[R-390] Tell me about Single Sideband Converters

[Sheldon Daitch]

I might disagree slightly about the CV-157 not being
designed as a voice SSB converter, in fact, I'd say that was
probably one of its design parameters.

John is correct in regards to the pilot carrier operation, but I'd
further say that if the CV-157 were phase locked to the pilot carrier,
there would be little or no frequency error.

One of the systems applications for the CV-157 was four channel
ISB operation, 16 kHz bandwidth, with two 4 kHz audio channels on
each sideband.   And usually one of the four 4 kHz audio channels
was devoted to a 16 channel AFSK tone pack.  I suspect the tone pack
was always one of the "inner" audio channels to eliminate a frequency
translation on transmit and receive.

If this isn't readily clear, let me try to explain.  The upper sideband, for
instance, would be modulated with one voice channel roughly 4 kHz wide,
that was not translated in frequency.  The second voice channel, also roughly
4 kHz wide, was translated upwards by 4 kHz, so that in the side band, it occupied
the sideband bandwidth of 4 to 8 kHz.  The same for the lower side band.   Since
the AFSK TTY frequencies are critical, the AFSK channel would be on the
lower portion of the sideband, to eliminate that 4 kHz shift.   I don't recall what
units were typically used for the 4 kHz shift, maybe it was a TD-97/98 combination,
but the brain cells aren't working too well as I type this.  Whatever the
nomenclature was, they weren't normally part of the  transmitter or receiver
set.

When VOA ran the ISB/SSB feeders, we ran a pilot carrier, about 20 dB down from
the PEP power rating of the transmitter, and our RCA SSB-3A receivers were capable
of ISB reception, and used a motorized AFC system very similar to the CV-157
AFC loop.

73
Sheldon
WA4MZZ




John Kolb wrote:

> The CV-157 wasn't really intended as a voice SSB converter - it was
> intended for applications where
> a pilot carrier was transmitted. By phase locking to the pilot, the
> transmitted audio frequencies
> were recovered  within a couple of hertz of error. We had a couple
> aboard the USS Providence
> in the Navy for use in receiving multiplex RTTY transmissions. These
> had, as I recall, an 85 hZ shift,
> so the receiver had to be pretty exact. I believe a set of two CV-157
> and two R-390s in a single
> rack was known as a FRR-39. The production numbers for these would have
> been very low. No the
> other hand, many of the R-390's I saw aboard ship (early/mid 60's) were
> in a cabinet along with
> TWO CV-591's.
>
> John
> http://www.jlkolb.cts.com
>
> Craig wrote:
>
> >Hey guys. Thanks for all the replies. I see Rick Mish works on these models - CV-591A, CV-657A, CV-1722A and CV-1758A. Is there a big difference between them in ease of use and reliability?
> >
> >I was told that the CV-157 was "the best", but that they are impossible to find.
> >
> >Looks like the CV-591A is the most common and probably easiest to find parts for. Anyone have a picture of the inside of one of these?
> >
> >Thanks
> >
> >  --
> >
> >  Craig Westerman
> >  westerman at cableone.net
> >
> >__