750 CP's

Dave Doherty dave@skywaves.net
Thu Jun 4 21:57:14 EDT 2009

Hi Dan-

The old Class 1-A clears were originally protected by virtue of having no 
other stations operating at night on their frequencies. I believe that was 
the NARBA language, but it was definitely in the FCC rules way back when. 
Once we abrogated NARBA, the standard treaty obligations protecting service 
only on home soil came into play.

And yes, the FM rules are the same. I do a lot of work in the border areas, 
sometimes with near-miraculous results.

-Dave Doherty
 Skywaves Consulting LLC
 PO Box 4
 Millbury, MA 01527
 202-370-6357 (DC)

----- Original Message ----- 
From: "Dan.Strassberg" <dan.strassberg@att.net>
To: "Sid Schweiger" <sid@wrko.com>; <bri@bostonradio.org>
Sent: Thursday, June 04, 2009 8:58 PM
Subject: Re: 750 CP's

> WJIB is a US Class D AM on a Canadian Class A channel. There are many
> such stations, but as a group, they constitute a special class as a
> result of stations of all classes in North America (I think this
> applies to FMs as well as AMs) now receiving protection within their
> normally protected contours only over land that lies within their
> national borders. The reason these US Class Ds can now operate at
> night, albeit in most cases with very low power, whereas they
> previously had to sign off at local sunset, is that Class A AMs used
> to receive protection within their 0.5 mV/m 50% skywave contours even
> when those contours extended into areas outside the Class As' national
> borders.
> The Toronto Class A (CFZM? ex-CBL) delivers a 0.5 mV/m 50% skywave
> signal hundreds of miles to the southwest of Boston. That's the
> contour that would receive protection of it were in Canada. As it is,
> the contour covers many thousands of square miles of US land where it
> no longer has to receive protection. However, WJIB must protect the
> point of land where this contour intersects the Canada/US border.
> Thus, WJIB could, indeed, increase its night power quite substantially
> if Bob wanted to spend millions of dollars to install a sufficiently
> complex directional antenna--assuming he could find land on which to
> construct it.
> In theory, WJIB could run perhaps 50W at night (give or take) if Bob
> wanted to pay rent to American Tower systems to use its towers at the
> WWDJ/WAZN site in Lexington. A two-tower array for 740 that protected
> the Canada/US border could be constructed using the tall (FM) tower
> and one of the AM towers. That array could limit the signal toward
> Canada to the equivalent of 5W ND over a substantial arc while
> delivering the equivalent of perhaps 80W ND over Belmont and parts of
> Watertown and Cambridge. Since WJIB would still be restricted to using
> much less than 250W at night, it would remain a Class D, meaning that
> it would not have to deliver an NIF signal to any of its CoL,
> Cambridge--and it probably wouldn't do so. But the densly populated
> area within a mile or so of the WJIB tower that currently receives
> pretty good signal at night would no longer do so because the
> transmitter would have moved further away.
> And it would be an expensive project. The FM tower would have to be
> skirted; it is a grounded-base tower, so a so-called Folded Unipole AM
> antenna would have to be installed on it and a ground system would
> have to be installed around the tower base. The expense and the
> problems don't stop there, though. Two stations, WWDJ and WAZN,
> already use the site, so the filtering problems would be quite
> complex. And the site is only a couple of miles from 50-kW WWZN.
> Filtering that enormous signal would be a huge headache. And remember,
> the second harmonic of 740 is 1480, only 10 kHz from WAZN. I hope
> that anyone who thinks this project might be practical knows how to
> pronounce engineering nightmare.
> -----
> Dan Strassberg (dan.strassberg@att.net)
> eFax 1-707-215-6367
> ----- Original Message ----- 
> From: "Sid Schweiger" <sid@wrko.com>
> To: <bri@bostonradio.org>
> Sent: Thursday, June 04, 2009 2:34 PM
> Subject: RE: 750 CP's
>>>it sounds like this applies to every station
> indiscriminately.  Apparently WJIB, with its 5-watt nighttime signal,
> can't make any transmitter upgrades without degrading its night
> signal.  Nor can WBZ, with its 50,000 watts clear-channel.  Does this
> really make sense?<<
> WJIB would certainly be able to show the Friendly Cookie Company that
> ratcheting back its nighttime signal would have close to zero effect
> on any other co- or adjacent-channel signal.  I can't say if a waiver
> of the ratcheting policy has ever been granted, but that doesn't mean
> they couldn't try.  Waivers are granted at the FCC for all kinds of
> reasons.
> Sid Schweiger
> IT Manager, Entercom New England
> 20 Guest St / 3d Floor
> Brighton MA  02135-2040

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