[aprssig] Mobile Off-Air Display

Dallas Clements dallas.clements at gmail.com
Mon Aug 10 14:11:11 EDT 2015


Several options have been shared so far to help you with your bike race.
I've used AvMap, WinBooks, Bluetooth TNCs, and soft TNCs. All have their
merits, but if you're looking for something that will be less expensive to
procure for multiple assistance vehicles and rest stops, I'd recommend
simply hooking an Android tablet or phone via audio cable to a HT. The app
APRSDroid has a connection protocol labeled "AFSK via Speaker/Mic" that
will decode the received packets heard on the radio and overlay them on a
map on the Android device's screen. The option to use an Offline Street Map
is there and with the device's built in GPS, you know where you are in
relation to the objects that you're receiving.

Simple. Inexpensive.

If you wanted to transmit, too, I'd recommend a more capable radio than a
HT, but it sounds like you're just trying to bring situational awareness to
more people. That being the case, the wattage of the device is irrelevant.
Depending on your peer group, it's not hard to find people who have an
older Android device gathering dust in their home from the last upgrade
cycle or two. That leaves your cost at $4.99 for the app and whatever money
you spend making cables. I'm assuming finding HTs and mag mount antennas to
borrow will also not be a problem within your local club.

This setup that I'm describing is the entry level APRS rig that we use to
get new amateurs in our club exposed to APRS. After they use it for a few
weeks, they tend to upgrade to something with more transmit power. However,
for your purposes, it may be ideal.

Here's the "how-to" we wrote for our club. It has a wiring diagram for
Wouxun, Baofeng, and some Kenwood HTs.


Dallas Clements

> ---------- Forwarded message ----------
> From: Charles Bland <root at blandranch.net>
> To: aprssig at tapr.org
> Cc:
> Date: Sun, 9 Aug 2015 17:25:00 -0700
> Subject: [aprssig] Mobile Off-Air Display
> I'd like to get the latest opinion from this group about putting together
> a simple mobile APRS display solution.
> Our local club does a couple of bike events each year. We have an ad-hoc
> network to support our trackers over the course area. I have been turning
> my attention toward broader use of the info. For example, our rest stops
> now have displays, and we run a Public Info table so that we can make event
> participants aware of what we do and how we do it.
> I am now turning my attention to our radio operators in the sag wagons.
> For insurance purposes, the bike club provides the cars and drivers. The
> radio op rides shotgun, using a Go-Box that has battery assist so that the
> cigarette lighter adapter isn't doing the heavy TX lifting and can be
> shared for other uses.
> I'd like to have simple, non-transmitting display setup so that the
> operator can "look" around the course as he has need. I'm not sure where to
> start looking for commercial solutions, if there are any at all. I also
> have been wondering, given the abundance of R-PI hardware, if a R-PI and
> display would be enough to run something like YACC. A simple RX and antenna
> would be enough, and the package could be small enough to occupy little of
> the precious space in the vehicle and not pose a safety issue. Even nicer
> if it could be on the dash.
> So, what do you folks know? How would you approach such a requirement?
> Chuck
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