I've done all those mods to #380, Don. I didn't
realize they were that effective! And after
reading of thermal stability issues some have had
in JT65 (e.g., using a KX3) I assumed the K2/10
would have even larger issues in those modes,
given the age of the design.
Your message is good news indeed!
73, Phil W7OX
On 4/24/16 3:52 PM, Don Wilhelm wrote:
Phil,
I cannot say if David did anything special for
frequency stability, but any K2 above SN 3000
had the BFO stability mod and the PLL
Temperature compensation mod installed which can
achieve the necessary stability. K2s below SN
3000 can be upgraded with those upgrade kits.
The stock PLL Temperature Stability Mod has
resistor RA as a 33k resistor. That resistor
value can be modified to achieve closer
temperature stability for any particular K2.
The K2 manual does not contain information about
how to vary and check the compensation, but that
information is contained in the instructions for
the PLL Temperature Stability Mod - download
from Elecraft.
The temperature change in the K2/10 is not
likely to be very much even for long periods of
transmit because the PA transistors and heatsink
are not close to the VFO/PLL and BFO areas and
there is a lot of 'air space' inside the enclosure.
With the KPA100 added, that air space is much
more confined and the heat from the KPA100 PA
transistors will have an influence.
In other words, while the stock K2/10 may be
sufficiently stable, the K2/100 may need some
'tweaking' of the RA resistor value for
equivalent stability.
73,
Don W3FPR
On 4/24/2016 6:23 PM, Phil Wheeler wrote:
David,
Do you do anything special to ensure frequency
stability in those modes with your K2?
Phil W7OX
On 4/24/16 3:02 PM, David Giles wrote:
I've made hundreds of contacts using JT65 and
JT9 with my K2 at 5W. Most of these portable
on a 12v battery with solar charging. With a
48 second transmit period, it's probably more
of a stress test than BPSK31.
73 de David VK5DG / VK3TUN
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