James:
I looked at your tvfool report from the other thread:
http://www.tvfool.com/?option=com_wr...60b5a214cc43dd
It looks like there is not much chance of overload, so a preamp would help a lot.
Checking your local FM signals, the strongest is KLYY at -28.9 dBm, so it probably will not cause a problem; see attachment. If it does, then use an FM trap.
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I have a 15' quad 6rg cable running from the antenna 75 ohm down lead to a groundblock splitter. It is a two out splitter at 5 - 1000Mhz. The open side of the splitter is not capped.
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Are you using a 2-way splitter for a groundblock with one port unused? That gives a loss of about 3.5 dB. If you don't need the splitter there, then use a regular groundblock.
If you do need a splitter there, then it must be a powerpassing splitter for the preamp at the antenna.
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I am running a cable that I think is rg11 dual shield because of it's thickness compared to rg6 at approx 50' along underside of metal carport roof and in through a metal sided window to a coupler and then 6' of the rg11 into a splitter for cable/antenna (Mhz unknown.
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Are you using a splitter to combine antenna and cable signals? That's not a good idea; use an A/B switch. The cable company and the FCC would not be happy that your antenna is radiating cable signals.
RG11 does have less loss than RG6, so it helps with long coax runs. With a preamp, it's overkill.
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Guidelines say that the TV has AGC and that makes me wonder if it won't negate the boost signal enough to overcome the weakness.
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The AGC adjusts the gain of the tuner for the channel selected. The AGC is your friend because it adjusts the tuner gain to compensate for changes in signal strength.
With very weak signals, the AGC doesn't compensate because the tuner is being run at max gain. That is why you see intermittent pixelation and picture freeze when you are at the "digital cliff." See attachment #2 for my noise margin diagram, as defined by Andy Lee. Andy has an interesting post with two diagrams of signal reception and his explanation of Noise Margin:
http://www.avsforum.com/t/841787/tv-...#post_15700679 #397
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Also when I have an excellent signal will the boost be a risk to my TV electronics?
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No; even if overload happens, it shouldn't damage your preamp or tuner with OTA signals.
There are three types of preamp overload, in order of increasing signal strength:
1. The strong signals cause enough IM distortion to interfere with the reception of weak desired signals. This is the point that holl_ands uses in his
preamp charts to obtain max SFDR (Spurious Free Dynamic Range). No damage will happen.
2. The strong signals cause overload to the preamp or tuner that makes it impossible to receive any signals. No damage will happen.
3. The signals are so strong that the input transistor is toast. You are not likely to encounter OTA signals that strong.
I used to favor the CM7777 preamp until they changed the design. They should have called it 7777A after making such a drastic design change to keep it from being confused with the original. At this time there is not enough feedback to know how it compares with the original.
I haven't tried the AD CPA19, but a lot of people like it.