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[TenTec] Beginner Corsair II Questions

To: <tentec@contesting.com>
Subject: [TenTec] Beginner Corsair II Questions
From: turner@safety.ics.uci.edu (Clark Savage Turner WA3JPG)
Date: Fri, 12 Sep 1997 10:32:47 -0700
> For instance, I am confused about the interrelationship between the XTAL 
> filters (I have an optional one a position 2), the PBT knob and its 
> neighbor. 

The PBT will interrelate with the xtal filter in a way.  First,
the PBT should be near the top center to start, though mine is a
bit out of alignment (or else my ears are, hi hi) and mine sits
a bit to the left of center to make my ears happy.  This will 
indicate about a 700 Hz center freq for the CW signal zero beat.
In other words, the PBT at center will put the CW signal in 
the center of the passband with about a 700 Hz beat note.  It
is not very noticeable when you use the 2.4 kHz SSB filter,
because you have wide skirts and will not notice when the 
CW signal is not in the center anymore.   However, when you
kick in a 500 or 250 Hz CW filter, you have to be quite close
to the center to hear the signal.  

What I do is tune the desired CW signal in to about a 700 Hz
tone, and then kick in the CW xtal filter, and the signal 
should pop out at me.  If I have tuned the CW signal to 
500 Hz or 900 Hz it is likely to disappear with the CW
xtal filter because of the narrow passband and steep skirts.

The interreaction with the PBT is that you can tune the PBT
off the center freq and the passband will shift, the CW filter
window of 500 Hz will "move" relative to the first IF 2.4 KHz
filter and you can "move" the center freq in a sense, to 
get the narrow CW filter to look like it has a 500 Hz center
freq and get a lower beat note on a CW signal you have
zero beat.  I like to tune my PBT to the left just a little
bit, and the beat note with my narrow CW filter is more like
500 Hz, where my ears are happy.  Now, with the PBT here,
you need to tune the CW signal  to the 500 Hz beat note
before engaging the CW filter or else it might disappear
on you.

The audio BP filter has a fixed audio center freq of about
750 Hz I believe.  If you want to use it, you either do
not also use the CW filter, or you must very carefully get
the CW xtal filter to center at 750 Hz also, by centering
the PBT at the top and making sure the beat note is right
(you can check by comparing it with the sidetone I think).

If you like to set the PBT to the side and get a lower beat
note, like I do, the audio BP will not help and can kill the
audio you would like to hear.  When I am in tough shape with
QRM, I move the beatnnote up to 750 Hz with the crystal CW
filter and crank the audio BP filter in, and not much QRM

The notch filter can come in handy for close in QRM at times,
too, you adjust it entirely independently of the other controls,
just move it till you notch out the unwanted signal.  Keep it
all the way to one side when not in use.

The "spot" button can be used to zero beat a CW signal very
precisely.  Tune in the desired CW signal and try to get 
it to 750 Hz by ear.  Then push the button, and tune a little
more till you just "zero beat" or you do not hear any beat 
note left at all.  You may want to play around to get the hang 
of it, you will probably tune a little to get a clear tone, then
back down till the tone just disappears, then don't tune down 
any further.  That will give you the right spot in the
passband for the CW filter as above, when you let the button
go, you will hear a 750 Hz tone if all is aligned fairly well.

Hope this helps.  Write again if you have more questions, there
are a bunch of Corsair nuts on this group.


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