[Milsurplus] CMS spy set

[Dennis Monticelli]

Mike,

Yes, regarding connections for phone operation.  But I seriously doubt this
set saw phone use.  A carbon mic in the cathode of a relatively low power
crystal osc PA is going to have little punch due to the low level
modulation.  The set came with a key; it did not come with a mic.

Yes, separate receive and transmit antennas would seem likely.  It came
with two reels. Either that or a simple manual T/R switch.  Maybe two reels
is to have a backup wire because one sometimes loses the wire to breakage
or tangle.

I am convinced that this unit was originally designed and intended for
clandestine use; all evidence stemming from its design as well as other
clues point to this.  I also believe this set was likely re-purposed later
in the war.  So the records of its use in ship-to-shore are believable.
The highest recorded serial number is the high 90's and half of the sets my
investigations have turned up have been in the 90's, including mine.  These
latter sets are in good shape.  They may have been lightly used or not
issued before the war ended, which would explain their abundance relative
to lower serial numbers.

Other clandestine sets do not pay much attention to ground.  Maybe it's
because the antenna is usually hi-Z so some capacitance to ground from a
short ground wire is sufficient.  But I really don't have a good answer to
your question.

Denny

On Sat, Dec 13, 2014 at 3:48 PM, Michael A. Bittner <mmab at cox.net> wrote:
>
>  To Dennis and Al Klase, thanks for all the neat and very helpful pics of
> the rcvr, and Dennis, thanks the other information that I requested.  The
> mechanical drawings for constructing the set are coming along nicely.
>
> More items for anyone on the list who may wish to comment::
>
> One thing that is bothering me is the apparent lack of a ground
> connection.  I don't see one on the rcvr or xmtr, and there seems to be no
> mention of it in the instructions. With all the emphasis on matching
> antenna impedance, there must be a ground connection somewhere?
>
> Also, no mention of a T/R switch.  I guess the set is meant for separate
> rcv and xmit antennas or hand switchover of a single antenna for rcv and
> xmit.  It seems to me that neither of these options are compatible with the
> suggested use of this set for shore-to-ship communications during landing
> assault and re-supply missions, although the hand switchover method makes
> sense for quick one-time use during spy missions, i.e., receive, send, pack
> up and move out before the DF-ers find you.
>
> Although it doesn't say so in the instructions I assume that in order xmit
> voice, a key must be plugged in with its shorting bar shorted, and the mic.
> must have a mic-switch in series with the mic element.  Does this sound
> correct?
>
> Mike, W6MAB
>
> ----- Original Message -----
> *From:* Dennis Monticelli <dennis.monticelli at gmail.com>
> *To:* Michael A. Bittner <mmab at cox.net>
> *Sent:* Friday, December 12, 2014 7:54 PM
> *Subject:* Re: CMS spy set
>
> Hi Mike,
>
> Good to hear back from you.  That's a great project and I'm interested in
> how it turns out.
>
> Here is the info you seek:
> 1)   R1 is 1M so you made a good guess.
> 2)   I have only one of the original transmitter coils.  The dimensions
> are 1.5" in dia for the coil winding portion of the form.  The total length
> of the form is 2.25", which includes the lip on both top and bottom.
> 3)  The suitcase dimensions are 13 7/8 x 11 13/16 x 4 7/16.  It is
> finished naturally but worn off in places on my set (photo attached).
> 4)   The receiver coil size is indeed 5/8" dia.  The length is 1.5".
>  (photos attached)
> 5)   FYI.  The receiver panel dimensions are 6 1/8 x 5 1/4 while the
> receiver box outer dimensions are 6 3/8 x 5 1/2 x 2 1/4.  The transmitter
> box is the same size.
>
> Dennis AE6C
>
>
>
>