[BC]a question for the CFR experts

Sat Dec 31 20:32:12 CST 2005

thank you Tom!!  this is one of those replies to store and reread from time 
to time.

   I guess I'm just carried away with how much torque the FCC would have... 
the picture I've had in my mind would be the man with a badge asking me why 
I didn't do something to stop it from happening again, once I knew we were 
"interfering" with someone else's contour...  I figured it was up to me to 
be able to prove out how it was happening due to something external to my 
stations...

Jason
----- Original Message ----- 
From: "Tom Taggart" <tpt at eurekanet.com>
To: <broadcast at radiolists.net>
Sent: Saturday, December 31, 2005 7:15 PM
Subject: Re: [BC]a question for the CFR experts

> Jason Russell asked:
>
> "Isn't it spec'd in the CFR that it is indeed patently illegal to
> intentionally attempt to communicate by commercial radio communication 
> with
> parties beyond your licensed contour..? (Or some fancy language version of
> that...)"
>
>
> Nope, nada, nich, nyet,non..
>
> Contours are specified in the CFR for several reasons:
>
> 1.  For allocation purposes.  Contours, either predicted or measured, are 
> used to determine if a new station, or a modified system would cause 
> interference to existing authorizations by overlapping with certain 
> contours of those exilsting stations.
>
> 2.  To determine if a new station, or a modified authorization meets 
> minimum coverage requirements of the city of license. (e.g. coverage by a 
> 5 mv/m AM signal or 70 dbu FM signal)
>
> 3.  For purposes of ascertainment, usually using the 1 mv contour to 
> determine the "community" covered by a station and hence the area within 
> which the station must provide a service to the public and demonstrate 
> that its programing covers issues of importance or interest to this 
> community.
>
> 4.  For cross-ownership purposes, where the market size is determined by 
> the number of city grade signals that overlap with the stations that are 
> to be acquired.  (Superceded by a different test now in the metro counties 
> of rated markets)
>
> If you've followed the "DX Test" thread, its obvious that if you 
> accidentally left your daytime AM station on overnight, it might not be 
> very wise to respond to requests for QSL cards.  However, if you are 
> operating legally, and propogation conditions allow some DX'er to make a 
> rare catch, there is certainly no law preventing you from responding. 
> Indeed, especially if the listener is a teenager, why not respond, 
> explaining why he heard your station, what kind of equipment you are 
> using, and other distant locations you've been heard in.  With most kids 
> ignoring radio in favor of computers and I-pods, we need new people 
> interested in this business.
>
> AM: We all know AM will go long distances at night, even with a little 
> power.  DX'ers have always looked for daytimers on winter evenings just 
> before sunset.  Here in the midwest, I've heard a number of east-coast 
> daytimers over the years come booming in around 4 in the afternoon, just 
> before their sunset. On the other side of the coin, when I owned a 
> daytimer on 1570, I remembered being 15 miles away from the tower at 9 in 
> the morning listening to another station in Alabama.  It's not 
> intereference, just physics.
>
> Of course, nowadays, theree are so many stations with some kind of 
> nighttime authorizations that many channels are nothing but a jumble at 
> night.  But stranges conditions may make for interesting DX.  I remember 
> about a year ago or so, with a low in the sunspot cycle, I picked up some 
> low power stations in Florida that suddenly emerged from the usual jumble 
> one night; while some of the normal powerhouse clears vanished from the 
> dial.
>
> FM:  The basic tool for predicting coverage on FM is the Commission's 
> 50/50 chart, which is based on  a series of measurements made long ago 
> creating a set of curves based on an antenna 30 feet above ground.  It is 
> called the 50/50 chart because it represents signal strengths for given 
> powers/ahaat at "50% of the receiver locations 50% of the time."  So if 
> the 50/50 chart predicts that your Class A station should have a 60 dbu 
> signal 17 miles out from your transmitter, if you went out to that point 
> with an FIM, popped your antenna up 30 feet, you might find 1 mv/m signal. 
> Or 1.5 mv/m. Or .75 m/v. And, like Ohio weather, if you didn't like what 
> you saw, you could just wait a few minutes and the reading would change.
>
> Hence your FM station's "contours" are nothing more than "best guesses."
>
> Ducting and Sporadic E are natural phenomena affecting VHF, just as the 
> night to day cycle affects medium wave propagation.
> A friend of mine and former business partner in my FM station has caught 
> FM stations from all over the country from a short tower in his backyard. 
> Including a Class D station out in South Dakota, or Iowa somewhere. Again, 
> if your FM comes crashing down on another station for an hour or two 
> because of ducting, it is technically not interference, but something we 
> live with as FM broadcasters.
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