Identification Racal transmitter modules

[Peter-bbu]

I have some Racal transmitter modules but do not appear to be able to find any information about them on the web.

They are from a 1.5-30 Mhz 500W/1Kw tansmitter I believe that they came from a Government service some time ago.

The transmitter consists of MM724 Control unit
2 x PA modules:
MM650 ( 2 x 4cx250B)
MS652 Eht PSU

I have no idea what vintage they are, though they seem to be newer than the TTA127 and older than the TTA1850 series, I suspect 1960s / 70s vintage.

I am particularly interest in the interconnect information.

Thanks

Peter G4BBU

[Herald1360]

Are these half rack width units with the 4CX250s at the back, motorised capacitor tuning and solenoid selected coil taps? If so they post date the TTA 1860 etc and were actually designed sometime about 1976. If this sounds familiar, I've got a stand pic from the Marine Exhibition in Brighton late '70s that might interest you- it has 500W and 1KW versions of the amplifiers and a few other bits of contemporary stuff. ISTR travelling down from Bracknell each day in my Triumph 2000 and making a nice little sum on the mileage allowance. (Probably still cheaper for the company than putting me up in a hotel, though).

I think the 500W amp and PSU was the TA1820 and the 1000W with two of each the TA1821.

Nothing special about them (other than being designed down to a price), I had the dubious honour of involvement in the design of the discriminators and servo drives.

A lot of extra reinforcement was added to the PSU module after we saw what the transformer did on the vibration test rig

Can't help with information about connections- I think there was a multipole blue McMurdo connector, an EHT connector and a coaxial output connector on the back of the amp module along with a couple of lineup pegs so it could be just rammed into place in the rack. I suspect the solenoid control lines came in from the control unit along with anything else needed by the autotuning system. The TX itself was intended for a few crystal controlled channels, but you could always drive it from a MA1724 or another exciter.

Edit: added pic.

The thing on the wall was a self tuning ATU good for a kilowatt 1.6-30MHz into a 10 metre whip. It was pressurized with dry nitrogen inside!

[Peter-bbu]

Thanks Chris,
Yes they are the 1/2 rack width units with a pair of 4cx250Bs at the rear and motorised tuning with a set of control PCBs that set the channels.
Each unit producing 500w with a splitter combiner in the control chassis to allow operation of either pa or both together.

I also have a 1720 exciter though that came from a different source.

Peter

[Herald1360]

Ahh.... my recollection about auto tuning may be inaccurate, now you mention control PCBs, twiddly pots for several preset channels come to mind. I was involved with the simple dc servos, though.

MA1724 should have been MA1720 too

My recollection about discriminators and auto tuning relates to a later single valve (4CX1500) design with variable inductor tuning, the TA1823. I don't know whether that one was ever marketed since I left Racal around the end of its development time.