[TenTec] Argo 515 selectivity improvement

[Clark Savage Turner WA3JPG]

I had mentioned to the group (a while back) that I wanted to put
the 8 pole crystal filter into the 515, and when I did, I still
noticed a form of blowby on the opposite of center.  I had 
eliminated the problem by inserting an old 4 pole filter (from
my old Corsair I when I replaced that filter with the 8 pole 
option) and it worked fine.  I got to thinking that I could just
put the 4 pole filter back in and stick the spare 4 pole filter
in line afterwards, that equals 8 poles :-) .  It works just
great.  So, if you have a spare TenTec 4 pole filter lying 
around and you want to tighten up your Argo 505, 509, 515, it
is very easy, just involves some mini coax and careful wiring.
Loss is very little.

One more note, the carrier oscillators need to be moved for the
8 pole filter, and I had to move them back for the 4 pole filter.
I had gotten that RadShack freq counter on sale last week and 
found a use for it right away!  The resolution is not enough to
get exact 750 Hz offset for CW, but I don't mind 50 Hz away
from that one.

Makes my 515 a lot like the Triton IV, pretty nice receiver, none
of the old chatter that the standard 4 pole filter used to let 
through.

Clark
WA3JPG

P.S. If any interest, I don't mind posting the wiring details, 
though they are in some old QST's and QQ's if you have them.

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