[BC] FCC Modulation measurements

[Joe Rother]

I was a contractor for a small AM in Ohio several years ago when they got a
surprise inspection. The inspector found several issues in the stations PI
file including the fact that they never assigned a CO, and the station had
not kept up with the EAS box (It had been out of paper for an extended
period, and they weren't sending tests). Then the inspector asked to see the
transmitter site. I rode along with him in his explorer, and I saw the
system in action. He was DFing the station while we were driving, and It was
very accurate. IIRC the system he showed me had a touch screen that
controlled the DF with GPS mapping and a Spectrum analyzer all tied into the
Icom receiver. He mentioned the fiberglass roof, and the antenna that as I
understood was a loop antenna laid flat, and had several taps off of it that
allowed it to DF. Other than the touch screen and Icom screen mounted down
low on the hump between the front seats, you couldn't see anything that made
the vehicle stand out. I always assumed that the rest of the Icom, and the
computer that fed the touch screen were in the back somewhere. The Icom
sounded very broad, but I noticed that about every second or so the audio
would drop very briefly. He said that it had to do with the way the antenna
scanned to be able to DF.

When we got to the tower site we went in, he stood back and looked at all of
the equipment briefly, never checked any measurements, or asked any
questions. Then he drove me back to the studio site.

I always suspected that he saw the Optimod 9200 at the studio feeding the
STL, and he suspected that there was nothing else at the tower site between
the STL and transmitter to meet NRSC. (I had an inovonics 222 that I used as
a 10Khz low pass filter on the transmitter)

Joe

-----Original Message-----
From: broadcast-bounces at radiolists.net
[mailto:broadcast-bounces at radiolists.net]On Behalf Of Dana Puopolo
Sent: Wednesday, October 03, 2007 9:04 PM
To: Broadcasters' Mailing List
Subject: Re: [BC] FCC Modulation measurements

15 years ago, I went to the FCC office in Quincy, MA to pick up a form. Vic
was there and he saw that I had my 2 way walkie with me. He said to me
"check
this out"  We went back into their radio room and he asked me for my radio.
It
was a modified Heath/Standard walkie and was on (oh oh) WHDH's 2 way
repeater
frequency (I was CE at the time). He looked, grinned at me (He knew!),
punched
the frequency into a computer keyboard and pushed the transmit button.
IMMEDIATELY, the screen on the computer popped up and showed a map with a
mark-right where we were!  THEN he hit a function key and this funny looking
trace appeared. He smiled and said, "This is our newest tracking system. It
works immediately!".
And that-he pointed to the screen-is the fingerprint of your radio's
transmitter! No two are exactly the same.

He told me that they used three sites (including one right where they
are-they
are on a big hill-not by accident!) and it was accurate to better than 100
feet.

I was blown away.

NOW, I understand they can use this capability from their Explorers...

-D