Two amps possible? (1 Viewer)

ralfyguy

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Is it possible To have a pre amp mounted on the mast, fed by a power inserter and then add a UHF/VHF Cable signal amplifier inline towards the STB? Or will this fry something?
 

Jim5506

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The purpose of the pre-amp is to maintain the signal through your distribution system to the STB. Too much amplification is just as bad as none, maybe worse. You can over load the tuner.

Remember you cannot amplify a signal that the antenna doesn't receive. Also, when you amplify the signal you are also amplifying all the static and stray RF the antenna is receiving.

Unless you have a long RG-6 run from antenna to receiver AND need to amplify that signal again to distribute it to multiple TV sets, the second amplifier is probably at best useless and at worse counterproductive.

If you are in a difficult signal area, the best plan of attack is a large antenna mounted as high as feasable.
 

Jim5506

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Pre-amps are usually recommended for cable runs over 100'.

Look at www.antennaweb.org/address.aspx and input your exact home address to see which stations you should expect to receive. Compare that with what you actually get. If you have stations in the purple area a pre-amp is recommended to go with your fringe antenna.

If you have stations with low signal strength (<60) a pre-amp may help. If you have strong stations with signal dropouts, that is caused by multi-path and is more difficult to deal with.
 

ralfyguy

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My stations are 75+ miles away. I got a CM3020 with only the UHF (Front) part mounted on the roof, because all my stations are UHF. I got a radioshack preamp that is supposed to have 30db gain, Don't know the noise values. I wonder if a CM7777 would be better. If I turn down on the radioshack amp, I lose all channels. I have to have it turned to the max.
 

Jim5506

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The CM7777 (UHF/VHF) or the CM7775 (UHF only) are very good amplifiers with low noise figures (2.0dB on CM website).

Radio Shack amplifiers are not known for their low noise performance. They cost less and here you definitely DO get what you pay for.

The CM amps are 26dB on UHF. I would buy the CM amp myself if I needed one.
 

Jim5506

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Are you wishing to amplify OTA signal diplexed into a satellite cable run, or are you talking about amplifying the satellite signal itself?

For the former, if your diplexers pass the amplifier's voltage from the injector you can place an OTA pre-amp at the antenna and it will work. In fact there is a pre-amp that will use the voltage from the satellite receiver so you don't have to have a seperate injector.

As for amplifying the satellite signal, there are special amplifiers to boost satellite signal especially in the case of very long cable runs.
 

bhelms

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Jim5506 said:
Are you wishing to amplify OTA signal diplexed into a satellite cable run, or are you talking about amplifying the satellite signal itself?

For the former, if your diplexers pass the amplifier's voltage from the injector you can place an OTA pre-amp at the antenna and it will work...
jim5506 - I'm really curious about that one! I'm assuming the diplexers are between the LNBs and the receiver or switch in which case they're already passing the power for the LNBs. So how can you also pass the power for the preamp that is likely different? The diplexers won't know the difference.
Jim5506 said:
...In fact there is a pre-amp that will use the voltage from the satellite receiver so you don't have to have a seperate injector...
That option (the preamp uses the same power as the LNBs) is still viable. I think that's the ONLY option in a diplexed system like I described - please correct me if I'm wrong...!
 

Jim5506

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Both the Channel Master 0065DSB and 0265DSB are designed to use the +18VDC output from a satellite receiver to power their amplification. You must ensure that the 100mA current draw does not overload the satellite receiver.

As has been mentioned here and elsewhere, I would not recommend someone using an OTA antenna diplexed with satellite because there are inherent line losses that need to be amplified. Some diplexers pass voltage on only one branch, so you must be sure the one you have passes voltage to both the LNB and the pre-amp.

A solid cable is best, but diplex if you must.
 

dapack5

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Apr 15, 2006
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Jim5506 said:
The CM7777 (UHF/VHF) or the CM7775 (UHF only) are very good amplifiers with low noise figures (2.0dB on CM website).

Radio Shack amplifiers are not known for their low noise performance. They cost less and here you definitely DO get what you pay for.

The CM amps are 26dB on UHF. I would buy the CM amp myself if I needed one.
i have the same radioshack preamp that was stated above. it is radioshck part number 15-2057
the noise rating on these are between 4.0 and 4.5dB.
i am contimplating the purchase of either a CM 7775 / 7777 or a winegard unit.
most people you talk to recommend the CM 7777,but, since i only have 1 vhf station and it's channel 11 and going to be digital channel 9 i think i'm going to opt for the 7775 myself. i'm using roughly a 20 year old winegard yagi type antenna and the rs preamp and i my antenna will pull in channel 6,7,8,10,12,13 and it also triies to pull in 2 from miami,3 from tampa and 4 from miami. funny thing is the tampa stations are being received from the backside of my antenna,not,the front. i am currently pointed in the direction of miami and i'm receiving tampa stations
 

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