[arm-allstar] High pitch hum on audio

[Derek Chauran]

David, do you use the more basic version of the cm108 mod? I recently noticed in one of the docs somewhere a mod that didn't use any external components, but have not given it a try yet.
________________________________
From: ARM-allstar <arm-allstar-bounces at hamvoip.org> on behalf of "David McGough via ARM-allstar" <arm-allstar at hamvoip.org>
Sent: Monday, February 7, 2022 10:29:25 AM
To: "Randy K7RHT via ARM-allstar" <arm-allstar at hamvoip.org>
Cc: David McGough <kb4fxc at inttek.net>
Subject: Re: [arm-allstar] High pitch hum on audio


Randy,

What type USB adapter were you using?  Was the only change you made to
swap the RPi out for the Dell?  ....OR, other changes, too?

The reason I'm asking these questions is I've got a *LOT* of RPi2/3/4
systems deployed and now am starting to use Z2W hardware.  No "hum" or
other noise issues at all--ever.

There are a few rules I live by, as my systems have evolved over the
years.  First, I ONLY use WiFi for RPi's attached to radios.  Second, I
power the RPi using good quality DC-DC converters, powered from the radio
power supply.  Third, I almost always use a single RPi per radio/repeater.
However, with the current RPi shortage, I have started adding more than
one radio per RPi.....This hardware/chip shortage is getting old!

I'm still using the same inexpensive DC-DC converters, over many years
now. I've had no failures or problems with these.  Make sure to pre-set
the output voltage to 5V *BEFORE* putting the converter in the circuit!

https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.ebay.com%2Fitm%2F223524573272&data=04%7C01%7C%7C86a2542d0ba54e6ca62308d9ea67c8b2%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637798553750635835%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=NE9bJML5L4OvFLPG8cPruYDeWKHCxV34fyFdqkvAfSc%3D&reserved=0

Since I'm using WiFi, I also use Ubiquiti Nano/Loco M2 Access Point radios
at almost every site.  The WiFi power level is set to 0dBm. These AP's
don't skip a beat.

I don't have Bluetooth turned off anywhere, however I don't actively use
it.

I'll mention also that I always keep several radioless USB adapters
available for plug-and-play testing.  This speeds node setup time to a few
minutes, while also providing a "HiFi" audio test set.


73, David KB4FXC


On Mon, 7 Feb 2022, "Randy K7RHT via ARM-allstar" wrote:

> I have had the same issues and finally switched from a Pi to a mini dell to run the link for a test, besides the software issues created, the noise went away so now to find the problem in the Pi.

Randy Thomas - K7RHT
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