Re: [IRCA] Local 2nd and 3rd Harmonic

["Chuck Hutton" <charlesh3@xxxxxxx>]

Craig:

You're very close (and a lot closer than I was), but it's actually a little
more complicated than that. Here's a cut and paste from an FCC document at
http://www.fcc.gov/eb/Orders/2003/DA-03-1033A1.html:

Section  73.44(b)  of  the  Rules  requires  that   the 
  emissions of  an AM station  that are removed  by more than  75 
  kHz from the carrier be attenuated at least 43 + 10 Log  (Power 
  in  watts)  or  80 dB  below  the  unmodulated  carrier  level, 
  whichever  is the  lesser  attenuation.


So our 1 kw station on 1450 ought to be 73 dB down, or 50 microwatts. Sounds
like Dave has a goodreason to call them - there's no way they are within
spec.


Chuck

-----Original Message-----
From: irca-bounces@xxxxxxxxxxxxxxxx [mailto:irca-bounces@xxxxxxxxxxxxxxxx]
On Behalf Of Craig Healy
Sent: Sunday, January 21, 2007 12:38 PM
To: Mailing list for the International Radio Club of America
Subject: Re: [IRCA] Local 2nd and 3rd Harmonic

> My recollection is that harmonics must be down 40 dB from the carrier.
> That's .1 Watt for WCTC. You didn't say how strong a signal you are
> receiving - if it's very strong it's surely more than .1 Watt and deserves
a
> mention. If it's a wispy DX level signal, they may be within legal limits
> and wouldn't appreciate a false alarm.
>
> If the 40 dB rule has changed since I last had to know these things, I'm
> sure one of our broadcast engineers will speak up right away.

The last time I had a spectrum test run at a client, I think the figure
was -73db.  It is measured about a kilometer away from the site.  If the
signal is -73db down from the fundamental, then it's good.  I might be wrong
on the figure, but I think it's more than 40db.

What I would do on that station is make sure that the harmonics are heard at
other locations.  Sometimes they are locally generated by things like
aluminum downspouts that have dirty of corroded junctions that form defacto
diodes.

Craig Healy
Providence, RI

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