[R-390] Local Gain Control "Problem"

[Flowertime01 at wmconnect.com]

Mike,

You wrote:
>  
> Here's the current problem, with a relatively strong station tuned in and 
> the RF gain control at "10" the audio is about the right level with the 
> local gain control all the way down. (Against the "0" stop)  The local gain 
> control functions normally, when it is turned higher the audio level becomes 
> uncomfortably high.  The RF gain control also functions normally, setting it 
> to "5" results in the local gain control range being normal, or at least 
> what I think is normal.  It's as if there's too much gain somewhere.  The IF 
> gain pot was set as per the manual, although I haven't re-checked it.  The 
> meters are functional but not original, so they aren't really reliable for 
> trouble shooting.


A good long wire or other antenna on a R390 and a strong local signal will 
put the receiver into over driven.

Turn the AGC on.
Set the RF gain to 2 or 3.
Set the Audio to a nice level.
Hang an AC volt meter across the speaker and find a mid scale reading.

Now as you turn up the RF gain the AGC should hold the audio level about the 
same value. 

Until you get the RF gain so high it over loads the AGC circuit.

Remember R390's are for getting the QRP out of the noise.

Real signals over drive the receiver.

It may be time to get a signal generator on the receiver with a power meter 
so you can do some nice stage gain and signal to noise measurements.

You can get some real "hot tubes" that will drive the receiver to high levels.
Along with the high levels is high noise.

This is OK for strong signals but not for working that DX stuff.

I think your receiver is acting "normal" from your posting.

It's not how the receiver responds to strong signals.
It's how the receiver reponds to the weak signals.


Roger AI4NI



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