cannot receive 3 vhf channels with amp.

[bveedub]

I just installed a new winegard 8200u antenna with a signal amplifier that has a 15dB gain. With the amplifier on I get 20 uhf stations, but no vhf stations. When I disconnect the amp I get the 3 vhf stations but no uhf stations. What am I doing wrong?

[ADTech]

What are you using for an amplifier? Some amps are frequency specific, others require that a proper internal configuration be made.

Could you post a TVFool plot for your exact address? See this post for instructions.

What direction is the antenna (narrow end) pointing?

Estimated cable length from the antenna to the TV set (furthest, if more than one). Any splitters? If so, identify them and describe your cabling layout.

[bveedub]

Here is my tvfool plot http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d9e7418d796d270 I have the antenna pointed at 350 degrees. The amplifier I am using is from radio shack, there is no model # . the specifications on the box are: frequency: 54-806MHz FM trap:>20dB@100MHz There are 2 tv's connected, one at 50' the other @100'.

[GroundUrMast]

You have several high power FM stations on the same azimuth.

Try adding an FM trap (http://www.radioshack.com/product/index.jsp?productId=10939219) before the input of the amplifier. I suspect those strong FM signals plus the gain of the HD8200u in the FM range, combine to overload the Radio Shack amplifier causing it to generate interfering distortion products.

One step at a time... We can talk about a different amplifier if the trap doesn't solve the problem.

[bveedub]

I am so sorry.... I forgot to mention there is an fm trap .. 20dB @ 100MHz. sorry I forgot to mention this, there is also a GAIN adjust that I tried at different settings.

[Tower Guy]

With the amplifier on I get 20 uhf stations, but no vhf stations. When I disconnect the amp I get the 3 vhf stations but no uhf stations.

Replace the Radio Shack amplifier with a Winegard AP-4700. It is designed to bypass VHF and amplify UHF.

[GroundUrMast]

Replace the Radio Shack amplifier with a Winegard AP-4700. It is designed to bypass VHF and amplify UHF.

And a NF of less than 3 dB.

I agree.

(If you leave your existing FM trap in the system, it needs to be between the antenna and the amplifier.)

[bveedub]

Thank you, I will buy a winegard ap-4700. You also mentioned a NF of less than 3dB. What is it? Thanks for your help, I will let you know how it turns out. Jeff

[GroundUrMast]

Thank you, I will buy a winegard ap-4700. You also mentioned a NF of less than 3dB. What is it? Thanks for your help, I will let you know how it turns out. Jeff

NF = Noise Figure. It's a measure of the amount of noise the amplifier will add to the signal as it passes through the amplifier. It would be nice if the amplifier did not add any noise which would be expressed as a NF of 0 dB. The reality is that all amplifiers will add some noise. The lower the NF, the better. I would not be at all surprised to find the NF of the Radio Shack amp to be around 6 dB.

Once noise has been mixed with a signal, an amplifier can not remove it.