John and Gene and team,

My commentary will dance around a bit, no particular order.

For Gene and those proposed VOA ISB systems, I suspect the intent in that day was to go with

Harris systems, most probably Harris RF-590A receivers, RF-595A1 ISB option, the RF-575 diversity

combiner and RF-591A Pre/postselector.

Most of the VOA receiver sites, by the early 1970s or so, had upgraded to the RCA SSB R-3 receiver

systems. Greenville C Site had 8 of these two-rack receivers. These RCA receivers could not do frequency

diversity, only space diversity, with two RF sections fed from two different antennas.

Greenville C Site did have one diversity receiving system which we kept on WWV, not an RCA system

but apparently something from previous days of diversity operations, using two Racal RA-17 receivers

feeding what I recall was a Pioneer Diversity Combiner. Not the Pioneer of Japan. One receiver was

probably on 15MHz the second was probably on 10MHz so we had reasonable WWV reception any time

of day.

The VOA museum has a display General Electric Single Sideband Selection Model 4SR1S1, said to have

been from the Munich receiver site, near Überacker.

I never saw any of these GE units at any of the other stations.

I do know that there were several RF-590A receivers purchased for use at several of the "newer"

VOA sites, probably Morocco and Thailand, maybe with the ISB combiner. I just don't remember

exactly the configurations installed. While they could have been used for program feeds,

considering they were at the same location as the transmitters, successfully receiving programs

from VOA sites, especially in the United States, could have been interesting, considering the

transmitters at those sites. The station staff probably used them more to monitor the on-site

transmitters.

As for the ISB feeders, my personal knowledge for the older TMC systems will be limited to what

was installed at Greenville. The original TMC installations had two GPT-10s at each site, A Site and

B Site and they were located on either side of the shift supervisor's office. That would have been

1962 or so, Later, VOA needed/wanted higher power on the feeder circuits, and upgraded the TMCs

to GPT-40s, with the additional of the 40KW amplifier unit. Because these transmitters were too

large to fit in the space used for the GPT-10 locations, the transmitters were moved out into the

rear of the building, near the GA-3 and GB-3 Continental 420A power vaults.

The TMCs at Greenville originally had the TMC SBE-1/SBE-3 exciters, and please, I just don't know

what specific version was installed, and at some point, the systems were upgraded with TMC

MMX-2. Neither site was using the older SBE units by 1979.

As John noted regarding the wider audio on the ISB feeders, I am sure all of TMC exciters had

that wideband filter option.

At some point, after the three Gates/Harris HF-50Cs were removed from each site at Greenville,

one of the spaces which opened up was filled with a Continental SSB transmitter and I believe

there was a transition to the Harris RF-1310A series exciters.

Oh, jumping back to those Gates/Harris HF-50C transmitters, there were several Kahn built

units which would allow these transmitters to operate full carrier with one side band. This allowed

VOA to operate these transmitters on the utility frequencies as "SSB" transmitters, where standard

AM transmission was not allowed.

When Morocco and Thailand were built, each site had a Continental 616A1 which used the Harris

RF-1310A exciter. Morocco closed in 2008 and I have no idea what happened with that system.

The Continental 616A1 with the Harris exciter was still in place in Thailand when I was there a

few years ago.

Looking at some old photos taken at the Baguio (Philippines) receiver site from the early 1950s,

SP-600s were used as the receivers in the diversity systems. I cannot tell what the diversity

combiners were from the photographs, but it also appears that in those racks, three SP-600s

were used, possibly with some degree of frequency diversity. There were also several R-388

receivers use, but I am not sure of the purpose.

I am guessing but I suspect by the 1970s, all of those systems were gone and replaced with the

RCA SSB-3 receiver systems. The earthquake of 1990 centered in the Baguio area pretty much

was the death toll for that receiver site and while the techs did major work in getting the

receiver site back in operation, the satellite distribution network was already on the horizon.

And more background, VOA had already started a transition from the HF ISB feeds to

commercial cable circuits. I don't know the entire network but I do recall there were four

program grade circuits to Kavala and Rhodes, both in Greece and four program circuits to

Philippines. The ISB HF feeds were both a backup for the commercial cable circuits and

for additional program feeds when a transmitter site needed more than four programs

on the air.

In regards to the BBC feeders, into the early 1980s, VOA ran BBC World Service English on

Greenville transmitters and BBC Spanish on Delano and maybe Bethany transmitters. All of

the program audio was received over-the-air at the Greenville Site C receiver site and

English sent over to the two transmitter sites. The Spanish went up the microwave to

Washington and then over to Delano and again, maybe Bethany.

An anecdotal story and I wasn't working that shift, but the shift supervisor responsible for

selecting the program feeds from the receivers was tuning around looking for some

BBC feeds because of less-than-optimum, ran across what he thought was a new BBC

frequency and tuned up one of the RCA receivers and put that audio on the air. Oops.

it was one of the Greenville transmitters and we had a few moments of feedback as the

program.

Another anecdotal story, but one from me. I was in Vietnam in the early 1970s and had a

portable shortwave receiver and I would listen to VOA. I didn't know anything much about

the VOA transmitter sites and nothing about the HF feeder network. I would be listening

to fairly strong signals but was amazed at hearing the effects of signal fading on the audio,

but the carrier of the signal I was listening to was pretty good. Once I understood the

HF feeder network I understood that the audio fading was no doubt due to the fading

between the United States transmitters and the receiver site at Baguio, but the strong

signals was because I was listening to one of the Philippines VOA transmitters. And

never thought that 20 years later, I'd be in the buildings where those transmitters were

operating.

