[R-390] Receiver Overload?

[Roger L Ruszkowski]

Does this IMD occur with both antenna inputs..? 73 de Jordan...

Jordan,

The difference in circuit and receiver performance between the
two antenna inputs presents such a mix that using this criteria
to judge a trouble shooting procedure on is not easy.

When we do dial the antenna gain of peak, does the IMD
decrees faster than the signal loss? This could then be
excess RF hitting antenna. Then OK so how do you identify
the over load signal frequency. It may or may not even be
a broadcast signal doing the overloading.

Just getting up the connectors to do antenna testing it is a problem. We
need to think on this a bit.

Even on a meter test for oiled antenna shaft isolators it is hard
to get a reading that reflects what is happening at RF.

You ask a real good question. I just do not think with every thing
I have in my shack I can make a good assessment and report out an
answer on my receiver.

Please do not drop this subject. I suspect I have it in my receiver.
I am afraid the solution will come from doing a by the step ABC process
to inspect test and replace until problem is solved.

I feel we are stuck with observing the problem and realizing it is
between the antenna and the grid of the 6DC6. More observation and
front panel testing is not going to further isolate the problem. I can
be wrong on this.

Now after we check the voltages at the test points, how do we use the
deviation high or low to properly conclude what has changed in the circuit
so we replace parts to bring the circuit back into design limits.
Thus fixing the observed IMD problems.

I think some of us have high AGC voltages and IMD and do not
understand there is or were is the problem.

As an aside, I now have an IF deck where the gain is just hot
as hell. The signal to noise is good. From my days on the bench,
I just know this deck has a problem. It is not normal. It is just
two good.

How do we check and decide if an IMD problem is internal or external?

Roger KC6TRU