Jump to content

Can a FRS radio work like APRS?

Recommended Posts

I was wondering if could send my location through FRS frequecncy (I pretty sure it would be illegeal, but I am wondering about the physics)? I managed to get my platnium hooked up to my my FRS radios mic out area, and the GPS appears to send data over the radio, could that be used by a computer if I found a way to get it to come out of the speaker port? Would this require four radios? Or is that not even possibly with out some type of converter on each end?


Wyatt W.


The probability of someone watching you is directly proportional to the stupidity of your actions.

Link to comment

FCC regulations state that FRS frequencies are for voice-only. Garmin received a waiver for doing APRS-like GPS position packets on FRS, unsure why. You *could* set up an APRS network on FRS freqs using at least two radios, modems (TNC's - terminal node controllers) and computers running APRS software - only difference is that TNC's typically have tones set for ham radio FM deviation, and FRS deviation is narrower. But, again, it's not allowed.

Link to comment

In theory, yes. Legally on FRS, no.


However, you probably won't have much luck just hooking the serial port to the transciever. You need to convert the data stream into something that can be easily handled by the communications equipment. In this case, an analog audio signal that can fits within limitations of the radio chanel. On the receiving side, you need something that can convert an audio signal into something the serial port can handle.


From your setup, you've found you can get some sort of sound going straight from the GPSr to the radio, but chances are it won't be very intelligble on the other end. In a sense, you have built a very simple digital-to-analog converter, but you've probably lost a lot of the information in the process.


Simply put, something needs to convert the digital signal from the serial port into an analog signal that can be transmitted across the communications channel, then something else needs to convert that analog signal back into a digital sigal on the other side. That's typically callled the TNC (terminal node controller) in APRS. It's similar in concept to modems with computers on phone lines.



Link to comment

That's true. However, I was under the impression that it wasn't under user control, but could only be implemented by the manufacturer. Kind of like the prohibition against user-supplied antennas.


But I could be reading it wrong. I've just had the feeling that the FCC is pretty restrictive on what the technical issues end-users can fiddle with on that band.



Link to comment

The data needs to be modulated onto an audio signal that the radio is capable of transmitting, ie within the frequencys the radios can transmit and recieve. What you are transmitting probably has no usable information, but rather is just noise. Like stated before, you could build a setup with a couple of radios, TNCs and computers, but you would be be in danger of a visit from the FCC. You could do it, given the time and effort, but Rinos are inexpensive enough to make the homebrew system unattractive. So just get a couple of Rinos, or go ham.


Predicting is difficult, especially when predicting the future.

Link to comment

If all you want is to send your position, and if you arnt worried about receiving positoins, you may want to try using a radio that can transmit on the MURS frequencies. You are allowed digital and other modes on these frequencies. Also check out www.byonics.com and look at TinyTrack II this takes place of the tnc so all you would need is that and a transmitter. Hope i helped.




Link to comment

The best suggestion of all I have read is the use of TinyTrackII with a MURS transiever. I have used this application for tracking Search & Rescue units in the field. MURS transievers are really cheap right now. I saw RadioShack had some on clearance for about $35 not too long ago. You will also find that you will get better performance out of a MURS tranciever anyway since MURS operates around 154Mhz and FRS operates at around 462Mhz. The lower frequency VHF signals offer better penetration in wilderness settings then UHF. You will not have any luck with hooking the GPS directly to the radio as others have pointed out. The TinyTrackII will serve this function.

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...