Batboard

Here is one for the old guys. I am looking for info on or manual for a PA deck used in a upright base made in 1949. 30 Mhz (UHF back then) used 2 100-TH triodes. Part number on the deck is P8233A. Hope there is someone out there like me who thinks that "Real radios glow in the dark."

Yes, "Real radios glow in the dark."

Look for armature radio amplifier schematics that used the 100TH tubes. That may help.

Thanks, I have all of that info at hand. I am looking for something on the base station or RT that this would have been used in.
This is more of a interest in the history of this than how to make it work. Having worked in a radio shop for years (MSS) it is just hard to not want to look at the original manual. Sad to say but everything I have is just too new.

This is probably the amp from a T-19-32H 250W AM transmitter dating from 1940 (and still sold through about 1951.) There was also a T-19-31H which used a single tube, as I recall, and ran 100W.

The stations communicated with police cars which were usually equipped with a T-69-17 "Police Cruiser UHF" 30-40 Mc. receiver, and those cars had a separate two piece T-69-20A "UHF" AM transmitter which ran about 8 watts. This setup didn't offer much performance, as the state of the art wasn't that advanced in 1940 for "UHF" equipment. It was more common to find stations transmitting AM on frequencies right above the AM broadcast band ("Medium Wave") and receiving the cars on "UHF" either AM or FM, on a 30-40 Mc. frequency. This was a full duplex situation, by the way. Many cities didn't even have transmitters in the police cars until after the war.

When Fred Link introduced the first 2-way police all-VHF FM system in Connecticut in 1940, there was a scramble by the other major manufacturers to do the same, and they all had their own FM products on the market a few months later. Motorola slightly modified the existing AM design PA and ran it in Class C to use with the Deluxe Line FM exciter. Your PA may be from this transmitter series.

Motorola almost totally quit advertising AM gear by 1941, although they still manufactured and sold it through about 1951. Many major cities were still using medium frequency AM for dispatch up to the 1950's. In fact, the Los Angeles Police system was still dispatching on 1730 Kc. AM until 1965!

I have some scans and photos of 1940's Motorola gear over on my web page at:

http://www.mbay.net/~wb6nvh/Motadata.htm

I don't think I have the manual for this particular PA but I do for most of the mobiles from 1938 up.

Thanks Geoffrey I thought it was a carry over with the conversion from AM to FM. The sad thing is I had one of the base stations years ago. It went by the wayside with a lot of other things when I moved after my wife died. Seemed like a good idea at the time not now. Lost a bit of history when I did that. Too soon old to late smart. This PA will be cleaned up and put on 6 meters with the tubes I pulled from the base I junked. There was no way I could let the tubes go. I will try and send you some pix of it when I get is cleaned up and glowing.

Ted WB0TDV

Did some digging around in the files and it appears your PA went in the FST-250 "central station" 250W 30-40 Mc/s FM transmitter. The PA deck, run class C, went on the top of the interior and a Deluxe Line "doghouse" mobile style transmitter with an AC power supply deck (50W) went right below it, with the connectors facing vertically. The brochure says the PA deck was run at 2000 volts (younger Batboard members take note - - real radios can kill you!)

The brochure just shows the 6' rack cabinet with the door closed, but there is an article in a 1944 issue of FM and Television which shows one with the door open. The PA has a couple of controls facing out from the chassis apron, and the chassis is mounted horizonally so that the tubes are vertical (as I recall, you can't mount 100TH's lying on their sides.) The rest of the interior chassis are mounted vertically. Receivers were the Deluxe line FSR-13B types, which were mobiles with AC supplies replacing the vibrator PS decks.
The mobile chassis installed in the cabinet did not have the covers or the side ears installed.

There was a big power supply in the bottom with mercury vapor rectifiers.

Other than the electric bill, this was a pretty high performance piece of equipment at the time. A 250W transmitter and a receiver which could hear at better than 1/2 microvolt...

I had one of these stations that I got from the Red Cross. I think they used them nationwide and there may be some old units in basements and back rooms that you may get for a small donation. Some were FM for sure. ANOTHER WARNING:THESE CAN KILL YOU IF YOU GET INTO THE B+