I have a 622 that shows signals in the 90s for my two OTA towers, located about 60 miles away. One tower always locks the picture, the other pops in and out and never holds a lock. I put up a new antenna on my 50 ft. tower, mast pre-amp, high-grade coax with weatherproof connectors (I had some old stuff on the tower). Same story. Three previous 622s had always held a picture on both OTA towers!
I bought a Samsung DTB-H260F OTA receiver (my DLP set does not have an internal HD tuner). The H260F brings in both towers (and sub-channels) with rock solid pictures. I can switch inputs quickly on TV and compare H260F and 622 OTA. Never a dropout on the H260F. One station, the one that drops out on the 622, is 10 bars (the max) the other station which always stays locked on the 622 shows 8 or 10 bars on the H260F.
I also have an HDTV tuner in my WinXP PC (Cat's Eye DTA-150, software is BeyondTV) which gets 100% locked signal from both distant towers. The add-on on-screen Signal Meter shows 100%. Only after I inserted a huge amount of attenuation was I able to budge the PC tuner off of 100% signal. All three receivers are fed from same coax system in the house.
So, it appears that something is fishy with the 622 tuner. I talked with engineers at both stations, and they run about same power and antenna height. They have nothing going on at their sites that would account for my problem. One is at 300 degrees from me and the other 317, which is clearly within the beamwidth of the antenna, because I aim more toward the one that is dropping in and out and still get solid pic from the tower that I am not aimed at dead on.
I had a Ph.D. elec engr. friend examine my tests at attenuation and print a Topo map from my house to the two stations.
As I kept inserting 6db attenuators in the line, the one station that kept dropping out finally stayed locked with about 36db of attenuation and the 622 showing a signal in the 60s (down from about 91).
Topo doctor notes that the path of the signal from the "in and out" station is closer to the ground than the path from the other tower. It would be more subject to multipath. He notes, "It will be interesting to see what happens when the leaves come back." Yes, Virginia, tree leaves affect the UHF signal over a long-haul - especially here in the country with mucho trees. In theory, the signal should be stronger in Winter when the trees are barren. RF-sucking leaves, no less.
My topo Ph.D friend says that it is probable from the maps and my tests, that I have some multipath from the "in and out" station. BUT ..... that since both my Samsung OTA HD receiver and my PC card HD tuner both handle all sigs with no attenuation in the line - the 622 has some tuner issues. In particular, it would appear that the 622 I have now does not handle multipath well, if that is indeed the problem. Or the 622 does not handle strong signals well.
I had 3 previous 622s that always stayed locked on both distant towers, even with my old beat-up antenna. Only the current one (#4) would not not lock in when there is a strong signal present. That started the new antenna purchase and all that followed.
Forgive me for the long post, but I have spent several hundred dollars and weeks of testing and querying engineers to see if I could finally fix the blame on something within the 622 tuner. I think that fact is now established, although not in a position to know the exact issue. I have kept Dish techs (one in the receiver div) advised on this process.
The point is that if you fail to get a picture lock with a high 622 signal reading (mine are in the 90s), if you are able to move your antenna, and/or can insert some incremental db loss in the coax - I am sure Dish techs would be interested in your results.
To review: I have 622, separate Samsung OTA tuner, and PC HDTV tuner card. ONLY the 622 fails to lock on ONE of my two distant towers here in the sticks.
The next time I send a guy up my tower, I am installing a new rotor, which I did not think I would need, since my previous antenna was fixed in place - and my 811 and 3 previous 622s always locked onto both distant towers. I am 96 GPS miles from Dallas HD towers.
So, I am working OTA from two towers across the border in S. Okla. The one that always locks on with 622 has CBS, MyTV, and FOX. The in and outer is NBC and CW. Network feeds have nothing to do with my problem, I am close to being positive about this. Out here in the sticks, you can chat for half an hour with a station engineer. I have done some testing for them, too, so it is a two-way street.
