<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<div class="moz-cite-prefix">On 12/5/2012 3:23 AM, Chris Moulding
wrote:<br>
</div>
<blockquote cite="mid:50BF0472.9050304@crosscountrywireless.net"
type="cite">About 4 years ago I made a 10W transmitter for 30m
with AX.25 frequency shift keying of a crystal oscillator.
<br>
<br>
It worked really well.
<br>
<br>
I'd forgotten about it until I spotted your posts. I'll take look
at it again. It would be relatively easy to add it to an APRS TNC
Digi Tracker to make a self-contained HF APRS tracker with it's
own GPS receiver.
<br>
<br>
73,
<br>
<br>
Chris, G4HYG
<br>
</blockquote>
<br>
1) We are talking about a really lightweight package for
high-altitude balloons, where every gram counts. I envision a
small styofoam box with a small naked PC board inside that combines
a basic microcontroller and a QRP xtal transmitter, at the center of
a 30-meter wire dipole made from 28 or 30-gauge AWG copperweld
wire. This stuff (copper-plated steel) is strong, but very
lightweight. The top half of the dipole is attached to the balloon
itself, while the bottom half dangles below the box. <br>
<br>
2) Classic AX.25 packet is a terrible mode for low power / weak
signal operation on HF. The symbol rate at 300 baud is simply too
high to tolerate multipath propagation or popping-type noise well.<br>
<br>
3) The MFSK16 mode could be implemented with a simple FSK scheme
on a crystal transmitter just about as easily, and would gain an
absolutely enormous advantage in weak signal operation. <br>
<br>
4) (I forgot to mention this in my original post) With APRS
Messenger, we already have a virtually turnkey way to create instant
ground stations / igates for the MFSK mode. Anyone, on the
spur-of-the-moment, can setup an igate with just a radio and a PC
with a sound card, since Messenger already has the sound card modem
AND the ready-to-go igate stack built-in, in a single app. <br>
<br>
<br>
<br>
<br>
<br>
</body>
</html>