View Single Post
Old 17th Feb 2015, 10:03 am   #10
David G4EBT
David G4EBT's Avatar
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 4,393
Default Re: Trio 9R-59DS communications receiver (1970)

Iíve just looked at the manual and see that as I recalled, there is a valve socket present for the OA2 150 Volt stabiliser valve, so all that is needed is to plug one in.

The manual also explains how to build in a crystal calibrator for which holes are already punched in the chassis to accept the crystal and valve sockets. It suggests using a 3.5 MHz crystal if the main interest is in the amateur bands, to mark the band edges of 3.5, 7.00, 14 & 28 MHz. Otherwise, a 1 MHz/100kHz crystal could be used. The manual explained that a spare switch on the RF Gain control could be used to switch the calibrator on and off. It provides a simple one transistor circuit for the calibrator. (Instead, I added a valve calibrator using a 6BA6 valve, as described in the Radio Constructor mods).

It seems rather odd that Trio made provision for these useful added features, yet didnít install them at the factory for the minimal additional cost involved, which from a marketing point of view, would have enhanced the features and benefits of the receiver, but it must have been a very price sensitive market so they were clearly trying to keep the retail price down. I don't think any manufacturer these days would include in the user manual diagrams to show how you could hack the printed circuit board about, cutting through tracks to modify the receiver! (No disclaimer either). Simpler less litigious times, when if people did something daft or negligent, they'd accept personal responsibility for their mistakes - not shift the blame onto someone else.

It has a send/receive switch to switch off the HT when used with a transmitter, back in the days when it was commonplace to have a separate receiver and transmitter, which is a handy feature for anyone who might want to use the receiver in conjunction with say a home-brew QRP transmitter.

The original 13-page manual can be downloaded F.O.C from the ĎBAMAí website (Boat Anchors Manual Archive) here:

The excellent Radio Constructor Magazine articles in Oct 1970 and in March/April 1971 by Martin Lindars covered extensive modifications which included such things as:

Improved power supply,
Fitting screen grid resistors,
Adding a tape recorder socket,
Separating the RF/IF gain controls,
Improved oscillator stability above 15 MHz,
Eradicating unwanted RF coupling along the heater line,
Fitting a double-tuned RF stage, voltage stabiliser & crystal calibrator,
A separate 6.3V supply for bandspread/bandset dial bulbs, to facilitate the fitting of an 'S' meter dial light,
Reducing mains hum (noticeable when using 'phones) by repositioning the OPT beneath the chassis away from the mains transformer,

Finally, full alignment.

Happy days!

Hope thatís of interest.
BVWS Member.
G-QRP Club member 1339.
David G4EBT is offline