[Milsurplus] Navy MBM photo

[Hubert Miller]

The output power per manual is 20-12 watts; the lower power, I could have made clearer, is
when you're doubling the xtal freq to work the higher freq range. The set I saw here has some
xtals in the 4500-6000 kcs range. The manual as I recall specifies a list of crystals ( kind of like
the PRC-5, I think, in that respect. )  
The manual language about mode is kinda odd. It says the radio is for A1 use but  "also has
provision for A3 reception. That means you can switch the BFO off, big deal ! 
There is no date on the manual. I guessed the date from the date on the crystals, still in the box;
they're dated Jan. 45.  I wasn't aware of the catalog listing, so this mention is worthwhile to me
to get the date right.  Also if I recall, the classification is "CONFIDENTIAL", not the usual 
"RESTRICTED". 

I have so far only heard of 3 existing. I have this one, and one absolutely complete set ( no - wait -
someone abstracted the tool set ); Steve Bartkowski has one only slightly less complete. His
came from the Muchow estate in Chicagoland. 
Limited time at the present. I'll tell a possibly interesting story later how I came to get this 
set. 
The photo I sent isn't that great, doesn't give you the overall perspective. Later on I'll get some
better photos of the thing plus the power supply. I tend to think including a 6 volt wetcell storage
battery in the power unit was not the best of ideas. But I suppose it did free you, theoretically,
from being dependent on the crank generator or mains supply in dicey situations.  The set I have
does still have the battery in it; was never filled and charged.
-H 

-----Original Message-----
From: milsurplus-bounces at mailman.qth.net [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Mike Morrow
Sent: Wednesday, August 16, 2017 8:32 AM
To: milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] Navy MBM photo

Hue wrote:

> For updating your Navy catalog pages, here is an image of the rarely > 
> encountered Navy type MBM CAPI-43066 transmitter-receiver.
>
> Manufacturer: Jefferson Travis
> Year of production: 1945 only
> Production: at least 157, this unit's serial. 
> Weight: 20 lbs ( trans-rec unit only ) Freq range:  4-7.5, 7.5-14 Mcs.
> Modes: receive A1 A2 A3, transmit A1
> Emission power: 20-12 watt; lower power on crystal harmonic.
> Transmitter, 6V6, 6L6.
>
> Employment: coastwatcher and forward operations in Pacific War theater
> Power: handcranked generator, or internal 6 volt storage battery in 
> Power Supply  unit (not shown ), or external 6 volt battery.
> 
> 4 screw holes at 4 corners receive the fasteners for the waterproof 
> lid. 3 composite units are supplied in luggage-style suitcase:
> radio unit; power-supply with internal battery; handcrank generator.
>
> Right 1/3 of radio pictured is storage area for spare tubes, crystals, 
> headphone, key.

The description in the Navy Type Number Catalog

 http://www.virhistory.com/navy/manuals/nt/NT-900109-3.43.rcvr_xmtr.pdf

differs (and is obviously incorrect) in some interesting details.

CAPI- 43066 MBM
RADIO TRANSMITTER-RECEIVER: 
FREQUENCY RANGE 4·14 MC IN TWO BANDS
(4-7.5, 7,5-14). POWER OUTPUT ON A2 IS
l5-20 WATTS BETWEEN 4-7.5 MC AND 6.5·12 WATTS BETWEEN 7.5-14 MC. RECEIVER OUTPUT IS 5OO MW INTO 600 OHM PHONE.  CONTINUOUS TUNING EMPLOYED FOR RECEPTION AND FlXED FREOUENCY CRYSTAL TUNING IS USED FOR TRANSMISSION. JACK ON PANEL IS PROVIDED FOR PLUGGING IN REMOTE TELEGRAPH KEY.
RECEPTION IS A2 & A3.
01/20/1945 MBM UNIT 1
FEB. 1945

That description indicates NO capability for A1 transmission or reception!  That would have been bizarre, were it correct.  Hue's picture shows a receiver "C.W. ON/OFF" switch and "C.W. PITCH" control.  The type number manual description should have shown exactly what Hue wrote.  The manual for the MBM is NAVSHIPS 900,581.

It would be interesting to have a collection of these late-WWII unusual-purpose small HF sets like the AN/PRC-1, AN/PRC-5, AN/TRC-10...and now the MBM.

Is the set pictured in your collection, Hue?  Very interesting...thanks for showing it.

Mike / KK5F
(Does anyone have any info on the MBN, a.k.a. AN/PRC-7(XN-1)?) ______________________________________________________________
Milsurplus mailing list
Home: http://mailman.qth.net/mailman/listinfo/milsurplus
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Milsurplus at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html