RCA TVPRAMP1R Preamp: A Technical Review - Page 5 - AVS Forum | Home Theater Discussions And Reviews
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post #121 of 146 Old 10-30-2018, 10:56 PM
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Quote:
Originally Posted by rabbit73 View Post
Thank you for the current measurement. It's much lower than mine.

I measured my RCA TVPRAMP1R Preamp again. I got different readings than when it as new, and used two meters as a double check. I don't trust it now.
oh that's strange i guess there must be something wrong with most of the power supplys that they shipped with the amplifiers

does your amp seem to be working though?



RCA did email me back and the guy asked for my address & said he will see if there is anything he can do for me but he said he can't make any promises
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post #122 of 146 Old 11-02-2018, 03:52 PM
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TWO Defective RCA TVPRAMP1 Preamps

Quote:
Originally Posted by jmm83 View Post
oh that's strange i guess there must be something wrong with most of the power supplys that they shipped with the amplifiers

does your amp seem to be working though?
Ah, no.

My first RCA TVPRAMP1Z preamp had these measurements:
Voltage out of power inserter without preamp: 19.5 VDC
Voltage with preamp connected: 9.5 VDC
Load current: 70 mADC
Gain 23 db

I thought it was strange that the voltage out with no load was so high because the power inserter contains a voltage regulator, but it worked.




Recent measurements of first TVPRAMP1Z:
No load voltage: 13.5 VDC
Voltage under load: 7.37 VDC
Load current: 18 mADC
Gain: 0 dB; Uh-Oh! Then, when I checked again, there is gain. Intermittent from a cold solder joint?

Second (new) TVPRAMP1E measurements (note the "E" instead of "Z" or "R" at the end of the model number, supposedly for a change in packaging. You see a simulated American flag with only 5 stars and IN THE USA on the box and think that it is Made in America. If you look again, you see Designed and Engineered IN THE USA on the front panel and MADE IN CHINA on the end panel.):
No load voltage: 9.11 VDC
Voltage to preamp under load: 9.11 VDC
Load current: 75 mADC

well, that looked good so far, but
Gain: 5 dB; not so good

I thought there was something wrong with my signal level meter, so I substituted a CM7777HD at low gain:
Gain: 17 dB; right where it should be.

My meter is OK, the RCA preamp isn't OK.

Nice box. Too bad the quality control for the preamp isn't up to the same standard.
The seals on both boxes were intact when received, indicating they were new, not returns

I can not recommend the RCA TVPRAMP1 preamp.
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Last edited by rabbit73; 11-03-2018 at 04:10 PM.
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post #123 of 146 Old 11-08-2018, 12:41 AM
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Oh that's not Good

I'll let you know what mine is when i get it
what kind signal level meter do you use? and how do you hook it to the booster?
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post #124 of 146 Old 11-08-2018, 07:13 PM
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Originally Posted by jmm83 View Post
Oh that's not Good

I'll let you know what mine is when i get it
what kind signal level meter do you use? and how do you hook it to the booster?
I use a Sadelco 719E and a Sadelco DisplayMax 800. The 719E is designed for measuring analog TV signals, but can be used for measuring digital TV signals with a correction factor, and the 800 is designed for measuring analog and digital TV signals.



I pick a fairly strong stable LOS signal and measure it without the preamp:

Antenna > coax > F-81 adapter > short coax > signal level meter

I then substitute the preamp for the F-81:

Antenna > coax > preamp > short coax > power inserter > short coax > signal level meter

The difference between the two meter readings is the preamp gain.

OTA signals constantly vary in strength, so I have to do it a few times to get consistent readings.

As a test, I used a Channel Master 7777HD preamp at the low gain setting of 17 dB. It's a nice amp for indoor tests, but I don't like the housing design for outdoor use. The connectors need to be on the bottom of an enclosure for weather protection, and a mast clamp would have been better than plastic zip ties.



Channel 31

719E without preamp: -5 dBmV
719E with preamp: +11.5 dBmV
Difference: 16.5 dB

800 without preamp: -3.5 dBmV
800 with preamp: +13.3 dBmV
Difference: 16.8 dB

Used Sadelco meters can be found on eBay. The last 719E I found (used for above test) was in good condition and cost $75 including shipping. I don't bid any more than I am willing to lose if returns aren't allowed.

