Posted by
Don Wilhelm-4 on
Mar 17, 2009; 5:53pm
URL: http://elecraft.85.s1.nabble.com/K3-Manual-change-suggestion-tp2479552p2492822.html
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
Stephen W. Kercel wrote:
> Don:
>
> It is a sensible question.
>
> A string of dots sent at nominal weight typically has a duty cycle of
> 50% off and 50% on. This is the weight to which I keep my keyer
> adjusted, and after sending that way for 45 years, I'm used to it.
> Typical SSB and CW sent as real characters have a duty cycle closer to
> 33% on and 67% off. The idea of the tuning pulser is to adjust the
> amplifier using a duty cycle similar to what it will encounter in normal
> operation.
>
> Now it is true that I could tune the amplifier by temporarily
> readjusting the keyer weighting for a 33% duty cycle, ramping up the
> speed to about 40 wpm, keying the radio (which requires actually keeping
> a hand on the key) and tuning. Then to revert to normal sending, I reset
> the keyer to my normal 20-25 wpm, reset the weight to normal weighting,
> and then have at it with my newly retuned amplifier. Note however that
> I have added about four steps to the tuning and I am in the extremely
> awkward position of trying to keep the string of dots going with one
> hand on the key and twiddling the knobs on the amplifier with the other.
> To make matters worse, I use a WinKey and the N1MM logger; the N1MM
> logger preempts the manual controls on the keyer. That means that in
> order to reset the weight of the keyer, I need to go to the N1MM's not
> especially friendly parameters menu twice, once top set up the pulser
> sequence, and then again to restore normal keying.
>
> As you can see, the above is possible in principle, but extremely
> awkward in practice.
>
> In contrast, if I connect the keyer and the tuning pulser (which is hard
> wired for a 33% duty cycle) to the K2 via a DPDT switch (one pole
> selects keyer vs pulser, the other controls the power to the pulser), I
> get my tuning pulses with a single flip of the switch. In addition, both
> hands are free to twiddle the amplifier, which means I get the tuning
> done non-trivially faster. Finally, to get back to normal sending, I
> just flip the switch back the other way.
>
> Unlike the Ameritron pulser which costs about $80 and has a lot of
> features that are totally unnecessary, this little pulser costs about
> $25 for the parts, and a lot less if you have a decently endowed junk
> box. This seems a small price to pay to greatly streamline the tuning
> process.
>
> 73,
>
> Steve
> AA4AK
>
>
>
______________________________________________________________
Elecraft mailing list
Home:
http://mailman.qth.net/mailman/listinfo/elecraftHelp:
http://mailman.qth.net/mmfaq.htmPost: mailto:
[hidden email]
This list hosted by:
http://www.qsl.netPlease help support this email list:
http://www.qsl.net/donate.html