[Icom] IC-756pro2

[George, W5YR]

Yes, Earl, I have done extensive time and frequency domain keying studies of
the PRO, PRO2, 746PRO and the K2.

On the PRO2, as on the PRO and 746PRO, the menu adjustment sets both the
rise and fall time of the actual r-f output keyed waveform. I run normally
at 4 msec and find that gives a slight hard edge to the keying whereas 6
msec, the next step up, is a little too soft for me.

The lag between key down and the start of the leading edge of the r-f output
is around 10 msec for all the PROs. This can be compensated with an external
keyer such as the CMOS or Logikey K3, etc. by simply using a K factor of 10.
On MixW, the compensation factor is 7. Most of the remote control and
logging programs provide for keying compensation in this manner.

Icom could have easily included this simple correction in their keying
algorithm but model after model, they continue to not understand how to set
up a keyed waveform.

The problem shows up only on the first dit of Break-In and on every
character element of Full Break-In since it takes the rig about 10 msec to
complete the transition from receive to transmit and then back again.

I find that the uneven dot/space time intervals are no problem up to about
30 wpm - above that speed, the dots start sounding too light. Since my
"sweet spot" is around 25 wpm, I usually just use the internal memory keyer
and don't worry about it - never had a complaint yet with any of the PRO
rigs on CW.

As to the wording of the manual, it is poor as usual, but they are trying to
say that the time interval you are setting is the time from zero power
output at the start of the keyed character to full power output - in other
words, the rise time of the leading edge. The trailing edge is always the
same time as the leading edge.

The keying transition from start of leading edge is rounded and smooth.The
completion of the leading edge is somewhat abrupt and probably accounts for
a slight click or other keying artifact. There is, however, no overshoot to
cause problems. The start of the trailing edge is well rounded as is the
completion. So there is only the one transition that needs smoothing. All my
PROs have had this identical waveform.

For some unknown reason, Icom provides for adjusting the DASH length - which
is probably the most useless thing I can imagine for setting up a CW rig.

CW is, in my experience, the only thing where Icom fails to match up. But,
with an external keyer with timing compensation, that is not an issue.

I find that break-in on the 746PRO to be better than on the PRO and PRO2,
but none are as good as my IC-765 when it comes to QSK. Icom got that one
right!  <:}

If you have further questions, fire away.

73/72, George
Amateur Radio W5YR -  the Yellow Rose of Texas
Fairview, TX 30 mi NE of Dallas in Collin county EM13QE
"In the 57th year and it just keeps getting better!"
<mailto:w5yr@att.net>





----- Original Message -----
From: <k6se@juno.com>
To: <icom@mailman.qth.net>
Sent: Monday, August 04, 2003 9:45 PM
Subject: [Icom] IC-756pro2


> I asked Icom America the following question:
>
> Page 43 of the instruction manual describes a CW keyer menu item called
> "Rise Time".  The adjustment procedure says, "Rotate the tuning dial to
> select the time which the output power becomes the set transmit power".
>
> Is "Rise Time" the cw waveform rise time or is it a delay to allow time
> for an amplifier's keying relay to close before the 756's RF output
> occurs?
> ==========
> Here's the answer I received:
>
> The instructions you refer to have puzzled me too.  I believe that this
> is a misprint of some sort, because it doesn't make sense.  By turning
> the main tuning dial, you increase or decrease the rise time of your
> signal, so you can make the tone harsh or softer by changing the rise
> time.
> ==========
> As you can see, the answer does not appear to be all that definitive (to
> me, at least).
>
> Has anybody on this reflector looked at the CW waveform on 'scope and
> know the correct answer to my question?
>
> 73, de Earl, K6SE
> ----
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