Re: Walter's Telephones [Telecom]
- From: "harold@xxxxxxxxxxxxxxx" <harold@xxxxxxxxxxxxxxx>
- Date: Mon, 27 Jul 2009 01:07:08 -0400 (EDT)
***** Moderator's Note *****
Since many (most?) transmitters were controlled by voltages that were
simplexed on the audio pair, I think the FCC's logic was that if the
audio pair was cut or damaged, there'd be nothing to broadcast anyway.
Bill Horne
None of the stations I worked with put their control on their program
line. The program lines were generally driven with a WE 111C
transformer to drop the 600 ohm source resistance (studio equipment)
down to 150 ohms to drive the line. Another 111C converted it back to
600 ohms at the transmitter. There was then an equalizer (parallel
resonant LC with a series pot) across the transmitter site transformer
secondary. That then drove the transmitter site equipment (typically
an audio limiter).
Control was generally on another pair (or two). The first system I
worked with was a Gates RDC-10. It used different voltages and
polarities on each wire of the pair to ground. One wire was held at a
constant voltage by the RDC-10 "filament" switch. At the transmitter
site, relays and steppers would interpret the control signal and send
the metering sample back on a second telco pair. During my first FCC
inspection, the inspector shorted out the control line and told me the
transmitter was supposed to drop. I pointed out that the rule said
"line faults causing loss of transmitter control" were required to
shut the transmitter down. I then turned off the RDC-10 filament
switch, and the transmitter went off. So, we still had transmitter
control.
The next remote control I worked with was the Moseley WRC25, or
something like that. It used vacuum tube circuitry to put dial pulses
(tone pulses) and other control tones on a single pair to the
transmitter site. There, the tones were detected, drove a stepper that
sent DC sample voltages back on the same pair for indication on an
analog meter at the studio.
Next came the Moseley PBR-15 and TRC-15, which continued to use tone
for control, but also returned metering as another tone on the same
telco pair. These could also be used on STL, FM, or AM subcarriers
(for AM, it was in the 20Hz to 25Hz area).
Harold
(author of the NAB Engineering Handbook chapter on transmission
control systems)
***** Moderator's Note *****
Never let it be said that I can't take a hint.
.
- Follow-Ups:
- Re: Walter's Telephones [Telecom]
- From: David Lesher
- Re: Walter's Telephones [Telecom]
- References:
- Re: Walter's Telephones [Telecom]
- From: Neal McLain
- Re: Walter's Telephones [Telecom]
- From: T
- Re: Walter's Telephones [Telecom]
- From: Robert Bonomi
- Re: Walter's Telephones [Telecom]
- From: harold@xxxxxxxxxxxxxxx
- Re: Walter's Telephones [Telecom]
- From: harold@xxxxxxxxxxxxxxx
- Re: Walter's Telephones [Telecom]
- Prev by Date: Re: Walter's Telephones [Telecom]
- Next by Date: Re: Walter's Telephones [Telecom]
- Previous by thread: Re: Walter's Telephones [Telecom]
- Next by thread: Re: Walter's Telephones [Telecom]
- Index(es):
Relevant Pages
|
Loading
