[TriLUG] Television & RF interference -- yes computer related -- I think

[James Jones]

Joe,

The main idea of the drawing was to show location and connections of
the displays (monitors) since you had mentioned that my wording about
monitors was confusing.

And I did want to "show off" my block diagramming skills. :-)

Thanks for all your comments. I believe that I have more questions for
the producer & possible the preacher. I don't think I have the
complete story. Especially the part about -- "has anything changed
recently?"

jcj

On Thu, Mar 7, 2013 at 9:53 AM, Joseph Mack NA3T <jmack at wm7d.net> wrote:
> On Thu, 7 Mar 2013, James Jones wrote:
>
>> After finally getting around to transferring my notes to a block drawing (
>> see attached pdf ),
>
>
> these are stripped by the mailing list. But I'm not going to be able to
> pinpoint it from the diagram anyhow.
>
>
>> Your thoughts on this are appreciated. As a side note, their cabling is
>> more of a rat's nest and it looks like I get to help them organize it.
>
>
> Other people have had good suggestions, eg making sure the power cabling is
> earthed and wireless mikes (which you've eliminated). The lesson from them
> is not so much what to look for, but how to think about it.
>
> At the outset you have to face
>
> o you may not solve it, one of the problems being that you can't make the
> problem occur on demand. There is nothing harder to fix than an
> intermittant. You will have to accept bad recordings in the short term and
> maybe long term. To know when it happens, you'll need the recording device
> running 24*7, which presumably will require a human on hand.
>
> o it may take a long time. Before you start, decide how much time are you
> prepared to put into it. When that time comes, will you really quit, or will
> you just keep going?
>
> If you do fix it, the explanation will almost certainly be obvious after the
> fact, but it's unlikely that you'll be able to find it by rational means. In
> that case you'll have to take the monkey-typewriter-sonnet approach.
>
> Finding the problem here is no different, thinking wise, than fixing a
> software bug that only appears intermittantly.
>
> You'll have to find out what all the cables are doing and simplify it as
> much as possible (are all the cables shielded? - I don't know what you have
> - are the twisted pairs individually shielded? it the bundle shielded? is
> the shield earthed at each end? - this itself will be a nightmare.). Make a
> plan for what to do when the next RFI event happens and be prepared to start
> disconnecting cables. Have some idea of how you'll interpret what is going
> on if the RFI remains/stops.
>
> You need to get to the simplest setup that reproduces the problem and have a
> list of what stops it. Can you take out the video switcher and record
> directly from the camera? (You may need to borrow gear from a different
> manufacturer, but with similar specs, to substitute to see if anything
> different happens.) You may wind up in the unhappy situation that
> eliminating RFI means you can't record.
>
>
> Joe
>
> --
> Joseph Mack NA3T EME(B,D), FM05lw North Carolina
> jmack (at) wm7d (dot) net - azimuthal equidistant map
> generator at http://www.wm7d.net/azproj.shtml
> Homepage http://www.austintek.com/ It's GNU/Linux!
> --
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-- 
Jc Jones
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