[R-390] Alignment help.

[Roger L Ruszkowski]

Hello to the group,

All work fine, except that as the alignment progresses, the
radio becomes so sensitive at the higher bands, that the signal generator
will not attenuate enough to keep the diode load at approx 7-8 volts.  At
this point I have been reducing the radio RF gain to reduce the voltage
present at the diode load point.  This works fine, except that the higher
bands are ALIGNED WITH THE RADIO RF GAIN REDUCED to about 1:00 position.

Sincerely,

Jim
73, KF4ICZ
-----------------------------------------
Jim,

There is no reason the signal generator needs to be connected directly to
the receiver.
When we want to measure signal to noise and stuff, OK you need a setup
where you know
what is happening. But for the alignment, what ever, works OK. If your
signal generator leaks
to much to get you down to 1uv, you just are not going to do 1uv testing.

Put your real antenna on the receiver, string some wire off the signal
generator to get
a signal coupled into the receiver antenna. Your not going to radiate more
than 1 watt
from the signal generator, so do not worry about QRM. Vary the signal
generator out put
and antenna to wire coupling to get the lowest usable signal level you can.
Low level
just lets you find a sharper point in the alignment of any slug or cap your
adjusting.

Jordan says,

The method I use to set the IF gain is by listening to white noise, and
using the line level meter with the line terminated with a 610 ohm
resistor... all I do is adjust the IF gain control to a point just before
the carrier level meter 'takes off '...try it and you'll see what I mean...

This is a good way to finish up, or set the IF gain if you do not have
a signal generator with known output level. What good does it do to tell
you to put 150 uv at 455 into the IF and adjust for -7 volts if you can
not establish what 150 uv is on your bench.

Jim, you have more than enough hardware and wetware in the shack to get
your R390 up to snuff.


Motorboating sounds more like a capacitor problem than anything else, and
it could perhaps be due to the failure or leakage of the 2uF cap on the IF
deck.. does this occur on all settings of the AGC switch..? 73 de Jordan...

OK, so you have at least one more problem to find.

Stay with it, once you get the problems out two things happen.
You become a very happy radio owner / operator / listener.
Future problems occur one at time and can be fixed one at a time.

Roger.