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TOPIC: Output power and meterreading

Output power and meterreading 25 Mar 2020 18:36 #1

  • Gerben
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Power output varies per band and the power meter gives very different readings. Here is what I read on the SunSDR2 DX and on my Expert 1.3K-FA:
Band Sun - Expert - Tune slider
20m - 113 - 107 - 100%
17m - 74 - 75 - 100%
15m - 80 - 94 - 100%
12m - 110 - 101 - 100%
10m - 102 - 94 - 72%
Above is with max power setting. On 10m with full power the radio gets in its protection mode, so I reduced power until no protection status anymore. At low power levels it seems the meter is hardly ready any output. I'm not so concerned about the accuracy of the power meter but more about the max power levels that differ a lot and the protection when at 100W output level.
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Output power and meterreading 25 Mar 2020 20:46 #2

  • DL9NBJ
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Hi Gerben,
Did you measure with a dummy or with an antenna?
I see no problem with the values of the transmission power, but with the slider position at 10 m.
vy 73 de Thilo DL9NBJ

Problems with my SunSDR2DX:

VOX - works only on 2m, not on HF
TUNE - does not work, reduces power when tuning if SWR is bad
Displayed supply voltage has incorrect values
Crosstalk betwen antenna ports A2 <-> A1
Solved: ... ;-(
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Output power and meterreading 26 Mar 2020 09:08 #3

  • Gerben
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Hi Thilo,
I did measure with antenna (have no 100W dummy). But I also see that at low power the meter of the SunSDR does not give the realistic value. I have no idea why I get the protection on 10m. I will test this weekend again and use a tune to make sure that the SWR is not the problem. Perhaps I can use my dummy when making short transmissions. I will present the result here again.
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Output power and meterreading 26 Mar 2020 11:12 #4

  • DL9NBJ
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Hi Gerben,
you cannot actually make exact power measurements without a dummy load, because if you tune your antenna, then you have pretty much exactly 50 Ohm + - J = 0 at the output of your pa, but after one or 2m coax cable it looks a bit different again . It also depends on the input SWR of your power amplifier. Power measurement is therefore always a voltage measurement, and the measured voltage varies depending on the impedance. A power measurement is always only accurate if you have exactly 50 ohms without reactive components.
I would say that it would be enough for me if the sliders correspond to 5% actual reading (at 50 Ohm + -J = 0).
vy 73 de Thilo DL9NBJ

Problems with my SunSDR2DX:

VOX - works only on 2m, not on HF
TUNE - does not work, reduces power when tuning if SWR is bad
Displayed supply voltage has incorrect values
Crosstalk betwen antenna ports A2 <-> A1
Solved: ... ;-(
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Output power and meterreading 26 Mar 2020 11:56 #5

  • Gerben
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Hi Thilo,
I agree and also know that it works like that. The only thing is that I have also a PRO version and now see that the DX version acts different. That is not a accurate thisng but I see that it is different. Nevertheless, let me use the weekend to do some further experimenting and measurements and get back to you with my findings.
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