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 - https://aprsdroid.org/

(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: https://github.com/johnboiles/BaofengUV5R-TRRS (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.

*** Update v3 ***

See the updated photo of the volume settings... This will be completely silent, sending all AFSK out the headphone jack to the radio.

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 aprs.fi 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 (http://unsigned.io/projects/microaprs/) 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



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    9 Discussions


    Question 5 weeks ago

    I don't seem to be receiving any packets. What volume level did you set the radio volume at? Did you change any other settings on the baofeng? I have driven from over 250miles and I can see my data getting on to APRS.fi but I am not seeing any packets coming in and I would have thought I would have seen something.

    1 answer

    Answer 5 weeks ago

    I don't think it is a BaoFeng volume issue. If you are seeing tracks on APRS.fi then you are getting out of the radio and an iGate is receiving. I reviewed my instructions and updated one pic but all the other settings for the radio and phone are good.

    When you run APRSDroid, your callsign will be at the top of the screen. Tap your callsign to see all the TX and RX traffic. There is a .log file that is saved on the phone which can be read with a txt editor. Review this log for TX records from your phone and RX records back to you. I copied mine onto a microSD to transfer to my laptop. This will have everything your APRSDroid has TX or RX.

    Let me know if this helps.


    4 months ago on Step 1

    Man I'm bummed. First, this is a great tutorial. I've been eager to monitor APRS traffic on the go and thought since I can easily use my RTL-SDR on the computer and decode APRS traffic, I thought for sure I could use my Baofeng and my Android pbone. The only problem is I'm not licensed and I didn't realize until after I bought the audio cable and APRSDroid, that the app is useless without a callsign. I completely understand that fully utilizing APRS you need to transmit, but it sucks there isn't a monitor-only mode that doesn't require a callsign.

    3 replies

    Reply 4 months ago

    With SDR, you should be able to pull the signal and use an AFSK interpreter to decipher the audio without the need for a ham licence. Theres a few linux based tools that the SDRs work with that can help. APRS is not encrypted but the app presumes you are going to transmit thus requires a key/callsign to use.


    Reply 4 months ago

    Thanks for the reply, k-twitzel. Indeed you are correct. I've been using qtmm for Windows and it works well on my PC.. Albeit it's just raw data. APRSDroid has a cool way of laying it all out in a nice table that made it look attractive.. I was hoping to use my mobile phone and my HT to see if I could see the same data while on the road. Either way, it's more motivation to study and get that license :-) I suppose I could use some of the Linux tools on android, but it is a bit cumbersome to run command line utilies on a mobile device.


    Reply 3 months ago

    Need to get your ticket and join us on the APRS map! Its easier than ever now to get licensed! 35 question multiple choice test and the question pool with answers is online plus practice exams on websites too! Only gotta make a 70% to pass I think it is. 70 or 71% I forget.

    www.qrz.com is the most popular site I think. tons of resources even for those without a call sign!

    Also depending on your local I-gate you can see National Weather Warnings boxes on the map once you get a Call sign and run APRS software. All from the RF channel! Plus tons of other features too! Text like messaging, Objects ( events, traffic issues, local repeater info, club meetings and even disaster / emergency info ). Email features, call sign data base features and tons other stuff not just tracking as most people think what APRS is for! Automatic Packet Reporting System not just station tracking! =]

    They even have APRS on the International Space Station! ( although its intermitten due to what is taking place on the ISS). I see it and PCSat ( another satellite running APRS ) on my APRS map all the time from the RF feed. Online anyone can but say in a grid down situation its tons of stuff APRS can offer to local Ham NETs and Emergency Management. It offers a ton of more visual information than just talking on a voice channel and is available when ever you need it vs having to listen to a voice channel waiting for a call that may not ever come!

    But even with APRS aside its tons of things to do on Ham Radio! Join us! =]



    3 months ago on Step 3

    Good job!

    I have been looking at the best way to put it on my Rover ( dog ). Argent data has a nice dongle with built in GPS but requires external battery power. Thus adding more weight. It finally hit me.....HEY! I have this old phone ( Kyocera Duraforce Mil Spec Phone ) let me run APRSdroid and my Wolphilink interface. Pretty small package with a UV5R. Least expensive for me too as I already have them. I was about to wire up a cable and found your post. But I may do the cable KE5SBP build instead.

    Also its a interface on Amazon too. $17 bucks I think it was. ( I can find the link if you wish ) I just went ahead and got one those coming so I will put my Wolphilink back in my go bag. Wolphilink is very nice. Has TX and RX level rheostats. Allows you to run lower phone audio drive level and fine tune with the rheostats. Mainly for the TX level. Works great portable with my FT-857D and my phone on PSK31.

    But saving a $ is the bottom line for me! I build almost all my antennas which gives me the most satisfaction of all my Ham projects! Circuits are great I just cant see to great any more and my hands shake so I tend to bridge and burn solder pads! lol

    One thing to keep in mind while Portable. ( different ball game for a base / fixed station ) Just like on HF any missed section of AX.25 ( Packet ) and the whole string is junk! So keep it short and to the point! A shorter string sent more often is better than a long string sent less often. =]

    de WW5RM


    1 year ago

    I appreciate this instructable. I had a KPC3+ tnc way back in '93 or '94. I didn't do a whole lot with it and sold it along the way. Now I'm interested in APRS again, but I live in an area with little to no amateur radio activity. I can't decide if jumping back into APRS will hold any value for me, but I do have a couple of UV5 radios and an Android phone I'm not using. Thanks for sharing your experience.

    1 reply

    Reply 3 years ago

    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.