[aprssig] Re: Sending messages from the keyboard.
Stephen H. Smith
wa8lmf2 at aol.com
Thu Sep 15 00:39:54 CDT 2005
bruce.coates at sasktel.net wrote:
> A fellow ham has asked whether he can send an APRS message using just
> a plain TNC-2 and simple terminal program such as HyperTerminal.
> I'll be operating a station at a search and rescue command center
> under VE5BNC. The other ham will be operating a portable station with
> a TNC-2 and a laptop running a terminal program under the call
> VE5RY-??. His home station will be setup up for digipeating under the
> call of VE5RY.
> The question is, "What exactly would he type into his terminal program
> so that it creates and sends an APRS message to me either direct or
> via the digipeater?"
1) If his station IS the digipeater, then there is no distinction
between working him direct and via the digi. Using the digi (or putting
the digi in your path) is pointless, unless third parties somewhere
outside your own direct range are listening.
2) With his TNC in command mode, set MYC inALL to his callsign,
MYALIAS to "WIDE1-1" or some such for digipeating, enable the digipeat
function, and set his NONPROTO path to "APRS". Since this isn't a true
APRS-savvy WIDEn-N dig, but rather a dumb classic packet digi, you will
have to set YOUR path to exactly match his to get digipeated; i.e. if
his alias is set to WIDE1-1, you have to set your path to WIDE1-1 (or
his actual callsign VE5RY).
3) Command the TNC into non-connected conversational mode (usually
something like "CONV" at the prompt) after making the settings, so that
it will transmit every time he types a line of text and hits enter
without being connected.
4) Transmit a few messages and beacons to him from your own APRS
client. Transmit a posit in normal human-readable APRS (not compressed)
format. Have him turn on logging (text capture) in his terminal
program and save some of these into a text file. Most TNCs in monitor
mode display the headers (to and from calls, paths, length, time, etc)
on a separate line from the packet payload. You only want the payload
part of the packet.
5) APRS posits, status reports, and messages use a very precise format.
A single typo or omitted space will break the transmission. Use the
logged samples as templates to construct his own transmissions by
editing the samples, then copying and pasting them into the terminal
program transmit buffer. (Use the usual Windows cntrl-C to copy a
high-lighted block, then cntrl-V to paste it into another window.)
6) Have him take one of your posits and edit the lat/long values (and
possibly the symbol codes and comment field) to match his QTH. Save the
revised string into a text file, or assign it to a macro key in the
terminal program. [Most terminal programs have programmable keys to send
canned strings of text normally used for passwords, network logon
sequences etc.] Anytime he wants to send a posit, copy and paste the
modified string into the terminal program transmit buffer and hit
<ENTER> (or hit the macro key) .
7) Edit the sample posit several times, entering a different lat/long
each time corresponding to points on a highway, change the symbol code
from a house to a car. Save these altered strings to successive lines
of a text file. During the demo, have him copy, paste and send one of
these every few minutes to simulate a mobile in motion.
Or, ahead of time, log your own real mobile moving around. If he
pastes only the payload of your posit packets into his send buffer, the
TNC will add his callsign and path to them, making them look like HIS
(virtual) mobile. Just don't let the cat out of the bag by leaving your
callsign, email address, etc in the comment field of the packet!
Stephen H. Smith wa8lmf (at) aol.com
EchoLink Node: 14400 [Think bottom of the 2M band]
Home Page: http://wa8lmf.com
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