Discussion in 'Working Different Modes' started by N8MLP, Mar 16, 2019.
If you unplug that cable, what happens?
The mobilinkd uses a cable to connect between the TNC and the radio. The TNC connects to a tablet or phone via bluetooth, no cable involved.
So if you're using this method, the tablet isn't passing data via the 3.5mm jack. There would be no wires at all connected to the tablet.
You can also set up APRSdroid to connect directly to a radio, without a separate TNC. The software generates the audio tones via the soundcard on the tablet/phone in this case, so it would be passing data (modulated in AFSK audio tones) via the 3.5mm audio output jack. I have only seen this work for one-way sending of beacons, without receiving anything.
I've used APRSDroid directly connected to a radio (with no TNC). I did it with a cheap Baofeng and an old cellphone. I had to use a special attenuating cable sold by Baofeng (or BTech, whatever the seller on amazon is) for this purpose. Also have to set the radio to VOX, which works - but the PTT wouldn't close quick enough to hear my own digipeated packets (this was when using the combination for ISS packet). I suspect that is radio dependent, though.
I have all of the Kenwood APRS radios previously mentioned and they're great for it. Kenwood really does APRS well.
It's hard to do APRS cheaply and elegantly at the same time. I'd love to put something on a dog collar but I've started that project 10 times and never finished, but would have ended up with something like this: https://www.hamradio.com/detail.cfm?pid=H0-015928
An RPi with a USB GPS key and USB sound dongle (to get the mic input) and a cheap 2m radio will do the trick though.
u can builda mobilinkd with a Pi Zerow, direwolf and blutooth. works with aprsdroid. i turn the truck into a digipeater while at the lake too.
TH-D72/74 or TM-D710G/A have messaging built in
Otherwise, YAAC or Xastir on Pi or PC, APRSDroid on Android.. With Apple, I don't know..
I do quite a bit of APRS and have a mix of systems. For a tracker, the radios with the built in TNC's are the least cumbersome option. You don't have wires or extra bits hanging off the radio. You an also work a repeater or simplex while having the second VFO doing the APRS work in the background. The trouble with them is the display is meager, battery life using the GPS is fairly short, and trying to send a message is just painful and awkward.
The mobilinkd is a great compromise. Paired with an H-t and a phone or small table, you get full use of APRS while being able to see maps and send messages clearly and easily. You can strap the TNC to the radio which makes it fairly easy to manage and then use the Bluetooth to link with the phone. A couple of negatives with this setup: You now have to keep 3 separate batteries charged, and radio is dedicated to APRS or voice only as you would have to unplug the TNC to use it on voice.
You really have to decide your needs and engineer the system around it.
The D74 is a pretty slick set up for APRS.
You are marked as living close to Columbus, which means that a portable radio would work for reaching Digipeaters given a good antenna. Even so, as others point out- a mobile *dual-band Kenwood ( one more example, TM-D700a )or Yaesu or Alinco would make your signal stronger if you would be further from home. With FM, there is no need to use extra power- and most rigs allow 10 watt or even 5 watt transmit. Built-in TNCs are a great idea, because most folks are not aware that it is possible to over-modulate a radio- and that if you do not use a built-in TNC -and- you are using direct coupling- then you should also check deviation with a service monitor or spectrum analyzer or deviation meter ( this is not typically found on every tech's bench ). Should you go with older radios which do not have 'data ports' for AX.25 ( basis of APRS ), please find a friend in a local ham radio group who can direct you to a two-way radio shop or free test at a Hamfest. Other users of APRS would appreciate a signal that they can receive. In the interim, listening is best ( unless you choose a radio that has a built-in TNC or get the deviation adjusted ). If you have not already purchased that new radio, most folks find that 70cm allows them access to more voice repeaters*- and sometimes more advanced digital repeaters. The cost of most dual band mobile radios is generally not much higher than that of single-band rigs. BTW- the Kenwood noted requires a 'gender-fix' cable on the RS-232 port for connection to most PCs- a 'null modem'. These usually cost an extra $8.00 or so. For APRS only, you would not necessarily need the cable for transmit-only of position. There is a NMEA jack included for your GPS. The TM-D710 has an improvement for the RS-232 port.