[arm-allstar] ARM-allstar Digest, Vol 71, Issue 59

[Chris Smart]

Yep, I'm going to ask for that on my next one.



On 4/26/2020 6:00 PM, "Patrick Perdue via ARM-allstar" wrote:
> That is exactly why I had G7RPG add an SMA connector to my Microhub 
> rather than using the internal antenna, so I could get the antenna 
> away from the Pi and the rest of the components.
>
> On 4/26/2020 4:54 PM, "Chris Smart via ARM-allstar" wrote:
>> Thanks Ken. Very interesting. I'll pass this on to the guy who built 
>> my node.
>>
>>
>>
>> On 4/26/2020 12:57 PM, "Ken via ARM-allstar" wrote:
>>> Hum is often caused by some AC current flowing through the 0 vdc 
>>> side of
>>> whatever audio fob you are using. Voltage drop in the zero-volt 
>>> wiring of
>>> the USB/fob connection is effectively in series with both the 
>>> transmit and
>>> receive audio path.  A wall wart almost always puts some 60/120 Hz 
>>> AC on the
>>> DC minus lead (relative to ground elsewhere on your system) and the 
>>> USB fob
>>> offers no isolation for this.
>>>
>>> If you can figure out how to do it, the cheap answer is to connect a
>>> short/heavy wire from the DC minus lead of your RPI 5 volt supply to 
>>> the DC
>>> minus side of your radio's power supply.  These are the two sources 
>>> of the
>>> unwanted AC.  Second-best is to connect a short/heavy wire from some 
>>> 0 volt
>>> on the RPI to the chassis of your radio.  That is the critical part 
>>> of the
>>> circuit.
>>>
>>> Using a 12/5 volt DC/DC converter to power the RPI also helps (using 
>>> the
>>> same 12 volts as supplying your radio).
>>>
>>> Ken
>>>
>>>
>>>
>>>
>>> ----------------------------------------------------------------------
>>>
>>> Message: 1
>>> Date: Sun, 26 Apr 2020 04:04:45 -0400
>>> From: Jed Barton <jed at jedbarton.com>
>>> To: arm-allstar at hamvoip.org
>>> Subject: [arm-allstar] hum on my allstar nodes
>>> Message-ID:
>>>     <CAOYEAerhpLL_neibghwjjS81bU_xt_cMo2cmWG_HR1rsO6R7cw at mail.gmail.com> 
>>>
>>> Content-Type: text/plain; charset="UTF-8"
>>>
>>> Hey guys,
>>>
>>> So i'm sure i'm not the only 1 with this problem. I've got all my 
>>> allstar
>>> pies plugged in.  They each have their own power supply. It's the 
>>> typical
>>> wall wart.  They all produce a nice little hum that's just annoying.
>>> I'm sure a lot of you guys have delt with this.  You hear it on the 
>>> node
>>> transmitter such as the Shari.  Any ideas for getting rid of it, or 
>>> reducing
>>> it?
>>>
>>> Cheers,
>>>
>>> Jed
>>>
>>>
>>> _______________________________________________
>>>
>>> ARM-allstar mailing list
>>> ARM-allstar at hamvoip.org
>>> http://lists.hamvoip.org/cgi-bin/mailman/listinfo/arm-allstar
>>>
>>> Visit the BBB and RPi2/3/4 web page - http://hamvoip.org
>> _______________________________________________
>>
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>>
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