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Discussion Starter #1
I have a Winegard HD7080P antenna and AP8700 pre-amp mounted in my attic.


I just got the pre-amp and notice that for some channels the signal strength is less when using the pre-amp. Even if I leave the pre-amp inline and remove the power injector some signals are stronger.


I'm running with the FM trap fixed.


On a ten bar graph for signal strength this is the net gain of the pre-amp


Channel

2 no change

4 no change

7 -1/2

20 no change

50 -1

56 no change

62 -1/2


Whats up? The pre-amp is a modest 17-19db gain so I was expecting a slight boast at least. Is this thing even working?
 

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Go to www.tvfool.com , enter your address or coordinates to get a list of the stations in your area which includes signal strength information, and post the resulting file here.


Decreased signal quality with a pre-amp usually means an incoming signal is overloading the pre-amp, or the amplified signal is overloading your receiver.


An ATSC receiver's "signal strength" display doesn't really display signal strength, but rather a measure of the overall quality of the signal, which can be messed up by over-amplification or distortion.
 

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A preamp can make things worse not better if the preamp is over-driven. The preamp is amplifying everything coming in from your antenna all at once. If the total level of all signals combined is more than it can handle you can get what is called intermodulation which means that the signals are mixing with each other to produce signals at the sum and difference frequencies. If there are a number of signals present the result is the production of many signals that were not present at the preamp input that can cause interference with the signals that you want.


It is also possible for the preamp to produce signal levels at your sets input that are too strong for it to handle. 17 to 19 dB increase in signal level is far from modest. That is an increase in signal power of about 64 times.
 

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Discussion Starter #4
Other than a signal strength meter is there another way to check the line and see if the signal is over amplified?
 

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Discussion Starter #5

Quote:
Originally Posted by Rick0725 /forum/post/12912406


-antenna model

Winegard HD7080
Quote:
Originally Posted by Rick0725 /forum/post/12912406


-distance from towers (follow jtbell's instructions)

10-15 Mi.

Quote:
Originally Posted by Rick0725 /forum/post/12912406


-description of surroundings ...trees hills whatever

two story Homes, no trees flat terran
Quote:
Originally Posted by Rick0725 /forum/post/12912406


-where installed roof , attic

In attic
Quote:
Originally Posted by Rick0725 /forum/post/12912406


-length of runs

~150 ft. RG6 quad antenna to power inserter 20-40 ft. to the tuner/TV
Quote:
Originally Posted by Rick0725 /forum/post/12912406


-how split with complete description of your setup with all the pieces

out of the power inserter to a 5-1Ghz 3db splitter, one lead to a OTA tuner, the other to a Plazma TV.
Quote:
Originally Posted by Rick0725 /forum/post/12912406


all setups and circumstances are different and not cut and dry...if you want to install the proper device without risk, provide more detailed info. then you might get a more suggestions.
 

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Quote:
Originally Posted by AFryia /forum/post/12889535


Channel

2 no change

4 no change

7 -1/2

20 no change

50 -1

56 no change

62 -1/2

Which channels do you want to receive that you aren't receiving currently? As Rick notes, most pre-amps are likely to overload at your distance to the towers.


The HDP269 might get it done, but we need to know what problems you are having first. Are some of the channels dropping out now? If some target stations are off the main line, do you have a rotor?
 

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Discussion Starter #7
I receive all the channels I listed. Occasionally 2,4, 56 drop out.


I have a rotor but I don't use it, I don't have the attic space. So I just aimed the antenna at 224 deg. mag. average between the stations I want.


Rick, I'll try moving the pre-amp to the distribution panel and see what happens. Is there a simple way to attenuate the signal to see if it is an overload situation?
 

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I wanted to buy the Winegard 28dB preamp but had to get the 19dB because the local broadcaster, which is 23.3 miles away (and slightly off-axis), would've overloaded the preampllifier. With the 19dB installed, the strong local one is one notch down from full-strength on the set so I made the right choice. If nothing else, this backs up what the others are telling you.
 

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Discussion Starter #9

Quote:
Originally Posted by Rick0725 /forum/post/0


-Disconnect the preamp and power supply


-install a barrel connecter to connect the 2 coax pieces at the antenna.


-get a baseline signal reading at the tuner without amplification


-connect the preamp at the distribution point and see if any channels go down in signal strength...this will be the overload indicator.

All signals stayed the same. I even tried with the pre-amp powered and un-powered and there was still no change.

Quote:
Originally Posted by Rick0725 /forum/post/0


-then try passing vhf with 2 cm0549 or uvsj vhf/uhf combiners and just amplify uhf and see if that helps.

http://www.solidsignal.com/prod_display.asp?PROD=UVSJ


the hookup would be.

-coax off hd7080p to common port of combiner

-loop thru from vhf port to vhf port

-install preamp between uhf ports

-common port of 2nd combiner to splitter to tv's

Again no change on any channel.

Quote:
Originally Posted by Rick0725 /forum/post/0


Then try attenuators... but try above first. Attenuators are a band aid compromise. would prefer to see you use the appropriate amp and get your setup in shape first.


-you are compromising your aim with the antenna in the cramped attic...that does not help the situation either.

Is this the next step? Do I have an overload condition?


The one odd thing I did measure was the DC power supply for the pre-amp. It is rated at 18VDC and only puts out 15.12 VDC unloaded. How much tolerance does the circuitry of the preamp have for an under-voltage condition?
 
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