[R-390] R-390A Improving Sensitivity by Tube Optimizing

[k1jos at att.net]

Great post, thank you Larry

HNY
Jerry NY2KW

-----Original Message-----
From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> On Behalf Of Larry H
Sent: Sunday, January 8, 2023 1:13 AM
To: R-390 Forum <r-390 at mailman.qth.net>
Subject: [R-390] R-390A Improving Sensitivity by Tube Optimizing

Many years ago, Roger Ruszkowski posted a procedure on our R-390 List Forum that identified an important noise level criteria for the IF and AF system.  This 30 db criteria is necessary in order to be able to get your R-390A overall noise figure to a good point (< 1 uv sensitivity).  It is not documented in any official documentation, but is elsewhere.  This is important because if your rx does not meet the overall sensitivity requirement, this is a very good place to start.  This test will help you determine if the problem is in the IF/AF section or the RF section.  And, if it is in either, how to optimize tube selection to obtain improved noise levels.

I have used it many times over the years and appreciate having it very much.  Thank you Roger.  It's in the r-390 list forum archives, his 'R-390A Checklists' on our website in the 'Tutorials' section (first entry, newly highlighted), in the 'Pearls' 'Sensitivity Alignment' section, and in the Y2K R3 Tech Ref.  Unfortunately, it's not easy to find.  Here's where it's
at:

1.  Y2K R3 Tech Ref: Chapter 9 – Supplemental Repair Info - part 1, p.
9-15.  The 'Tube Optimization' follows through p. 9-19.
2.  Roger's 'R-390A Checklists' in the 'Tutorials' section in paragraph Q on PP. 16 - 18.  RF Optimization is on PP. 25 & 26.
3.  The 'Pearls' 'Sensitivity Alignment' section has it on PP. 472 - 476.

I hope this makes it easier to use Roger's valuable procedure.

Regards, Larry
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