[Milsurplus] CU-63/APT

[Mike Hanz]

On 9/2/2013 12:24 AM, Jack Sullivan wrote:
> Found this on eBay. Appears to be 1:2 balun for matching unbalanced 50 ohm output of jammer transmitter to 2xbalanced 100-ohm antennas. Dayton contract code of 1945, so likely late WW2 or after.  I'm not up on impedance calculations but most effort at end of war was focused on jamming circularly polarized Wurzburg radars. Turnstile/fishook antennas for this had 36 ohm impedance. Anyone have any info on this?

I have one of those CU-63s, along with the two AT-41/APT "thick"stub 
antennas that it supports.  It ostensibly covers 150-210MHz, though I 
have tried it on the high end of the 2 meter band with some success.  
Actually, it works just as well with a pair of AT-36, AT-52, or AT-114 
stubs...they all cover about the same frequency range.  Its 
characteristics and deployment is described as the RRL M-2804 near the 
bottom of page 3 in the pdf I posted on my website at 
http://aafradio.org/docs/Countermeasures.pdf

That's about all the information I have on it.  There are chapters on 
the thick stubs and coupling methods in the excellent 1947 copyright two 
volume set "Very High Frequency Techniques" by the staff of the Radio 
Research Lab that describe the design aspects of both baluns and ECM 
antennas of all kinds.  They drew heavily on the 1946 classified 
publication "Radio Countermeasures" published by the NDRC, but you have 
to already know something about the particular device you are seeking 
from drawings or descriptions, as all military nomenclature has been 
stripped out of the VHF Techniques books.  For example, there is a 
detailed design review of the AS-251 Broad Band Crossed Element Phased 
Antenna (http://aafradio.org/countermeasures/AS-251.html ) that isn't 
identified by that number in the VHF Techniques book - you just have to 
recognize it in the drawings.  I would recommend finding copies of both 
publications, as they contain a wealth of knowledge in this area.

>   No further info as folks with Gov't publications that might cover this were unwilling to share copies.

Just an aside observation - that assertion is may not be an optimum way 
to continue getting assistance from those on this list who might be in a 
position to help you.  Some folks are busy at this time of year, and, 
while willing to help as much as practicable, don't have the time to 
satisfy instant gratification desires on the part of others.  When I ask 
for help, I try to be patient.  YMMV.

           73,
  - Mike  KC4TOS