Rick,
It's not easy to follow some of these message threads because there's so
much information. In a nutshell, I am saying that:
1) The Omni Six/Six Plus does NOT have a leading edge power spike, but it
DOES have a steep leading CW waveform edge.
2) I have noticed a leading edge power spike on several Omni Vs.
3) On these transceivers, there is a balance between achieving good ALC
control, minimizing the leading edge power spike, and obtaining symmetrical
leading and falling waveform edges without steep edges.
Jerry brought out another point concerning ALC and the potential for the
leading edge power spike in that by controlling a transmitter's drive
control, the spike can be controlled. My Triton IV allows me to do this
from the front panel, my Omni Six and Omni V does not. What about other
Ten-Tecs?
-Paul, W9AC
-----Original Message-----
From: RICHARD ANDREN <andrenr@ul.com>
To: tentec@contesting.com <tentec@contesting.com>
To: <tentec@contesting.com>
Date: Friday, January 08, 1999 8:20 AM
Subject: Re: [TenTec] One last chirp
>
>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 noticeable 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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