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Old 19-Jan-2017, 10:08 AM   #1
johnodon
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Need Help: UHF Signals dropped

Hi all. I am in need of some assistance.

Updated TVfool report: http://www.tvfool.com/?option=com_wr...e6a4280acc5946

I have yet to go up into the attic to refresh my memory but I will try and describe my current setup...

I have two antennas pointing at the same towers in Philly. One is a CS600 for pulling the VHF channels and a DB4E for my UHF needs. These are then combined into a RCATVPRAMP1R . This is run outside, down to the basement, and connected to a distribution amp.

This setup has worked perfectly for about 2 years. I was getting mid 80% on my lo-VHF channels and 95%-100% on most of the Hi-VHF and UHF channels (at least the ones I watch consistently). However, about 6 months ago things started to go wonky. I have comepletely lost the 17s (RC17). I cannot get any UHF channels to get a signal better than 85% (typical is ~65% now) when most used to be ~100%.

Like I said, I haven't gone up in the attic yet but what do you think the cause could be? Introduction of some new interference (maybe a new FM station)? My DB4E fell/moved? The RCATVPRAMP1R is experiencing a failure?

My first plan of attack (other than checking the state of the antennas) will be to disconnect the main lead from the TVPRAMP1Z and attach directly to the DB4 to see what that does for the UHF channels. Any other suggestions?

TIA!

John

Last edited by johnodon; 19-Jan-2017 at 10:16 AM.
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Old 19-Jan-2017, 10:29 AM   #2
johnodon
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One quick note...

The power for the RCATVPRAMP1R is run to the basement so I was able to unplug it easily.

I'm guessing that I never really needed to power it. When unplugged, the Lo-VHF channels signals remained the same and UHF picked up ~15%. Better but still nowhere near my typical 95-100% for UHF and still no channel 17.

John
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Old 19-Jan-2017, 12:04 PM   #3
ADTech
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Disconnecting the power to an amp doesn't remove the amp from the circuit, it turns the amp into a 20-30 dB attenuator.

You'll need to go up in the attic and make the manual changes to the cabling.

What are you using for a distribution amp?
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Last edited by ADTech; 19-Jan-2017 at 12:19 PM.
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Old 19-Jan-2017, 1:52 PM   #4
johnodon
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Thx ADT.

I plan on going up to the attic later today and removing the pre-amp from the path and connecting the main lead directly to the DB4E. I'll report back.

Question: does the fact that I actually gain signal (on UHF) when I take power away from the pre-amp indicate that it is hurting rather than helping when powered (overload)? Or could that be more a side effect of a faulty pre-amp if that turns out to be the case?

Dist. Amp is this: http://www.solidsignal.com/pview.asp?p=pctma28p

On a side note, if I pull power from the dist. amp, I lose signal altogether. I don't know if this by design or if it indicates that the power is really helping that much. Does that amp require power to operate (no passive operation)?

John
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Old 19-Jan-2017, 2:32 PM   #5
ADTech
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Quote:
does the fact that I actually gain signal (on UHF) when I take power away from the pre-amp indicate that it is hurting rather than helping when powered (overload)
That suggests that there is overloading taking place somewhere in the system. Excessive amplification is a common problem brought on by self-diagnosis, generality caused by the "mo' better" idea. If a little bit of amplification is good, then more is better. Doesn't work for medication, either, there are consequences.

One amplifier, if any are indeed needed, is usually sufficient if properly selected. Two are almost always one too many. There are isolated instances where a second amp is needed and are plenty of others where it does not harm or help reception.

TV signal meters that display only a percentage are not measuring power, they are measuring quality. The only important number on this scale is the one at which reception fails. Knowing that number and keeping the signals above it are all that is required, there is no need to chase numbers trying to get to 100%. As long as reception is unimpaired, the number is good enough.

Quote:
if I pull power from the dist. amp, I lose signal altogether.
Now you've added another 30-40 dB of attenuation. As noted previously, removing power from an amp is not a valid test unless you actually need 20-40 dB of attenuation. Note that the 8-port amp is actually a 15-16 dB amp followed internally by an 8-port splitter. That splitter is expected to have 10-11 dB of insertion loss (attenuation) by itself which would be added to the attenuation of the un-powered internal amp.
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Last edited by ADTech; 19-Jan-2017 at 2:35 PM.
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Old 19-Jan-2017, 5:46 PM   #6
johnodon
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And all is right with the world again.

I took the pre-amp out of the path and looky looky...



Thank you ADT for your help.

Last question: I don't think I really have a need for a pre-amp. I only need to combine my CS600 and DB8E. I assume this product will suit my needs: http://www.solidsignal.com/pview.asp?p=ZUVSJ

John
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Old 19-Jan-2017, 6:01 PM   #7
WIRELESS ENGINEER
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too much amplification

Yep, AD is spot on.

This is why I always try and operate without a preamp first.

Low vhf don't need boosted because losses are far less at those frequencies and high vhf will also do very well without boosting.

TV tuners are barely capable of dealing with the massive amount of rf interference sources today as it is.

Adding a preamp or dist ampthats not needed simply desenses or AGC overloads the tuner.

Remove the preamp and run coax from the antennas straight to the distribution amp for starters
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Old 19-Jan-2017, 6:18 PM   #8
johnodon
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Thx WE.

Per my post above, I still need to replace the pre-amp so I can combine the VHF and UHF antennas. Is this the correct product: http://www.solidsignal.com/pview.asp?p=ZUVSJ

John
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Old 19-Jan-2017, 7:56 PM   #9
ADTech
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Quote:
Originally Posted by johnodon View Post
Thx WE.

Per my post above, I still need to replace the pre-amp so I can combine the VHF and UHF antennas. Is this the correct product: http://www.solidsignal.com/pview.asp?p=ZUVSJ

John
That one will work all except for where it says it's discontinued.

We do offer a UHF/VHF combiner, it's on our website under accessories.
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