What if WBZ had gone 500KW????

[Dan.Strassberg]

You'd be surprised at how little improvement in daytime coverage there
would have been. Go to fcc.gov and compare the coverage maps of AMs
that have applied to increase from 5 kW to 50 kW. The increase in the
area within the 0.5 mV/m groundwave contour usually increases by
something on the order of 20%. Of course, the percentage increase
depends on many factors, frequency, soil conductivity, and antenna
efficiency being the most important. The lower the frequency and the
better the conductivity, the greater the percentage increase. In the
case of WBZ and the other Class I AMs that were contemplating
increases to 500 kW or 750 kW, antenna efficiency would not have been
a factor; they were already using very efficient half-wave radiators.
WBZ, being in the middle of the AM band in an area of notoriously poor
conductivity (except for the part that really is salt water), would
probably have achieved a bit less than the average percentage increase
in daytime coverage. For example, would Providence have been inside
the 5 mV/m contour? (5 mV/m is considered city grade for
AM.) Maybe. It would have been a close call. For reasons discussed
below, I don't think Worcester would have received an improved signal
at all.

Meanwhile, the huge power bills would have considerably raised WBZ's
break-even point. In the end, I believe it was the cost of the
improved facilities plus the increased operating cost that caused the
dozen or so US stations that might have received these super-power CPs
to sour on the idea.

Another consideration would have been the effect on co-owned KDKA.
WBZ's nighttime skywave signal would have blown KDKA out of the water
right in the city of Pittsburgh. In all likelihood, WBZ would have had
to use a directional pattern that contained a modest radiation minimum
to the west to protect KDKA. (Could still probably have been done with
two towers that were spaced farther apart than the existing pair.) The
combination of the Tx move to the east--away from Boston--and the
modified DA would actually have resulted in a poorer signal in much of
metro Boston! Can you say "law of unintended consequences?"

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

----- Original Message ----- 
From: "Kevin Vahey" <kvahey@comcast.net>
To: "(newsgroup) Boston-Radio-Interest"
<boston-radio-interest@bostonradio.org>
Sent: Wednesday, November 12, 2008 1:04 AM
Subject: What if WBZ had gone 500KW????


> This discussion we have been having over AM in Europe makes me
> wonder
> what if WBZ had gone to 500KW transmitting from Provincetown which
> was
> being talked about 40 years ago.
>
> What kind of daytime coverage could they have expected? I would
> think
> 500KW would have given a listenable signal as far south as
> Philadelphia and north into Montreal.
>
> Also were other clear channels trying to go to 500KW?