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

Thu Mar 7 23:46:31 EST 2013

Pete,

Thanks for the comments. Some fit my understanding of RF interference
from my many years with AM and FM broadcasting.

I appreciate the link. I don't know why I haven't gone to the ARRL before now.

Thanks again.

jcj

On Thu, Mar 7, 2013 at 6:10 PM, Pete Soper <pete at soper.us> wrote:
> Folks not interested in this subject should most definitely hit "delete" or
> "next" or something.
>
> I think Rod and the earlier poster may be non-violently agreeing with each
> other that most consumer electronic equipment in this country is subject to
> FCC Part 15 rules and modern (with vanishingly rare homebrew) amateur radio
> equipment interference that is legally the amateur's fault is very rare,
> while US equipment is very susceptible.
>
> IMO wireless microphones have zero chance of being a problem. Fergetaboutit.
>
> But the FCC regs and your neighbors exist in two worlds. If you fire up
> 1.5kw on 160 meters to see if you too can connect with somebody in Australia
> from here in North Carolina and your neighbor's house goes bat sh*t, it
> won't matter at all that all of their equipment is covered under FCC Part 15
> and your equipment is perfect relative to part 97. Folks can sue other folks
> for a small filing fee, but long before that they can appear at your door,
> beet-red and implying that because your actions are interfering with their
> viewing of the (insert sports event here), you are the devil, but more to
> the point ask  *what are you going to do about it RIGHT NOW?* I'm speaking
> hypothetically now, but the short answer is if I'm holding onto my expected
> position in a contest I'll weigh the cost of telling the neighbor to go
> pound sand (while wondering just how bad it's going to be with my wife). But
> otherwise (and in all my experience in the real world, and everything I've
> heard or read about with my amateur friends, and because I never got
> seriously competitive), I STOP and then bend over backwards to help the
> neighbor eliminate their interference as soon as I can, even if it means I
> spend a lot of time in their home installing equipment I paid for.
>
> To proceed I'm assuming this is about radio interference and not something
> correlated with the equipment in the church that is also only used at time
> X.
>
> Amateurs do quite often tend to talk for a few minutes at a time. In
> contests talking for more than about 1 1/2 seconds at a time meant you're
> losing. :-) Morse code traffic can vary even more, from a fraction of a
> second bursts to long "rag chews."
>
> RF overload is frequently the culprit, and so it doesn't matter if the
> nearby transmitter is squeaky clean from a spectral purity standpoint. If
> it's close enough, the receiving end has to have profound levels of bandpass
> filtering to avoid problems. Put a
> different way, if you bring a transmitter close to a receiver and the
> transmitter is on frequency X and the receiver is on frequency Y, at some
> point Y is going to respond to X's signal and become unable to receive other
> signals on frequency Y and it *will* demodulate X's signal for many
> modulation types, putting crap downstream like video hash bars, buzzing,
> "Donald Duck imitations", etc.
>
> Early on with my amateur hobby I was in a contest and there was another
> signal that was so incredibly loud I thought the person involved was
> obviously breaking one or more rules. But no, he was a few thousand feet
> away and I was pinning his signal strength meter too. Normal.
>
> In my experience most often the interference gets into the neighbor's
> equipment via the  electrical wiring. Wrapping *all* of the power cords
> involved with their troubled equipment through ferrite cores can sometimes
> provide relief. You want to ask yourself "where are the long runs of wire
> here?" and create a very high (usually common mode) impedance at the
> frequency of interest. But what frequency is involved, and what kinds of
> common mode chokes (aka ferrites) are needed? The frequency involved and the
> ones that provide relief, of course. :-) And "long wiring" includes
> telephone wiring and home entertainment speaker wiring too. If I had a
> nickel for every time some non-linear component in a sound system rectified
> my SSB signal and put Donald Duck imitations into the speakers...
>
> Using the blind shotgun approach, I have to say these filters below have
> been the best for me *for HF frequency interference* (HF is technically
> 3-30mhz). If the problem is a UHF or VHF source, these might or might not be
> effective. More is better, if there is any overlap with respect to effective
> frequency. As a citizen I must apologize for the fact that after all this
> time Radio Shack doesn't publish the specs on these devices.
>
> http://www.radioshack.com/product/index.jsp?productId=2103979&locale=en_US
>
> There is of course a boat load of information on this subject available on
> the net. You might start here:
>
> http://www.arrl.org/radio-frequency-interference-rfi
>
> -Pete AD4L
>
>
> On 03/06/2013 09:49 PM, R Radford wrote:
>>>
>>> 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.
>>
>> Hmmm, that is not how I interpreted the action, and also does not seem
>> to match up with what I read on the ARRL website.  In fact, the ARRL
>> was one of the big proponents of the bill that basically states that
>> as long as you are doing everything legal in your transmitter (ie: a
>> ham radio operator), it is not your responsibility if it causes
>> interference on another device. The FCC has the authority to
>> investigate and go after noisy transmitters, but if the transmitters
>> are operating within specification, there is no requirement that they
>> must stop or change if it interferes with your equipment.
>>
>> This kinda makes sense to me as the old method would make each ham
>> radio operator responsible for tracking down and fixing interference
>> from their equipment, even if the fault was not in their equipment.
>>
>> A little discussion about it here:
>>
>> http://boards.straightdope.com/sdmb/showthread.php?t=85072
>>
>> And a good writeup on the ARRL site on their efforts to push the bill into
>> law:
>>
>> http://www.arrl.org/bill-becomes-a-law
>
>
> --
> This message was sent to: jc jones <jc.jones at tuftux.com>
> To unsubscribe, send a blank message to trilug-leave at trilug.org from that
> address.
> TriLUG mailing list : http://www.trilug.org/mailman/listinfo/trilug
> Unsubscribe or edit options on the web  :
> http://www.trilug.org/mailman/options/trilug/jc.jones%40tuftux.com
> TriLUG FAQ          : http://www.trilug.org/wiki/Frequently_Asked_Questions

-- 
Jc Jones
Blogs -
http://www.wendellgeek.com/weblog/
http://www.wendellgeek.com/kixtech/

webmaster for:
http://www.cottonseedchronicle.com
http://www.trailblazersofnc.com
http://www.steelmagnoliasgardenclub.org
http://www.wendellgeek.com
http://classof1955.org
http://www.tuftux.com
http://www.therealpatpatterson.com
http://jonesjc.freeshell.org
http://www.trilug.org/~jonesjc