High Transmit Power

[KN6IPZ]

I just got an assembled (legit) truSDX and when I enable the power display, it shows I'm transmitting over 10w. I can only fix this by adjusting my variable power supply down to 9v, this allows me to transmit at 5w according to the display. Any suggestions on what is going on?

[DL2MAN]

Hi,

There´s a few things, you might want to look into:

- Use a Dummy Load ! Real Antenna with SWR and Reflections might affect measurement
- If you use external Wattmeter, make sure it´s accurate at the lower end. Most commercial Watt Meters have a large range (eG 5W-100W or even up to 400W) and are not accurate at the low end.
- If you use OnBoard Tools: Measure in CW only. CW uses SWR Bridge to determine PWR, SSB PWR measurement (available in latest Beta only) uses different approach internally (Estimates PWR by Current = Less accurate).
- Band Dependency: On 80m I also get up to 6,5W in some cases.
The most accurate method to measure output Power I know, is to measure Voltage over 50 Ohm Dummy Load with Oscilloscope, then calculate PWR. This is anyway the very first thing to do, when you get your new TRX..... Confirm internal measurements by accurate external measurements. Determine true efficiency and calibrate efficiency readings by adjusting RShunt Value.

If all that does not apply here, and you really have 10W Out, then the band dependent coil needs re-tuning.
In this Video: https://www.youtube.com/watch?v=qN7hHsvcNMM
I also have one case, where I have too much Power and explain what to do in order to get it back into safe limits.

73 Manuel; DL2MAN

[KN6IPZ]

Thank you. I learned a little after watching the video. Mainly how to make adjustments but not really exactly why, but I'm capable of research and will look into inductance and everything. So I moved on to each band and recorded the radio meter results like you showed in the video, the results are below and were all taken in the CW bands. I'll work on VNA readings next and will post them once available. I'm also going to double check my antenna for any issues but this is where I stand today.

80m: 7.8w @ 87%
60m: 3.3w @ 99%
40m: 13w @ 99%
30m: 4.4w @ 93%
20m: 7.4w @ 69%