[Milsurplus] U.S. Navy ECM gear in WWII?

[Brooke Clarke]

Hi again Jack:

The VT fuze transmitter is a simple LC type, not crystal controlled so the Tx frequency can vary over a wide range.  The 
jammer described in one of the referenced papers used a receiver with motor driven tuning coupled to a high power 
transmitter tuned to the same frequency as the receiver. A very bulky and heavy arrangement. Today this could easily be 
done with a DSP based spectrum analyzer queuing the jamming transmitter.  A counter counter measures spoof that 
transmitted a high power signal in the same band of frequencies as the VT fuse might jam the fuse so would not be an 
effective spoof.  Maybe transmitting a comb of low power CW carriers would confuse the motorized receiver?

The construction of a family of VT fuzes was made easier by standardizing many of the internal components.  For example 
the reserve battery (which consumed all of the U.S. production of Christmas tree light bulbs for a couple of years) was 
of a standard size and terminal location.  The same is true of the setback switch which was part of the safe and arm 
function.  There were some early detonations that happened just out of the barrel and that's not a good thing.
http://www.prc68.com/I/ChinaLakePatents.html
PS the above China Lake web started out focused on the Sidewinder missile, but I discovered that's where a number of the 
VT Fuze patents were so expanded the page to include those patents as well and some other China Lake projects.

More modern proximity fuzes make use of FMCW doppler.  This allows the trigger point to be set in terms of a distance.  
I worked on a proposal to do high volume testing of a Hittite GaAs IC designed to to this.
This is a version designed for quad copters and so much more complex, but you can see the functionality.
http://www.analog.com/en/design-center/evaluation-hardware-and-software/evaluation-boards-kits/EVAL-DEMORAD.html#eb-overview 


-- 
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html