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Oldest Continuously-operating Main Transmitter?

K

K8PLW

Plenty of old stuff hanging around in a standby capacity, but is anyone aware of a station nursing along an "Antique" as their main? A facility that remains essentially unchanged since, say, the 60s, 50s, or older?
 
This is definitely a fun question. I can't wait to see other folks' responses. As of 2017-ish, KEOS 89.1 FM in Bryan, Texas was using a 1963 Gates 1kW FM (unsure of the model) as the main, probably fitted with a modern exciter I'd imagine. It's been 5 years though, so it may or may not still be in service.
 
If I still had an old tank of a transmitter that was on the air at one of my facilities, there's no way I'd be bragging about it. Trying to keep an old relic on the air is quite frustrating, as parts and customer service typically no longer exist (been there). For some stupid reason, many owners *just don't* want to spend the money on a new transmitter, while at the same time, expect engineering to perform miracles keeping an old beast on the air. After a while, that gets really old.
 
This is an intriguing question for a non-engineer. I will have to visit a local AM that originated in 1953 to see if they are still using their original 1K transmitter.
 
Greg Goodfellow said:
This is an intriguing question for a non-engineer. I will have to visit a local AM that originated in 1953 to see if they are still using their original 1K transmitter.
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The problem with old hollow state transmitters is the almost total lack of availability of tubes. While ceramic-enclosure tubes can be rebuilt, the re-builders are fading away.

And glass envelope tubes are not re-buildable and few are available and at huge prices.

1669591023651.png

I used to get 4-400A's direct from the US for around $60 each in the 1960's. Given the life of those tubes, perhaps 3000 to 4000 hours at best (using European QB-4-1100 equivalent for longer life) that means about $2000 a year for 4 used tubes for a 1 kw transmitter.

The other common 1 kw AM tube was the 833, and they are still available in Europe for around $200 each. But they are very fragile for shipping so none of the suppliers there will send them internationally.
 
DavidEduardo said:
The problem with old hollow state transmitters is the almost total lack of availability of tubes. While ceramic-enclosure tubes can be rebuilt, the re-builders are fading away.

And glass envelope tubes are not re-buildable and few are available and at huge prices.

View attachment 3883

I used to get 4-400A's direct from the US for around $60 each in the 1960's. Given the life of those tubes, perhaps 3000 to 4000 hours at best (using European QB-4-1100 equivalent for longer life) that means about $2000 a year for 4 used tubes for a 1 kw transmitter.

The other common 1 kw AM tube was the 833, and they are still available in Europe for around $200 each. But they are very fragile for shipping so none of the suppliers there will send them internationally.
Click to expand...
Thank you, David! I imagine they must have retired the original, but you never know until you ask those in the know. Great information-very much appreciated!
 
DavidEduardo said:
The problem with old hollow state transmitters is the almost total lack of availability of tubes. While ceramic-enclosure tubes can be rebuilt, the re-builders are fading away.
Click to expand...

The venerable 4CX5000A final tube that Harris used in their popular 3kW FM transmitters circa 1970 looks to be unobtainable now. We had trouble sourcing these for a station I worked at 20 years ago.
 
PTBoardOp94 said:
The venerable 4CX5000A final tube that Harris used in their popular 3kW FM transmitters circa 1970 looks to be unobtainable now. We had trouble sourcing these for a station I worked at 20 years ago.
Click to expand...
They can still be rebuilt. However, there seems to be a limit on rebuilds. I never did more than two rebuilds of a tube in the past, and the second was purely to have an emergency spare in case the main and normal spare both failed.
 
DavidEduardo said:
The problem with old hollow state transmitters is the almost total lack of availability of tubes. While ceramic-enclosure tubes can be rebuilt, the re-builders are fading away.

And glass envelope tubes are not re-buildable and few are available and at huge prices.

View attachment 3883

I used to get 4-400A's direct from the US for around $60 each in the 1960's. Given the life of those tubes, perhaps 3000 to 4000 hours at best (using European QB-4-1100 equivalent for longer life) that means about $2000 a year for 4 used tubes for a 1 kw transmitter.

The other common 1 kw AM tube was the 833, and they are still available in Europe for around $200 each. But they are very fragile for shipping so none of the suppliers there will send them internationally.
Click to expand...
I figured availability of tubes would be what ultimately retired most older transmitters. I recently discovered that a local AM here in the Detroit area had been running the same transmitter continuously since the late 70s (Harris MW-1). I'm not a broadcast engineer, but this is impressive to me. 40-50 years (or longer) of service from the same transmitter.. incredible 😀. Really speaks to the expertise of whoever was looking after it.
 
Over in the world of shortwave broadcasting, Greenville VOA's GB-4, GB-5 and GB-6, the GE transmitters, still on the air, were built in the early 1960s.

The old Continental 420A transmitters at Greenville, also from the original installation days in the early 1960s, were actually built in the early 1950s for a VOA facility which was never built. Those three 420A transmitters were removed about four years ago and replaced with Continental 419Fs relocated from other VOA/RFE/RL locations which had been closed.
 
Another big reason to replace tubes with solid state is power consumption. Depending on the band, MOSFET transmitters are at least 60% more efficient, and 100% more reliable. The utility and maintenance savings alone, typically make the payments on a modern rig.
 
At least since a couple years ago when I visited; WWV in Fort Collins, they were still using vintage transmission gear, including original CCA rigs. There were plans to update with solid state transmitters, but not sure whether that happened.
 
gr8oldies said:
WLW put their old Western Electric rig back on the air for a few minutes to welcome in the year 2000.
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I did the same with KOMO-AM in Seattle on New Year 2000. I fired up the RCA BTA-50F for one last time, switching it to air exactly at midnight, running it on the air for one hour in the 21st Century before switching back. The GM was really pissed at me when he discovered the utility bill for that month went into the next rate tier. He said had he known that would happen, he wouldn't have allowed me to run the old girl.
A year or so later the RCA was disconnected from the switch gear and a new Nautel transmitter installed.
 
Kelly A said:
I did the same with KOMO-AM in Seattle on New Year 2000. I fired up the RCA BTA-50F for one last time, switching it to air exactly at midnight, running it on the air for one hour in the 21st Century before switching back. The GM was really pissed at me when he discovered the utility bill for that month went into the next rate tier. He said had he known that would happen, he wouldn't have allowed me to run the old girl.
A year or so later the RCA was disconnected from the switch gear and a new Nautel transmitter installed.
Click to expand...
WLW only ran the Western Electric for 15 minutes, that may have been why.
 
Back in the early '80s, KOB, Albuquerque, had a Harris MW-50 main transmitter. The transmitter just didn't sound good so I called Harris and they sent a field tech to help diagnose the issue (it was a non-symetrical RF bandwidth).
While the MW-50 was down, I switched to the aux transmitter, a plate modulated RCA BTA-50E. We ran on that transmitter for a day or two.
When the monthly electric bill arrived, it was about twice the normal amount. The MW-50 had a PA efficiency of 91% while the BTA-50E had a PA efficiency of something less than 70%. The RCA also had a 5kW driver which operated in class "A" mode and many times more tubes than the Harris.
From then on, I ran the RCA transmitter on the generator rather than on commercial power.
 
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