[Elecraft] Tuning Pulser with K2

[Stephen W. Kercel]

Don:

Certainly, for A CW guy like me, sliding a book against the dot paddle 
would probably work.

However, flipping a toggle switch to get a pulse stream is much more 
convenient, especially when the electronics attached to the toggle 
switch cost only a few dollars. (Side note: The tuning pulser is one of 
the few instances where I have found that home brew is substantially 
cheaper than getting "store bought.")

The idea that the tuning point is affected by the duty cycle is claimed 
on several different a RF amplifier Web sites. Perhaps they are 
mistaken. I must admit that I wonder why a genuinely linear system would 
have its tuning point affected by the duty cycle.

Anyway, your suggested fix turned out to be correct. After some 
searching through my junk collection, I did find a capacitor of the 
proper value, and increased the pulse duration from 12 to 24 ms while 
preserving a 33% duty cycle. That completely resolved the "one bar less" 
effect. I do find that it takes more than 3 dots for the transmitter to 
come up to full power when I change bands and then run the pulser. The 
higher the frequency band, the longer the delay, taking only a few dots 
to come to full power on 80 meters but several seconds to come up to 
full power on 10 meters.

73,

Steve
AA4AK


Don Wilhelm wrote:
> Steve,
>
> Not to belabor the point, but if simply tuning the amplifier is the 
> goal, a 50% duty cycle should get the job done.  Assuming the amplifier 
> is supposed to be linear, tuning it at low power should get the settings 
> close to the correct point and then a very short tuning time would be 
> needed at full power.  As long as the amplifier has a little bit of 
> reserve (you are not pushing it to its max), a 33% duty cycle should not 
> be necessary - I just can't understand why the amp's tuning points would 
> change with the duty cycle.
> If you intend to tune the amp for a lengthy time at full rated power, 
> then yes, it will be stressed at a 50% duty cycle, but for a reasonably 
> short tuning period, I just don't see the need.
>
> I would just push a book against the dot paddle and tune away, move the 
> book when done - no extra steps.
>
> 73,
> Don W3FPR
>
>