Kenwood NX5000 Series Mobiles and APRS

[dapaq2]

Hello Group,

I am interested in the Kenwood NX5000 series mobile communicating with the APRS system. I understand this radio has a built in GPS unit, so curious how the APRS device could obtain its data from the built in GPS instead of having to purchase an APRS device and an external GPS unit. Also I am not sure what all is available regarding make/model APRS unit/devices, I would be interested in the smallest options available. I could also use help with the wiring schematics/pinout for communicating with the NX5000. Any help is greatly appreciated.

Thank you,
Doug

 

[mmckenna]

The NX-5000 series mobiles do have an internal GPS receiver and it's possible to get the GPS data off the rear DB25 connector, either the COM1 or COM2 output (both on the same connector)

You will need to provide your own GPS antenna with a SMA connector.

You'd need an outboard TNC to form the packet data correctly, and that could be fed back into the radio using the rear DB25 connector using the PTT and data/mic input.

The radio will send GPS data on it's own, but only in digital mode.

My question to you is: Why?

Tying up a $900 radio, plus all the work to have it just run APRS? It can be done easier and cheaper.
But, if you really have to....

GPS data can be pulled off COM 1 or COM 2, you'll have to program the radio to send the position data out that way.

The following pins on the DB25 connector will interest you:
2 - RX Data 1
3 - TX Data 1
6 - Mic in 2 - feed from your TNC.
9 - TX Data 2
10 - RX Data 2
14 - Switched Battery - use it to power your TNC.
17 - AF Output - feed to your TNC 0.7 volts p-p level.
18 - Ground.
19 - Detector output.

There's several programmable I/O pins that you can set up for the PTT.
There's some programming involved, also. You'll need to set it up so it'll send GPS data out either COM1 or COM2. You'll need to set it up to take the input from the TNC, mic audio in, PTT and feed audio out to the TNC.
You'll also need the GPS antenna that will handle the 5 volts DC, which is just about all of them.

Personally, I'd get an old used VHF radio, a TNC and a GPS. Keep the NX-5700 for better stuff, but I can understand the challenge.

 

[dapaq2]

My question to you is: Why? Tying up a $900 radio, plus all the work to have it just run APRS?

Never said I want to tie up the radio for use only for APRS, I was under the impression that I could use the radio to do both APRS and voice. I can't do both? I am wanting to do exactly the same thing the Ham radios do that have the BUILT IN APRS, but I want to do it with the NX5000 (as far as functionality, not integrating into one housing)

Doug

 

[mmckenna]

Never said I want to tie up the radio for use only for APRS, I was under the impression that I could use the radio to do both APRS and voice. I can't do both? I am wanting to do exactly the same thing the Ham radios do that have the BUILT IN APRS, but I want to do it with the NX5000 (as far as functionality, not integrating into one housing)

Doug

Sure, it'll work. I haven't done it myself, but I know on the NX-x00 series mobiles you can set up a "data channel". It'll let you have it on another channel using voice, and when it gets a data message on the DB-25 input, it'll switch to the data channel (if you aren't transmitting) and send the data, then switch back.
So you'd need to set up your TNC interval appropriately.
On the RX side, that's going to be difficult as the only way I can see to do it is to either leave it on 144.39 and scan the other channels, or set up the scan list to listen on 144.39, but you'll probably end up missing most traffic since it'll get cut off. So, it won't fill in for a dedicated APR radio or a dual receiver amateur rig like a Kenwood TM-D710.
If you want it to receive APRS, you'll have to leave it on 144.39. That's why I mentioned "tying it up".

 

[AK9R]

If you want it to receive APRS, you'll have to leave it on 144.39. That's why I mentioned "tying it up".

This would seem to be the biggest issue. It's very difficult to receive APRS beacons on a radio that is scanning RF channels. Invariably, by the time the radio stops on the active APRS channel, the radio will miss enough of the packet thus making the packet undecodable by the TNC. And, in some parts of the world, the local APRS channel is very busy which means that once the radio stops on the local APRS channel, the radio will stay there for several minutes.

