[TenTec] T/R turnaround times for TT xcvrs??

[Paul Christensen]

> I recently read the ARRL review of the Elecraft K3, finding it to have
> splendid specs indeed. One spec, though, that I found a
> bit high was the T/R turnaround time of 25 msec.

Allan,

My K3 arrived last week, but I will be putting off the kit build until I get
past some eye surgery in the next couple days.

Recently, I have been documenting T/R turnaround time and keyed waveform
integrity for my transceivers.   Part of the overall delay is in the time it
takes for RF to become generated after the key closure is made.  The time
delay from key closure to RF for my IC-7800 is 9 ms.  My Omni VII measures
at ~ 15 ms.  The ARRL measured the Omni VII complete T/R turn-around time of
20 ms.

Just guessing, but I would put the K3 QSK speed (where one can hear between
keyed elements) at about 35 WPM.  Can anyone here confirm?  That's not bad,
but it's not great.  Ultra-fast QSK in a DSP rig is quite a challenge.  The
best QSK I've heard on any recent radio tried here, is about 45 WPM.

The trick to fast QSK is to make everything switch fast enough without the
nasty side-effects from the T-R transition -- like clicks, unstable PLL,
etc.  These side effects have to settle before the actual transition back to
receive occurs.

I'll know more about the K3 after I start the build but right now, my
expectations aren't too high.

Paul, W9AC