Cell tower interference

[Shockwave]

There are no megawatt DTV stations on VHF. Maybe there should be.

Audio is now muxed into the same datastream as video. They both use the same exact bandwidth.

Tube front ends usually have a very high dynamic range. Much better than the average solid state cb.

Intermodulation of a transistor final by high power VHF signals is a very remote possibility and practically impossible with a cb tube final.

If the housekeeping at the site is bad expect to encounter weird signals from rectification.

Kamikaze, I did some more investigating and it seems you are right about DTV on VHF. Even though there are still some on VHF low, they are not running the power they did a few years ago. They also do not have the coverage they had before and that's the bad part. I'll take this opportunity to thank you for teaching me something on the forum.

I'm still a little confused about you're saying video and audio use the same bandwidth. It makes sense if you're referring to the fact they are mixed together in the datastream. It does not make sense if you're implying the datastream would require as much bandwidth if you removed the need to carry the video content. For example digital radios use less bandwidth then DTV.

What you say about intermod is different then RF desensing but another common problem I wasn't even thinking about. Chain link fences in the area of the transmitter site can cause problems. Any large conductors with loose connections can rectify RF. As I recall, it is then re-radiated by these conductors with all of the harmonic content the rectification produces.

 

[Kamikaze]

I'm still a little confused about you're saying video and audio use the same bandwidth. It makes sense if you're referring to the fact they are mixed together in the datastream. It does not make sense if you're implying the datastream would require as much bandwidth if you removed the need to carry the video content. For example digital radios use less bandwidth then DTV.

You're welcome. Always fun to have a good discussion.

Audio and video are muxed into the same datastream in DTV. It's a 19.39 megabit-per-second stream. If sub channels or anyhting else is added such as mobile TV some bandwidth must be allocated from the 19.39 max figure.
Maybe this shows it well enough to make sense:
HowStuffWorks "How Digital Television Works"

The DTV bandwidth is of course close to the old analog bandwidth of 6 mhz and is defined under FCC mask standards which makes lots of sense to me.
Shut off the audio and there's no difference.

It's important to look at average power of DTV verses analog as one of the things which is a lot different.

Yes megawatt VHF DTV would be a help to some viewers. Problem is band openings and protection of other stations. That is a very detailed card game these days.