Mode Zero

This might tickle Phil's RC museum.
A chum recently acquired this mystery Rx installed in a 3M glider. The Rx appears skillfully built with many surface mount ICs and discrete components that could date it to the mid 1980s. Rx antenna length implies 27MHz but there was no crystal in the holder to confirm that frequency. Thru board vias use Veropins, or similar. Output stages share the RF box while the the servo mechanics use a pair of internally geared 'instrumentation' servomotors, reminiscent of the 1970s.
The rechargeable AA cells are absolutely dead but without better information, I will resist applying power.

Any clues to the origin of this gear ?

What a wonderful receiver!

Looks almost like a home-brew unit. Based on the IC date-code it seems to be end 90ies (74HCT164 has date code of 98; 74HCT04 has date code of 93).
The board looks like it was made with a PCB software and not hand-drawn. A double-sided board with no vias but wires to make contact between the layers. Clearly hand-soldererd. Hats-off to who ever built this back then!

Such a beauty! Thanks for posting these high-res images!

cheers, Werner

I love the servo brick, the set up is proportional with the output on the shaft of a pot Clarostat??? Bourns??? or former east countries? In any case the pots looks to be military standard. The builder sure new his stuff

It came from the Northampton (UK) area so could have been a student electronics project at Cranfield, or even an apprentice piece from RAE Bedford. As a hobby job, the builder must have had access to some sophisticated tools for the time. I have no other information about it.

Very interesting. The RF board looks like it could be UHF with the screening and component placement. That aerial could be a full wave at 459mhz ?


Was it a well built glider ? I seem to recall an advert for an interesting glider of RAF or similar origin being for sale ?