EMRFD Message Archive 7794

Message Date From Subject
7794 2012-09-20 20:20:46 nm0s_qrp Proposed new digital mode
I had a thought while driving home tonight, and wanted to share it with the group for whatever it's worth.

Soundcard-based radio is now pretty common, and is the most common implementation of the more modern digital modes. The frequency waterfall display is a useful tool for observing signals within a band of interest. Of all the types of modulation, only CW is directly readable (by those knowing code) on a waterfall display. How about a mode that permits text to be displayed directly on a waterfall?

If you consider text as written graphically in a 5x5 matrix (like on a scrolling LED marquee display) , you can transmit this as a five tone Hellschreiber modulation, with each row of the display represented by a CW modulated tone. These pulse-modulated frequencies would show up directly readable as text on a frequency waterfall display (albeit with characters rotated 90 degrees)

A back-of envelope estimate predicts a 30WPM text would fit into about 200 Hz bandwidth, with tones separated by 40 to 50 Hz. Conventional SSB gear could be used. Transmit encoding could be done very simply, and RX decoding is done visually by the operator.

Has anything like this been done, or is there interest in building hardware?

73 Dave NM0S
7795 2012-09-21 01:26:15 Fábián Tamás L... Re: Proposed new digital mode
Hi Dave and everyone,

I've seen something similar when I was experimenting with QRSS reception
(with self-written python script). One particular beacon sent it's
callsign not only in CW, but as slash/backslash combinations, up/down
pointing triangles, and also by "drawing" characters onto the waterfall
display (I think it was G0PKT).

I don't think that it would be terribly difficult to hack a prototype
program that can encode characters in a way you suggest. Maybe it's
feasible to send low-res grayscale images in this way, creating a kind
of "narrowband SSTV" or "SSSTV" ( Super Slow Scan TV :P ) mode.

I'm also interested in this mode. I can publish the (very experimental)
receiver script, if you are interested.

on 2012-09-21 05:20, nm0s_qrp wrote:
>
>
> I had a thought while driving home tonight, and wanted to share it with
> the group for whatever it's worth.
>
> Soundcard-based radio is now pretty common, and is the most common
> implementation of the more modern digital modes. The frequency waterfall
> display is a useful tool for observing signals within a band of
> interest. Of all the types of modulation, only CW is directly readable
> (by those knowing code) on a waterfall display. How about a mode that
> permits text to be displayed directly on a waterfall?
>
> If you consider text as written graphically in a 5x5 matrix (like on a
> scrolling LED marquee display) , you can transmit this as a five tone
> Hellschreiber modulation, with each row of the display represented by a
> CW modulated tone. These pulse-modulated frequencies would show up
> directly readable as text on a frequency waterfall display (albeit with
> characters rotated 90 degrees)
>
> A back-of envelope estimate predicts a 30WPM text would fit into about
> 200 Hz bandwidth, with tones separated by 40 to 50 Hz. Conventional SSB
> gear could be used. Transmit encoding could be done very simply, and RX
> decoding is done visually by the operator.
>
> Has anything like this been done, or is there interest in building hardware?
>
> 73 Dave NM0S
7796 2012-09-21 03:15:15 Alberto I2PHD Re: Proposed new digital mode
7797 2012-09-21 03:29:50 Alan Melia Re: Proposed new digital mode
I think you ill find that there re several "modern" variants of "Hell" that
have been used for some time on the LF (real LF, below 300kHz) bands. Check
out Spectrum Lab there is probably code in there for transitting it, else
there is a stand alone program by an Italian station. DF6NM is another
user.

Alan
G3NYK
7798 2012-09-21 04:36:54 Johan H. Bodin Re: Proposed new digital mode
Here are two other examples from the 30m band in 2006:

http://dl.dropbox.com/u/107227836/on5ex_mm.jpg
http://dl.dropbox.com/u/107227836/on5exinv.jpg

73
Johan SM6LKM

-
7801 2012-09-21 10:25:10 Eduardo Alonso Re: Proposed new digital mode
image from ea4bvz in 136318 hz

https://sites.google.com/site/ea3fxf/_/rsrc/1267552472883/manuelmadridespanya-custom-size-641-213.jpg



On 9/21/12, Johan H. Bodin <jh.bodin@telia.com> wrote:
> Here are two other examples from the 30m band in 2006:
>
> http://dl.dropbox.com/u/107227836/on5ex_mm.jpg
> http://dl.dropbox.com/u/107227836/on5exinv.jpg
>
> 73
> Johan SM6LKM
>
> -