For a more accurate measurement of preamp gain, I use the video carrier from an analog modulator as a signal source for a stable signal.

Blonder Tongue HAVM Modulator with fixed attenuator on output set for analog channel 32:

Modulator without preamp: 9.9 dBmV
Modulator and preamp: 26.9 dBmV
Difference: 17 dB

It is possible to measure preamp gain without a signal level meter. The technique uses the dropout point of a TV tuner, which is about -84 dBm. All you need is a variable attenuator and a few inexpensive fixed attenuators. Calaveras has described a similar technique that uses the dropout point to determine SNR; see this post by him:
https://www.avsforum.com/forum/25-hd...l#post24727115
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post #125 of 146 Old 11-09-2018, 09:17 AM
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Measuring Preamp Gain Without a Signal Level Meter Using Tuner Dropout



The gain of a preamp can be measured without a signal level meter if a few precautions are observed.
The preamp must be close to the tuner. If it is up near the antenna, you will be able to measure a difference between with and without, but it probably will not be the preamp gain.

As above, use a fairly strong stable LOS signal. Weak 2Edge signals will give misleading results. The tuner noise figure can be ignored because it will be the same for both measurements. The preamp noise figure can be ignored because it is well below the test signal, and it will be attenuated when the signal is attenuated.

Antenna > coax > F-81 > short coax > variable attenuator > short coax > tuner

Channel 31

Attenuation required for dropout without preamp: 28 dB
consisting of 20 dB fixed plus 2-1/8 counter clockwise turns of ATT-1 attenuator (8 dB)

This also means that if the signal is 28 dB above dropout, its strength at the tuner input before attenuation is
-84 dBm + 28 dB = -56 dBm



Antenna > coax > preamp > short coax > power inserter > short coax > variable attenuator > short coax > tuner

Attenuation required for dropout with preamp: 45 dB
consisting of 40 dB (two 20s) fixed plus 1-1/2 counter clockwise turns of ATT-1 attenuator (5 dB)

Preamp gain = 45 - 28 = 17 dB

The CM 7777HD preamp that I used has the preamp and power inserter combined when fed power into the DC connector on the preamp housing. I like the CM 7777HD for use as an instrumentation amp, but I don't like the housing for outdoor use. The connectors need to be on the bottom of an enclosure for weather protection.

Although it wasn't necessary for the test, I split the signal after the power inserter to feed a signal level meter and the tuner to see the dropout point:

-18.1 dBmV - 17 dB meter amp - 49 dB convert = -84.1 dBm

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post #126 of 146 Old 11-10-2018, 02:17 PM
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I'm Getting 9.04 With no Load and 8.98 With a Load on it & 62.8 MA

It Did not seem to make any difference in reception or in signal strength
I Guess Most of these amps Must have a problem with them

i will be sending it back
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post #127 of 146 Old 11-10-2018, 03:48 PM
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Thank you for the report.

Quote:
Originally Posted by jmm83 View Post
I'm Getting 9.04 With no Load and 8.98 With a Load on it & 62.8 MA
That seems within normal limits.
Quote:
It Did not seem to make any difference in reception
Once the signal is strong enough for good reception, you probably will not notice any difference in reception with an even stronger signal.
Quote:
or in signal strength
That would require an accurate measurement.
Quote:
I Guess Most of these amps Must have a problem with them

i will be sending it back
I understand your feeling. Some users like their RCA preamp, but I certainly don't have confidence in the RCA TVPRAMP1 now.

If you can not measure it, you can not improve it.
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post #128 of 146 Old 03-18-2019, 03:50 PM
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Bandpass for RCA preamp way above UHF frequencies?

Does anyone know if the RCA preamp will pass any frequencies well above the normal UHF channel range? Specifically, 1090 MHz? Totally unrelated to HDTV I have an indoor 1090 MHz antenna for receiving aircraft navigation messages (ADS-B), and it would be great if I could piggyback that antenna onto my existing outdoor TV antenna stack and pass it on through the existing wiring.

