[TenTec] One last chirp

[RICHARD ANDREN]

This is confusing.  A few weeks ago many of you told me how there was NO 
spike.  Now I read that there is a spike "smack dab in the power area that 
drives many amplifiers".  Maybe I'm the only one that remembers this?

73, Rick N9THC
-------------
Original Text
From: "Paul Christensen" <paulc@mediaone.net>, on 1/7/99 7:20 PM:

>This hard edge won't show on a lot of radios because their crystal and
>mechanical filters have a rotten time response and so are slow to start
>(and ring to fill in the holes between line noise pulses as well as
>lightning crashes).

Very True.  There's a marked difference in received keying dynamics between
radio with ladder or Cohn  I.F. filters and crystal lattice I.F. filters.
The lattice filters tend to even those waveforms with fast waveform rise 
and
decay.

Steve made a point not to be missed: when assessing the keying dynamics, 
try
both LSB and USB and note the difference.  I detect noticable differences 
on
both my Omni Six and Yaesu FT-1000MP.

The TenTec filters seem to have a better time
>response so make the hard leading edge of the Omni VI really sound hard.


Yes, for the same reason above.

>You can't judge leading clicks with fast TenTec AGC, its best judged
>with AGC turned off and manual RF gain because on FAST AGC TenTec
>receivers make their own click on the leading edge.


True.  The Omni Six's leading edge is VERY steep.  Why?  I believe it was
designed that way to offset a sharp leading edge power spike that I could
see on my Omni V.  Both the Omni V and Omni Six use a ramped integrator
circuit to achieve the desired waveform rise and fall. On the Omni V, the
waveform is gorgeous.  The keying and timing circuitry between the two
radios is again nearly the same.  So what happened on the Omni Six?  The
answer lies in the Omni Six's ALC circuit.  Until the signal path reaches
the 9 MHz Mixer Board, the keyed rise and decay time is as gorgeous as the
Omni V.  It's here where there's a slight departure in circuitry and
component values.  It took me three weeks to find the right component
combination to achieve a symmetrical waveform, AND without a leading edge
power spike.  There's a delicate balance between the ALC response time and
the waveform edge...and logically so when you think about what the ALC is
attempting.  In essence, I slowed the ALC attack time just enough to keep
the leading edge keying dynamics and without a sharp power spike.  The 
spike
is only noticable bellow full output, smack dab in the power area that
drives many amplifiers.

-Paul, W9AC



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T


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