[Boatanchors] Short Wave Broadcasts

[Sheldon Daitch]

Richard,

I can't speak for how the west coast VOA operations ran their ISB transmitters, but the Greenville ISB transmitters always ran a slight bit of carrier, roughly 200 watts or so - that seems to be the number I remember.

The original ISB complement at Greenville was four GPT-10Ks and at some point upgraded to GPT-40Ks.  The original exciters were the SBE units and by 1979, they had been retired and replaced with the MMX-2 series.  For TMC purists, I don't know what exact models were involved, my tuning notes don't make any mention of the specific model.  

At some point, there were two Continental ISB transmitters moved to Greenville, from the west coast, and they were installed in the old location where GA-7 and GB-7, the location of the left most of the Gate HF-50Cs, and had some limited life.

Bethany, Delano and Dixon no doubt were fed with AT&T long line circuits - Greenville, to the best of my knowledge, always had the Washington to Greenville microwave system for program feed, until it was replaced by the satellite circuits.

There was no audio processing between Washington studios and the Greenville transmitter plants, until the TX plants and when I left Greenville, we were using the Urei units, again, I can't remember the model, but probably 1176, based on a review of some on-line photos.

Currently, we are using Orban processors at almost all locations - different models, whether the transmitter is MW, HF or FM.

73
Sheldon
________________________________________
From: Richard Knoppow <1oldlens1 at ix.netcom.com>
Sent: Saturday, April 19, 2014 6:48 PM
To: Sheldon Daitch; Rob Atkinson; Boat Anchors List
Subject: Re: [Boatanchors] Short Wave Broadcasts

----- Original Message -----
From: "Sheldon Daitch" <SDAITCH at bbg.gov>
To: "Rob Atkinson" <ranchorobbo at gmail.com>; "Boat Anchors
List" <boatanchors at mailman.qth.net>
Sent: Saturday, April 19, 2014 1:23 AM
Subject: Re: [Boatanchors] Short Wave Broadcasts


Rob,

wish we had had this discussion 25 years ago, and I could
have checked the AME signals from Greenville for audio
quality.

Remember, too, for the VOA use, those AME transmissions were
for program feeder service and the receivers were not AM
receivers, but SSB receivers - almost always the RCA SSB-R3
series in the latter years.

VOA isn't the only user of the curtain arrays, but I agree,
they are on the expensive side.

Formerly WSHB and now WHRI, near Cypress Creek, SC
32°40'47"N   81°7'53"W appears to have a few curtain arrays,
actually, 12, per their web site:

http://www.whr.org/Technical-Information.cfm

73
Sheldon

     Along with Leonard Kahn's system for transmitting
sideband signals on AM transmitters he also developed the
technology of synchronous detectors for DSB signals. These
will yield low distortion output from an AM signal
regardless of whether the carrier is there or not. A low
level carrier can be transmitted as as pilot to synchronize
a local oscillator but the synchronous detector synchronizes
on the basis if the comparative phase of the sidebands.  It
can't work for a SSB signal although would probably lock on
a low level carrier if present.  The double sidband and
synchronous detectors would have worked well for relay use.
I do remember hearing VOA relay stations who used SSB. They
may have had a pilot carrier, I don't remember. The audio
quality of the VOA stations I remember (and I listened a
lot) was fairly good but usually had heavy processing plus
many were fed through the AT&T network and had the usual
distortion one could hear on domestic radio networks on long
lines.
     I certainly heard the Greenville station but the
strongest here were those at Dixon and Delano California. I
saw the curtain antenna at Delano several years ago when
driving to Sacramento. I wanted to visit but my lady friend
was very single minded.  Too bad.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com