Hi Rick
see comments below 5 spaces in
Les VK2DSG
From: Rick
Sent: Sunday, January 27, 2008 3:38 AM
To: digitalradio@yahoogroups.com
Subject: Re: [digitalradio] Report on RFSM2400 vs. OFDM
I was using the 10/Nov/07BETA of EasyPal which I downloaded fairly
recently. I noticed that there are images that are sent with an RS 1
through 4 and then I think it converts them to jpg? I could not open
those files with other programs. Perhaps you an give us some tutorial on
it. The RS turned out to be Reed-Solomon coding so at least we know what
is being used.
Always use the latest from the KC1CS site
You cannot Open an .rsx file - it is the means to transfer the file
encoded
and is automatically displayed in its original form at the receiving
end
Since it was the first time I ever tried EasyPal for transmitting, I
don't have much background on this. I don't have a lot of interest in
SSTV, per se, but I am using image as a surrogate for the data that I
would rather be sending.
EasyPal may be used for normal data transfer by loading as an ANYFILE
but of course this is limited by the file size and the length of time
to
to transfer it depending on the mode and conditions existing at the
time
Because of an active group here in the
midwestern part of the U.S. on daytime 40 meter SSTV (7173 kHz) I will
sometimes leave SSTV programs on the frequency and automatically receive
some of the images when signals are good.
When you use the repeater function does that work with one to many as in
nets? Or is that intended for one to one?
Yes it is one to many - each station individually asking for any
corrections to the original transmission by the repeater
Can you send chat along with the image? Or at least send chat in between
images?
You can sent chat by Waterfall text or you can directly send a text
message
in a separate screen --- Action Send text
I did not change anything for conditions and used whatever the defaults
are. What are some of the options that you recommend?
See prior post
Based upon the conditions, and my experience with receiving (not
transmitting) DRM type of OFDM data, the roughly 1/6 throughput seems
about right. When conditions are very good, such as NVIS daytime on 40
meters or close to NVIS anyway, with maybe 5 or 6 S units between the
noise and the signal, it is posible to receive the majority of the
packets (blocks) on the first try.
Use the correct mode and always use encoding suitable for the noise on
the path
The question becomes: if you had two modems, one using single tone high
baud rate vs. one using multi tone OFDM, which one would perform the
best in varying conditions.
Maybe the answer is to have available BOTH and use the one which is
most suitable at the time to suit the conditions
Various documents on the internet suggest that there is not much
difference, but there is at least one that does show a difference with
computer simulations in favor of the multi tone modems. I tend to
discount computer simulations as not adequate and prefer the real world
under many different conditions that gives you a more accurate practical
feel for what can and can not be done. That same document, done as a PhD
paper, admitted that some waveforms that worked well on computer
simulation, actually did not work at all in an actual real world test.
73,
Rick, KV9U
