[R-390] RF Gain control

[Roger Ruszkowski]

Dog.

The 4 K is still to narrow for standard broadcast AM. Normal operation.

The RF gain pot is also a normal. Not what we expect.  But the real world there is a wide contact that averages a few ohms of resistance under the contact area. Current limitations in the resistance of the control suddenly go to a closer zero resistance and things thump. The AGC mode may have more thump than the manual mode. In the real world these receivers set on frequency weeks at a time doing RTTY receive with no human listening  to any audio. No one cared if the RF gain pot caused an audio thump as the circuit was adjusted from time to time.

The 10 turn IF carrier control does improve the maintenance procedures. The ten turn resolution is 10 times easier to dial the resistor to its desired performance setting. 

I will listen to an R390 or A over any cell phone any day.

How are you doing for noise to signal plus noise in IF and audio deck.
Are the tubes up to the 28 29 30 to 1 meter performance the receivers are easily capable of?  

Respectfully,

Roger Ruszkowski
 
 
-----Original Message-----
From: dog <agfa at hughes.net>
To: R-390 <R-390 at mailman.qth.net>
Sent: Sun, Jun 17, 2018 11:30 am
Subject: [R-390] RF Gain control

Think I've got one of my IF modules set up pretty good, but a couple questions. I notice the RF Gain control has glitch at the CW end (10) of the control. That is when I advance it all the way up there you can hear a sort of thump when it goes from the resistive part of the control to the short. I've opened up the control on both radios I have and they're both the same and they both seem to operate the same. Is this just the way they are? I notice on an ohmmeter there is resistance until the wiper just all of a sudden jumps to the short on the CW end, not a smooth transition.Also, I notice that AM broadcast in the 4K position sounds a bit distorted, but in 8/16K it sounds fine. Is this typical?I put a 10 turn pot in this IF for the Carrier Control and boy is that much better.  Dave N3DT______________________________________________________________R-390 mailing listHome: http://mailman.qth.net/mailman/listinfo/r-390Help: http://mailman.qth.net/mmfaq.htmPost: mailto:R-390 at mailman.qth.netThis list hosted by: http://www.qsl.netPlease help support this email list: http://www.qsl.net/donate.html