If all one wants to do is beacon their position using APRS, there are, in my opinion, many more functional options than trying to press a radio that can only operate on one channel at a time into dual mode voice/APRS service. Dual-band amateur radios, such as the Kenwood TM-D710G, can receive two channels, including two channels on the same band, simultaneously which means that the radio can monitor or scan voice channels while also monitoring the local APRS channel. If an APRS packet is received, that "side" of the radio simply sends its received audio to the TNC for decoding. If the user is transmitting on the voice side of the radio on the same band as the local APRS channel, the TNC waits until the user releases the PTT before it will key the PTT to send the APRS packet.

 

[dapaq2]

Maybe I just don't fully understand how APRS works or what it is actually for... I just wanted it to report my position to the aprs.fi website. I think I will set this on the back burner for now or forget about it all together. But if I want to pursuit it further it sounds like the radio need is probably the Kenwood TM-D710G, but it does not transmit outside the Amateur bands, which is something I need. Thus why I want to use the Kenwood NX5000 series mobiles...

 

[mmckenna]

It'll do what you want, but it's sort of like taking a nice new corvette, taking the engine out, and installing a lawnmower engine. It might look cool, but it's not going to make a good lawnmower.

APRS just needs one frequency. Often, amateurs will dedicate a radio to it. It'll just sit there humming away doing it's thing automatically. With suitable used commercial radios on the market by the ton, it doesn't make financial sense to take a brand new $900 radio with all that capability and tying it to a TNC just to send out position reports. A much better solution is to dedicate a small/cheap radio to that task since it doesn't require much on the radio side to make APRS work. If you look at the byonics website: Byonics - TinyTrak4 GPS Position Encoder you'll see that you can purchase a small purpose built radio to do this for a lot less than what an NX-5700 would cost. Some even just take an old non-narrowband commercial radio off e-bay, often available for $30 or so, and use that.
In reality, you really don't want a full 50 watts on APRS. Unless you are in a super rural area, like out in the desert southwest, there are usually more than enough digipeters to pick up even a 1 watt signal and get it to a gateway. Running 5 watts is usually plenty, running 50 can actually cause problems on the APRS system when you just hit way too many digi's.

It'd be an interesting project, but I still say there is an easier/cheaper way to do it.
If you need a Part 90 VHF radio, then the NX-5700 is a great option. Lots of features, NXDN, P25, DMR, analog, etc.
But for just amateur radio APRS, get an old Motorola GM300, Radius, or some older radio and dedicate it for that.

 

[dapaq2]

Apparently I need to learn a bit more about this APRS system to get a better understanding on how it works and what I can do with it as it apparently is not what I thought it was. And I understand what you are saying about there being an easy and cheap solution by adding an additional radio to my vehicle that is strictly for APRS, but will also result in having to add an additional antenna to the roof of my car for that additional radio and that is out of the question as I have enough antennas on the roof of my car already, and I am not really interested in having to add a dedicated radio for APRS usage. Its obvious that APRS is not going to work for me (at this time), so please disregard my original post. Moving on...

 

[03msc]

dapaq2,

I would recommend a ham radio for APRS, even if you wanted a NX5xxx for other communication. Much cheaper that way and you aren't tying up the radio. I know you said you don't want that but that's really the best option if you want APRS to work best.

See, to use APRS the radio has to stay on 144.390 to listen for packets and then transmit packets at whatever interval you have set. If you have the radio on another channel, it won't hear or transmit to the APRS system via the gateways, etc., around you. That's a very basic description. Some radios, like the Kenwood D710, can run ARPS on one side of the radio while you use the other side of the radio for talking, etc.

Don't feel bad about asking, that's how we learn.

If you get some time, search APRS on YouTube and you'll find countless videos and some of them should better describe how it works and what you need to make it work.