[R-390] Greetings from Sydney, Australia.

[djed1 at aol.com]

 Welcome to the heavy metal club, Eric-
I think that a well-working R-390A should have fairly uniform calibrator signal on all bands. I get 30-40 dB on all bands.  If you think the alignment is OK, then the radio might need some further attention.  However- a couple of suggestions-
check that the calibrator is zero beat on each band: It's not uncommon for the band crystals to be off by several KHz.  If centered in the pass band, then an alignment or component problem may exist..  Have you checked all the tubes?  Maybe the IF is low. 
See how much the meter changes if you crank up the IF gain  
If you have, or can borrow, a signal generator, you can check the gain on each band.  You can also use the manual procedure to set the IF gain.  In theory, the meter should indicate dB relative to 1 microvolt.  This is affected by the IF gain, and most listeners set the IF gain for best noise figure, not most accurate meter reading.
Keep us informed of your results.
Ed  W2EMN

 

 

-----Original Message-----
From: Eric Gauja <ericgauja at optusnet.com.au>
To: r-390 <r-390 at mailman.qth.net>
Sent: Wed, Apr 18, 2012 9:52 pm
Subject: [R-390] Greetings from Sydney, Australia.



                   
                      Generally, I am very pleased with the 390A.  I do have 2 
initial questions that I would like to put to the group.   
1)  AGC performance.   It seems that my R390A needs a relatively high value of 
input signal before its AGC activates, and the Carrier Meter moves.  I note that 
in the AGC circuit description in the technical manual it states that the AGC 
circuit operates only for signals in excess of 5 microvolts – this to me seems 
to be quite a high signal level  for a communications receiver,  and in general 
listening to non local stations, the R390A does not use its AGC circuit.  I have 
zeroed the Carrier Meter , and the IF gain pot is set to  midway, so it is not  
a case of my 390A having excessive IF gain.  Is this normal , or do I have an 
AGC fault?

2) Calibrator circuit .   What sort of variation should be expected in the 
Carrier Level Meter reading for different calibration frequencies?  Calibrating  
my 390A at frequencies XX.700 MHz gives zero beat Carrier Level Meter dB 
readings  of between 20 and 30dB in the 0 to 15 MHz range.  At 16.700MHz the 
reading drops down to only 0dB,  (although the signal off zero beat is still 
easily audible). From 18.700MHz to 24.700MHz , the carrier level at zero beat 
stays at 0dB.  It goes back up to 10 dB until 29.700 MHz, before dropping down 
to 5 and 0 at  30.700 and 31.700MHz. I have checked the RF deck alignment using 
the procedure outlined by Dallas Lankford in Hollow State Newsletter 29 , and it 
seems fine.

Thank You for accepting my group membership, and I look forward to sharing my 
390A experience with you all!
Best Regards,           
                        Eric.
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