[R-390] ssb converters

[bernie nicholson]

The Collins SSB converter is a BEHEMOTH ,it has twin motor driven BFO s driven by phase discriminators ,FORESTS of Tubes, and I have seen smaller power transformers in 2KW linears the unit also weighs MORE than a 390 ,BUT they do work ,I have repaired lots of converters for people in OZ and the best and simplest unit is the TECHNICAL Material Corp MSR 591 , with this unit and using the 2KHZ filter in the 390A  the Signal to noise ratio is the best I have heard on any receiver EVER ,my personal Bias is towards the IF module conversion as per HAM RADIO Magazine ,BUT using a 12AU7 double triode in the Ballast tube hole as a product detector, I also have removed the 2KHZ&4khz filters from a module and substituted dedicated asymmetrical USB&LSB filters and Crystal controlled the bfo with a 455.00 khz crystal from the 1khz filter can , I use a High resistance relay to switch the Audio line either through the product detector or for AM it reverts to the original circuit using the supply to the BFO ,so only the module needs to be modified and the unit can be transferred from one RX to another [I have 3 receivers the 390a type and quiet a few spare modules ] my favourite RX is this 390 a with SELECTABLE Sideband , the agc has also been modded to give attack and decay times more compatible with ssb I use the Slow  switch position  for this , Hope this info is of interest Regards to ALL