[Hammarlund] sp600 frequency question

[Grant Youngman]

> A's.  The probe on it says "AC-DC VTVM PROBE" but does not 
> give any other info. Do I need an "RF Probe" for the vtvm? Or 
> will this one do?

Eugene ..

Frequency adjustment is done using the generator with an unmodulated signal
and the BFO -- you set the generator and the tune the oscillator coil slug
(low frequency end of the range) or cap (high frequency end) in the turret
for zero beat, so no meter is needed.  And you do that over and over and
over ... and over :-) ... until the end points look good.

Other stages (mixer, IF, RF) are done with an AM modulated RF signal from
your generator (1Khz, 30% modulation) along with an audio output meter or AC
voltmeter to measure the audio level at the speaker terminals and tune for
the peak. 

If your generator doesn't provide an AM modulated signal, you can also use a
DC meter on the AVC line and tune for maximim negative voltage.  Ignore any
instructions to turn AVC off, and adjust your RF generator output to keep
the RF meter below mid-scale or so.  In this case, a high-z meter is a
necessity.  The typical ratshack 1000 ohms/volt multimeter will upset the
applecart on the AVC line.

As someone else indicated in another post, it can be tricky getting to the
caps and slugs in the turret, because you have to reach in through the small
holes in the top cover, essentially blind, with a long narrow tool and
"feel" for the slug screw or cap.  Just takes a little practice, although it
can be frustrating the first time :-)

Grant/NQ5T
http://www.globeking.com
http://www.globeking.com/pro310