Mark Schubin wrote: >I've been traveling and just got in. Let me add some two cents. > >The earlier LG 5th-generation tests were truly plug-&-play. It didn't matter >what antenna I used or (within reason) where I positioned it or >how I oriented it. Even rabbit ears worked for the UHF DTT stations. There >was only one station -- far away -- that required any care in >antenna positioning. > >With Bob's new box, no matter what we did, we couldn't get WABC-DT at all. >That station IS adjacent to WNYW-DT, and maybe it was off the air at the time. > >Of more concern was WCBS-DT. It's on channel 56. As best I know, the nearest >adjacent station is an NTSC WAY out in Riverhead (the center of Long Island's >"fish tail") on channel 55. That NTSC station has barely registered on a >spectrum analyzer in previous tests. WCBS-DT stands alone. > >We know it was on the air at the time because it came and went. Bob says we >could count cars. Well, no. But the breakup DID seem >indicative of varying multipath. Certainly, reception was affected by us >walking around the room. That's the first time that has happened on >WCBS-DT since the second generation boxes. > > I disagree with Mark on this one point. I think that you could literally count cars as they passed by counting drop outs. Maybe I paid more attention to this. Minor point however. >We tried multiple antennas in multiple positions, including affixing them to >the window. Nothing allowed WCBS-DT to be received reliably. >Surprisingly, WNYW-DT, which does have adjacent and co-channel issues, came in >fine in a number of antenna positions and orientations. > >TTFN, >Mark > >Manfredi, Albert E wrote: > > > >>Bob Miller wrote: >> >>Doug wrote: >> >> >> >> >>>>It's now time to try the el-cheapo 5th generation box >>>>with a really really good single-channel filter >>>>(Blonder-Tongue?) in front of it for the difficult >>>>channels. If it really is the front end, that should >>>>make it work. It could also be something else, like >>>>the chip allows different amounts of external memory, >>>>or uses aid from the main box CPU, and these were >>>>lacking in teh cheapo box. >>>> >>>> >>>> >>>> >>>Not being an engineer I don't know but at Mark Schubin's >>>you could count the cars going by by watching the >>>monitor for drop outs on CBS for example. That sounds >>>like multipath to me. >>> >>> >>> >>> >>It does sound like multipath problems, but Doug might >>still be on target. If you recall from the Rhodes >>discussions, IM3 products occur in the passband, and >>eat at your signal margin. So if you have a cheapo front >>end, the IM distortion created from loud stations at >>adjacent, or also bad news were the third over, >>either above or below your selected station, the "louder >>than one might think" IM product will erode the signal >>margin you have upstream of the equalizer. >> >>So, a cheapo front end that causes the signal margin to >>fall below ~15.2 C/N, even with excellent equalizers, will >>cause the thing to fail. >> >>A good front end is the best and quickest defense. More >>innovative FEC schemes will also play a part in the future, >>by lowering the required margin closer to the Shannon >>limit (10.47 dB). >> >>Bert >> ---------------------------------------------------------------------- You can UNSUBSCRIBE from the OpenDTV list in two ways: - Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word unsubscribe in the subject line.