Hi Peter I will email John to see if he remembers it.
Yes DFCW is more like cable telegraph code the elements are the same length
and there is no need for inter character spaces. I dont beleve any of the
decoding was done electronically so some of the information dot-and-notdash
or dash-and-notdot is not used. It prime use was to make best use of the
favourable fade conditions by getting information transmitted in the minimum
time for a given element length. Even with condition unfavourable and not
supporting full identification it was easier to detect a frequency shifted
signal that OOK on a steady carrier.
Thanks for your table it is very interesting.
Best Wishes
Alan
G3NYK
----- Original Message -----
From: "Pieter-Tjerk de Boer" <[email protected]>
To: <[email protected]>
Sent: Sunday, January 11, 2015 12:34 PM
Subject: Re: LF: Eb/N0 values for amateur modes
On Sat, Jan 10, 2015 at 10:13:20PM +0000, Alan Melia wrote:
Hi Pieter, Dave G3YXM and I did some quick and dirty estimations of
QRSS about 10 years ago on 136kHz I cant remember whether we did
DFCW where the main advantage is that it is faster, but the decode
threshold is about the same as QRSS It is a little subjective but
the results seemed reasonably what we might suspect.
They may be on his web-site still www.wireless.org
Found it, at http://www.wireless.org.uk/signoise.htm . No DFCW there
though.
The QRSS line in my table is based on ON7YD's tests,
http://on7yd.strobbe.eu/QRSS/
I believe someone in the States also did some tests, John W1TAG
could probably help there. They may be on the LWCA web-site.
I'd be interested, but can't find something relevant on the LWCA site.
B.t.w., what I wrote earlier about DFCW is wrong; I somehow thought DFCW
was simply morse code sent using FSK instead of ASK, but it's different,
using 2 tones for dots and dashes. Hard to say what this does for the
required SNR and Eb/N0 compared to CW, as both the average power and the
data rate increase.
73, Pieter-Tjerk, PA3FWM
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