[TenTec] INRAD 2.4khz 10 Pole Filter

[Jim Reid]

Aloha,  Barry just wrote:

> I installed the INRAD 2.4khz 10 pole filter in the
> standard first (non-switched) 9 Mhz position,
> replacing the Ten Tec 2.4khz filter.  I find that the
> INRAD filter has less loss than the Ten Tec, with the
> result that with RF gain full clockwise, there can be
> some feedback.  If anyone else has this filter
> installed in that position, try this: disconnect the
> antenna and crank the RF gain control (no filter
> option switches engaged in either if).  In cw, my
> audio starts to whistle and in usb starts a swishing
> whistle.

I just tried Barry's suggested test.  Result:  No problem
here,  hooray!  But,  wait,  just realized my set up is
different,  or at least Barry's is different from what
I thought George at INRAD had in mind.

Barry said he put the new 10 pole,
2.4 kHz filter there!!  That is not where that one is supposed
to go,  as I understood the situation.  It  is the 2.8 kHz, INRAD
#754 that is supposed to go up there.  That is the slot where
you must remove the entire bottom cover from the Omni
underside to get to it.  The 2.4 is to go in a slot under
the small optional filter access "hatch".  I put the new
2.4 kHz INRAD # 756 into the first IF N-1 slot.

Maybe what Barry did is not correct?  Or maybe it should 
work anyway?  Why not,  TT's standard in that slot is a
2.4kHz filter.

Perhaps Paul Christensen, W9AC, knows or can suggest what 
might be going on.  I believe he  was one of the gurus 
who came up with the 2.8 filter as the fix for the Omni VI+ 
CW "thump", click,  or whatever solution.   The 2.8 is supposed
to eliminate a fab tolerance problem occurring in some
of the TT standard units in that IF front end which clipped
the leading edge of CW "pulses" during transmit.

But in my set up,  with all filters out,
and only the new INRAD #754 in that very first position,
there is no evidence of Barry's feedback problem.
Can the gain through that front end filter be jumpered,
as in the optional filter slots?  Maybe it is on high
gain,  Barry;  just a guess.  Or,  perhaps there is 
something else about the 10 pole filter that just
won't work in that first slot replacing the TT "standard"
2.4 filter there.

73,  Jim,  KH7M



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