I need some help or ideas on how to achieve a project I am working on.  

I know that there are software packages for public safety to monitor audio from a radio and then send an email or text message etc.  But they require a dedicated computer.  Often Windows based.  

I am looking for a way to monitor a radio say a Baofeng HT set to a frequency and have it forward transmissions to an email address, MMS, etc.  I would like something that is hardware based if possible so that no computer is needed. I am trying to setup something small and low power consumption.

Just to give an example, think of the NWS. When they transmit the SAME tones for a weather alert I want to send an email or MMS that contains the audio (~30s) to a specific email address.  I know that there are subscription services specifically weather related that do some of this but I am just using this as an example.  

I know there are regulations about connecting some radio services (GMRS is one) to the public switch network (telephone).  But that is not exactly what I am wanting to do.  I am not looking to make telephone calls.  I just want the audio from a radio recorded and sent to a specific location.  No other interaction is needed.    

Any ideas where to look. I have been googling and reading up but I am not finding what I need.  Before building I wanted to see if there was any COTS solutions you guys knew of.  

I don't see any legal issues with what you want to do since you'd simply be monitoring a frequency. Basically you want the radio and hardware to listen for a certain event, optionally record audio, and then email/SMS the audio. I don't know any hardware out there that does it. There may be.

I'll stick with the standard reply of it could be done with a raspberry pi.

There is acutally software that you can piece together with some hardware to do this. I know of a fire dept that does exactly this with dispatch audio that is recorded off air. I just sent an email to the guy who set theirs up.

Thanks Jazzemt.  I am aware of some of that.  But as I indicated they require a dedicated computer which is typically not low power.  Not to mention PC based  

A stand alone solution would be optimal.

I know of a ham who crossed SMS with the messaging system in the APRS. But nothing quite of this design.

yup I could think of a couple packages off hand that combined with a bash script would put you in business.

Easy. Use COS to trigger a switch that closes contacts on an interface. Set the radio to the freq but set a DSQ tone on the RX.

Program a memory in your baofeng with that freq and DSQ and ptt when you want an email sent.

You could use the GPIO on a raspberry pi.

My plan would use audio-recorder and its built in signal detector. It has a really simple scripting language and can be set to do a number of things. After you record the file you upload it to dropbox or the like and send an email to your email or cell providers sms gateway with a link using sendmail.

You may look up the NWS emergency broadcast radios. I forget what kind of signaling NWS uses for emergency weather announcements but I do remember that most commercial FM radios can utilize it.

... IP stack without a computer?

Raspberry Pi + Rtl-SDR + rtl_fm + EAS decoder = what you want.

I think multimonNG will do the EAS decoding. I can't get to the site here at work though.

1050hz tone. In band signalling.

The NWS alerts were used as an example.  I am looking for something a bit more flexible.      My idea is similar in nature to a repeater but the recipients may not carry a radio with them so that would be pointless.    This is not for SHTF or emergency use but it needs to be small, low power, and dependable or its not worth the effort.

Look at pymultimonNG. See if it looks like I can do what you need. GCW or I can probably walk you through configuring it, via 17m. :D

A number of microcontrollers can do it, although since OP is asking about it, that's probably not in his wheelhouse

Why the aversion to using a "computer"? Raspis are $35 and low power.

The are all computers,  too.

The aversion to "computer"   is   boat anchor, power hog, typically windows based.  

I am not against something smaller if it can do the job.  

I have not gotten involved in the Pi, or similar micro-computers world yet.  I would need to do a ton of learning to program them.  I like looking for COTS before building when possible.  Usually someone else has already been down the path and it helps save me time and money.

If you go with this solution you wouldn't even need a radio.

Raspberry Pis are the size of a pack of smokes, use very little power, and run Linux.

There's enough open source software that does most of what you're looking for that you likely won't have to program anything.

Also, microcomputers are what we had in the late 70s

Yes, I know what a Raspberry Pi is.  I know how big they are.  But I have no experience programming one.  Its just not an area I have had interested in diving into.  I will take a look at them now.  

No, I do not need EAS decoding.  I used the weather service notification as an example.  My original concept was using the Baofeng as it has digital squelch built in. All I need from it is the audio.  The bigger issue is getting the audio into an email or MMS.  

The duty cycle of this is going to be very low.  So I don't want to over complicate it.  More parts can mean more points of failure.  

While digging I had thought about one of the barebone mini-PC's running one of the tone decoding apps in windows.  Setting it up each time would require a keyboard and monitor and I would like to avoid that.  So that entire idea is out.

You could take a baofeng, or an equally cheap radio with ctcss decoding built in, and pipe the audio to a raspberry pi with a usb audio input. Have it trigger based upon input level, and record the file and email it to you.

MultimonNG has a fork that supports ctcss decoding too, if you want to use an rtlsdr (could allow you to monitor 2MHz of spectrum simultaneously.)



I'm not sure how to help without knowing more about the project.

I modified the rtl_sdr receiver code (literally a one line change) to trigger another app when squelch was broken (sent USR1 when squelch was broken, USR2 when it closed). Used for my RasPi repeater controller.

I think that would be easier than detecting audio.

Add an sd card for spooling and you're there

Yup. I prefer to keep my OS partition read only with a tmpfs in RAM so I can kill the power without a care. Add an init script to nuke your data partition if it's damaged and you're almost done. Upon receipt of the USR2 signal encode the recorded wav as an mp3, OGG, or whatever you like, use any of a bajillion email libraries, and you're done.

OP, this project should take you less than 1 beer.

Which is why you're really looking for something running as a server with a set and forget config file…like what you'd find in Linux distros.

I run a MultimonNG fork on my server (pymultimonaprs) for an I-gate. It was running off a RTL-SDR…I'm in the process of switching it over to run off an old Bearcat 560XLT. Probably wouldn't be too difficult to add some sort of notification method for NWS alerts.

What solution did you end up using?

I put the project on hold until I can get a PC.  As much as I feel dirty having to do it...   I cannot keep windows running the background on the mac.  I figured I would wait until after the holidays.

Some MDC signaling comes to mind for some of your project.