Introduction: APRS and the UV-5R

So... What is APRS? APRS stands for Automatic Packet Reporting System. Amateur Radio Operators (Hams) use APRS for many different things. In a nutshell, APRS lets you transmit your GPS location out onto the radio net for others to pick up and place you on a map. This is the basic function. Other functions include messaging, relaying, I-Gating, and Weather (I'll touch on these parts later).

What is a UV-5R? It is a great entry-level, hand-held radio. Inexpensive and forgiving for those new to the hobby.

Why am I putting this together? Well, to share the knowledge and put all the research I found into one spot.

I'd like to call out to KF7BBI (Dave) and KG7IOE (Terrance) for helping me troubleshoot the issues I was having. And KC2UHB (Diana) just because.

How do I use APRS? I like to snowshoe in the winter and it is one way I can let others know where I am in case of emergency.

Step 1: Things You Need for APRS

Three basic needs (plus one requirement)

1) A radio

2) A cable

3) An APRS solution. Mine is a smartphone with APRSDroid -

(The requirement is having an Amateur Radio License)


My trusty UV-5R with extended life battery and upgraded antenna (check the Amazons or eBayz for the cool dealz)

This cable was a great find by Dave. It provides ground isolation so the that the PTT is activated on transmit. If you don't have this (or a TNC) the radio will key open and disturb others (see Ham Etiquette). The cable was put together here: (another call out to John Boiles for this awesome project).

My phone is a previously used Samsung Android-based smartphone. The key to this is to factory reset the phone and not log it back in to Google... more on that later.

To operate (that means transmit) on Amateur Radio frequencies, one must get a license. The best way is to search around your community for a local club that can guide you the study material for the test. 'Technician' is the first level of license and is all you need to Transmit. If you want to monitor or listen, no license is needed... but what fun would that be. I've had mine for 3 years now... KG7IOA.

Step 2: Configuration

It all comes down to the details!!! This is were Terrance really helped out.

This configuration is how I was able to put all the parts together and make it work. I did struggle as my transmissions were not hitting the relay or being rebroadcast to the I-Gate. Terrance had a known-good working setup on his phone that I was able to test with and compare configurations to my phone to get it too work.

What was happening ... well when APRSDroid would transmit, I would see the transmission from my radio but I wouldn't see it come back from the Relay or hit the I-Gate. Turns out that the default setting in APRSDroid is to send the signal out on the 'phone/voice' of the phone. This signal was so incredibly weak that I couldn't get the relay to pick it when I drove past it.

I switched to the 'Ringtone' setting in APRSDroid. This kept sufficient signal power for the transmission to be picked up by the Relay which passed it onto the I-Gate.

The Vox on my radio was an enigma wrapped in a mystery as well... the radio documentation (and much of the Interwebz) couldn't really tell me that Vox setting 1 was open-all-the-way sensitivity and 10 was just-slightly-open sensitivity. I only found this by trial and error on my own while watching my signal being push out from my radio. The radio has an LED that illuminates, to the color of your choice, on Tx and Rx (transmit and receive).

*** Update!! v2 ***

Phone volume must be 3/4 of the bar. You will hear the 'squawk' of the transmission but if the volume is too low, even with Vox at 1, nothing will transmit. I put a sound muffler on my phone speaker so it doesn't spook me while driving.

These are the settings that worked best for me to get this whole thing working properly... your mileage may vary.

Step 3: Conclusions...

Filling in the gaps...

Why did I not log my phone into the Googlez? Once you do, all the notifications from Insta-Face, Snap-Books, and the like will come through the phone when one of your compadres posts a new cat video or a new noodle truck. And if you are APRSing, those notifications will then be transmitted over the air. "Das ist verboten" per the us FCC rules for spurious transmissions. Also, I don't have a SIM card in the phone.. who wants to get a phone call out in the mountains. That's the whole reason for getting out and about.

What is a Relay and what is an I-Gate? A Relay is just that... it takes your transmission, usually of lower power, and rebroadcasts at a higher power so that it covers a larger area... Search and Rescue can't get to you if your coordinates aren't pushed out.

APRSDroid takes advantage of the GPS of the smartphone for coordinates. That is what get transmitted along with your callsign and and optional short message.

APRSDroid also allows for direct messaging to individuals... just slide over to the "Messaging" tab to send a note to another Ham using their callsign. They can then ack from their APRSDroid.

I didn't forget... an I-Gate is a relay that is connected to the Interwebz. Why? A very cool Fin put together to take APRS transmissions and post them onto a modified Google Maps (uses the Maps API). That way you can see the Hams in your area or those traveling through or if you want to send a message to a fellow Ham in Australia or Scotland, you can see if they are out and about with APRS capability.

(Pro Tip: If you are geographically separated from one of your compadres [not in LOS between the radios], a message can be sent through an I-Gate similar to IRLP. This is untested by me, though).

Oh and Weather!!! One of my other hobbies... APRS can be used to transmit weather data from compatible weather stations... why? For the fun of it!!! The APRS Wx packets are simple enough to program into your 'duino/bone and send over the link. I have an additional project that I am ruminating on to inject Wx data into my APRS tracking while out snowshoeing.

Finally, if you are into hard-core 'tactical reclamation operations' (e.g. hacker, et al.) this chap ( has a home-brew version that could easily accommodate a GPS shield to his 'duino project.

Thanks for following along and sharing my excitement. 73 - KG7IOA clear


ThomasK19 (author)2016-03-06

Interesting how German idioms crawl into foreign languages ;-)

Nice insight into an area I know that exists, but that's out of my horizon.

k-twizel (author)ThomasK192016-03-07

Bien sûr, mon ami!

Thanks as well. My intention was not to do an APRS primer as there are many of those. Device configuration is not really discussed well.