No I'm using Cox cable. I assume that the lines comes from overloading and the snow from a weak signal. I don't have any channels with both snow and lines. The lines goes away from most channels when I put an attenuator on the cable, but the snowy channels gets worse. There was no lines when I had the LNA turned off.
The signal seem to change slightly over time, but I'm always referencing the tuner on my TV. I have not found a static solution that works, I have to change the attenuator to get a good signal on different channels. Generally the lower frequencies (<100Mhz) are week, and the higher are strong (over channel 60). I don't know how to measure my signal, but I'm guessing the signal from the cable provider is relatively strong. - Haavar On Dec 5, 2006, at 7:07 AM, Andrew Dodd wrote: > Comment: I haven't been following the PVR-500 issues as much as I > should have. Somehow my Samsung-based 500 started working perfectly > after a few weeks with no intervention (I'm still running the > 0.5.something or 0.6.something - I'm not home at the moment to check.) > I honestly can't figure out why, but I've been afraid to touch > it. :) > > I think I need to browse through the archives this weekend to see > where things are normally, as it sounds like a lot more is known about > the card now. > > Quoting Haavar Valeur <[EMAIL PROTECTED]>: > >> Do you mean there was no clear criteria when to turn on or off the >> amp, or do you mean that it was not clear if turning it on or off >> would improve the picture? > Unfortunately, when you're dealing with receiver nonlinearity and > frontend overloading, things are never cut and dry in the RF world. > :( Nonlinearity pays my bills (I'm an RF engineer by profession.) > >> What I think is that the lines people see is when the signal gets >> clipped. That is when the signal strength is too high. This will >> occur when the amp is on when it should not have been. I think the >> picture is snowy when the signal is too weak. That is the case when >> the amp is not on, but it should be on. >> >> When I had the amp on, some channels where clear, but others had the >> lines. When I turned the amp off the most of the channels that was >> clear now turned snowy, but the channels that had the lines where >> generally a lot better. >> >> Looking at the picture over time I get the impression that the signal >> for each channel changes. Channels sometimes has the lines and >> sometimes not. The same with the channels that are prune to snow. I >> don't think there is a static list of channels that should use the >> amp and not, but there are some channels that are more likely to need >> the amp (<130Mhz). > Unfortunately, depending on the receiver design (Hans, does the > datasheet happen to have a block diagram showing where in the signal > path the LNA is located?), moving the LNA in/out of the signal path on > a channel by channel basis will likely not help much. Usually LNAs > are placed as early in the signal chain as possible (It can be > mathematically shown that the noise figure of the first amplifier in > your receiver chain is the most important, thus LNAs are usually the > first thing in the signal path, with a few exceptions.) > Unfortunately, this also means the LNA does not have too much > filtering in front of it, which will make it more prone to getting > overloaded by a strong signal. This strong signal can be anywhere in > the receivers' frontend passband, which is usually pretty wide. Thus > a strong signal on one channel can foul up reception of every channel > in a given band, as tuning of the channels and selectivity *usually* > occurs after the LNA. > > I'd really need to know more about the signal chain to be sure though. > > Given that you are indicating significant differences in signal > strength between channels, I'm guessing you are using OTA reception > and not cable? Signal strength that varies over time is to be > expected with OTA reception, since both multipath and weather can > affect VHF and UHF propagation significantly. > > > _______________________________________________ > ivtv-users mailing list > [email protected] > http://ivtvdriver.org/mailman/listinfo/ivtv-users > _______________________________________________ ivtv-users mailing list [email protected] http://ivtvdriver.org/mailman/listinfo/ivtv-users
