On Sep 8, 9:49 pm, "David Eduardo" wrote:
"Telamon" wrote in message

...



OK, maybe I frame questions badly. Radio waves are EM waves where the
volts per meter (V/m) is a measurement of the E field. You could
measure similar for the magnetic field (H/m) since in a far field the
energy is equal in the E and H fields. Since radios waves are the same
thing as light waves where photons that have no mass are the carries of
or direct these fields. The E field measured as V/m is just a vector
and if the terms are squared so that the area is considered
perpendicular to the direction of travel and you also take in account
the impedance of free space you can then calculate the power of that EM
wave per meter squared at some distance from the tower.

I doubt if one broadcast engineer in a thousand could state that. At radio
stations, we are talking about 10% theory and 90% practical aplication... if
that. It is beyond any practical application, photons and all.

What you have to understand is that the heavey hitting is done by consulting
engineers, who will design the directional systems and even put together
most FCC applications. The station engineers often do not even install DAs,
and are somewhat like the contractor who gets designs from an architect; we
do not know why a certain mixs of concreat, or diameter or rebar or specific
sort of I-beam is specified, but we know how to build from the design specs
and make it work.

Again, what is important to a station engineer is to comply with the license
and the rules. DAs must have the right null depth. Occupied bandwidth,
harmonic separation, s/n, THD and such must meet FCC requrements. And when
all else is done, there must be "good engineering practice" ranging from
proper grounding, well dressed cable, interlocks functioning, fences around
tower bases, etc.

The objective is keeping the licensed facility operating within the maximum
parameters of the license so that management can program and sell
advertising and the owners can make a profit. Some of us have built
transmitters, exciters, processers, but most of us use stuff right out of
texts and the NAB or even ARRL handbooks, not new designs. Those who do
create new designs go on to be equipment manufacturers like Frank Foti of
processing fame or the late John Pate who created remote control and audio
devices after being a CE at WSM, Nashville Network, WERC (where I worked
with him) and WMCA.

Our use of signal strength is primarily to know if we are operating legally.
Management uses it to know where they can expect, if programming is right,
to get audiences... and where they can't.



So from this the lines on the broadcast maps are not a boundary where
on one side you have good and on the other side poor reception.

If you think I said that, I appologize. I said most measured FM listening,
for example, was inside the 64 dBu contour. In fact, 80% is in the 70 dBu
contour and another 15% in the area between that and the 64. Obviously,
population density is a factor in each area... a rimshot like KQMR and KOMR
in Phoenix get about 80% of their listening between the 70 and the 64
because the 70's on each of these cover mostly desert... but the rule stands
on the average station... given equal population density, reported listening
falls off as the signal falls below 70 dBu and is almost non-existent by the
time you get to the 64. Is that clearer?

Also obvious, but apparently not understood is the fact that listening data
is granular only to the ZIP code level. Some ZIPS may be bisected by one of
these contours. and some may have a 70 dBu in one part and, behind a hill,
nothing. So the studies I have done and those I have seen elsewhere tend to
take data from multiple ratings periods, such as a year, and look for total
diary counts over such a period. And no matter how many years of data you
analyze, there is pretty much no listening beyond the signal intensity
levels I have mentioned.

This is not a matter of having contours mean that there are abosolutes, like
moats in the sky, but that a station will certainly not spend money to put
up billboards or do promotional events in areas where the signal is not good
enough to get listenership. This is what I mean by programmers and managers
looking at signal contours to see where there is potential for audience
generation and where all efforts will be useless.

We don't spend a lot of time on photons and light waves. It's knowledge that
does not contribute to the business and can really be distracting.

The
energy of the EM wave falls off as a square of the distance in theory
(but somewhat more in reality due to other factors) and so these lines
do not behave as if they are some kind of demographic line as your
posts appear to indicate.

Gee, you mean you have to quadruple the power to double the coverage area?
How amazing. I think I learned that when I was about 13. The ´practical
application of this is to demonstrate to the non-technical manager (about
99.9% of them) that raising the power by 10% will probably not be cost
effective... 50% maybe, depending on population, and by even more, likely.. I
remember the expectations of the non technical staff at our New York FM when
we went from 610 to 660 watts on the ESB... somehow they thought they would
get 10% more coverage.



Theoretical hand waving aside the empirical data I posted that you
rejected out of hand from an expensive receiver was used by me because
it has a good linear power meter. Readings from it show the relative
field power received from a single turn interior loop antenna of low
gain. In addition I related those readings to a hand held portable
radio used indoors. In addition to that I also compared the reception
of a car radio. Only good reception on all three counted toward the
number of stations I considered as strong noise/interference free
stations as measured in broad daylight. My recollection was you stated
everyone had on average three stations and I reported something like 11
or 13.

And my point is that there is little listening to many of the stations you
cited as recievable. This is because they are not at a level that the
average listener finds to be "listenable" and they do not use the stations.
You might be interested in a site run by one of the engineering firms (that
produces software for coverage contours, interference studies, etc) that
shows field strength by ZIP code for the entire USA: There is an enormous
correlation between ratings data and these calculated contours in each
place.

http://www.v-soft.com/ZipSignal/default.htm



I hope this sheds some light on how your posting behavior looks to me.
It's not good and most other people reading the news group are of the
same opinion.

The only difference is that radio broadcasting is a practical application of
technology, not a place where theory is examined daily.

It seems to be a place where you examine your navel daily.