Will Dist. amp also send power to preamp? Recommendation on amp?

[twaw]

I have a Winegard 7084 antenna with a channelmaster 7777 (30db) preamp. To fix an issue with one channel I installed a 15 year-old Archer UHF/VHF/FM variable gain amp I had lying around (15db-25db, 1 in 1 out), which fixed the issue. I currently have it set to around 20db of gain, which seems to be the best.

My question is, should I install that amp BEFORE the power inserter for the Channelmaster 7777 preamp?

Also, the unit's noise floor is 6db, which is decent and seems to be about what current models are... but is there a cleaner unit with around 3db NF that will send power to the 7777 AND give me about 15-25db of variable gain, with just one output? I've looked a bit and can't seem to find one.



More info: Currently I have it after the power inserter, between the inserter and the Tablo unit, so at least it's before Tablo's internal splitter. I did it that way because I was concerned that it's old and may not have proper return path to power the 7777 correctly, and I'm not sure if doing so would hurt the 7777...?

I have about 55' of coax from antenna to the TV/Tablo. I've been having issues with one channel (Real 26, and I'm on the fringe). It was odd because the TV would receive it fine (I had a splitter going to TV and to Tablo at that point) but the Tablo was getting a lot of pixellation and dropout. Eliminating the extra splitter made no change. But then I realized the Tablo has 4 tuners so it also has a 4 way splitter. I know it also has some kind of internal amp too...so it should have been fine, but of course it wasn't. So I tried this amp after trying everything else...given the 7777 preamp and Tablo's internal amp, adding yet another amp to my relatively short cable run should have just added more noise, I think. So I was kind of surprised it worked.

[ADTech]

My question is, should I install that amp BEFORE the power inserter for the Channelmaster 7777 preamp?

Probably not.

Also, the unit's noise floor is 6db, which is decent and seems to be about what current models are...

6 dB NF is actually pretty pathetic. A decent amp is under 3 dB, a very quiet amp is under 2 dB. FWIW, I had a collection of amps from Radio Shack that I'd accumulated over the 15-20 years before I came to work here. Once we acquired test gear to measure amps, all of them ended up in the trash.

but is there a cleaner unit with around 3db NF that will send power to the 7777 AND give me about 15-25db of variable gain, with just one output? I've looked a bit and can't seem to find one.

No. There are no TV pre-amps in the consumer arena, except for some satellite line amps which may or may not cover the OTA frequencies, that will pass power further upstream to additional amps.

So I was kind of surprised it worked.

Me too. With a 30 dB amp on the front end, you have enough gain for an 8 way splitter and 250' of RG6 coax. If you have to add additional amplification, something isn't right. Perhaps the Tablo's tuner is somewhat deaf.

There are ways to provide power to an upstream pre-amp around a distribution amp, it does take a bit of finagling to pull it off and it's not without its potentially negative consequences.

[rabbit73]

ADTech beat me, but I'll give you my two cents anyway.

My question is, should I install that amp BEFORE the power inserter for the Channelmaster 7777 preamp?

No, it will keep the 7777 from getting its DC power from the inserter.

Also, the unit's noise floor is 6db, which is decent and seems to be about what current models are... but is there a cleaner unit with around 3db NF

A Noise Figure of 6 dB for a distribution amp is not decent. A Channel Master 3410 has a gain of 15 dB and a NF of half the Archer, IF you really need two amps in series. There is such a thing as too much amplification. If you add enough gain for your weakest signal, your strongest signals might cause overload of the tuners.

Is this still your tvfool report?
http://www.tvfool.com/?option=com_wr...8e039f0febf911

It was odd because the TV would receive it fine (I had a splitter going to TV and to Tablo at that point) but the Tablo was getting a lot of pixellation and dropout.

Your TV tuner is probably better than the Tablo.

I've been having issues with one channel (Real 26, and I'm on the fringe).

No surprise there, you are behind a hill:
http://www.tvfool.com/?option=com_wr...ALLTV%26n%3d12

[rabbit73]

7084 > 7777 > coax > grounding block > power inserter > 2nd amp IF needed > splitter >

So I tried this amp after trying everything else...given the 7777 preamp and Tablo's internal amp, adding yet another amp to my relatively short cable run should have just added more noise, I think. So I was kind of surprised it worked.

The noise figure of the 7777 primarily determines the System Noise Figure, so the Archer noise was well below the noise floor that was raised by the 7777 amplification.

[twaw]

Thanks for the help! That all makes sense. And yeah, that's my tvfool report, and yeah I'm behind a ridge, so that one channel is especially tough. And yes, keeping the archer after the power inserter also makes sense.

That's a good point on the noise floor being below the 7777 NF, I hadn't thought of it that way before.

So now, arrmed with all of your info, I think i'll just leave it the way it is for now. I guess this is a case of "if it ain't broke don't fix it". This little archer amp seems to have fixed the issue, all channels working well, no overmodulation of signal on the stronger channels.

I do plan to move the antenna to a better location once the ground thaws, so maybe when I do that I won't need the Archer.

Again, many thanks for the advice and your expertise!