Max TX PA time?

[N6JSX]

My previous KX3 used the whole METAL case (plus of heat-sink mod add on) as a PA heat-sink (as 10W could get the PA very warm very fast).

SDX has no metal case nor external PA heat-sink. In FM/CW mode (worst case) what is the max TX time per output Wattage & what is the minimum TX to RX for cooling cycle time?

at 5V DC power input =
at 13.7V DC power input =

[N6YWU]

The KX3 uses a lower efficiency transmitter amplifier design, so will get hotter at the same wattage output.

The (tr)uSDX uses a class-E amplifier which allows the filter to manually tweaked to up to around an 85% efficiency. At 5 Watts and 85% efficiency, that results in (5W/0.85 - 5W)/3 = 293 mW per BS170, which according to some of the BS170 data sheets, appears to look acceptable for continuous use (100% duty cycle until your battery runs out) at an ambient of 25C.

If you don't tune the filters your (tr)uSDX RF board, the efficiency will be lower, so you'll probably have to measure the efficiency on your particular unit, and/or put a thermometer on your transistors to check their temperature. I aimed an infrared thermometer at the transistors on my unit, and did not see a dangerous heat rise during a 50% duty cycle series of FT8 transmissions (I do not recall the exact measurement numbers). YMMV.

73, Ron, n6ywu

[N6JSX]

So YWU is telling ALL that 100% duty cycle (FM/CW) at ~10W TX (max DC in 13.8V) output (into 1:1 load) will NOT cause the PA any thermal over-heating life-degradation and NO adjacent PCA part degradation?

YWU has actually tested this at >5 minutes continuous TX into a 50ohm dummy-load on each band? YWU are you speaking for MAN? Or is this arm-chair guru-ship talk?

[N6YWU]

If you search the forums, you will find a report from DL2MAN on 100% duty cycle testing. I've only tested 50% duty cycle. I don't know if anyone has tested 10W output, as that appears to be out-of-spec use of this design. If you can find a component manufacturers data sheet for the 170 that specifies part degradation over time, that would be very interesting information. 73, Ron, n6ywu

[DL2MAN]

So YWU is telling ALL that 100% duty cycle (FM/CW) at ~10W TX (max DC in 13.8V) output (into 1:1 load) will NOT cause the PA any thermal over-heating life-degradation and NO adjacent PCA part degradation?

YWU has actually tested this at >5 minutes continuous TX into a 50ohm dummy-load on each band? YWU are you speaking for MAN? Or is this arm-chair guru-ship talk?

JSX, That´s a pretty rude posting towards someone who was trying to help you...
No, Ron is not talking for me, he was just trying to help you with -what I can see- valid Information.
And No, Ron did not suggest to go 100% Duty Cycle at 10W Out. The (tr)uSDX is rated max. 6W @13,8V
At SWR better 1,5, I personally tried doing WSPR for 24 hours at full 5 W Out. WSPR is 3 Minutes constant TX (100% Duty Cylce) every 20 Minutes or so. All I can tell is: My rig is still OK.
There is no Amazon Prime guarantee. It´s a hobby project, created by hobbyists. Never meant to be sold assembled. You need to tune filter section, in order to get thehighest possible efficiency. If you don´t like that, buy ICOM/YAESU/KENWOOD !

73 Manuel; DL2MAN