R Shunt value setting

[VK2VD]

Hello Manuel & Guido
Many thanks for this great radio. I have enjoyed very much building and using and modifying to classic version.

My question is in reference to the R Shunt setting. I am aware it is the resistance between R7 & R8, this I can measure. Now how does this figure relate to the value set by R Shunt in the sandwich? I get with the default setting of 19 around 50-60% efficiency.. to get your efficiency level I need to set R Shunt to 22. Both units I have. They are similar. There is no reference to this setting in your video on tuning of RF section. I wonder if you could talk about this.

Regards

Richard
VK2VD

[DL2MAN]

Hi Richard,

RShunt is the resitance of the shunt PCB-trace, for Drain Current measurement on RF Board around U1 (INA219). It turned out, PCB Trace resistance is not as constant as we thougt it would be.

It is not intended to "fake" Efficiency, when there is none, but to have a possibility to "calibrate" your internal measurement, so it matches external measurements.

So what should you do with it ?

try to measure as exactly as possible:
- Input Voltage (Uin)
- Input Current at RX (Irx)
- Input Current at TX (Itx)
- Output Power (Pout)
Calculate Input Power by
Pin = Uin * (Itx - Irx)
Calculate Efficiency by
Eff = Pout / Pin *100%

Compare it with onboard measurement, and adjust RShunt Value in Menu, until displayed Efficiency matches your Calculated externally determined efficiency.

Usually this varys over frequency, so try to find a middle value, that works on all bands. Usually displayed accuracy can be adjusted to below 5% over all bands this way.

73 Manuel; DL2MAN

[VK2VD]

Hi Manuel
Thank you for the detailed response. That answers my question very well.
Most appreciated

[SP9TKW]

It is not intended to "fake" Efficiency, when there is none, but to have a possibility to "calibrate" your internal measurement, so it matches external measurements.

So what should you do with it ?

.....

Compare it with onboard measurement, and adjust RShunt Value in Menu, until displayed Efficiency matches your Calculated externally determined efficiency.

Usually this varys over frequency, so try to find a middle value, that works on all bands. Usually displayed accuracy can be adjusted to below 5% over all bands this way.

Hi Manuel,

At what point do you recommend to do above procedure? Before or after LPF is tunned for best performance?

73 Marek

[DL2MAN]

It´s the first thing I do before start tuning.
This way I can use the internal measurements and tuning will be faster.

73 Manuel; DL2MAN

[vk2tty]

Usually this varys over frequency, so try to find a middle value, that works on all bands. Usually displayed accuracy can be adjusted to below 5% over all bands this way.

Can you spare four bytes of EEPROM to store the R Shunt value separately per band? I'm OK if I can only see it or edit it by first switching to the correct band.

Separately, is there a way to determine a correction to R Shunt from its existing value, displayed power or efficiency, and measured power or efficiency?

[WR8RW]

Good day...thanks for the great rig! I am new to the concept of "RShunt".

One question. Does the value of R Shunt (Menu 8.6) materially affect the operation of the rig itself? My RShunt value is set to 18. Is that value OK, or is there a recommended "default" value for normal operation?

Thanks and best 73.
Robert (WR8RW)

[DL2MAN]

R Shunt doesn´t say anything about quality of the rig.
It´s the resistance of a shunt-track on the pcb in mili-ohms,that needs to be set correctly in order to show the correct efficiency on display.
If that´s 10 or 20 has no meaning for you.

73 Manuel; DL2MAN

[JL2CPA]

Hi Manuel

Thank you for the wonderful radio. I enjoy making kits.

Please tell me about Output Power (''Pout'') when calculating R shunt.

Is it okay to use the power displayed in USDX as ``Pout''? Or do I need to connect a power meter to measure it?