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

[Roy Morgan]

At 03:15 PM 12/8/03 -0500, JMILLER wrote:
>  ... I believe that DF can be determined by measuring phase or time of 
> aarrival differences from multiple receivers / and fixed antennas at 
> known positions...  ... I suspect there were 3 or more receivers, with 
> matched IFs, and one IF post processor doing the bearing 
> calculations.  Any thoughts?


Yes, some:

In one system I read about, the multiple antennas were fed to a phasing 
network which was adjusted by hand or by automatic system to produce two RF 
signals exactly in phase.  The R-390 balanced input circuit allowed for 
in-phase signals to cancel in the input transformer. One part of the R-390A 
alignment is to adjust the input transformer trimmer cap to achieve maximum 
balance and thus maximum null for two equal in-phase signals. It could very 
well be that the IF output was used in such an automatic nulling system and 
that flat phase vs. frequency characteristics at the IF were needed to make 
it work well.

One article that tells of early DF equipment was in October, 1944 QST.  It 
tells about the radio stations used by the Army Air Corps to guide aircraft 
over Canada and Alaska to the western Pacific. Adcock arrays were used.  I 
can't remember if they were steerable or if they were fixed with adjustable 
phasing networks in the feed system. In any case, my reading of that 
article made me want an example of the SX-28's shown in use.   Now I have 
two of them, both awaiting restoration.  I have no plans for Adcock arrays 
here.

Sooo many projects, sooo little time.

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
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