Australian Ham Radio Discussion Forum ( AHRDF )

fast beacon keyer

Hello,

I have written firmware for fast beacon keyer for mega16. With 16Mhz xtal it sends a message
at 4400bps in about 20mS. This needs vhf radio with asynchronous FSK link. The idea is to find
out how often short burst tropo exists over ocean path (if it does). Tropo signals are strong
signals and only about 50watts of power is required; but the FSK link performance probably
depends a great deal on transmit deviation setting.

www.qsl.net/zs1agx/mega16/keyr003.html

Experiment with signal polarization over ocean path is also of interest.

This keyer needs a serial connection at 19200bps to display received text. The keyer has a selcall
counter to count number of valid beacon detects. The message is sent as delay modulated varicode so
the FSK works at any fixed phase shift and has no DC component.

73 agx

I have written new firmware for keyr.
This sends characters that can be read (maybe) off waterfall, or multi -tone Hell.
The attached .jpg is picture from mshv waterfall of test audio across desk and the
inter-letter underline seems to have got phased out in the capture. But the program
is intended for offsetting a xtal oscillator frequency for direct RF (offset FSK)

www.qsl.net/zs1agx/shell/shell.html


right click on the test .wav
www.qsl.net/zs1agx/shell/dc.wav
to save it
then, with spectran, select for input the .wav file.

or look at the attached picture from android soundanalyser..

The android screen above shows a ghost (mirrored) image. This is the result of aliasing.
When I saw the explanation involved a discussion of negative frequencies, I quickly
skipped ahead and installed an additional low pass filter.

A program to display the dc.wav file:
www.qsl.net/zs1agx/shell/shell.html#dl

This is for win32 with .net 2.0 , so a really old winxp or win7 should be ok.
unzip the file into maybe d:\programs

The program displays a slowly scrolling waterfall from either .wav or line input
across 750...2300Hz. The display is averaged to reduce noise, so the character pixels
of dc.wav soften a little. Keep to low input level. This program takes less than 3% cpu
time and less than 15M RAM (even less when reading a .wav file rather than line input).

Additional extra program setting items have been included (especially for you in
particular) so as to allow you to experience the highest level of click satisfication
possible with such a program.


alias.jpg scribble01.jpg