[SBE] FCC R & R 73.318: FM Blanketing Interference

[jer hill]

I tell people that the FCC rules require that their speakers, computers,
audio amps etc. have to be somewhat immune to radio station energy but they
didn't think to mandate an RF immunity level of protection standard that
would have included the situation for when you live in the neighborhood of
an AM or FM radio transmitter. So this makes it the FCC's fault and I am
going to try to help you fix what they should have never allowed the
manufacturer to get away with in the first place! 

-Jer

-----Original Message-----
From: sbe-bounces at sbe.org [mailto:sbe-bounces at sbe.org] On Behalf Of Dennis
Sloatman
Sent: Sunday, September 20, 2009 5:20 PM
To: 'sbe member discussion mail list'
Subject: Re: [SBE] FCC R & R 73.318: FM Blanketing Interference

Thanks, Chriss.

This is the sort of thing every engineer dreads dealing with.  The engineer
(who often has no management or interpersonal skills training whatsoever) is
thrust into potentially volatile situations with liability exposure (see my
previous responses to emails and my thoughts on liability).  It seems to me
many in our business, management AND we engineers, often do not take that
into consideration.

You raise an excellent point when you said: "Would it be cheaper and quicker
to purchase for the neighbor another set of PC speakers or a new telephone
to eliminate the problem? Possibly."  Yes, it would be, but as is often the
case, you may find yourself dealing with an intransigent complainant who
takes the "why should I have to change my computer speakers because of your
station being off-frequency and running over-power" (an quote from a real
instance).  When I jokingly, with a big smile, replied that our transmitter
could barely make the licensed power as it was, this led to the retort, "So,
you admit you have problems, eh?"  It's funny, but the lesson of this is you
have to choose your words as if you were on the witness stand in a trial.

A lot of questions to be answered indeed and in my view, the FCC is vague on
this rule (a new rule was proposed a few years ago to clarify the Blanketing
Interference rule, but it's still not in the rules).

We should write a comprehensive "toolbox" book on this when it's all over.

Best Regards,

Dennis L Sloatman
Sloatman Associates
MCSE/CSRE/AMD/CBNT/CNE


-----Original Message-----
From: sbe-bounces at sbe.org [mailto:sbe-bounces at sbe.org] On Behalf Of
chscherer at everestkc.net
Sent: Sunday, September 20, 2009 2:25 PM
To: sbe member discussion mail list
Subject: Re: [SBE] FCC R & R 73.318: FM Blanketing Interference

As was noted, the good neighbor approach is often the better course of
action than strict adherance to the rule.

Mike Langer noted installing ferrites in equipment. Like many solutions,
this involves time and testing for success. Would it be cheaper and quicker
to purchase for the neighbor another set of PC speakers or a new telephone
to eliminate the problem? Possibly.

As part of this discussion I would like to hear about specific products that
have shown to be immune or resistant to RF blanketing.


============

>From   Dennis Sloatman <dsloatman at sloatmanassociates.com>  

I am now, for the first time in a nearly forty-year career, dealing with FM
RFI complaints from a new FM station facility (15kW ERP/ 400' HAAT).  

These complaints include demodulated audio in PC speakers, garage door
openers that no longer work, as well as the customary "I can no longer pick
up a station I used to hear that's 95 miles away," etc.  My experiences in
this area have all been with AM stations as the facilities over the years
I've had with FM have been operating from towers in wide-open farmland or in
the swamps of Florida (I always seemed to be the C.E. for an AM  with its
site located in densely-populated residential areas).  AM RFI in some
respects, is easier to resolve inasmuch as good grounding can resolve most
complaints.

I'd like to hear of the experiences/solutions from all of you on this board.
I believe sharing these would be of benefit to all of us.
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