I am sure there are some other things that are floating around in my 77-year old read

only memory system.

Sheldon

WA4MZZ

On Wednesday, February 4, 2026 at 10:17:02 AM EST, John Vendely <[email protected]> wrote:

Howdy,

Fascinating story, and interesting that VOA was planning a new HF feeder system at that late date. I often listened to the VOA via the HF ISB feeders from the Greenville, NC and Bethany, OH sites, which relayed programs to the overseas transmitter sites. Broadcast-quality in two 6 kc wide sidebands, with reduced-level pilot-carrier AFC with the receivers phaselocked to the transmit pilot carrier. I recall hearing VOA live coverage of the Republican and Democrat conventions in the Carter/Reagan presidential race. Commentary in English was on one sideband, in Russian on the other sideband. There were once a number of these HF broadcast feeders, and BBC also had some for their World Service. VOA's broadcast feeders eventually went totally satcom, and the HF-ISB feeders were taken off the air in 1994. The transmitters and receivers were retained for some years, "just in case"...

73,

John K9WT

On 2/3/2026 5:07 PM, Gene Smar wrote:

In the late 1980s, I worked on specifying the design for a VOA relay station that was to have been built in the Negev Desert in Israel. The intended target audience was all of the -stans in southern Asia. It was being built to counter the jamming currently being perpetrated by the then Soviet Union.

The gummint requirements included a couple of 2-ISB HF transceivers (other than Collins, I'm sure) at the Negev site to receive data and programming from the main transmit location in the US. These radios, plus very large LPDAs, were backups to the satellite earth station that was the primary method to receive programming. I'd never heard of ISB until then; I've since learned that AT&T/Bell used similar tech for its analog microwave transmission systems beginning in the 1950s.

BTW - The Negev station never got built. Mr. Gorbachev's "glasnost" programs turned off the jammers, so the need disappeared in 1989 or so.

73 de

Gene Smar AD3F

On Tuesday, February 3, 2026 at 04:44:08 PM EST, John Vendely <[email protected]> wrote:

Howdy,

Multichannel 2-ISB and 4-ISB HF systems were pretty common from the late 50s through the early 2000s. The Navy had numerous 4-ISB systems for multichannel data using TMC equipment, and AT&T and others had overseas telephone systems in use into the late 1990s using Harris RF-740M 4-ISB transmitters. With the proliferation of satcom, HF ISB systems are less common today, but you can still find 2-channel ISB systems carrying Link 11. In the Gemini and Apollo space programs, NASA used TMC 4-ISB TSTE-10K transmitters and DDR-506 receivers with 1200 baud modems for passing mission control data to and from the Range and Instrumentation Ships in the NASA Ground Network. These were in use from 1964 to 1980 when they were replaced with the Collins HF-80 system.

Originally, 4-ISB was accomplished with wideband ISB equipment having two 6 kc or 7.5 kc sidebands and used baseband multiplexers to provide 4 voice bandwidth channels within the two sidebands. By the mid 1960s, 4-ISB radios eliminated the need for the baseband multiplexers. Collins, Harris, TMC, RACAL, Sunair, and others made 4-ISB HF equipment. Around 2004, Sunair displayed a 4-ISB HF system at the Melbourne, FL hamfest. The Sunair guy told me they were used in long-distance telephone systems in South America.

73,

John K9WT

On 2/3/2026 3:40 PM, Ray Fantini via Milsurplus wrote:

Have the documentation on the 851S-1 and from looking at that it appears a lot of the same cards are used in both. The 8054 receiver in the video only has a 100Hz step via the front panel but allows you to move in 10 Hz increments by remote control and they do have an option of 1 Hz on that family of products. Yes, for band cursing nothing beats a knob! Think that’s my biggest complaint about the Harris RF-350K family is it’s a real drag tuning around with them. Have the Harris R-2368 for RTTY but the companion exciter, the RF-1310 has to have frequency manually entered and that’s a real drag. Also the Harris Falcon stuff is far from soring when it comes to band cursing. Just goes to show the difference in mind sets between military and commercial think and Ham use.

Along those lines, the 8054 has four independent side band cards, upper, lower upper upper and lower lower. Use to seeing things like the General Dynamics R-1051 sets with independent USB/LSB and know of applications where two audio streams were carried at the same time but have to wonder if there were any four channel Collins links established? Maybe up north or something? I know it will cheese of all the Collins people out there but the entire HF-80 line always looked a bit like telephone carrier equipment to me.

Ray F/KA3EKH

From: W2HX <[email protected]>
Sent: Tuesday, February 3, 2026 2:42 PM
To: [email protected]; Ray Fantini <[email protected]>; [email protected]; [email protected]
Subject: RE: HF-80 video

Very nice! I have that receiver along with a 1KW transmitter setup. My plan, however, is to replace the receiver with an 851S-1 I bought. That way you get the VFO. I like to have a VFO on my receivers (at least). Find a station and then punch that into the transmitter (if controlled separately).

73 Eugene W2HX/4
My Youtube Channel: https://www.youtube.com/@w2hx/videos

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