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What type/brand of amplifier are you using? I have found that some of the noisier high gain amplifiers actually do more harm than good (to a digital signal). Have you tried removing the amp? Also, if your amp has an FM trap, is it on or off?
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!!!!!!OUCH!!!!!!
You shouldn't be needing any amplifier in Manassas except for maybe channel 50 or 22. Channel 30, broadcasting from just south of Manassas is most certainly overloading your amplifier. A good rooftop antenna with a low gain pre-amp (12 db), or a quality distribution amp should provide excellent reception for you. Channel 7 & 9 have always had a very robust, easy to recieve signal in Manassas.
Thanks everyone for suggestions (my first post on page 357,
http://www.avsforum.com/avs-vb/showt...8#post17220828). Here is a bit more about my setup in Manassas: some kind of rooftop antenna is in the attic - don't know brand and don't know whether it is VHF/UHF or just UHF. Then RadioShack amplifier (I think it is 36 db, but maybe 24) and then 2 2-way splitters. My first digital to analog tuner is after the first splitter relatively close to amplifier. My HDTV sits after both splitters and relatively long cable run. Like I said, before the DTV switch I had a bit noisy, but watchable analog channels and after buying HDTV very watchable same digital channels.
Among analog VHF WUSA (9) was the best and 7 WJLA was close second. 5 was worse and ch. 4 was difficult to watch. So I deduct that my antenna has VHF capability.
Ch 14, 20, 26 were very good. When putting amplifier and orienting antenna I've spent quite a time to figure the best reception and amplifier is on max gain, reducing the gain slightly degraded weak channels. Before putting in amplifier I've tried just antenna - almost everything was very weak and noisy.
So, after the switch, 7 and 9 disappeared, being the most strong analog channles. Heck, I even found official very detailed map, which shows that in my location there should be no change whatsoever in reception after the switch. The only reason I could think of is that with the switch power of the transmitters was reduced thinking that digital signal is more protected against noise.
After increasing power on 7 I see 40% of strength on my digital to analog tuner and almost no dropouts. Whereas 9 shows also 40%, but then dropouts are frequent and during them slider jumps between 0 and 20%. I tried to experiment by Steve's suggestion with FM trap on amp. It has 2 positions "in" and "Off" and always been in "in" position. When I switch to "off" channel 7 goes from 40% to 0% right away.
All other channels are at 100% except a couple very close at 90-95%.
HDTV at the end of the line shows ch.7 at 20% and after long stable reception 10 - 120 minutes bad dropouts suddenly appear for 1 - 30 minutes. I considered that something interferes with a signal - my first thought was - refrigerator. But after observing for several days - I cannot pinpoint the problem in the house, maybe something outside. Air conditioning is completely off these days.
So if anything - I consider putting addtional 10 db amplifier for the HDTV line only, providing that increase in power on 7 is permanent.