Radioless node sounds TOO good?

When Radioless nodes connect they both seem to have full audio quality, rather than radio or telephone grade. Is there a way to get them to sound more “filtered” so they sound similar to radio link nodes?

Tried only allowing ulaw but that did not seem to make the difference.


Can you better define a Radioless node?

I might point out that users of a radioless are not using a radio microphone and likely high(er) quality.

I’m sure you could lower the quality of the default codec if you want them all to sound narrower bandwidth. But that is a matter of handshaking as both nodes negotiate the codec and the others would have to have the narrower one enabled.

It’s the only option I can think of, but there perhaps is some other way ?

Also see ‘asterisk codec priority’ on the web

A case of Allstar sounding too good. That’s a new one.

Like @Mike said, I guess you could use the GSM codec.

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Steve, They connect a microphone and speaker to the node’s sound fob instead of a radio.

That’s what I wanted to make sure of rather then using DVSwitch Mobile.

Let me get this straight… You want the owner of the radio-less node to restrict their audio bandwidth and possibly add some distortion so they sound like others on the network? Good luck with that… But - to answer your question - yes, it can be done.

One of the problems that can occur in a radio-less set-up is an operator with audio that lacks punch. This is because no audio processing has occurred after their microphone, which is a normal action in a real radio. It would be best if these folks added a bit of audio processing between their MIC and the audio interface. Audio processing adds punch at the expense of some distortion. This distortion adds content that needs filtered by the “splatter filter” so the adjacent channels don’t get occupied or “splattered”. This filter is what typically limits the high end of the spectrum making the audio less brilliant. This low-pass filters knee is usually at 2.5 - 3kHz and rolls off significantly at a 18dB /octave rate (or more).

The other filter that’s not automatically in place in a RL node is CTCSS talk-off filtering. This is filtering that exists in most radios that rolls off the low end of the microphone audio so low fundamental frequencies don’t impede the operation of CTCSS signaling. This is a high-pass filter that is usually at 350 - 400 Hz rolling off the frequencies below that sharply.

I suppose you could ask people to implement high and low pass filters so their audio sounds as constrained as the rest of the people using real radios, but I don’t think you’ll get any traction. People aren’t going to spend money to make their audio less full sounding. Of course - YMMV.

Why would someone want to make their audio sound worse? Maybe consider DMR? (it’s a joke folks, no need to rage at me about disliking DMR or anything like that).

They say there is no such thing as a “dumb question”, but I am afraid I ask them all the time:)

“kuggie” got it right, the radio-less sound lacks the “punch” or dare I say intelligibility of the radio signal. What I am hearing from the radio-less connection sounds much better than G.711 and possibly better than G.722. I avoided GSM as I think it destroys the signal, but this would at least let me know that I have enabled it. I thought maybe that radio-less connections might bypass the codec negotiation somehow, but I have been told this is not correct.

I guess I just want to learn more about the “nuts and bolts” so have picked this exercise as a way to twiddle the knobs to see what happens. I guess I am back to Asterisk documentation until I can get this straight in my head. Likely in the end I will agree that it is not only a dumb question but a dumb idea, but at least I will understand the path.


Okay - so it’s more about the lack of punch, than being wider. That is something that can be addressed at the RL node with the addition of “normal” microphone audio processing. Someone should make a little module that goes in the audio path between the MIC and the radio-less interface to correct for that. By doing so it will add a bit of intelligibility, and knock off some of the extreme high end because of the required harmonic filtering.

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I think he needs a circuit that will inject a small bit of background noise, a filter to restrict the audio to between 300 and 3000 Hz and a maybe a squelch tail when unkeying. I’m not saying a bit of punch won’t help, @kuggie. But if it’s going to sound like a radio it needs more than that.

I think you fix what does not work and not what works.
Cheap hardware gets away with it again.
Why would anyone strive to make better?
If we are going to make junk our new setting standard DeFacto, we are all in trouble.

Most of those radio’s are not even on freq and being received by the same kind of radio also not on freq compounding the issue. The private pi node leaves a lot to be desired. Not the node, the radio’s many use with them.

Working and working well are not the same thing. Everyone is getting by though. It works.
The minimum standard being applied.

Finished some audio dynamics processing optimizations to my radio-less node design a few days ago and was thinking the same thing, the audio quality on this sounds better than the vast majority of other nodes.

This design can use an Analog Devices MAX9814 preamp+AGC module, or a MAX4466 mic preamp + SSM2167 audio dynamics processor module, either of which give very smooth audio on par with a good desk mic with compression. The MAX9814 is more transparent whereas the SSM2167 sounds over-compressed if run with sufficient gain to stay above its (relatively high) noise gate threshold. See AllScan - How To - Build a High-Quality Radio-less AllStar Node for Under $100 for more details. (The SSM2166 might be a better option but those don’t seem to be available on a low-cost module.) This node can be built for about $80 not including mic or speaker. I do recommend a genuine Alinco EMS-57 mic for best audio quality and DTMF command support.

The design could have additional filtering added with an op-amp circuit – or just use usbradio driver instead of simpleusb and voila, the outgoing network audio gets bandpass filtered with a nice sharp 24dB/octave slope, though some dynamic range and loudness are lost because usbradio seems to limit outgoing network audio to -10dBFS.

Update: After more testing I am now going with the MAX9814 and simpleusb driver for this node design. The SSM2167 has significantly more low frequency noise when used with higher gain, which results in usbradio’s sharp filtering being needed. I have a simple RC HPF ahead of the 9814 @ 250Hz which while only having a slope of 6dB/octave sounds great. Thus simpleusb in this case provides fuller and louder audio while not being too loud or having too much low end.

73, NR9V