In the ideal dream world a station would own its monitoring sites or have them on easements such as along roadways (on the side, not in the middle of the road), between properties, utility rights of way, public space.
But with as many as 14 monitoring points that would be very hard to arrange.
I imagine the engineering and paperwork to get a monitoring point moved is probably a major hassle.
I'm not in broadcasting, but I love the
topic, and have heard a lot of stories
from my engineer friends.
I guess there used to be a station in the
U.S. with a 14 tower array. That must have
been hard to measure and maintain. I have
heard that the station is still alive and has
fewer towers now, but I'm not sure.
In the town I grew up in, a few miles away -
there was a 1 kW country music daytimer. It had
a 2 1/2 watt presunrise authorization. This was
quite a while back and the station was doing
OK financially. The owner wanted to go to
all talk and be on at night with a complicated
directional pattern (different day and night) and
a large multi-tower array. I have talked about
this station many times, because I worked there.
It's a 6 tower AM station. My friend built it -
as I have mentioned.
But before that - he begged the owners not
to change format and go nighttime. He said -
"I can build you this new transmitter site, but
you shouldn't do it. You will lose all of the
listeners you have now, and you will never
get that amount of listeners back." Also, you
will lose money on the expensive transmitter
site change. And that's exactly what happened.
The station change was a disaster. Since then
it has been through many format changes, with
a lot of callsign changes from lots of different
owners. It's back on now, but I don't know how
long it will last. Before that, it had been off for
a while.
There was another station that went from a relatively
low power (I can't remember) to 10 kW. This was
many years ago. The owner wanted to say this
station, WNLC, 1510, New London, CT - was the
second most powerful AM station in Connecticut.
And it was in terms of transmitter power.
(WTIC in Hartford was #1 in power -
50 kW on 1080.) But most of the transmtting
power went out over the Atlantic ocean, especially at
night, and New London was not covered well - ESPECIALLY
at night. To make things even worse, nearby WMEX in
Boston, also on 1510 - was on the same channel. It fired
north, but still it was a disaster for WNLC. 1500 and 1520
had powerful signals at night from fairly nearby 50 kW
stations. WNLC crumbled - not right away - but after a
while. I have heard other stories like this - and for every story
- I guess some poor engineer had to run around
all over the place with an FSM.
The stories are fun to talk about - but the work
requirements for the engineers was huge, and
my hat is off to these guys. I never would have
been able to do it.
Bruce, Monitoring station (no transmitters now), CT
A lot of Part 15 AM people have mentioned
coverage changes with rainy weather. For
some people, the coverage has increased.
(I guess that's because ground conductivity
increased with the ground full of water.)
For some other people, the rain and water
has detuned the antenna/antenna coil, etc.,
so coverage has gone down.
The best "Part 15" example I have ever
seen took place when I was young, in
1969, or 1970. I put Part 15 in quotes.
I thought I was on 1600 kHz, but the 1600
was a spur from the transmitter or from
the bad RF front end in the radio. In any case,
1600 was the strongest signal - or so I thought.
The dreaded Lafayette Radio "explosive" KT-195
transmitter (many of you will remember what
I mean) OR the AWFUL Korvettes Korsonic
multiband portable - or BOTH - had fooled
me. The strongest transmitting signal was
on 2100 kHz. (What a WEIRD place in the
spectrum.) My friends and I eventually figured
that out, and I kept transmitting there. (I didn't
know any better.) My friend could hear it on
his Knight Kit R-100A receiver. He was about
1/2 mile away, and it was S-7 on the meter.
(I remember that like it was yesterday.)
(Hey! I don't remember ANYTHING from
yesterday! Was it Thursday?)
ANYHOW - and here's my point - my friend
could only get the signal when the ground
outside was soaking wet from the rain.
If it was dry outside - he received nothing
at all, or a very weak signal.
A few other notes - regarding the Lafayette
KT-195 (with it's two 50BM8 vacuum tubes -
and also the dreaded 36AM3B recifier tube) -
- - which I destroyed the first time I turned the
transmitter on because we didn't build it correctly...
Well - anyhow - mine was lost. (We had another one here
at the university for a whlle not too long ago - it was
missing parts and was fried.)
I know a member here (MRAM?) got one on
E-Bay and restored it. He made it electrically
safe and greatly inproved the modulation.
- What a great thing to do!
There are lots of KT-195 stories, mostly
weird/unsafe ones - I'll save for another
time.
I wish I had the Korvettes Korsonic multiband
portable from that time. It didn't work well, but
it was my first shortwave radio, and I heard a lot
of stuff on it. You could sort of say it was my
first "communications" receiver.
As Carl might say - Ï think I'll make a copy
of this message and got out and bury it
in the ground.
Bruce, Monitoring station, CT
In addition to building an outdoor antenna with ground rods and radials, I figure that 10,000 aluminum cans should be neatly covered over with fresh soil and this might be the world's most powerful Part 15 antenna.
Unless the cans don't add to the field strength.
This experiment will require a lot of drinking.
It'd be nice to own the monitoring points, but it's tough enough to own the property for the towers. Generally, if you have a 250 foot tower, for example, you also have 250 foot radials from the base in a wheel spoke pattern, all the way around. Especially if the station was built many years ago with old style engineering. One of the reasons few new AM's come along. We have three towers. It's a pretty big hunk of property, purchased in 1971 for the purpose, in what was then farmland. When I came here to work in 1988 we were still leasing the property from the farmer and he had livestock grazing on the property -- we had to remember to shut the gate before going to the transmitter building lest the critters escape. A couple years later we bought the property, which has quadrupled in value since then.
Monitor points were originally worked out to be on public roads, or very near them. But roads and real estate are in constant flux. Roads move, get re-routed, two lanes become four lanes, bridges get replaced and relocated. What was open land become housing projects, farm houses, and I know one engineer who has a monitoring point that is now in an exercise yard at a state prison! Yes, you can get them changed, but the engineering work is quite expensive and the FCC paperwork ain't cheap either. Usually if you have one that's nearly impossible to use, if you work at it, you can find a new spot along the same heading that's a bit closer to the tower. If you still come in under the limit you're generally considered to be OK, since being closer on the same heading would make the signal stronger than it would be at the further, correct point. For our night signal, 3 points are measured in nulls and one in a lobe.
Other weird things can happen too, like if someone puts up a big metal Morton Building (or as some call 'em a "pole shed" with long metal sides, that's positioned just right in relation to your monitoring point, signal can reflect off it to you and give you a false high reading!
The field where our towers are is generally kept clear of trees and anything more than field grass and daisies. But we had one owner who let it go for years and up here in northern Minnesota pine trees grow like weeds. We had dozens of 8-15 foot trees on the property and our contract engineer (the guy we call when I can't fix something) said we were losing signal with the trees near the towers draining signal off to ground before it even got off the property. We hired a guy to chop all the trees, and I did field strength readings before and after and it did make a small but readily measurable difference! And ya can't pull the trees out of the ground, gotta saw 'em off even with the ground so you don't screw up a ground radial!
Tim in Bovey