Yes, I could just give it a try and find out, but I am being a bit lazy before I climb on the roof and start connecting cable etc.
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post #129 of 146 Old 03-18-2019, 06:03 PM
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I doubt there's any kind of cutoff filter in the RCA preamp. More likely it's just a gradual roll-off as you go to higher frequencies. Since 1090 MHz isn't that much higher than the old channel 83 (890 MHz), it probably passes at least some signal through at that frequency. Whether it'd be enough for your purposes, though, is hard to say.
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post #130 of 146 Old 03-18-2019, 08:40 PM
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Quote:
Originally Posted by tustinfarm View Post
I have an indoor 1090 MHz antenna for receiving aircraft navigation messages (ADS-B), and it would be great if I could piggyback that antenna onto my existing outdoor TV antenna stack and pass it on through the existing wiring.
How are you going to combine it with your TV antenna stack? Will the 1090 MHz antenna still be inside, or will you move it outside?

If you can not measure it, you can not improve it.
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post #131 of 146 Old 03-19-2019, 05:34 AM
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How are you going to combine it with your TV antenna stack? Will the 1090 MHz antenna still be inside, or will you move it outside?
I am moving the 1090 MHz antenna outdoors to literally be on top of my antenna stack mast. For the aircraft signals at that frequency even just going from indoors to outdoors at ground level makes a significant difference. The antenna is vertically polarized (1/4 wave, 69 mm) so I believe it could be combined with the UHF TV antenna (91XG) signals without causing too much "mayhem", using a simple 2-way splitter in reverse...and I believe my UHF signals can tolerate the splitter losses. I was hoping that the preamp could provide some gain in order to overcome the cable losses, given that it's about a 75 foot total run of RG-6, and also the greater losses at higher frequencies like 1090 MHz. If the preamp just passes 1090 MHz with unity gain then I may as well just T it in after the preamp, and take my chances on how strong the incoming 1090 MHz signals are.

All that said, this query is more of an academic "what if" exercise, until I get enough ambition to do the actual rooftop work. Heck, I just remembered I have a spare RCA preamp laying around somewhere that I use to do a quick indoor test to see whether it can even pass/amplify 1090 MHz.
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post #132 of 146 Old 03-19-2019, 07:10 AM
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The RCA is rumoured to be very similar to the old Channel Master 7777 (the one with two inputs). I use a 7777 to amplify 1090 MHz very effectively (from a coaxial colinear antenna at 35' agl, with 100' run of RG6).

Sent from my LG-H812 using Tapatalk
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post #133 of 146 Old 03-19-2019, 11:47 AM - Thread Starter
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Quote:
Originally Posted by tustinfarm View Post
Does anyone know if the RCA preamp will pass any frequencies well above the normal UHF channel range? Specifically, 1090 MHz? Totally unrelated to HDTV I have an indoor 1090 MHz antenna for receiving aircraft navigation messages (ADS-B), and it would be great if I could piggyback that antenna onto my existing outdoor TV antenna stack and pass it on through the existing wiring.

Here you are, gain measured on my RCA preamp from 700-1200MHz.
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post #134 of 146 Old 03-19-2019, 02:32 PM
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Originally Posted by Calaveras View Post
Here you are, gain measured on my RCA preamp from 700-1200MHz.
That is excellent news - and the gain at 1090 MHz should be more than enough to compensate for the line loss at that frequency. Armed with that knowledge I will happily climb up to the outdoor antenna stack and T the new antenna in.
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post #135 of 146 Old 03-19-2019, 02:41 PM
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Originally Posted by DXer01 View Post
The RCA is rumoured to be very similar to the old Channel Master 7777 (the one with two inputs). I use a 7777 to amplify 1090 MHz very effectively (from a coaxial colinear antenna at 35' agl, with 100' run of RG6).

Sent from my LG-H812 using Tapatalk
Thanks for the information, I can't wait to get my homemade antenna mounted outside (1/4 wave "Coketenna" made from an aluminum soft drink can). It'll be about 35' AGL, and I am close enough to Atlanta to catch quite a few planes on their initial approach/departure routes.

That inexpensive RCA preamp has been a real winner for my weak HDTV signals, and finding out that it can go up to 1090 MHz makes it even more so!
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post #136 of 146 Old 03-27-2019, 03:54 PM
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Originally Posted by Calaveras View Post
Here you are, gain measured on my RCA preamp from 700-1200MHz.
I can (happily) confirm that the RCA preamp performs like a champ with my homemade 1090 MHz "coketenna" for aircraft signals. Testing it indoors at the moment, and it has provided a significant boost to the quantity and quality of the aircraft signals I am receiving with a cheap RTL-SDR dongle.

