[arm-allstar] Question about TX levels and audio

[Patrick Perdue]

Hi Stephen:

The AURSINC modules are, let's say, less than well built. They have been 
known to be quite spurious in their output as well. I don't know if this 
uses a real SA818 or a clone. Maybe even a clone of a clone, at this 
point. I trust those AURSINC modules about as much as a Baofeng without 
a rubber duck to hit a repeater 100 miles away.

First of all, the TX audio level has nothing to do with TX power output. 
This isn't single sideband. There is a carrier even with no modulation, 
and I'm pretty sure you can't actually adjust the power output level of 
the radio module itself. The SA818 doesn't actually include a working 
register for adjusting it.

Second, if you are getting reports of high audio, you should turn down 
the  RX level in simpleusb. My parrot node (55553) will give automated 
level reports, as well as play back your audio, so you can get a pretty 
good idea how it sounds.

It is also possible that your emphasis curve isn't properly set up in 
the radio, simpleusb or both, which would cause muddiness either on RX 
or TX, depending on how things are. Without hearing the result, I can't 
say more.


73

N2DYI


On 5/7/2024 5:03 PM, Steven M Mold via ARM-allstar wrote:
> I'm currently working with the "AURSINC Allstar RF Node UHF SR-FRS Radio
> Programming Module Pi-hat for Allstar, Echolink, APRS, Digital Modes
> Compatible for Raspberry Pi 2/3/4 | Pin to Pin Replace SA-818 Module| UHF
> Freq 400-470" that I bought from Amazon ([link](
> https://www.amazon.co.uk/dp/B0BNKS4GGH?psc=1&ref=ppx_yo2ov_dt_b_product_details)).
> Setting it up has proven to be quite challenging, but I'm making progress
> toward a fully operational node. However, I'm encountering an issue with
> unexpectedly high power output. Despite adjusting the software levels to
> reduce audio output, the transmission power remains excessively high.
>
> To mitigate this, I've introduced 90dB of attenuation, which has had some
> effect. Interestingly, the node still manages to transmit when enclosed in
> a makeshift Faraday cage, suggesting that the USB cable might also be
> functioning as an antenna.
>
> I suspect this excessive power output could be contributing to the high
> audio level reports I've been receiving, prompting me to reduce the mic
> gain on my 991A from 50 down to 20.
>
> Has anyone else experienced similar issues with this device? Any guidance
> would be greatly appreciated.
>
> Thanks, 73 M7OOR
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