OK I promised that I'd reply back if I tried removal of the preamplifier. Well, I did and it resulted in degraded reception.
Before removing the pre-amp, I could receive DTV channels 5 (with artifacts), 7, 9, 11, 32, 35, 38, 44, and 50. After removal, I received only 9, 32, and 50. So I guess the pre-amp is not introducing any noise into the system affecting the DTV tuner. I get all the analog channels: 2, 5, 7, 9, 11, 20, 23, 26, 32, 35, 38, 44, 50, 56, 60, 62, and 66... which leads me to believe my antenna isn't too bad off yet. As an aside, I did notice that the DTV tuner itself results in a MUCH less viewable *analog* signal (remember, my boxes are "pass-through"). There seems to be a LOT of insertion loss attributable to the tuner. Again, my box brand is Magnavox - not what I would consider a "fly-by-night" or "no-name" manufacturer. I don't know how to resolve this - or if it is even a resolvable situation - but analog channels that were perfectly viewable before placing the box inline became terrible afterward. (I hate to use an arbitrary reference for this, but it was as if a 20dB attenuator or similar had been placed inline.) And I understand that many channels have "moved" from VHF to UHF... Well, it certainly looks as if I'll need to install a new antenna outside again... but I can't climb the tower now - I just had surgery. Plus, it's plain too cold to do it now. So we'll see when Spring breaks. But until then I won't be able to support/patronize those who advertise on the channels I can't see. <grin> Mark - N9WYS -----Original Message----- From: Repeater-Builder@yahoogroups.com On Behalf Of Mark ----snip ---- I do like the suggestion about the pre-amp - I may give that a try this afternoon (if it isn't too cold in my attic!) and I'll report my results. (BTW - mine is not a "hardware store" variety, it's a Winegard that I spent probably $70 on about three years ago.) Mark - N9WYS -----Original Message----- From: Repeater-Builder@yahoogroups.com On Behalf Of TGundo 2003 ---- more snippage ---- I hear once a day: The antenna in my attic/ my old antenna system does not get the DTV stations that I get in analog. My Response: Well, this is a technical group with a high level of RF knowledge. How well does your 440 antenna (or any band) work in the attic compared to on your roof or tower? There is some implied responsibility on the part of the end user to ensure that their equipment is optimized for the best performance. That being said, I have many many clients with antennas in the attic that work just fine. What I do find to be the typical problem is that most people with antennas in their attics have an amplifier installed to make up for being in the attic. I'm sorry to say that the $15-20 amplifier you pick up at the hardware store sucks, to prove that just bench test it on your specturm analyzer & look at a DTV signal. They typically distort the waveform badly and that is more common a problem why you can't tune the DTV station. I have pulled those from an antenna system that were receiving analog but not digital. Once out of the system, while the analog was virtually unwatchable now (which the amp had boosted enough to tolerate), the DTV signal suddenly came thru with flying colors! Would you put a crappy preamp on your repeater receiver? I hear once a day: My converter box does not seem as sensitive as my new DTV set in the other room. My Response: Let's use some common sense here. The government mandated that the LOWEST COST possible converter boxes be made available for people to convert their OLD analog TV's. The bottom line: You get what you pay for. Was not that long ago a wise jedi master here on RB posted findings on PL circuits in radios with his test equipment and found that the cheaper radios did a poorer job. Your $50 converter box is not going to have as good of DTV tuner in it as your new $5000 Sony HDTV. This difference existed in analog tuners as well. Nuff said. *A side note: We have found that there are huge differences in converter boxes. For what it is worth the Zenith model seems to be one of the best, in case your shopping. I would stay away from brands you have never heard of at the big box stores.
