Power Levels vs. Battery voltage vs. dif. Radios

Discussions related to the firmware code development
OE5DMF
Posts: 13
Joined: Sat Jul 24, 2021 8:23 am

Re: Power Levels vs. Battery voltage vs. dif. Radios

Post by OE5DMF » Fri Jul 30, 2021 3:23 pm

VK3KYY wrote:
Fri Jul 30, 2021 11:22 am
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.
they are within the specs for 1W/5W. No fault for radioddity. :roll:
as you can see in the diagram from about 500 downwards the power stays the same.
are there schematics of the PA part available?

i compared the PaDrvIBit value (AT1846S, Reg.0Ah, 14:11) in the calibration data. all the same at all radios.

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F1RMB
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Location: Grenoble, France

Re: Power Levels vs. Battery voltage vs. dif. Radios

Post by F1RMB » Fri Jul 30, 2021 4:12 pm

Question 3: FM ? ;-)

Well, what it looks really wrong, is the output power at DAC == 0...


Cheers.
---
Daniel

G4EML
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Joined: Sat Nov 16, 2019 10:01 am

Re: Power Levels vs. Battery voltage vs. dif. Radios

Post by G4EML » Fri Jul 30, 2021 7:20 pm

I wouldn’t waste time trying to fix something that is not broken.
The radio was designed to give 1W at low power and it does that. Just because some radios can be persuaded to go lower doesn’t mean that they all can.

The pa bias current output of the AT1846 (PADrvIBit) is not connected. So varying that should have no effect. The DAC output for power just controls the source current of the driver and PA FETs by adjusting the gate bias. It is quite possible that even with zero bias these still have significant gain. The only way to reduce the power would then be to reduce the drive level. Some diagrams of the AT1846s chip show the rf output amplifier having variable gain, however I can’t find any reference to this in the available documentation. It may be another of those undocumented registers.

Colin.

OE5DMF
Posts: 13
Joined: Sat Jul 24, 2021 8:23 am

Re: Power Levels vs. Battery voltage vs. dif. Radios

Post by OE5DMF » Fri Jul 30, 2021 8:43 pm

G4EML wrote:
Fri Jul 30, 2021 7:20 pm
I wouldn’t waste time trying to fix something that is not broken.
The radio was designed to give 1W at low power and it does that. Just because some radios can be persuaded to go lower doesn’t mean that they all can.

The pa bias current output of the AT1846 (PADrvIBit) is not connected. So varying that should have no effect. The DAC output for power just controls the source current of the driver and PA FETs by adjusting the gate bias. It is quite possible that even with zero bias these still have significant gain. The only way to reduce the power would then be to reduce the drive level. Some diagrams of the AT1846s chip show the rf output amplifier having variable gain, however I can’t find any reference to this in the available documentation. It may be another of those undocumented registers.

Colin.
correct. as i mentioned before. it is within the specs.

it is correct that the AT1846 pabiase_pin is not connected.
but it is not controlled with padrv_ibit.
padrv_ibit controls the RF output power of the chip.

pabias_voltage (Register 0ah, Bit 0:5) controls the not used bias voltage.
Bildschirmfoto 2021-07-30 um 22.34.36.png
Bildschirmfoto 2021-07-30 um 22.34.36.png (24.01 KiB) Viewed 3639 times
i am just looking for a simple fix for this low power thing. a lot of people use this radios with there hotspots. me to. and more than some mW easily overdrive the hotspot input or is transmitted way to far out of the house.

OE5DMF
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Joined: Sat Jul 24, 2021 8:23 am

Re: Power Levels vs. Battery voltage vs. dif. Radios

Post by OE5DMF » Fri Jul 30, 2021 8:44 pm

F1RMB wrote:
Fri Jul 30, 2021 4:12 pm
Question 3: FM ? ;-)

Well, what it looks really wrong, is the output power at DAC == 0...


Cheers.
---
Daniel
Answer 3: Yes FM. :lol:

VK3KYY
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Location: Melbourne, Australia

Re: Power Levels vs. Battery voltage vs. dif. Radios

Post by VK3KYY » Fri Jul 30, 2021 11:10 pm

FYI.

Unfortunately the circuit is not publically available.

I agree the output level from the AT1846S could possibly be varied, but this would add one more known variable to the already inaccurate PA drive calculations, so I won't be messing around with that control.

G4EML
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Joined: Sat Nov 16, 2019 10:01 am

Re: Power Levels vs. Battery voltage vs. dif. Radios

Post by G4EML » Fri Jul 30, 2021 11:48 pm

That datasheet looks more complete than the ones I have seen before. None of them made any mention of the RF power control bits 11 to 14, only listing the PA Bias Bits.

If you really want try lowering the output power then it might be worth experimenting with those bits.
Because the DAC controls the PA standing current it probably would need setting to a low value (or zero) before then reducing the 1846 output.

However I agree with Roger that it could get very complicated having to adjust both the DAC output and the 1846 power control bits. Without individual calibration of each radio at each power level it would be difficult to come up with a universal solution.

Colin

VK3KYY
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Location: Melbourne, Australia

Re: Power Levels vs. Battery voltage vs. dif. Radios

Post by VK3KYY » Sat Jul 31, 2021 1:53 am

The fractional power values below 1W already vary a lot from radio to radio.

The 50mW value probably varies by +/- 100% across an average sample of radios, and the power output if further complicated becuase the PA supply voltage is derived directly from the battery, so as the battery voltage drops the power output drops.

I did consider attempting to adjust the PA drive to compensate for the drop in battery voltage, but I decided it would be impractical to implement, because of variation of voltage to gain ratio of FETs in each radio probably varies too much.

OE5DMF
Posts: 13
Joined: Sat Jul 24, 2021 8:23 am

Re: Power Levels vs. Battery voltage vs. dif. Radios

Post by OE5DMF » Sat Jul 31, 2021 9:14 am

chip pa - power.png
chip pa - power.png (31.55 KiB) Viewed 3576 times
i played a bit with the chip output power
Possible Values: F to 0 (hex)

the 3 lines are F, A and 8 (F line is missing some values :-) )

as you can see the minimum power changes (all at the same battery voltage)
but the maximum output power stays the same

now it is a bit of a challenge to find the sweet spot where the calibration calculation meets the power curve.
1W DAC-Value * 0.59 = 50mW DAC-Value

@VK3KYY is it possible to get the padrv_ibit value into the calibration window?
(development version, password protected or hidden button to set it visible) you find my email on qrz.com ;)
Last edited by OE5DMF on Sat Jul 31, 2021 4:45 pm, edited 1 time in total.

OE5DMF
Posts: 13
Joined: Sat Jul 24, 2021 8:23 am

Re: Power Levels vs. Battery voltage vs. dif. Radios

Post by OE5DMF » Sat Jul 31, 2021 9:16 am

and now it is the point were i have to figure out how to calibrate the 4FSK power. :lol: :lol: :lol:

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