Strange Signal Issue

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Trip
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Strange Signal Issue

Post by Trip » Sun Sep 06, 2009 8:26 am

Hello, all:

I posted this on AVS, but I've decided to cross-post it here, as maybe the good folks here might have more insight. :)

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I've got a really strange signal issue with a digital radio signal. I have a Sony XDR-S3HD hooked to the included dipole, duct taped to my ceiling.

I first noticed it last year. During the school year, I live in Charlottesville and attend UVA. I noted that WCNR 106.1A had added digital sidebands to its signal, and was almost impossible to kill. Meanwhile, the stronger signal of WVTW 88.5B1 was finicky and would lose its lock suddenly.

Investigating with the spectrum analyzer in a not so great location showed that the signal on the sidebands would just barely rise out of the noise floor for WVTW while WCNR's sidebands were clearly defined 20 dB down, as they should be.

This year I'm in a different apartment that is on the opposite side of the complex and up a floor. I now have only a single wall separating me from WVTW and WCNR, whereas last year I had several buildings in the way. Investigation today revealed that WCNR's digital signal has vanished entirely, as I can't even flash the little icon on my receiver anymore.

WVTW still refuses to cooperate, even after spending a lot of time trying to find a decent position for the dipole today. The really interesting part is that sister simulcaster WVTU, which is 1Edge and 16 miles away (instead of LOS and 4 miles like WVTW) locked digitally without effort. I've switched to using WVTU for my NPR listening, but this doesn't really get to what the actual problem might be with the WVTW signal, which should be much stronger, in theory.

Last semester I'd called and spoken to an engineer about it but nothing ever came of it, even though I was able to tell him what I saw on the spectrum analyzer. I'm tempted to call again and this time ask to speak to the chief engineer, who I've spoken to about WVTF's digital signal before, but I'd prefer to get some opinions before I do so. Any ideas?

Thanks.

- Trip
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BroadcastDoc
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Re: Strange Signal Issue

Post by BroadcastDoc » Sun Sep 06, 2009 10:00 am

Are you having any multipath issues where you're at? I know it's basic, but that's always the first place I start...
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Trip
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Re: Strange Signal Issue

Post by Trip » Sun Sep 06, 2009 10:19 am

I know there are multipath issues, but that never prevented WCNR from locking before their digital signal went away, and it's on the same mountaintop. WVTW only has 2 dB more power.

I know there's multipath from watching TV. My newer tuners handle the multipath okay, but the WinTV-D chokes and doesn't show anything unless my antenna is positioned just right. Even still, the multipath is better this year than last, as last year I couldn't even find positions where the WinTV-D would lock anything. This year, I found a position where 1000 kW worth of WVIR-DT locked completely by accident, and all the others (except WVPT-DT2 11 at 0.04 kW) have positions that work as well.

- Trip
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Re: Strange Signal Issue

Post by NECRAT » Sun Sep 06, 2009 11:38 am

It is possible that WCNR's digital is actually off (went off between times when you monitored them).

Have you tried them outside, away from the building?

As far as WVTW's digital is concerned, it sounds like the digital amplification is non existant (are they doing high level combining with a small amplifier transmitter like a BE FMi-31, where the module is failing.
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Trip
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Re: Strange Signal Issue

Post by Trip » Sun Sep 06, 2009 12:39 pm

Yes, I'm pretty sure WCNR's digital signal is gone. I'm not worried about it. It's always been very easy to receive when it is on the air, while WVTW's signal has been very lousy.

I haven't tried outside because I have no way to power my radio outside. I did my spectrum analyzer testing from outside of one of the Electronics labs, and WVTW's signal was no better there. WCNR's was fine.

I don't know what kind of setup they have.

- Trip
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w9wi
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Re: Strange Signal Issue

Post by w9wi » Mon Sep 07, 2009 6:34 am

KJ4IEA wrote:Yes, I'm pretty sure WCNR's digital signal is gone. I'm not worried about it. It's always been very easy to receive when it is on the air, while WVTW's signal has been very lousy.

I haven't tried outside because I have no way to power my radio outside. I did my spectrum analyzer testing from outside of one of the Electronics labs, and WVTW's signal was no better there. WCNR's was fine.

I don't know what kind of setup they have.

- Trip
I wouldn't rule out the possibility WVTW is in fact running less than the standard 1% injection.

WNRQ here ("WLAC-FM") had a quite wimpy HD signal for some time. It looks like they've since fixed the issue, whatever it was.
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