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Setting up SDRuno to detect Amateur VHF tone coded squelch frequency?

Posted: Wed Sep 04, 2019 8:32 pm
by E63S4Me
Hi All,

New to SDR and the SDRuno, well not new to SDR as a concept, but new as an owner of the RSPduo.

Got my unit working over the weekend and was listening to various and sundry signals, including some local VHF and UHF repeaters.

Also fired up one of my HTs and transmitted some signals to monitor (I'm a licensed ham). In fiddling around with SDRuno, I did not yet figure out how to set up the display to zero in and see if I could detect the sub-audible tone coded squelch signal being added to the narrow band FM to open up the repeater on the input, or the tone on the output used to open up my receiver's squelch setting.

Any help, hints, on how to do that would be great.

Thanks!

Re: Setting up SDRuno to detect Amateur VHF tone coded squelch frequency?

Posted: Tue Sep 17, 2019 7:23 am
by Phillip
I'm pretty sure you'll need an RTA of some sort. I use the RTA in my Behringer X18 mixer. The PL tones stick out like a sore thumb.
73
Phil
K7JBL

Re: Setting up SDRuno to detect Amateur VHF tone coded squelch frequency?

Posted: Tue Sep 17, 2019 7:32 pm
by mikeladd
Do you want to see the tone within the spectrum or do you want to decode the tone external to SDRuno or are you trying to filter out the tone completely from the demodulated audio?

Re: Setting up SDRuno to detect Amateur VHF tone coded squelch frequency?

Posted: Wed Sep 18, 2019 9:54 pm
by vk3alb
Hi,

Here's what I did. Tuned for a signal from a transmitter and looked at the audio spectrum. I zoomed in on the audio spectrum as much as I could to get the best chance of catching the PL tone. Note that I engaged the FMAP button. When I keyed up, the tone was really obvious. Since we know PL tones are at discrete steps you don't have to be super accurate with cursor placement to work out the frequency. From the attached image which shows my cursor displaying 91.6Hz and understanding the defined PL frequencies we can determine the PL from my TX is 91.5Hz.

2019-09-19 07_38_42-Clipboard.png
2019-09-19 07_38_42-Clipboard.png (160.03 KiB) Viewed 16466 times

Don't forget some repeaters do not pass the input PL through to output and some repeaters regenerate a PL on the output that may be different from the input.

Hope this helps

P.S. Hello to chook who I know is always watching ;)