[R-390] Alignment

[Roger L Ruszkowski]

I did the alignment, before my latest escapade, and it went well.  However,
I estimated the 150uV needed to obtain the 7volts diode load.

The signal generator is a Heathkit that has no meter, so the output is not
calibrated.  I measure the frequency with an HP freq counter, so I have
accurate frequencies.  I know that a calibrated output is not needed for
any
of the alignment, except to set the 7volts at 150uV.

Can the 150uV output be accurately measured with a VOM??  I think the
output
to be measured is RF voltage, so would a small RF detector, such as what is
in the ARRL handbook be suitable and accurate enough for the purpose.

Jim.


Jim,

Go read Chuck Ripples page on how to set the IF gain.

Chuck Rippel, WA4HHG A "must see" collection of R-390A information
http://www.r390a.com/


A lot of owners do not have calibrated test equipment to
set up the -7 volts.

This procedure provides the best setting that really works
in real life with your receiver at your Qth and your antenna.

Roger.


P.S.

If you want to meter the Sig Gen. Then use a good tight metal box with
high impedance detector (active amp) and meter. Put your own
attenuator into the box. Measure the sig gen at full (near full) output in
the
meter box and then use your step attenuator to reduce the output to the
level
you need. Consider it easier to meter a big voltage than a small voltage.
There is also the load impedance to consider in the metering.

A scope that will get you down to mill volts (AN/URM 25 is only .2 volts
max)
and some math would let you measure the sig gen full voltage into a fixed
load resistance.

You may want to meter the signal gen one time at specific frequencies
and then judge where to set the knob to get  about what you need.