Andy and all,
The KAT500 and KAT1500 tuner band segments are divided into frequency
band segments - 25kHz wide on the lower bands and 50kHz wide on the
upper bands if I recall correctly, so an 8kHz shift will not be
significant unless the frequency shift moves the tuning into the
adjacent segment.
There is also a limit to how far the firmware will go to reducing SWR.
In the interest of minimizing tuning time (and relay wear and tear). If
the match is less than 1.3:1 or so, tuning will be declared adequate and
will be stopped.
Since the typical driving transceiver can tolerate an SWR of at least
2:1 without power foldback or damage, setting that 1.3:1 limit is
reasonable - unless you are a 'purest' and mentally can only tolerate a
1:1 SWR (big grin).
73,
Don W3FPR
On 11/29/2018 5:42 PM, ANDY DURBIN wrote:
"In addition the tuner may not always be in the segment you think it is. This is due to
the 8KHz resolution of the internal counter, that wins over you sending it a more accurate
frequency, and also the hysteresis algorithm that can require a 2 segment frequency change
before the tuner changes. Gary from Elecraft says "if you are off by one bin segment then
it should not matter too much"
I have the same frustration with my KAT500 tuner. I send it a frequency with 1
kHz resolution ( I was using 1 Hz resolution but found that was futile) but it
wants to override that frequency with a much less accurate RF derived
frequency. I suggested to Elecraft that the frequency received over the serial
interface should have priority unless the RF detected frequency differed by
more that a user set threshold. That proposal was rejected on the basis that
here cannot be two master frequency sources. That argument was lost on me since
I have worked in the development of avionics systems where master swaps are
common and dynamic data source selection is also common.
I settled for sending my KAT500 a new frequency any time the actual transmitted
frequency differs from the KAT500 reported frequency by more than 8 kHz. I
have also tweaked FCCS and FCMD (not easy because they don't seem to work as
documented) to make is less likely that RF detected frequency will usurp my
serial data frequency at least for CW transmissions.
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