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

[David Both]

Regarding the original question, has anyone considered looking at interference 
from cellphones? I have had that occur in the audio output from a computer when 
a cellphone close by (like my own) would repeatedly search for a signal in a 
weak signal area. Turning the cellphone off solved the problem. Who shows up 
Sunday but not Wednesday?? ;-) But that would be quite regular rather than 
random short period timing.


Other options:
Radar if you are close to an airport or weather radar.
RF from a bad sparkplug or ignition wire in a lawn mower. The mower would show 
up intermittently fading in and out as it got close to my house.
Refrigerator or A/C compressor motor, or HVAC blower motor.

Also, regardless of the source of the RFI, ensure that all of the power outlets 
into which all of the devices in question, including the cameras and video 
switcher have really good green-wire grounding. Fixing a poor or non-existent 
ground can resolve an RFI problem without ever having to know the source. Also, 
the green wire ground from each power outlet should never connect to the neutral 
bus in the breaker panels. If necessary, run separate green wire ground from 
each outlet to the grounding point, hopefully, a copper stake in the ground or 
copper water pipe either of which should extend at least 10 feet into damp earth.

And no cheater plugs.

Please let us know if you figure this out and fix it.


On 03/06/2013 09:39 PM, James Jones wrote:
> J. Mack -- During the live event, the Mac Monitor showed the beat
> pattern and it was present in the recording as well. The monitors for
> the individual cameras didn't show it ( according to producer of the
> video ).
>
> ****** removed the requirement that consumer devices have RFI and TVI
> filters on them.
>
> Does anyone make  filters for ac power? Would an Uninterruptible Power
> system have enough RFI/TVI filtering to help?
>
> G. Starling -- Thanks for the hints. Thremoved the requirement that consumer
>> devices have RFI and TVI filters on them. e beat pattern is a constant pattern. There is no constant to the interference. On for a few minutes, off for a few, back on -- but not the same length as the first, etc.
> Thank you all for your help.
>
> One of these days, I will get my ham license.
>
> jcj
>
> On Wed, Mar 6, 2013 at 9:15 PM,removed the requirement that consumer
>> devices have RFI and TVI filters on them.  Joseph Mack NA3T <jmack at wm7d.net> wrote:
>> On Wed, 6 Mar 2013, James Jones wrote:
>>
>>> A Friend asked for me to help trouble shoot their church video problems.
>>> They video recorded their sermon on a Mac from a video switcher through
>>> several pieces of equipment to their mac. All their monitors had clear
>>> pictures of the video, but the Mac had a beat pattern in the video.
>>
>> did the recording have the beat, or just the monitor on the Mac?
>>
>>
>>> The beat pattern would show for a couple of minutes, then clear up for a
>>> few and then back again. I am thinking it might be walkie talkies, handhelds
>>> or some nearby rf communication center of some sort. Since it happens only
>>> on Sunday morning and not during their Wednesday evening service, I believe
>>> it might be a ham operator, cb'er, etc.
>>
>> this could be a bit of work to track down.
>>
>> First thing you need to know is that at the request of the electronics
>> industry, the Regan administration removed the requirement that consumer
>> devices have RFI and TVI filters on them. As a result you'll see notices on
>> consumer electronics saying "this device must accept all interference". This
>> saves the industry about 50c/device and lets the consumer (you) handle the
>> problem. The rest of the world didn't fall into line with the USA, at least
>> initially, so the devices shipped elsewhere, still had the filters. I don't
>> know what the situation is now. I expect Germany will still require them,
>> even if no-one else does.
>>
>>
>>> Need any and every thought on troubleshooting this problem.
>>
>> first thing you can find is whether the interference is coming over the
>> wires or through the air.
>>
>> wires: wind the cables around ferrite cores, or put ferrite blocks around
>> the wires (you can get them at Radio Shack). If it works you're done. If it
>> doesn't work, the signal still could be come over the wires. If it's coming
>> over the wires, change the wiring (if you can) to see if it makes any
>> difference. You might have to change the order of devices.
>>
>> air: put a metal cage around (and under) the Mac. Expanded Al mesh would do
>> it. You can fold it over a table edge to make a box and lid.
>>
>> 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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>
>
>
> -- 
>
>
> *********************************************************
> David P. Both, RHCE
> Millennium Technology Consulting LLC
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