Of course, this topic is not exactly relevant for an HDTV forum, but anyone "geeky" enough to be reading a thread about a specific TV signal preamp model is also likely to have other radio signal awareness/interests .
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post #137 of 146 Old 05-04-2019, 08:15 AM
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Originally Posted by rabbit73 View Post
How are you going to combine it with your TV antenna stack? Will the 1090 MHz antenna still be inside, or will you move it outside?
Summarizing what I have found so far, the RCA preamp works like a champ for amplifying the 1090 MHz aircraft signals of interest, and will be absolutely essential to getting enough signal power through the coax, given the higher RG-6 losses at that frequency.

Now going to tackle combining this with my TV antenna stack, and I have come up with a couple of options. Currently, I have separate hi-VHF and UHF antennas feeding the RCA preamp. My options are:
1) Use a splitter device to combine the UHF/1090 Mhz antenna feeds into the preamp. Disadvantages for this would be the 3.5 dB signal loss for each antenna, and also the possible creation of interference patterns from the weak UHF signals coming in from the 1090 MHz antenna. Rather than a simple splitter, another option would be a satellite/TV diplexer, which is made for combining a 950-2300 MHz satellite downconverter feed with TV signals...so 1090 MHz would fit nicely into the "satellite" port. The claimed losses are about 1.5 dB for this option and it should reduce the interference possibility for UHF TV signals.
2) Perhaps an even better option would be to use the satellite diplexer after the RCA preamp to feed in the 1090 MHz signals.....AND....since the diplexer satellite port has "power pass" ...a second RCA preamp could be powered for the 1090 MHz antenna. However....now the question becomes whether the AC adapter has enough capacity to power TWO of the RCA preamps, through 50 feet of RG-6.

Curious to know whether anyone has attempted this scenario....powering two preamps from one coax line feed. The RCA adapter says 12V and "80 mA" is the capacity...which I recollect is about what ONE preamp consumes. So I might need to upgrade to a higher current 12V adapter. But even if the adapter has enough current capacity, what about the 2X additional voltage drop across the 50 ft. coax run? I guess a simple DC resistance measurement would give me an idea of what the voltage drop would be...E = IR !
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post #138 of 146 Old 05-04-2019, 07:59 PM
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A satellite diplexer sounds perfect for your project. But off-hand, I can't see much advantage in using two preamps vs. one. You would get the signals amplified before the 1.5dB diplexer loss, but your signals would have to be pretty close to the cliff for that to matter. If that's the case, you probably should also consider a different preamp with a lower noise figure.
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post #139 of 146 Old 05-05-2019, 05:12 AM
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Originally Posted by JHBrandt View Post
A satellite diplexer sounds perfect for your project. But off-hand, I can't see much advantage in using two preamps vs. one. You would get the signals amplified before the 1.5dB diplexer loss, but your signals would have to be pretty close to the cliff for that to matter. If that's the case, you probably should also consider a different preamp with a lower noise figure.
I think you're right, it now occurs to me that the diplexer is really the key to combining the 1090 MHz and UHF antennas, before a single preamp, with no significant advantage other than the 1.5 dB loss before the preamp. No compelling case for having two preamps, and the power feed complication that it leads to.
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post #140 of 146 Old 11-24-2019, 08:56 AM
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bumping this thread

So today at my local Menards I see they had them on sale but its a new version.....and newer isnt better

It has only one input now...no more separate VHF/UHF options (All the ones I saw previously had 2 inputs so maybe it was old stock??)

I still have the old one which works great

Last edited by unclehonkey; 11-24-2019 at 09:01 AM.
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post #141 of 146 Old 11-24-2019, 09:51 AM
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Originally Posted by unclehonkey View Post
So today at my local Menards I see they had them on sale but its a new version.....and newer isnt better

It has only one input now...no more separate VHF/UHF options (All the ones I saw previously had 2 inputs so maybe it was old stock??)
Thanks for letting us know about the new model. I see it on the Parts Express website:
https://www.parts-express.com/rca-tv...ennas--210-350



So now we will have to ask the same question we have to ask with the CM7777: which model is it; does it have one antenna input or two antenna inputs? If you have separate UHF and VHF antennas, you have to use a UVSJ, but they are getting harder to find. Antennas Direct and Radio Shack still sell them.

