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Power Levels vs. Battery voltage vs. dif. Radios
Posted: Thu Jul 29, 2021 4:15 pm
by OE5DMF
Hi.
i just got my 3rd GD77 and noticed that the TX Power at 50mW is about 800mW so i did some measurements.
Here is the link to my Results of a 2 Radio comparison:
https://docs.google.com/spreadsheets/d/ ... sp=sharing
perhaps this helps in future development. i just wanted to share it with you guys.
(Thanks for the UserPower setting!! helped a lot)
Markus OE5DMF
Re: Power Levels vs. Battery voltage vs. dif. Radios
Posted: Thu Jul 29, 2021 10:47 pm
by VK3KYY
OE5DMF wrote: ↑Thu Jul 29, 2021 4:15 pm
Hi.
i just got my 3rd GD77 and noticed that the TX Power at 50mW is about 800mW so i did some measurements.
Here is the link to my Results of a 2 Radio comparison:
https://docs.google.com/spreadsheets/d/ ... sp=sharing
perhaps this helps in future development. i just wanted to share it with you guys.
(Thanks for the UserPower setting!! helped a lot)
Markus OE5DMF
You need to change the calibration of the radio
Use the OpenGD77 Calibration screen.
If you set the 1W and 5W values then the 50mW will be more accurate.
Actually, you only need to set the 1W calibration, becuase the PA drive voltage used for 50mW is a proportion of the value for 1W, which comes from the calibration table data.
Re: Power Levels vs. Battery voltage vs. dif. Radios
Posted: Fri Jul 30, 2021 7:18 am
by OE5DMF
Thank you for your Comment.
What i did:
- Removed the Battery and connected the Radio to a benchtop power supply (6.4V, 7.4V, 8.4V)
- connected the Antenna Connector through a 60dB Attenuator to the Spectrum Analyzer
- set the Frequenzy to 145 MHz, 435MHz
- set "User Power" - Settings Menu from 0 to 4100 (4096)
- Every "User Power" step i measured the output power
in trx.c:
Line 997: Case 9: User Power is set 1:1 to txDACDrivePower. No Power clibration Data is used in this mode. Am i right?
Code: Select all
case 0:// 50mW
case 1:// 250mW
case 2:// 500mW
case 3:// 750mW
txDACDrivePower = trxPowerSettings.lowPower * fractionalPowers[trxCurrentBand[TRX_TX_FREQ_BAND]][txPowerLevel];
break;
...
case 9:// 5W+
txDACDrivePower = nonVolatileSettings.userPower;
break;
- as my measurements show the minimal possible tx power has nothing to do with the calibration data. (i know 50mW is trxPowerSettings.lowPower * 0.59, but im am talking about hardware limits not software settings)
- and the radios vary a lot from device to device.
- and the newer batches are not able to go very low on tx power
Re: Power Levels vs. Battery voltage vs. dif. Radios
Posted: Fri Jul 30, 2021 7:43 am
by F1RMB
Hi,
Roger meant calibration screen in the CPS (Extra menu).
Cheers.
---
Daniel
Re: Power Levels vs. Battery voltage vs. dif. Radios
Posted: Fri Jul 30, 2021 8:36 am
by OE5DMF
F1RMB wrote: ↑Fri Jul 30, 2021 7:43 am
Hi,
Roger meant calibration screen in the CPS (Extra menu).
Cheers.
---
Daniel
I know Daniel. You are right.
This is the "trxPowerSettings.lowPower" value in code and is not used in "User Power" mode as i mentioned.
User Mode writes the 12bit DAC Value (0-4096) direct to the output stage without software calibration (Which is a 0-255 interpretation of the DAC value)
Thats how i see the situation. @VK3KYY please correct me if i am wrong.....
Re: Power Levels vs. Battery voltage vs. dif. Radios
Posted: Fri Jul 30, 2021 9:05 am
by F1RMB
The case #9 in trx is simply set the DAC value from the one the user entered in the options menu (no fractionnal computation).
So, check your output power on 1W and 5W, it's probably off, and the reason why 50mW (and probably 250..750mW) is so high on your transceiver.
Thanks.
---
Daniel
Re: Power Levels vs. Battery voltage vs. dif. Radios
Posted: Fri Jul 30, 2021 9:44 am
by G4EML
Markus, I think Roger and Daniel have not realised exactly what and how you are testing.
I agree with your conclusion that some radios will never be able to output very low power levels.
The minimum power level that a radio can send is defined by the level it outputs with a DAC value of Zero. As you have demonstrated, that varies a lot between radios and probably depends on the batches of components used. Some may be able to go as low as 50mW but some, like yours, may not be able to go much below 1W.
It is probably wrong to display absolute power values on the radio, they can never be very accurate. Max, High, Mid, Low and Min would probably be more appropriate to display.
Colin G4EML
Re: Power Levels vs. Battery voltage vs. dif. Radios
Posted: Fri Jul 30, 2021 10:16 am
by F1RMB
Hmmm, Okay.
But I didn't see any DAC -> measured power list here.
Also, stupid question, but what is your measurement setup ?
Cheers.
---
Daniel
Re: Power Levels vs. Battery voltage vs. dif. Radios
Posted: Fri Jul 30, 2021 11:22 am
by VK3KYY
In the original post you said
TX Power at 50mW is about 800mW
This implies that you are using the 50mW setting not the -W+ setting, and that at that setting the 50mW power is outputing was 800mW
I'd almost say you radio has a fault, if setting the DAC value to 0 still outputs 800mW.
Re: Power Levels vs. Battery voltage vs. dif. Radios
Posted: Fri Jul 30, 2021 3:02 pm
by OE5DMF
F1RMB wrote: ↑Fri Jul 30, 2021 10:16 am
Hmmm, Okay.
But I didn't see any DAC -> measured power list here.
Also, stupid question, but what is your measurement setup ?
Cheers.
---
Daniel
Your Question 1:
Your Question 2:
OE5DMF wrote: ↑Fri Jul 30, 2021 7:18 am
What i did:
- Removed the Battery and connected the Radio to a benchtop power supply (6.4V, 7.4V, 8.4V)
- connected the Antenna Connector through a 60dB Attenuator to the Spectrum Analyzer
- set the Frequenzy to 145 MHz, 435MHz
- set "User Power" - Settings Menu from 0 to 4100 (4096)
- Every "User Power" step i measured the output power