Topband: W9AC's Omni VI+ key click mod
ac7a at earthlink.net
Sun Jan 23 16:57:34 EST 2005
Last year, I sought help from the list regarding key click mod's for the
Ten Tec Omni VI + and was directed to Paul's (W9AC) mod. The Omni VI+
has been know for a fast leading edge (<1ms) which resulted in clicks
that were especially noticeable when followed by an external amplifier.
And even though I don't have an amp, I don't like the idea of being on
the air with a wide, clicky signal. So across the holidays I delved into
Paul's modification procedure, made the changes and put it on the air
without knowing the end result.
This weekend I had access to a Tek 2465 oscilloscope and set it up to
trigger off the output of my CMOS II keyer. Even though the scope isn't
a storage scope, I was able to hold the envelope in place when sending a
series of high speed dits. What I observed was a nearly identical rise
and fall time; both about 4 or 5 ms. And no matter where I set the power
level the envelope was maintained.
Paul's mod can be found at:
The keying mod is a bit tricky as it does involve changing surface mount
components on the 9MHz filter board. I found that it was easier to use
some discrete, through hole components instead of surface mounts. For
C47, which is changed from a 0.01uF to a 4.7uF tantalum capacitor, I
left the 0.01uF on the board and then formed the leads of a discrete
4.7uF tantalum to terminate across the 0.01uF. I then bent the 4.7 uF
over so that it laid to the edge of the PC board. R39 is then removed
and replaced with a 0.22uF chip cap. The chip cap was much larger in
width so I set it on its side and soldered it in place. Last, C37, a
through hole 1uF electrolytic capacitor has a 10k resistor added in
series with it. I removed the electrolytic and soldered a 1uF ceramic in
one hole, bent it upward, and soldered a 10k 1/4w resistor in the other
hole. The open ends were connected together and soldered.
I think think this is a very worthwhile improvement to the Omni VI+,
that will be appreciated by other operators on the band. Thanks goes to
Paul for his fine solution.
Regards, Thomas - AC7A (Tucson)
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