On Thu, Sep 29, 2011 at 12:59 PM, Glenn <wa4aos@aol.com> wrote:
> Case and point. I can take two of my calibrated HP 8640B signal generators
> and set them both for .15 microvolts and separate the carriers by 75Hz.
> Then switching the output of one of the 8640B's OFF and ON rapidly using a
> shielded keying fixture, (see note below ) I built, I can clearly here both
> signals
> as defined dits and dahs. Using the same arrangement on the K3 or Omni 7,
> the signals are poorly defined with digital artifacts making neither decent
> enough to
> make understand the dits and dahs. Leading and trailing edges of both signals
> are distorted and copy would be nearly impossible at those levels. The analog
> front ends in the O6 and Corsair are difficult copy but you can make out
> what the keyer is sending.
Glenn, if you could make audio recordings of the test you described
showing good resolution by O6/Corsair and poor resolution by K3, you
would be making a huge contribution toward the 2-year old debate about
poor pileup readability on the K3. I've often though that the O6
might make a better run radio (i.e. to handle pileups) than the K3.
Appreciate your comments on variability of O6 sensitivity because this
has also been my experience. I've had 3 Omni 6/6+'s in the shack in
the past couple of months with vintages spanning 1992-2001 and the
oldest unit had the quietest/most sensitive front end. If someone
could document the front end diode replacement (i.e., how to remove
the board, what diodes to use), they would be doing a real service to
the user community. I understand it's a tough job and the pin diodes
commonly recommended for the O6 job are no longer available.
Just an aside, but I'm not a big fan of the O6 dsp circuit and my
initial efforts at bypassing it have yielded MUCH more pleasing audio,
although it remains a work in progress needing more of my time.
73,
Barry N1EU
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