[ARC5] DF-ing.

[Kenneth G. Gordon]

On 3 Jul 2013 at 9:42, J. Forster wrote:

> OK. In fact, then, when properly nulled, the loop is in the worst
> possible orientation for actually receiving the signal.

Correct.

> This is done
> to make the servo problem easier, since the phase of the loop signal
> reverses about 180 degrees as the loop turns through the null
> position, and this can easily be turned into a servo error signal to
> drive the loop to null.

Again, correct.

> Maybe, operationally, you don't need to actually hear the station you
> are locked onto.

Yes. Absolutely.
 
> Use a peak-seeking servo. This is done by slightly dithering the
> azimuth of the loop, and then using a phase sensative detector on the
> output, with a reference 90 deg. shifted from the dither. This is
> Pound Locking.
> 
> Something like this was used in the conical scan of the SCR-584 RADAR.
> 
> Another possible design would be a second loop at right angles, used
> to actually receive the signal.

Yes, and this was done quite early on. I cannot remember the military 
nomenclature of a unit I only recently read about that worked just exactly this 
way. As I remember it, the receiver used was unique in that it had two 
parallel RF/IF channels, one for each "loop" then combined them in the 
output. It used, as I remember it, a cross-needle "meter" for output 
indication.
 
Ken W7EKB