Bennett-ko2ok wrote:
> In your installation of ferrites on you speaker leads inside the
> tv,
> a) was the symptom just audio interference, or video as well?
[KØiL] Audio only at a constant level (didn't get louder with
volume control) indicative of final AF amplifier stage detection. No video
problems at all (unless I remove my Lo-pass filter, then all hell breaks
loose).
> b) from your answer to a foreign ham inquiring, and you asked about
> ferrites from a local Radio Shack, do you mean the pull apart
> rectangular ferrites from R/S is what you used?
[KØiL] Yes. Although I also use the other type for cable TV &
computer cables. I also buy some non-radio shack types at Surplus Sales of
Nebraska on occassion.
> if so how many in your particular case?
[KØiL] For the Sony stereo XBR TV, I only needed 1 package with its
two cores. I placed one on the right channel spkr and one on the left. I
used up all the excess wire it could spare and put windings on both sides of
the rectagular core. You can install these two cores as a single core
increasing the attenuation if needed. The biggest pain was getting the case
off and on again. Thing weighs a ton.
> c) Both on 49MHz phones and now on 900MHz phones, I give my own
> phones interference. Even on sideband, they can hear and under
> stand what I say. I installed 2 R/S inline filters, but they
> didn't seem to help much. These phones all use AC adaptors,
> and I even put a R/S ferrite on the AC adaptors, to no avail.
[KØiL] I've never heard of anyone getting into the 900Mhz models,
but then again it is just another telephone and should be just as
susceptable as most others. Have you tried adding a ferrite to the phone
line at the base of the phone? Also, is the telephone system ground at the
demarcation well grounded and is this ground tied to your single point
ground of the ham shack? It should be. Do you have any phones that do not
get interference? Make sure all connections in the phone system are good
and tight. Start simplifying the phone system: unhook everything, and then
plug in one phone device at a time until RFI starts up. (Don't forget
computer modems!)
> d) My neighbor mentioned to me yesterday that she had some inter-
> ference on her phone and thought it was possibly a nearby
> CBer (or so she was so polite to say). But after her describing
> the one-way talking she could hear, I knew she was listening to
> me on either 6m or 2m. She is using a Bell touchtone phone, not
> wireless. She contacted the phone company and they said they would
> come and check it out, but if it was a CBer, they would contact
> the FCC to investigate. Also said recently had some tv interference,
> and she has cable.
[KØiL] I'd be surprised if it were 2-meters unless you run high
power there. Call the FCC (888-CALL-FCC) and request a few copies (free) of
bulletin CIB-2 and FOB bulletin 10. These are the FCC's Interference
Handbook and Telephone Interference bulletins. Read them before giving a
copy to the neighbor and asking them to read it.
> e) Depending on channel, my antenna position and band, I give my
> tv's tvi. I also give my PC (up 2 floors from the basement where my
> radios are) interference in case of the small external speakers
> (no ferrites seem to help) as well as killing a modem connection
> if in use.
[KØiL] This really gets complicated doesn't it?! Sounds like
you've got multiple problems that may have multiple causes (each unit) or
maybe one common cause (system ground?). May I suggest that you contact
your local ham radio club (you are a member aren't you?) to see if they have
a ARRL Technical Specialist or RFI committee who would be willing to visit
your shack. They can inspect it for possible ground system problems and/or
help determine the cause(s). Until you troubleshoot the cause(s), you can't
come up with the right solution(s).
You may also want to get ARRL's RFI Handbook and start reading those
sections pertaining to the most troublesome RFI/EMI problems you have. I
have the previous edition and it is excellent. It is fun to learn about
RFI!
> In addition to the prolonged description of my symptoms, let me
> add a question as well as my setup.
> a) Why can my wife and neighbor not only hear me but also
> understand my voice, even though I am using SSB. Even a regular
> SW radio has a garbled sound unless it has a BFO or USB/LSB switch?
[KØiL] I don't know; I'd hafta hear it myself. I know I can
understand SSB while listening on AM if I have some idea what they're saying
(e.g. "Testing. One, two, three. Testing"), but I get the feeling that's
not what you mean so I'm atta loss. Now I've got something to think about
while I'm watching Sliders tonite!
> b) I have no external filters on my 6m radio (an icom 756 with 100w),
> connected to an ARRL book-designed 4 element beam at 50ft. I
> also have a 2m radio (icom 275a with brick amp to 150w) to
> an 11 element beam at 58ft.
[KØiL] The tower is well grounded and inter-connected to shack's
single point ground?
> My hf radio (also the 756) has
> a low pass filter on the hf antenna port. All is grounded
> pretty well (6 feet under foundation directly behind radio, 5ft
> away to main cold water pipe, and 12 ft away to 8ft solid copper
> rod in good moist soil.
[KØiL] Why multiple grounds? Should use single point grounding if
possible. 12 ft might be too far away for two-meters(?). Water pipe may
have a meter that breaks the pipeline. Make sure it has a jumper with good
electrical connections.
> I have a number of CRT yoke ferrite
> cores and 1.5" ferrite cubes and R/S ferrites on all my cables,
> but still have significant interference.
[KØiL] What are the materials of the CRT yokes? They may be wrong
for the application.(?) 43 mix is best for HF, and 77(?) or higher for VHF.
> I know I may not get easy answers, but I would like some further
> direction or process if you have a moment to share. I am sure
> at least of few other readers have one or more of the problems
> I have described.
> Thanks,
> Bennett ko2ok,
> in northern NJ.
[KØiL] I hope I've been some help, but I'm afraid I might've asked
more questions than you did!
73,
de ed -KØiL (make a good RF Choke!)
"Paradoxically, the healthiest people in history live in constant fear of
death."
-- Nicholas S. Martin, exec. dir. of Consumer Health Education Council.
>
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