[R-390] sweep alignment

[Bob Camp]

Hi,

Here's the basic problem with sweep alignment on the R-390 - you have to go
*slow*.

A number of people have given this a try and most of us oddly enough have
used the 3336 or one of it's cousins.

In this case passband ripple = narrow peaks in the filter = narrow band
stuff in the filter = long time delay in the filter.

It's the same reason you don't normally see mechanical filters in the IF of
a FM radio.

The only way to be sure you are going slow enough is to keep slowing things
down until the result doesn't change. Start with a sweep of just the
passband. Don't worry about the entire filter response. Try something like
30 seconds for the 2 KHz filter and see what you get. Back it off to two
minutes to be sure that the result is correct. From there you can speed it
up to the point is begins to look weird.

Since you can't do anything about the response of the mechanical filters
some of this may not be needed. The only thing you can do anything about is
the tuned coils in the IF strip. You may be able to set them adequately with
a sweep speed that does not properly display the response of the IF.

    Take Care!

        Bob Camp
        KB8TQ