[R-390] Cost reduction Ect Ect

[bernie nicholson]

Hi guys I have three 390a rx s and a 391 and I also have one of the last racal Ra17 rx s made the Aust. army date code for manufacture is 9th month 1974 , its a nice reciever and it is very slightly more sensitive than a 390A,  when evaluated with a signal generator  {The American RA17 RX s Had A FRAME grid tube in the RF section and the rest of the world got a Cascade Double triode } BUT in practical terms the the 390A  outperforms it due to a FAR better signal to noise ratio which is a function of the 2khz mechanical filter, [ I am Talking SSB reception here ] if I wanted to listen to a broadcast station the racal RA17 has nicer audio , the dynamic range of the 390A is Much  better than Ra 17 around 20Db in fact , the 100Khz I F  in the Ra17 Just cant compete with the mechanical filter for ssb and neither can the I F  stage in the 390 rx  ,I know that the 390A project was to save money and it achieved that end BUT  between the time of the original concept and the 390A project Mechanical filters were invented By Mr Adler at Zenith radio Corp and it became possible to exceed the original performance specsof the 390 with less stages and also to take advantage of more modern tube design , overall I see many advantages for owners of 390A receivers, The tubes are Plentiful and easy to source, here in Australia 6AJ5 /6BJ6 /6082 ,are in the same supply status as rocking horse droppings and from what I hear in the states people who have these tubes want an arm and a leg for them , on the minus side with the 390A  there is an ongoing problem whith the mechanical filters, the foam rubber packing inside the filter with the passing of the years has De -materialised and also become corrosive , especially the 4khz filter,I have replaced a couple myself in the last few years  but I bought a few spare IF modules many years ago , summing up I would say that there is no BEST receiver it all depends on what ones interests are, BUT if you want to work DX on forty meters at night in amongst the broadcasters on SSB or CW the 390A is the way to go !!!!!!!!!!!!!!!!!  PS  I wonder how much Collins Paid Zenith for the Mechanical filter production licence??????????? Best Regards to everyone  BERNIE N