Responding to N2PD's request for help with filter alignment...
I have a different approach than that used by anyone else I have heard from,
so I thought I would share it. But do know that absolute precision is not
possible as the resolution for alignment is limited. the best you can do is
quite close.
It is a good idea to have warmed up your radio for an hour before doing this,
and have a stable shack temperature as well.
You are going to use MATH, fancy that, in this approach. Let's say you have
chosen 600 cycles as your listening pitch. Move through the menu until you
have the BFO frequency on the screen.
Now, with no antenna, but gains turned up, close your eyes and tune through
zero-beat. Find the absolute zerobeat. It all depends upon finding the
zerobeat accurately, so take your time. Now, open your eyes.
Record the BFO frequency. Subtract your chosen listeing frequency for CW
regular and add for CW reverse. For example, my chosen frequency is 400
cycles. My center for my first filter is 4913.78. So I subtract or add 40
after the decimal (see, resolution is to plus or minus ten cycles, and
further, you sometimes can't get the exact number you want either because it
will flicker between two numbers, turn just a little and it flickers between
the next two). So my CW regular is 4913.38 and CW R is 4914.18.
After setting these two BFO frequencies for CW regular and CW reverse, go
back and forth between them to see if they are the same frequency. IF you
indeed found zerobeat, they will be very close. If they are not close, you
missed zerobeat. In that case, equalize them by changing both either one
number higher or one number lower, until they are indeed balance, very close
to a match.
Go on to the next filter. When the tone matches between CW regular and CW
revers AND they are exactly double your chosen listening frequency apart from
one another, they are set as closely as it is possible to set them.
I find that the settings are temperature dependent. In the winter ambient
shack temperatures are as much as twenty degrees (60) lower than in summber
(80). That difference moves the zerobeat BFO frequency a little and that
moves the regular and reverse frequencies apart since they are no longer an
equal distance from zerobeat.
73
Fred - KT5X
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