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Chuck Rippel

Copyright: 1996, 1997, 1998, 1999, 2000, 2001, 2002 

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The R390A/URR

Ultimate Performance, General Coverage AM & CW Receiver

R390A/URR Receiver Site Pages Accessible from Left Hand Navigation Bar

Setting IF Gain for Optimum Performance

The most common single item responsible for holding an R390A back is not lack of sensitivity. Rather it is internally generated IF deck noise. In an otherwise properly operating R390A, the cause of this excessive noise is IF gain control being set to high. Even the mfg spec of setting the IF deck gain such that -7vdc at the diode load when fed by 150uv @455kc into J-513 is far too hot.

Here is a recently refined procedure to set the IF deck gain control. Anyone can perform the procedure whether they have access to a signal generator or not:

Procedure to set R390A IF Gain:

Once the receiver has been fully mechanically and electrically aligned, the final procedure to perform before "buttoning it up" is to set the IF gain control. Many otherwise very sensitive R390A's are thought not to be due to weak signals being covered by noise generated by excess IF deck gain.

 Allow the receiver to warm up for at least 1 hour then:

 1- Terminate the antenna input
 2- Set receiver for 15.2 mHz
 3- Set the "FUNCTION" control to MGC
 4- Select the 4kc filter with the "BANDWIDTH"
 5- Set "RF GAIN" control to 10 or maximum
 6- Peak the "ANTENNA TRIM" for maximum noise as indicated on the "LINE LEVEL" meter
 7- Set "Line Meter" switch to -10db scale
 8- Set "Line Gain" control to full CW or "10."
 9- Adjust IF gain control, R-519 to cause "Line Level" meter to indicate between -4 to -7 VU.
10- Re-zero the carrier meter control, R-523
11- Set controls above for normal operation and reconnect antenna

Discussion:

This will yield the best compromise on all bands. I usually "poll" those bands which I normally spec out. Then, using an HP signal generator set for internal modulation of 800 hz @ 30%, "massage" the gain setting and even specific signal path tube selections for the best overall performance.

Contribution by: Chuck Rippel, WA4HHG