[R-390] The R-725 and the DF story?

[Roy Morgan]

At 04:27 PM 12/8/03 -0500, JMILLER1706@cfl.rr.com wrote:
>Where is a copy of this TM that can be had?  Sounds interesting.  I think 
>the goniometer was in fact a rotating antenna inside a shield/can with a 
>small opening or aperature, with continuous angle readout as it rotated (?)


One definition at:
<http://www.bartleby.com/61/2/G0190200.html>
is:
"A radio receiver and directional antenna used as a system to determine the 
angular direction of incoming radio signals. "

This is little help here.

As I understand it, the Goniometer is a rotating coil located with respect 
to two (or more) other coils so that it can couple to the others in a 
continuously variable way. If the energy in the other coils has certain 
phase relationships, the movable coil can be adjusted to create a null or a 
peak in its output signal.  Likely the goniometer was in a shielded place 
(can or room) so as to avoid unwanted pickup of signals other than from the 
antennas.

The "rotating coil" function was implemented in either software or software 
controlled reactive elements in later systems.


>    So you would tune the radio to the signal of interest, turn on the 
> gonio to start spinning, then a processor of some sort would detect the 
> pulse at the IF output as the gonio slit swept the direction of the 
> target, then read out the gonio angle.

The processor here could be a CRT with a trace which follows the angular 
rotation of the goniometer element.  Early radar and ECM direction 
indicators worked this way.  A bump (or perhaps a null) on the circular 
trace of the "PPI" showed the angle from which the signal was arriving.

Roy

- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Work: Voice: 301-975-3254,  Fax: 301-948-6213
roy.morgan@nist.gov --