If you must have a preamp with two inputs, Channel Master has the CM-7778HD Amplify+, but it is considerably more expensive than the RCA.
Quote:
I still have the old one which works great
You had better luck than I did. I bought two new RCA preamps in sealed boxes; they both failed.
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post #142 of 146 Old 11-24-2019, 01:19 PM
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Quote:
Originally Posted by rabbit73 View Post
Thanks for letting us know about the new model. I see it on the Parts Express website:
https://www.parts-express.com/rca-tv...ennas--210-350
glad I could help. I noticed the manual is still the old version

Quote:
So now we will have to ask the same question we have to ask with the CM7777: which model is it; does it have one antenna input or two antenna inputs? If you have separate UHF and VHF antennas, you have to use a UVSJ, but they are getting harder to find. Antennas Direct and Radio Shack still sell them.
Newark still sells a combiner although it has a 1.5dB loss
(for some reason the link takes you to the main page...newark.com and search part number 33-2230)

edit:Ebay has one from Ness Electonics which is based here in MN
https://www.ebay.com/itm/Weatherproo...s/172251624438

Quote:
You had better luck than I did. I bought two new RCA preamps in sealed boxes; they both failed.
weird. I have used mine at 3 locations now and its worked fine for over 4 years..even has survived the Minnesota winters

Although I might try the new one and just see how it compares. Only issue is at my location I only get VHF (KEYC 12 CBS/FOX and the soon to arrive KMNF-CD 7 which is testing and will be NBC & CW). The Godahl/St James translator farm is too far away (and I have some obstructions in the way...mainly the apartment complex)

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post #143 of 146 Old 11-25-2019, 09:46 AM
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Originally Posted by rabbit73 View Post
Thanks for letting us know about the new model. I see it on the Parts Express website:
https://www.parts-express.com/rca-tv...ennas--210-350



So now we will have to ask the same question we have to ask with the CM7777: which model is it; does it have one antenna input or two antenna inputs? If you have separate UHF and VHF antennas, you have to use a UVSJ, but they are getting harder to find. Antennas Direct and Radio Shack still sell them.

If you must have a preamp with two inputs, Channel Master has the CM-7778HD Amplify+, but it is considerably more expensive than the RCA.
You had better luck than I did. I bought two new RCA preamps in sealed boxes; they both failed.
Amazon has the RCA TVPRAMP1Z - but only ten units left.

https://www.amazon.com/dp/B003P92D9Y...2_01_t_img_lh#
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post #144 of 146 Old 11-25-2019, 01:11 PM
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Originally Posted by rabbit73 View Post
Thanks for letting us know about the new model. I see it on the Parts Express website:
https://www.parts-express.com/rca-tv...ennas--210-350
---
You can see old reviews on that page. Parts Express just reuses their internal part numbers for a totally different product. Buyer beware when shopping online.
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post #145 of 146 Old 11-26-2019, 02:17 AM
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Disappointing if RCA has discontinued the dual input version. Served a purpose for separate UHF and VHF antennas. But at least Channel Master restored a dual input version, although much more expensive.
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post #146 of 146 Old Yesterday, 02:14 PM
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Quote:
Originally Posted by rabbit73 View Post
Thanks for letting us know about the new model. I see it on the Parts Express website:
https://www.parts-express.com/rca-tv...ennas--210-350



So now we will have to ask the same question we have to ask with the CM7777: which model is it; does it have one antenna input or two antenna inputs? If you have separate UHF and VHF antennas, you have to use a UVSJ, but they are getting harder to find. Antennas Direct and Radio Shack still sell them.

If you must have a preamp with two inputs, Channel Master has the CM-7778HD Amplify+, but it is considerably more expensive than the RCA.
You had better luck than I did. I bought two new RCA preamps in sealed boxes; they both failed.
One thing to keep in mind is the more recent two input unit used the model number TVPRAMP1E so it looks almost like the new model which has a 2 after the one. I purchased one at Menard's about four months ago. The barcode is 044476071669. Pics are shown for identification:
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