-3 (2 IMD3 carriers -60 dB). The EN 50083-3 test shown is easily converted to a Third Order Intercept/OIP3 number with some simple math . Likewise, it is possible to start with an OIP3 value and work it backwards into either of the ROW specs.

For example, assume a device specified at +20 dBm OIP3.
Convert to a 50083-3 (2 carrier) value by subtracting 30 = -10 dBm
Convert to dBuV by adding 108.8 = + 98.8 dBuV
Convert from 50083-3 (2 carrier) to DIN45004B bay adding 3 = 101.8 dBuv (DIN 45004B)

As one standard's number was readily translated into the others, 3-tone testing and 2-tone -60 dBc test results correlated (within the accuracy limits of the HP8569B used for testing).





Pete:

Ordered from Walmart.com back around Christmas.

Ed's figures don't correspond well to the data I've measured summarized as follows (averages):
Low V - 3.9/16 High V - 3.1/16.2 UHF - 2.6/23.7
I'm sure he meant well, but something got lost in a translation somewhere.

The RCA's FM trap is around 30-35 dB at its deepest. I'd have to look closer at the numbers to be more precise.
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Old 2013-07-22, 07:48 PM   #3581
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Default Re: RCA TVPRAMP1R Amplifier

ADTech,

I really appreciate you taking the time to dig this information out. I’ve got to believe what you’re measuring is much more indicative of real world performance.

I want to confirm I understand your reply. I assume that you’re saying in your environment the amp exhibited:
Low VHF - 3.9 dB NF/16 dB gain
High VHF - 3.1 dB NF/16.2 dB gain
UHF - 2.6 dB NF/23.7 dB gain

The RCA's FM trap is around 30-35 dB

Based on other published and measured pre-amp test data (mostly yours) the results are not surprising to me and are pretty close to what I expected. Perhaps Ed’s data sheets reflect cherry picked samples or units evaluated in a screen room or anechoic chamber? Good for amplifier NF -signal reception not so much. I am surprised by the depth of the FM trap.

I’m only interested in high VHF & UHF so 3.1 & 2.6 NF seem to be right in line with other manufactures published specs. for consumer grade pre-amplifiers. Winegard publishes VHF 2.7 dB/UHF 2.7 dB NF for my AP-2870 and PCT publishes 2.7 dB (avg.) 4.0 dB (max) for their MA2-M drop amplifiers that I use (one of which is mounted with an F-71 right to your 91XG!).

When I looked to buy another AP-2870 neither Summit Source nor Solid Signal had them available. It seems everyone is going away from dual-input pre-amps., so I was tickled to find reference to this one in another post.

A lot of the shows my wife & I like are on CBS. We’ve been seeing ads for the last several days that Time Warner is planning on dropping CBS & Showtime. I am trying to reliably get RF channel 43 (LA channel 2.1) which TV Fool lists as 2-Edge @ -22.1 NM &-109.9 dBm.

Your 91XG/MA2-M combination frequently pulls it in with a ~18-19 db SNR but not 100% reliably. Neither my CM-4228 or HDB8X seem to be able to pick it up at all. I even tried swapping the 91XG & CM-4228 mounting positions with the same result. Stacking the 8-Bays improved my SNR by 1.2 – 1.7 dB on most channels but didn’t seem to help channel 43’s SNR.

Ironically, the 91XG rarely gets RF channel 36 NBC (LA channel 4.1) 1-Edge @ -16.8 NM -107.7 dBm but both 8-Bays pull it in like gang busters. This was also the case when I swapped the 91XG/CM-4228 locations. Both TV towers are almost co-located on Mt. Wilson so I’m not sure why they list as 1-Edge & 2-Edge.

Hopefully, Ed will get back to me with some form of overload spec.

Again, thanks for your efforts and the information.
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Old 2013-07-23, 01:12 PM   #3582
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Quote:
Winegard publishes VHF 2.7 dB/UHF 2.7 dB NF for my AP-2870
Probably overly optimistic if they're anything like the 269, 8700 or 8800 amps that I've tested (whose published NF specs were quite were far better than the actual samples tested)

Quote:
PCT publishes 2.7 dB (avg.) 4.0 dB (max) for their MA2-M drop amplifiers
I've tested the 4 and 8 port versions. My numbers are pretty close to those.

Quote:
A lot of the shows my wife & I like are on CBS. We’ve been seeing ads for the last several days that Time Warner is planning on dropping CBS & Showtime.
Carriage disputes are common. They usually get resolved at the last moment and only rarely cause an actual loss of service. In any event, your rates will have to go up next year to cover the increased retrans fees once there is a new agreement.

I'll try to get back to the RCA's test results, but I've got a new official project that just arrived that I'll need to do first.

Cheers!
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Old 2013-07-23, 03:54 PM   #3583
Pete Higgins
 
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Default Re: RCA TVPRAMP1R Amplifier

ADTech & All,

In response to my information request: “If available, the amount of onboard FM attenuation and the maximum input signal level(s) before 1 dB gain compression starts would be extremely helpful for me to reengineer my system.”

I received the following response:

Dear Pete,

I'm sorry, but the product manager and the engineer don't have the information that you are looking for.

Thank you for using Audiovox Electronics.
Ed.
Customer Service


So it doesn’t look like I’ll be able to get any more information on the RCA TVPRAMP1R Pre-Amplifier (from Audiovox). Hopefully, when ADTech completes his new official project he’ll be willing to help us out (and the competition?).
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Old 2013-07-24, 08:24 AM   #3584
balm
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Default Kitztech problems again...

My Kitztech amp beats all other amps hands down, about the only one I havent tried yet is the RC ...

That said, its the 3rd time in 2 years I have to have it repaired ...works intermittently

this amp really isnt robust enough in my layman opinion, and needs ways of improvement in terms of durability
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Old 2013-07-24, 01:19 PM   #3585
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Is it better than the ones out of the UK?
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