[R-390] Working on R-390A IF Deck

Flowertime01 at wmconnect.com Flowertime01 at wmconnect.com
Mon Mar 27 13:03:45 EST 2006


Fellows,

Bill Hawkins, is right on this stuff.

If you do not have a counter on the signal generator.
First run the 455 into the test point on the last stage of the RF deck.
point E211.

Use what ever signal level you need to get a good meter reading on the
diode load with the BFO off and signal generator modulation off.

Trim up the z501 cap C510 and coil L503 using the manual for setup
of the bandswitch and when to adjust each item.

Also trim up T208 and leave it alone after this. Unless you change the
6C4 in the mixer stage. Then retune T208

You have pushed this coupling stage to best pass through your receivers
455 crystal and that's the best you can do.

It may not be exact 455 but it sure is the peak band pass of your receiver.

Work the signal gen frequency into the 455 crystal and peak every thing for
maximum output on the diode load.

This gets the "IF" aligned into the center of that crystal and does it with 
the balanced input from the RF deck to the IF deck in place.

Some times you can get a little more out of the receiver this way.

If you are doing CW and narrow band stuff TTY and computer stuff
this is worth the effort.

Once you find the peak 455 for your receiver and signal generator then
go to the single end input to J518 and adjust the rest of the IF deck.

Leave Z501 alone.

The mechanical filters will lay over the crystal center.
We have seen from testing earlier this year that peaking the mechanical 
filters
does not change their center frequency but will change the signal level.

The mechanical filter trim caps act more like gain adjust than frequency 
shift adjust.

Trim up the IF slugs.

To stager or not to stager.

If you are a wide band AM listener try the stager tune in 16KC band width.
If you have a sweep generator adjust for nice band pass in 16KC band width

Else center adjust for 455 and 2KC band width.

Roger  AI4NI




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