[BC] Off Frequency Measurements...

[Burt I. Weiner]

A couple of years ago I was tuning across the band and heard a low 
frequency tone and decided, just out of curiosity of course, to 
investigate.  It turned out to be a station about 75 miles away was 
256 Hz high with their shiny new DX-10.  They were not a client but I 
felt obligate to call and let them know.  I got hold of the chief who 
happened to be a fellow I know.  He found a "solder splash" across 
the trimmer capacitor used for tweaking the frequency.  They are now a client.

One of my receivers is a Hewlett Packard 3586B that tunes from 10 Hz 
to 32 MHz continuous and has a GPS reference.  It's basically a fancy 
SSB receiver with I.F. filters of 20 Hz, 400 Hz and 3.1 kHz 
wide.  One of the neat features of being a SSB receiver is that when 
you hear a low frequency tone like that you can tune and see which 
station sounds like mis-tuned SSB and then tune it in.  The receiver 
will tell you precisely where it's tuned and then you can count the 
frequency to the nearest tenth-Hertz (cycle) using the 20 Hz filter, 
which is really more like about 15 Hz wide.

Burt

At 11:44 AM 3/21/2007, you wrote:
>Subject: Re: [BC] Frequency Measuring
>To: broadcast at radiolists.net
>Message-ID: <be8.12b868b2.3332761e at aol.com>
>Content-Type: text/plain; charset="US-ASCII"
>
>
>In a message dated 03/20/2007 05:30:52 PM Eastern Standard Time,
>tosenkowsky at prodigy.net writes:
>
> > As I was driving towards the station, I heard the "tone". I
> >  figured it was the Cubans. When Clarence called he had me
> >  play the cart several times. This was unusual. He then asked
> >  if I did any work on the transmitter. We were +420 Hz! That
> >  was the tone! He explained that the old freq meters would go
> >  to zero on overtones (above 40 Hz, I believe). So indeed he
> >  was able to receive a 5kW 1380 KHz Naugatuck, CT station
> >  in Mass.
>
>That's quite the "tone", alright! ;)
>
>When we first got our new transmitter, the *only* thing I didn't think to
>check was the frequency. Since everything was fine getting it on the 
>air, we we
>re
>just humming along every day for about a week. One Saturday morning, our
>Part-Timer got a call. It was the FCC, Belfast Maine monitoring 
>station. I came
>
>down to the station and fired-up our old TX into the dummy load. (I 
>knew it was
>
>very close to 5Hz high.) Using the FIM in just the right place, I could
>clearly see the heterodyne when I got the new TX closer to the old. 
>I got them
>as
>close to zero-beat as I could.
>
>The following Monday, I called the phone number the guy left with our PT'er.
>I told him who I was, and that i had made the adjustment later that same day.
>He said, "Hold on a second. OK, looks good."
>
>We were 23Hz off freq.
>
>Normally, I keep us running about 5Hz above WTWP. Why? The low freq flutter
>is far less annoying than a gradual zero-beat. It's quick enough 
>that most AGC
>circuits aren't too bothered by it, and it's low enough that most receivers
>won't reproduce it.
>
>Willie...

Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California  U.S.A.
biwa at earthlink.net
K6OQK