In general I am a fan of the home brew solutions for aprs, however I presume that there are a number of people looking for some reasonably simple and not too expensive solutions with something like an off the shelf set of hardware. I'm really one of them as well, though I very likely will put together a few other solutions along the way.
For the purpose of this note, a 'manpack' is a collection of gear for APRS that is worn by the amature as they are using the rig.
On the assumption that you want a simple GPS unit that isn't going to give you your own location directly, i.e. via a display of some sort on the unit, almost any of the pucks can be sewn into the shoulder of a safety or 'radio' vest. You will need to make sure that you provide some form of power for the receiver in most cases, but many of them are built so that the same power that supplies the receiver can be used to supply a tracker or pda that will perform the display function for you.
I would not recommend sewing a eTrex or similar receiver from Garmin, or most of the display gps recivers into a similar setup, as you very likely will want to do your own navigating with the receiver. You may be comfortable twisting your neck to read the display on your shoulder, but I don't think I would be.
An alternative would be one of the handhelds gps receiver with an external antenna that you could set up similarly. Just treat the antenna as if it were a puck, and the receiver as a component of the tracker. If you have a handheld with the built in TNC and aprs software, such as the th-d7a that is often recommended, you would be up and going shortly after setting up the appropriate call sign and other software configuration on the radio. If you have a pda that either has the capability, and software, you could use it as a TNC instead, though you will likely need to find some way to split out the appropriate lines on the serial port so that you can receive from the gps, as well as use the appropriate lead to trigger the PTT on your radio.
For those of us who are going to be using a fairly low end handheld radio, as well as a somewhat stand-alone gps receiver, we are going to need some sort of a device that will receive the nema strings and send them to the radio. I've used a TinyTracker3+ with a puck, and still do in my car setup, but since the gps receiver I will use in a manpack has it's own power supply, I will probably switch to a TinyTracker3 for that setup. An OpenTracker would work as well, but I already have the software for the TinyTracker, so I will stick with that for now. The radio I expect to use is the one I used mobile until I found an HTX-212 at a reasonable price and mounted that in my car. I will be using a Yaesu VX-150. A 120, 110, or 170 would work as well, and for some situations my vx-2r would also work, but I have the 150, and I like the fact that on it's own batteries it does transmit at 5 watts. Obviously getting a better antenna on the end of the radio is advisable, but even with the rubber duck, in an area with good aprs repeater coverage, I expect to work just fine.
My new favorite gps receiver for this situation is the Garmin ForeTrex series of recievers. There are shortcomings with the receiver. It has a small internal antenna, which means it will be less sensitive than those devices with external antennas. The setup to attach a serial cable to the rig makes it uncomfortable to wear on the wrist (which is probably not the best place to wear it anyway, on the upper arm or at your shoulder would be better) and there is no extension strap for the wrist band to make it easy to wear on the shoulder. The advantages are that it ouputs nema strings serially, is relatively small in size but has a usable display, and the 201 at least with an internal battery will operate for over 10 hours before it needs to be re-charged. The 101 can use off the shelf AA or AAA batteries (I don't know which.)
Alternatively with the 201, it will take a 5.0 volt in power supply and run (and recharge) off of that so someone with a 2Ah gell cell and a TinyTracker3+ (or other device to step down the power to 5 volts) could probably run all of the hardware for over a day.
I do not know if it will take dynamic updates to waypoints from a th-d7a, which I think would come in handy to work out how to get from where you are to where someone else is, as they move. Maps and such are pretty much useless on the receiver as well. The display is so small, that the text for a waypoint tends to obscure any recommended path anyway.
The physical design of the ForeTrex seems to me to almost be designed for search and rescue. It can double as a wrist watch (with superior accuracy, but rather short on the 'on' time.) It can operate either with 'normal or 'WAAS' gps reception, so you can get 'better' accuracy. Colors are Olive Drab and Black, with White, Red and Green lettering. It at least looks rugged. I don't know that with cables attached it would pass any milspec testing though.
I have used a forerunner as part of my exersize routine for a couple of years now. It is fundamentally the same device, but with different software. I would not recommend either as a serious geocaching system, and with six control buttons (including power) neither are particularly friendly for setting up waypoints and the like.
It will be some time before I am completely comfortable with the serial port capabilities of the ForeTrex, as I am not impressed with my ForeRunner's serial port. I'll toss a review up on the hardware reviews page for the receivers I have and have used.
73,
-Rusty - kc0vcu
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Topic: "manpacks" or wearable systems. (Read 7525 times)