Thanks for your reply Don.
I read the High Temp Limit is set for 60c so I figure I was not dangerously
high but just wanted to check if there might be a mechanical preference
between the shorter duty cycle with the lower temp but larger temp swing
causing more of a expansion contraction issue over time or the higher duty
cycle with higher temp but not near as much heating cooling. I know that on
some devices the thermo stressing of components due to repeated heating
cooling cycles is a issue.
This will probably be in continuous use for a while so my concern is the
long term effects.
I will keep a watch on the temp and maybe add the heatsink as you suggested.
tnx
George
WD0AKZ
-----Original Message-----
From: Don Wilhelm
Sent: Sunday, September 09, 2018 11:30 AM
To: George Pasek ; elecraft@mailman.qth.net
Subject: Re: [Elecraft] KX3 WSPR Thermo Stressing?
George,
Actually 53 degC is not that hot. Look at the specs for semiconductors
and you will find that is only a medium temperature.
Actually at 500mW, it is unlikely that the KX3 will be damaged by even a
continuous key-down.
If you are operating it outdoors, you should keep it out of direct sun.
If it concerns you, I would suggest adding one of the aftermarket heatsinks.
73,
Don W3FPR
On 9/9/2018 12:11 PM, George Pasek wrote:
I am using my KX3 as a WSPR beacon at 500mw with a Arduino based
controller which provides GPS time sync, WSPR data, and audio. Currently
I am running mono band at 1 two minute transmit cycle per 10 minute time
block. Now I want to add KX3 band switching to my controller and increase
my T/R duty cycle. Watching the PA.I current I see that my current 2
minute ON 8 minute OFF cycle shows a 30c ON – 46c OFF temp range. Running
a 2 minute ON 2 minute OFF cycle shows a stabilized 36c – 49c range after
about 5 ON/OFF cycles, and running continuous transmit cycles stabilizes
at 48c – 53c after 6 cycles. So based on these 3 duty cycles I see a 16c,
13c, and a 5c temperature rise. The 2 on/8 off has the lowest max temp
but the widest temp range, the continuous transmit has the highest max
temp but the lowest range. My plan would be to have my controller switch
the KX3 through 5 bands transmitting the 1 minute 53 seconds on a band and
switching to the next band during the 7 second opening.
I have done extended temperature calibration with the XG50 so frequency
stability should not be a issue.
My question is, 53c (127f) is hot, are there any thermo stress issues to
the PA or the KX3 in general with running any of these three duty cycles?
Obviously I don’t want to damage my KX3.
---
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