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TOPIC: Low Power Output on ALL Bands--Why?

Low Power Output on ALL Bands--Why? 11 May 2022 19:24 #16

  • W3FRG
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I thought this was an interesting test that has been done so I also tested my SDR2 Dx and my results for 160 - 10 m into a dummy load, using the LP-700 Power meter, I measured an average of 84.7 W. The lowest on 10m of 76 W and the highest on 12m of 90 w.
I drive the RF 2K+ amp so the max I ever need would be around 35 - 40W.
We can only hope that our test measuring equipment is calibrated and accurate as stated in their brochures.
My Palstar HF Auto Tuner power meter, which was fully upgraded last year, agrees very closely to the LP-700 readings.

Tom W3FRG
Last Edit: 11 May 2022 19:32 by W3FRG. Reason: Typo
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Low Power Output on ALL Bands--Why? 12 May 2022 11:58 #17

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Thanks Tom
I'm reading power from a meter with a 0-200 watt scale so I don't have the precision of your measurements.
I don't use an amp so the SunSDR2 RF output is relevant to me, although in real live the difference between 85 and 100 watts won't make or break a QSO.

I adjusted my supply up to 14.9 V. The SunSDR2 DX now shows 14.4 V and the Elecraft K3 plugged into the same powerpole distribution box displays 14.6 V.
On key down on 40 meters the SunSDR2 DX says voltage drops from 14.4 to 13.6, .7 V higher voltage than before, but the power out on the external SWR meter is still 85 watts.
There is a power calibration setting in ExpertSDR2/Options/Device/Expert, but it only lets you decrease power. It appears that the SunSDR2 DX is programmed to not produce advertised RF power.
73
Bob KD8CGH
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Low Power Output on ALL Bands--Why? 12 May 2022 17:36 #18

  • Svante
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Hallo from Sweden. I also get sometimes low output power. However. Now with a new tuner because I bought an amplifire, my tuner to my 85 meter loop antenna are, according to sunsdr 2 dx (software 3...) about 89 to 102 watts on different bands and I am happy with that. Power in sunsdr software showing 12.8 volt and on powersupply 13.8 volt. Last week I installed the same sunsdr 2 dx in my boat. Battery bank 300 Amp and sun regulated power showing about 14 volt. The Sunsdr software shows 13.8 Volt 1 volt more than at home. The wire antenna about 19 meter long grounded in the water shows often 110 watt but some band ex. 20 M shows 95 watt. (At home about 102 watt. I guess different antenna, grounding, tuner and more setups can give different results on the same tranceiver. But today I have around 90-105 watt output according to software when tuning. I using atomatic tuner in boat and sometimes it put out 85 watt and then I reset tuner and tune again and maybe get 95 watt or even more. :yes:
sm6usu Svante
sm6usu
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Low Power Output on ALL Bands--Why? 13 May 2022 10:19 #19

  • Rome
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Hello everyone.
1. Output power measurements for SS2DX should be tested with dummy load 50 Ohm, 100 W, in TUNE mode, with a stable power supply 13.8V even in TX mode.
2. Those who have issues with output power in mentioned above conditions, please contact us via email This email address is being protected from spambots. You need JavaScript enabled to view it.
We can offer you assistance via RMS remote access Agent (rmansys.ru/files/) and Skype (join.skype.com/invite/j1oLobDdANJB).
You'll need to prepare a power meter and dummy load 50 Ohm – 100W.
Роман, Roman
Expert Electronics
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Low Power Output on ALL Bands--Why? 22 May 2022 20:13 #20

  • N0BS
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Last night I was repeating and carefully documenting my power output experiments and experienced some odd behavior.
At one point, in TUNE mode with TUNE slider at 100%, the SDR2 DX started making a loud buzzing sound (the xcvr itself, not the software) and the indicating light was flashing rapidly.
Scared the crap out of me and I immediately mashed the power button to turn it off.
After a while I turned it back on and even at quite low power settings of the TUNE slider, the software voltmeter at the lower left (displayed as U:XX.XV) showed only 9.2 volts (!!!) however, the supply voltmeter still showed normal output voltage.
I just shut everything off fearing the xmtr had somehow "bricked" or was in some mode of partial failure. A sleepless night followed.
This morning, I turned it back on, touching or changing nothing, and operation and voltage indication was back to its previous behavior. Although, I still observe a higher than expected sag in the voltage indicated in the software in the TUNE state, i.e. it does not agree with the DVM reading at the power supply. I am using the factory supplied heavy duty power cable, and the 30amp supply is dedicated only to the SDR.
So... my question is - How and where in the xcvr is that voltage displayed in the software being read? It appears that it is some bus point in the radio and not at the power connection terminal point. This would imply that something internally is causing the voltage sag, and is not the power supply itself.
Can someone explain?
Seems like a support session like Rome suggests might be in order.
Any input or suggestions?
Tnx, Tom

Edit: Also wondering if the SDR2 DX implements any protective circuitry / fault condition to protect against undervoltage?
Last Edit: 22 May 2022 20:24 by N0BS. Reason: added question
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Low Power Output on ALL Bands--Why? 23 May 2022 03:13 #21

  • danielwee
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What kind of power supply are you using. If you're seeing a huge voltage sag, it will cause problems. The sag might be due to power supply line resistance (bad connection or cable) or under-rated PSU current delivery rating. Maybe you can try a different cable and see if that helps since your PSU is supposed to deliver 30A.
Last Edit: 23 May 2022 03:14 by danielwee.
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Low Power Output on ALL Bands--Why? 23 May 2022 15:15 #22

  • N0BS
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The power supply is an Astron SS-30M. I have tried several supplies and also a deep cycle marine lead acid battery capable of delivering large amounts of current at rated voltage.
I have also tried several different cables. All exhibit the same relative behavior with minor variations in the actual measured results.
I guess I have not asked the question clearly enough.
It is with regard to the voltage displayed in the ExpertSDR2 software - where and how is that value measured?
It does not appear to be the voltage at the power supply terminals, because the values at the terminals and the value on the software display are significantly different.
There appears to be a voltage sag INSIDE the xcvr. Why?
Tom
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Low Power Output on ALL Bands--Why? 24 May 2022 13:46 #23

  • Rome
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Hello Tom.
What does ESDR2 shows now? Low voltage, but OK current, or both low voltage and current?
Voltage and Current are being measured in the MCU in the PA. If you've heard a click in the TRX, it might be something physical, but to answer precisely we'll need to dive in the TRX, which is impossible remotely.
There are several types of protections in FW, UM, section 7.10 - eesdr.com/images/Document/SunSDR2_DX/SunSDR2_DX_User_Manual_ENG.pdf
There is also a reverse polarity protection on the hardware level.
Роман, Roman
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