Posted by
GeorgeP1111 on
Sep 09, 2018; 9:57pm
URL: http://elecraft.85.s1.nabble.com/KX3-WSPR-Thermo-Stressing-tp7644935p7644956.html
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 ;
[hidden email]
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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