[arm-allstar] Echo heard on Rx Audio

[Kevin Custer]

Sorry - I didn't make the connection. It looks like it will be delivered 
tomorrow - possibly.

If you will be using your DRA-30 for ASL - you'll need to install JU1 
and possibly JU2 for ASL compatibility.  They are shipped removed (side 
stepped).

Kevin

On 7/2/2023 8:19 PM, Dusty Smith wrote:
> Yeah Fahrenheit. Ok good deal. Thanks for the help sir. And looking 
> forward to the delivery from you as well 😉
>
> *Dusty Smith*
>   --W4MSI--
>
> (sent from my smartphone)
> *
> *
>
> ------------------------------------------------------------------------
> *From:* Kevin Custer <kevin at kc-wireless.com>
> *Sent:* Sunday, July 2, 2023 7:01 PM
> *To:* Dusty Smith; ARM Allstar
> *Subject:* Re: [arm-allstar] Echo heard on Rx Audio
>
> If those values are in degrees F - you'll be fine.  If the temperatures
> were getting to 140 degrees F - I'd start to worry about longevity.
>
> Kevin
>
>
> On 7/2/2023 4:20 PM, Dusty Smith wrote:
> > Excellent advice. I changed that out this afternoon. Removed the 
> high value inline resistors and added the 10k / 1k L network and the 
> audio is still a little hot but perfectly manageable...more so than 
> before and no more echo. Thanks a million for that advise.
> >
> > New question, more out of curiosity than anything. How hot would be 
> too hot for the heatsinks on a transmitter...specially these 
> CDM1250's. I've noticed during a long qso, the transmitter's heatsink 
> temp is up around 115-120 degrees. After qso ends, it'll fall 
> 10degrees pretty quickly, within a minute or two and continues to cool 
> down from there. Just wondering about possible overheating problems 
> and curious what the max safe temp range might be. Haven't been able 
> to find any specifics on that in my initial searching.
> >
> >
> > Dusty Smith
> > —W4MSI—
> >
> > -----Original Message-----
> > From: Kevin Custer <kevin at kc-wireless.com>
> > Sent: Sunday, July 2, 2023 10:08 AM
> > To: ARM Allstar <arm-allstar at hamvoip.org>
> > Cc: Dusty Smith <w4msi at outlook.com>
> > Subject: Re: [arm-allstar] Echo heard on Rx Audio
> >
> > Since you reference the discriminator audio is really hot - I'd 
> conclude that it's leaking into the transmit audio directly because of 
> cable cross-talk or another pseudo path.
> >
> > Instead of using a large series resistance to reduce the audio 
> level, consider a L network where you have something like a 10k 
> through resistor and a 1k to ground. This will keep the audio path low 
> impedance but accomplish necessary reduction without using high value 
> resistors.  Put this resistance at the connector on the radio so it 
> reduces cable cross-talk as well.
> >
> > Kevin
> >
> >
> > On 7/1/2023 10:50 PM, Dusty Smith via ARM-allstar wrote:
> >> Hello all, hoping to gather some info/pointers on where to look to 
> try to solve this issue.
> >>
> >> I've had a repeater running with hamvoip on a pi4 for a good long 
> while now...no major issues that I haven't been able to overcome at 
> least thus far.
> >> This evening I swapped out my radios on the repeater for some 
> different/newer rigs.
> >>
> >> The old radios that have been working fine were Motorola Maxtracs 
> and I've replaced them with some Motorola CDM1250 units.
> >>
> >> All seems to be pretty much equal on the surface, however, I've 
> noticed that there is a reverb/echo on my Rx Audio. Any audio coming 
> through links seems to be normal, but if I'm keying into the receiver 
> of the repeater...then the output of the repeater has this echo. It's 
> not a real loud echo, kinda faint, but it's definitely there and can 
> be noticed especially if you are speaking louder. Others on the same 
> frequency/repeater can hear it and if I do the parrot mode I can hear it.
> >>
> >> This wasn't here on the old radios. Same controller, same 
> interface, etc......there is a new interface cable but it's made up 
> the same way as the old one just different connections for the new 
> radios. I've tried adjusting audio levels and such and if I turn it 
> way down (simpleusb settings) then you can't hear the echo anymore, 
> but the audio is just too low in general. So really the echo is 
> probably still there you just can't hear it at that point. If I go 
> into "alsamixer" and turn off automatic gain control, it seems to get 
> better but it doesn't take it away entirely.
> >>
> >> One other note, the "flat/filtered rx audio" on pin 11 (where I'm 
> getting my rx audio from on the back panel pinout of the CDM1250) 
> seemed to be extremely hot audio. With it piped directly into my 
> soundcard interface (modified usb fob) I could turn the rx audio level 
> in simpleusb all the way down to 0 and it was still overmodulated by a 
> lot. So I added in 2Mohms worth of resistance to the rxAudio line 
> going from radio to interface (2 x 1Mohm resistors inline) and that 
> got it down to a reasonable level.
> >>
> >> Ok I think that's all I can think to include in this question for 
> now. If you need more info please ask. And thank very much in advance 
> for any assistance.
> >>
> >>
> >> Dusty Smith
> >> -W4MSI-
> >>
> >> _______________________________________________
> >>
> >> 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
>