[Elecraft] Interfacing K3 to TenTec QSK Amplifiers/Automatic Antenna Tuner

[Jim Brown]

On Thu, 20 Nov 2008 12:32:37 -0800 (PST), W7TEA wrote:

>Ben, I connect my K3 to a TT Centaur amp.  I just ran 
>a shielded cable between the K3 "Key Out" jack to the 
>amp "Key In" jack.  Seems to work just fine for QSK.

I'm doing the same with my K3 and Ten Tec 425. The K3 has a built-
in delay that causes XMIT to begin several msec after the power 
amp is keyed via the PTT line. This delay is variable, and as I 
recall, the default value is around 8 msec. I'm being conservative 
and setting it to 12 msec. It runs fine. I have reason to believe 
that some serious engineering went into choosing the default 
value, and that it's probably sufficient for most amplifiers. 

The original post in this thread says K2. The K2 also has a 
similar pre-delay circuit, but it's not adjustable. I forget what 
it's called, but I've used it and it works fine too. 

I've used both of these rigs this way in full QSK mode. The amp is 
set for PTT mode. 

The reason for the delay is simple -- it's quite important that 
the amplifier's T/R relay pull in before it sees RF. Switching 
with RF on it is called "hot switching" and is a great way to burn 
up a relay (and maybe to damage the amplifier if you do it 
enough). 

73,

Jim Brown K9YC