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TOPIC: RF Power spikes

RF Power spikes 21 Jul 2022 13:00 #1

Before hooking up any LDMOS amplifier in front of SunSDR2 Pro I would like to know if someone has already measured any "spikes" (quick power peak transient) at beginning and also during TX? A 15 - 20W peak would be enough to damage the LDMOS.

Tks

Ed PY2RN
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RF Power spikes 21 Jul 2022 13:54 #2

  • W3FRG
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Ed PY2RN

I have been using the RF 2K+ with the SunSDR2 Dx for one year and have experienced zero problems with RF Spikes using SDR2 or the SDR3 alpha FW.
Your amp should have an input RF level protect that would shut the amp back to Standby if a spike or overload should occur.
This was also a major concern of mine when I first connected the two devices.
I used my LP-700 and the Dx Spectrum screen to look for spikes also.
See attached pic

GL Tom W3FRG
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Last Edit: 21 Jul 2022 13:55 by W3FRG. Reason: correction
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RF Power spikes 21 Jul 2022 15:22 #3

  • VK6NX
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W3FRG wrote:
or the SDR3 alpha FW.
Wow-wow-wow!!! Be careful

ESDR2 is all good.

ESDR3 current public alpha may have issues in certain conditions. It is partially fixed in current dev alpha, but still work in progress (i.e. it is not expected that power spikes will be fully fixed in 0.13a). Hence extra care required to use it with MOSFET/LDMOS PAs. The issues and (sometime) recommendations can be found at Githib. As minimum - use Attn and lowered feed.
Last Edit: 21 Jul 2022 15:28 by VK6NX.
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RF Power spikes 21 Jul 2022 20:10 #4

  • oz1ctz
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I am running SDR3 on my sdr2pro . And I had periodical pwr spikes , it was worst running ft8 . so little strange . I found out that if the volume is very high , the audio from the RX signals is heard in the Tx signal few milisec and gives a spike .. if there is no station on RX I have no problem with TX spike .

It is easy to see the spike just press ptt on a frequency with a good rx signal like ft8 , the pwr meter jumps.

If i turn down the volume slider below 50% the audio spike rx to tx is gone .

I have a small 100w PA at it goes to fault pushing the ptt if volume on RX is high .

vy 73 de Brian



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RF Power spikes 22 Jul 2022 11:00 #5

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In recent under testing DEV 13 07082022 release which I certainly hope will be available soon to public
this has been pretty much resolved.

That said depending on using 3rd party applications and its input level, you could experience a problem

But from a TX mic input or CW level this has been pretty well worked out
73 Rick
Last Edit: 22 Jul 2022 11:02 by N8SDR.
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