Prov. shuffle: Rush, Buddy, etc

[Dan.Strassberg]

Yes. I suspect this happened with the old WHDH when it moved to
Needham in 1947 or '48. WHDH's amtenna system uses unequal-height
towers. Going from west to east, the towers are 640', 600', and 560'.
The objective--or so I'm told--was to minimize fading from phasing
between the skywave and groundwave in the primary service area (that
is, close to Boston) at night and during what are now known as
critical hours. Apparently, that part of the design was a failure.
However, the average height of the towers is 186.7 degrees, which is
slightly more than half a wavelength and should produce an RMS
inverse-distance field at 1 km of ~400 mV/m/kW or about 250 mV/m/kW at
1 mile. (The FCC didn't change AM to the metric system until sometime
in the '80s, I believe.) The consulting engineers, apparently feeling
that it would make the client happier if the proofs of performance
showed better performance than had been predicted, perposely
low-balled the predicted coverage. They did this by using the minimum
efficiency for Class I AMs of 225 mV/m/kW at 1 mile. Remember that
WHDH was a Class II station--not a Class I--so an efficiency of 175
mV/m/kW at 1 mile would have been acceptable to the FCC but would have
been a huge disappointment to WHDH, given the tall towers. I'm sure
that the coverage exceeded the consultants' predictions, and so the
Choate family was probably pleased.

However, the Hildreth family, owners of WLAW, which moved to Andover
to Burlington and increased from 5 kW to 50 kW at just about the same
time as WHDH moved from Saugus to Needham and increased from 5 kW to
50 kW. were probably even more pleased. Their consulting engineers had
predicted 175 mV/m/kW at 1 mile, whereas, with the tower height WLAW
used, the number should have been just about 200. I suspect that WLAW
more than met 200, but what was even more interesting was the
impressive coverage of Cape Cod, resulting from the salt water path
that exists once the signal gets through downtown Boston. And it
appears to me that the constraints on the 680 design were more severe
than those on 850. The station was to be licensed to Lawrence, whereas
the Hildreth's real objective was to serve Boston. That virtually
dictated a site midway between the two. The site worked out to be
close to Hanscom Field, which doubtless limited the tower height. I'm
guessing that the fact that the site turned out to be so nearly
perfect was a pleasant surprise to a lot of folks.

As for WHDH, the power increase, coupled with the move to Needham must
have accomplished the Choates' objective of bringing a better signal
to areas west of Boston, but if the Choates expected that their 10x
power increase would produce anything like ten times the former
coverage, they had to be bitterly disappointed. First off, even with a
salt-water path, the finite conductivity keeps the area covered from
increasing in direct proportion to the power. However, WHDH left what
was probably the second-best AM site in New England (WBZ's Hull site
being the best) for a rather average site. On paper, WHDH's Saugus
site must have caused a lot of head scratching. The station was
directional to the east at night, yet its transmitter was east of the
market's major population center. In those days, though, co-channel
interference was minimal at night and non-existent by day, so the 5-kW
night signal probably did OK as far west as Lexington, which must have
been right in the null that protected KOA. And the day signal (which
lives on as WROL) was a killer for 5 kW in a region of such poor soil
conductivity. The reason, of course, is that the signal reached so
much of the market via a salt-water path.

-----
Dan Strassberg (dan.strassberg@att.net)
eFax 1-707-215-6367

----- Original Message ----- 
From: "Laurence Glavin" <lglavin@mail.com>
To: "Dan.Strassberg" <dan.strassberg@att.net>; "Kevin Vahey"
<kvahey@gmail.com>; "David Tomm" <nostaticatall@charter.net>
Cc: "BostonRadio Mailing List"
<boston-radio-interest@rolinin.bostonradio.org>
Sent: Thursday, September 06, 2007 4:58 PM
Subject: Re: Prov. shuffle: Rush, Buddy, etc


>----- Original Message -----
>From: "Dan.Strassberg"
>To: "Kevin Vahey" , "David Tomm"
>Subject: Re: Prov. shuffle: Rush, Buddy, etc
>Date: Thu, 6 Sep 2007 16:38:21 -0400

>WKOX will NEVER have an "at least equivalent" signal to WRKO. WKOX's
>50-kW signal will be roughly equivalent to WWZN's. Except in unusual
>cases (such as where a salt-water path completely changes the story),
>50 kW on 1200 is not 50 kW on 680 (or 850). Also, WWZN uses almost
>200-degree towers, whereas WKOX's new towers in Newton won't even be
>90 degrees. Thus. WKOX will, in effect, be transmitting with about
>half the power that WWZN uses. That 2:1 equivalent-power advantage to
>WWZN will approximately compenstate for WWZN's frequency being ~25%
>higher than WKOX's. From a coverage standpoint, the 50-kW full-time
>AMs in this market fall into three groups: 1) WBZ, 2) WRKO and WEEI,
>3) WWZN and WKOX. In fact, because of its low frequency and good
>transmitter location, WEZE, a 5-kW station, really belongs ahead of
>WWZN and WKOX. Also, because of its lower frequency and superior
>transmitter location, WRKO has better coverage than WEEI--almost
>everywhere.

In your experience, has there ever been a time when, after a CP was
built,
the resultant signal turned out BETTER than what one would conclude
based
on some of the factors listed above: less-than-quarter-wave towers;
less-
than-ideal-soil-conductivity, etc?






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