[R-390] CV-157 SSB converter

Fri Feb 21 02:37:19 EST 2014

Thanks, John, for the nice explanation for the origins and common failure
points for the CV-157.  Folks, these beasts are heavy, over 100 pounds.
That is why mine sits on a heavy shelf in my storage, untouched for years.
I was never too enthused about it but after reading John's comments, maybe
it is worthwhile to buy a hydraulic crane and pull out the CV-157 and have
a second look.  It certainly is impressive with that huge double circuit
breaker.  You just expect the house lights to dim when you turn it on....

Glenn, you are asking for back trouble.

Don
W5OR

On Thu, Feb 20, 2014 at 7:53 PM, John Vendely <jvendely at cfl.rr.com> wrote:

> Gents,
>
> The CV-157 demodulates fully suppressed carrier signals just fine with AFC
> switched OFF--but with one serious drawback (relative to other converters).
>  Its 555 kc LO, which is motor driven in AFC mode, is inherently much less
> stable than the oscillators in the companion R-390(*) receiver, and the
> entire receiving system's frequency stability is somewhat degraded as a
> result.  This is particularly true during the first half hour or so of
> warmup.  The CV-157 was really designed for pilot carrier AFC operation,
> with the transmitter's carrier level typically reduced 16-20 dB below PEP.
>  In AFC mode, the drift was relatively insignificant.
>
> In the early 1960s when synthesized equipment began to proliferate, there
> was a big incentive to get rid of the wasteful pilot carrier and reallocate
> its power to additional sideband intelligence, and the stability problem
> became an issue.  The solution was the Manson Laboratories SBM-1
> "Stabilization Kit" designed as an upgrade for the R-390A and CV-157.  A
> number of AN/FRR-41 systems were retrofitted with it, especially by the Air
> Force.  The system consisted of the Model  299  Synthesizer, which provided
> a synthesized 2.455-3.455 in 100 cps steps for both 390As, and the Model
> 372  Stabilizer, which synthesized all the crystal injection points for the
> two R-390As, plus a synthesized 555 kc and 100 kc for the two CV-157s.  The
> FRR-41, thus modified, could be then operated either fully synthesized, or
> with continuous tuning and pilot carrier AFC as originally, .  I have one
> of these updated FRR-41 systems, and it works great, although the
> synthesizers are quite cranky and require frequent attention. The system I
> have was used by the 45th Space Wing as an ISB high speed computer data
> link on the Eastern Test Range in the mid 1960s.  This may have been the
> world's first computer wide area network--and on HF!  Later,  the enormous
> remotely-tuned DDR-506 receivers, developed by TMC, were used for similar
> purpose by NASA between NASA Goddard, Wallops, and the Range &
> Instrumentation ships during Project Apollo.
>
> But back to the CV-157.  Other than the matter of stability, it's a great
> piece of gear when it's working and properly aligned (which is a bit of a
> chore).  The main problems seem to be failed crystal filters (usually LSB,
> for some reason), and failed power transformers (usually the high current
> filament winding).  Some crystal filters have aged badly and have poor
> response, though they haven't failed altogether.  Carrier level meters tend
> to fail frequently, for some reason.  Of course, you have to reform all
> those electrolytics and replace a buncha toobs.  But when you're done,
> you'll have a marvelous piece of equipment.
>
> BTW, a common misconception is that the CV-157 is a Collins design, a
> natural assumption given its obvious R-390-like appearance.  It was
> actually designed by Hoffman Laboratories in the early 1950s, based on a
> patent they held.  Three companies seem to have made them, Hoffman (early
> units), Dubrow Electronic Industries (late 1950s), and Bridge Electronics.
>  Bridge seems to have made the largest quantity, on a 1962 contract.
>  Collins never made any.  I don't know how many were made, although it was
> obviously a tiny fraction of the number of R-390/390As produced.
>
> Please keep us all informed of your adventures as you dig into those
> CV-157s!
>
> 73,
>
> John K9WT
>
>
>
>
>
>
> On 2/20/2014 4:48 PM, Bill Hawkins wrote:
>
>> That's a good source, Norm.
>>
>> The manual says the 157 was designed to recover both upper and lower
>> sidebands.
>>
>> It does not clearly state that these are sidebands of a suppressed 100
>> KC carrier.
>>
>> *** Has anybody used one of these on the SSB signals available today?
>> ***
>>
>> As the manual says, the 157 was designed to provide the equivalent of
>> two multiplexed telephone lines to channels A and B.
>>
>> Maybe a channel can deliver a plain telephone voice signal. Really don't
>> know if it works without the 100 KC carrier.
>>
>> The control labeled AFC that looks like a circle with two dots on it is
>> actually a disk driven by a motor shaft that turns a variable capacitor
>> that trims the local 100 KC oscillator to match the received 100 KC
>> suppressed carrier.
>>
>> Like so much of what Collins did, it was the peak of what you could do
>> with vacuum tube technology at the time.
>>
>> Bill Hawkins
>>
>> -----Original Message-----
>> From: Norman Ryan
>> Sent: Wednesday, February 19, 2014 6:09 PM
>>
>> This link looks like as good as any -- a nice clean pdf copy:
>> http://www.militaryradio.com/manuals/CV-157/cv-157-tm11-266.pdf
>>
>>
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>
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-- 

Don Reaves  W5OR WD2XSH/15
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