[Elecraft] Tuning Pulser with K2

[Stephen W. Kercel]

Elecrafters:

I built a tuning pulser to use with my K2/100 to tune an external linear 
amplifier. The pulser is the AG6K design. The pulse is 12 ms on and 24 
ms off, and repeats about 28 times per second. This is (by design) much 
faster than the normal 25 wpm or so keying out of the keyer.

The interface between the pulser and the K2 is a 2N2222  NPN transistor 
used as a switch. The key line to the K2 is connected to the collector 
of the transistor (nothing else is connected to the collector), the 
switching data comes in through the base, and the emitter is grounded 
both to the ground side of the pulser circuit and the ground side of the 
keying line back to the K2.

I notice what seems to me to be an odd phenomenon when I key the K2 with 
the pulser. When I first switch on the pulser, the power level in the 
little LED power meter on the K2 shows the same power level as I get in 
normal keying. However, after the first instant, the power level 
indication drops one bar lower (and then stays there as long as the 
pulser is on) than the power level indication under normal keying. This 
effect occurs independent of the power level that I set. It happens with 
the K2's 100 Watt amplifier both in and out.

Is this simply an artifact of the metering circuit  caused by the 
peculiar duty cycle of the pulser?

Most critically, will it harm the K2?

Should I do as one alternative keying scheme shows, and use the 
transistor to key a reed relay and use the reed relay (which would 
simply hard short the K2 keying line on key down) to key the K2?

TNX & 73,

Steve Kercel
AA4AK