SSB Broadcast

[RadioFan2J3]

I remember those transmissions…weren’t they from the Greenville “C” site that was used solely for program routing and feeders, as opposed to the standard AM modulation at the “A” and “B” sites? Audio was quite good, though as they were ISB you had to have a receiver that could separately tune each sideband. Otherwise you’d hear a mix of two different programs!

Greenville C Site did all the program routing for the transmitters but those four, later six, ISB transmitters were out at the two transmitter sites, A Site and B Site.

The four original ISB transmitters were TMC GPT-10 units and later, sometime in the mid-1960s, updated to GPT-40 units with the addition of the 40 kW PEP amplifiers. The transmitters were also moved from the original locations on each side of the shift supervisor's office to the back hall area near the power vaults for the Continental 420A transmitters.

At some point in the early 1980s, when the four newest 500kW transmitters were installed, the old Gates HF-50C units, six total, were removed and position #9 at each transmitter site was then filled with a Continental 617A SSB transmitter. At the time, all of the ISB transmitters used TMC MMX-2 exciters with the wideband audio filter options.

I think Greenville may have one or more Harris ISB exciters, a little newer vintage in the GB-9 transmitter. Been a long time since I've actually looked.

True, but you need a receiver that is rock stable and precisely tunable. If the tuning is slightly off, the pitch of spoken word content will change while still being intelligible. However the harmonic relationships in music will be completely thrown off, resulting in a dissonant mess.

You are absolutely correct. But the RCA receivers, SSB-R3 systems and even the previous systems using the Pioneer SSB adaptors, used the reduced carrier of the transmitter to maintain that precise tuning.

That also reminded me of a program we used to monitor at Greenville and feed up to Washington on the microwave system, a program from ERT. The transmission network which ERT used between the studio and the transmitter site appeared to be a frequency division multiple system but it was not synchronized and there was a hertz or two difference between the TX multiple and the RX multiple. That frequency offset was not enough to affect spoken word content, but did mess with the music. I found that by unlocking the RCA receiver from the AFC circuit, I could mistune the receiver and get the program back to the correct audio frequency relationship and make it sound better, but the RCA drifted a little too much and it wasn't worth the effort to keep playing with the PTO setting. The Greek service in DC didn't seem to care, one way or the other, so I quit worrying about it.

 

[gr8oldies]

I seem to remember, from the cobwebs and dark recesses of my mind, that Radio Nederland used an IFB feed to send newscasts from Hilversum to Bonaire (the other programming was sent in advance on tape). Sometimes poor propaganda meant for a newscast with a lot of fading.

 

[KeithE4]

Sometimes poor propaganda meant for a newscast with a lot of fading.

I take it you meant "propagation." The content of the newscast wouldn't have anything to do with reception.

 

[Mediafrog+]

I seem to remember, from the cobwebs and dark recesses of my mind, that Radio Nederland used an IFB feed to send newscasts from Hilversum to Bonaire (the other programming was sent in advance on tape). Sometimes poor propaganda meant for a newscast with a lot of fading.

That was prior to the late 1970s when a satellite link became available for feeding all programming to the relay stations.

Before that in the 1970s, perishable programming, such as news and current affairs, was sent by a shortwave SSB link shortly before airtime.

In the 1960s the newscasts were fed from the Lopik home site with the same transmitters the rest of RNW programming employed. These were grouped together in transmissions the World Radio TV Handbook would list as “News in various languages”. Very easy to pick these up, and you had a sneak peek at the newscast that would shortly air on one of the regular transmissions.

 

[kevtronics]

I take it you meant "propagation." The content of the newscast wouldn't have anything to do with reception.

ISB would mean they were talking out of both sides of their mouth.

 

[boombox4]

Tuning around short wave by the west Wales coast the other week, the strongest thing on the dial was the religious programming from WBCQ on 9330, which at the time was presumably beaming straight at us as it was S9+20 and in English.

I've noticed the same thing as you on the ham bands - you tune around, e.g. 17m and think "there's nobody on, this band is closed" until you hit the FT8 frequency and hear the S9+ warbling. The band is wide open, there's just nobody on it apart from computers wailing at each other.

Yeah, this Solar Cycle there have been countless times I've heard EU stations and SE and NE US stations on 20M or even 40M -- I'm in the NW US, in WA state -- and I'd hear few takers for their CQ's, or minimal numbers of them considering the prop is in. Even when there is activity on bands like 20M, there are entire swaths of the band that are spare of decent signals, whereas 12 years ago there would have been a lot more activity, and in the 1980's the 20M band SSB and CW sections would have been wall to wall.

More hams (at least here in the US), but less active ones.....

 

[K6JHU]

20m propagation has been poor to bad. Operated today with 400w from ABQ and the best signals on 20m were from Arizona

Don't blame lasck of ham activity, blame propagation.

Or wait until Field Day on June 28-29