PR8800 and the CM7775...problems..argh!

[EricfromVA]

installed my PR8800 in my attic and without an amp was able to pick up my local OTA stations from DC with no problem. Signal was above normal but not pegged. I bought the CM7775 amp based on my past experiences.

I hook up the power source (to TV , from Antenna) I then go in the attic and hook up the pre amp and the signal drops. Is there a short on the line? I have reterminated my drops multiple times and even tried a different CM7775 and the same thing happens. What would effect the power going from the source to the preamp? Shielding touching a termination? Interconnects?

I am at a loss. My signal is good without it but I know these amps can get me pegged in the good range.


Any and ALL help would be appreciated.

 

[riggscm]

only thought that comes to mind is the gain on the powered amp. almost sounds like you are accidently overdriving the signal.

make sure you are on minimal gain and increase the gain very slowly.

just a suggestion

 

[ats7627]

Eric,

Is it possible that you have the antenna line running through a splitter somewhere?. If so, most splitters will not pass the DC voltage from your preamp power supply. If there are no splitters in the line and you have access to a Voltmeter, unplug the cable from the preamp and make sure you have 18Volts DC.

 

[EricfromVA]

No but would this make a difference...

I have 2 interconnects. One at my junction box in the basement and one at the wall plate. The line is not split. As a test I am going to run a direct line from the antenna to see if it clears anything up.

Thanks for eveyones ideas.

 

[Kevinw]

I'm with Riggs, How far from the towers are you? Sounds like you are overdriving the signal. If your signal was "above normal" why would you use an amp.?

 

[vsvier]

I agree also, sounds like an overdriven signal. I think a lot of people misunderstand what a pre-amp does. All a pre-amp does, is compensate for loss of signal over the cable run, It does NOT increase the signal gathering capibility of your antennea. For example if you were to hook up a signal meter, or monitor and tuner in your attic as close as possible to the antenea, and adjust the ant. for max signal (lets say you get 80%), and than you were to make all your connections, and than hook up your signal meter, or monitor /tuner in the viewing area, You MAY see a lower signal. this is caused by many things, for example: you can expect a 3 db loss for a solid 100' cable run, an additional 3.5 db loss for each splitter or diplexor in the line, and an additional 1 db loss for couplers. as you can see the numbers COULD add up quickly, or they could be negligable (no splitters, short runs). So, lets assume you have 2 diplexors, and 100' cable for a total of 10 db loss, and your signal in the viewing area is now, lets say 75%, the best you could do would be to place a pre-amp (something around a 10 db gain) in the system to get you back to the 80% you had right at the antennea. By putting in a 23 db gain pre-amp (CM7777), you are now "overdriving " the signal, causing noise, which translates to a signal loss for a digital signal. The increased gain would not get you any higher than the original 80% you had in the attic. The only thing you can do to increase that number is to try a different ant. Bottom line, A Pre-Amp does NOT increase the signal gathering capabilty of your ant.

 

[Carl B]

I agree that the situation sounds like an over-driven signal. Why are you installing a pre-amp when you can already lock all the OTA channels that you want? If you think your signal run from the antenna to your TV is losing too much signal, then simply add a MATV one-to-one amplifier at about 6 to 10 dB. You don't need a high powered pre-amp.

A pre-amp can be used as a low-noise line amplifier where signal loss between the antenna and the TV is very high. However, pre-amps are intended to be used where OTA signals are very weak due to distance, low power, or masking/shielding of signal (e.g., attic installations). In these applications, the pre-amp amplifies the weak received signal to make it useable for your OTA tuner, regardless of whether the downlead to your TV is one foot or 100 feet. A good, low-noise pre-amp like your CM 7775, can make a medium size antenna as effective as a large size antenna w/o a pre-amp. But again, if you lock the signal w/o the pre-amp, you don't need it.