[R-390] ssb converters

[bernie nicholson]

Ok Todd Most of the CV 157 s that I have repaired for people have lots of
faults due I think mainly to the Heat build up  causing component
deterioration , also they were designed for SSB with Pilot Carrier so that
the Discriminator can Lock on ,in the fifties in the days before frequency
synthesis, this was necessary to stay on frequency for SSB as we know it
today there is a lot of redundant electronics in the CV157, I have a similar
unit designed for the Racal RA17 and it only has about 10 tubes and is very
reliable and takes 4 inches of rack space and only weighs 25 pounds,so you
can see what I mean about over engineering , The TMC device is an elegant
little gadget and works really well and has a low component count making it
VERY reliable ,and you can tune about in passband of what ever Mechanical
filter you have selected ,I have never owned one but I have repaired them
and always been impressed with their simplicity operation ,Regards to every
one
----- Original Message ----- 
From: "Todd, KA1KAQ" <ka1kaq at gmail.com>
To: "bernie nicholson" <vk2abn at bigpond.net.au>
Sent: Wednesday, June 29, 2005 11:49 PM
Subject: Re: [R-390] ssb converters


Bernie -

That would be the CV-157. Unfortunately many of the nuvo experts
aren't even aware that it exists; only the smaller TMC model since it
is regularly discussed here.

I'd love to find a -157, but God pity anyone who has to service it!

~ Boomer,  KA1KAQ

On 6/28/05, bernie nicholson <vk2abn at bigpond.net.au> wrote:
> 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 2 , 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
>


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