[Milsurplus] CV-157

[Nick England]

The CV-157 is surprisingly un-modular! Even though it looks like the power
supply lower section is easy to separate, it isn't. It pulls out *almost*
far enough to work on.

It has been several years (and other silly projects) since I restored my
CV-157 but I'd say, technically, if you can repair and align an R-390A,
then you can certainly do the same for a CV-157. A scope is probably
necessary for any troubleshooting. The TM is clear and complete of course.
http://www.militaryradio.com/manuals/CV-157/cv-157-tm11-266.pdf

Basically it is three parallel sections -
1) a USB IF amp and product detector
2) a LSB IF amp and product detector
3) a carrier IF amp and motor drive circuit for the AFC

Here's another thing to consider -
The sideband filters are 6kc wide so that will may be an issue in a crowded
band. The CV-591 is the more usual 3.2kc so there is less adjacent signal
interference.
The 6kc width is because the CV-157 was really designed for multi-channel
AFSK RTTY - like 32 TTY channels in each sideband.

Repair parts - well if a 100kc IF transformer or filter is blown, only
another CV-157 will have those parts. Otherwise it is the usual caps and
resistors. There are a zillion IERC tube shields (well 40 or so) which
probably are worth more on eBay than a CV-157. IIRC, the tubes are
regularly available military types, no oddball ballast or regulators.

Overall it is an excellent unit for its intended use, but way complicated
for just regular voice SSB.
It will probably be an interesting and moderately challenging project,
which you may or may not enjoy. Or if it hasn't been messed with or been
stored in bad conditions, you may not have to do much at all.

And you'll probably be the only kid on your block running one.

73 & Have Fun
Nick England K4NYW
www.navy-radio.com

On Tue, Dec 22, 2015 at 10:55 AM, Reuben Popp <reuben.popp at gmail.com> wrote:

> Hey Nick,
>
> So what you're really saying here is that for the quasi-experienced
> technician it would most likely require some serious study as well as the
> help of a more experienced elmer ;)?
>
> I see that at least one manual (TM11-266) is available.  How difficult is
> it to acquire parts?  Is it modular like the R-390As?  Just curious to see
> if I'm potentially getting myself into deeper water than I care to wade at
> this point.  Then again, I would hate to miss out on a piece of equipment
> that others rate highly and I might be able to acquire at a decent price.
>
> Thanks again
> Reuben
>
>
>
> On Tue, Dec 22, 2015 at 7:00 AM, Nick England <navy.radio at gmail.com>
> wrote:
>
>> The CV-157 spec says 105 lb  but it seems much heavier. It is a great
>> ISB converter (simultaneous USB and LSB) which includes a motor drive AFC
>> for tracking reduced pilot carrier ISB transmissions. It has 44 tubes and
>> lots of circuits to align. I really enjoyed spending several weeks learning
>> how it works and getting mine running. Acquisition cost is low because sane
>> people don't want something that big and heavy. Anywhere from $10-100 is
>> reasonable. Hard to beat if you want an interesting and challenging
>> project. I enjoy projects but YMMV.
>>
>> The TMC CV-591 is much much smaller, lighter, easier to use, and more
>> expensive.
>>
>> There aren't any ISB or pilot carrier signals to copy anyways so audio performance
>> is about the same for regular SSB voice.
>>
>> OR just switch your rcvr to CW and MGC, offset the BFO, turn down the RF
>> gain, and turn up the AF gain and SSB voice sounds just fine.
>>
>> Cheers
>> Nick K4NYW
>>
>>
>> On Tuesday, December 22, 2015, Reuben Popp <reuben.popp at gmail.com> wrote:
>>
>>> Hey gang,
>>>
>>> Quick question here.  I might have an opportunity to get my hands on a
>>> CV-157... maybe.  The current owner said he's had it now for some years now
>>> and never used it.  Question is, what are they worth in good unused shape?
>>> Are there any gotchas for them (hard to find parts or tubes) as opposed to
>>> the much smaller TMC CV-159?  That said, are they as good a performer as
>>> the -159 or just mediocre?
>>>
>>> Thanks again, Merry Christmas (or Happy Holidays if you prefer) to all
>>> and 73
>>> Reuben
>>>
>>
>>
>> --
>> Nick England K4NYW
>> www.navy-radio.com
>>
>>
>
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