[BC] Class A stations "burning" power

[Dana Puopolo]

Just for clarification, Tom is talking about the AM unattenuated field not
being frequency dependent. When you factor in ground conductivity, 
frequency becomes a major factor in coverage.

-D


------ Original Message ------
Received: Fri, 30 Jun 2006 11:54:05 AM EDT
From: "Thomas G. Osenkowsky" <tosenkowsky at prodigy.net>
To: "Broadcasters' Mailing List" <broadcast at radiolists.net>
Subject: Re: [BC] Class A stations "burning" power

One of the earliest forms of respect I learned at an early
age was sharing. Pass around the J! Anyway, I believe the
confusion here is between Bands and Height. At 550 KHz
a 90 degree radiator will have a physical height of 447.4 feet.
At 1500 KHz a 90 degree radiator will have a physical
height of 164 feet (assuming 100% velocity factor). 50 kw
fed into either radiator, or any 90 degree radiator in the AM
Band will produce the same coverage circle. Changing frequency
without corresponding change in tower height will certainly produce
the field changes Mike describes. This was shown by Ballantine*.

An FM Band station with 50 kw ERP on 88.1 MHz or 107.9 MHz will
likewise produce the same coverage circle. The antenna element lengths
and spacings will be different between frequencies. The AM Band is the AM
Band just as the FM Band is the FM Band. TV service has three Bands.
VHF-Low, VHF-High and UHF. The power necessary to produce the
same coverage will be different because the Bands are different. Frequencies
within the bands are irrelevant, as long as they are IN THE SAME BAND.

* Ballantine demonstrated this by placing a large bottle of Ballantine
Ale on a polar plot and tracing the bottle's bottom with a pencil.

Tom Osenkowsky, CPBE

> Dave,
> What are you smoking this morning?
> 50KW on 1500 is akin to about 2.5 KW at 550 all other things being equal
> (90 deg. radiator, similar condcutivity).
> 50KW on 550 is akin to 1MW on 1500.
> HUGE difference.
> MM
> >As I have said many times if we started over with AM's and gave power
grants
> >based on ground conductivity and coverage area like FM, a 50 kW. on 540
kHz.
> >would have the same coverage as the 50 kW. on 1550 kHz.  Also maybe we
could
> >get rid of so many DA's
> >The 5 kW. on 550 kHz. would have the same coverage circle at the 5 kw. on
> >1590 kHz.
> >Seems only fair????
> >Dave in ranting mode


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