Message-ID: <7A19F206FAE04EB58AD0928D6921665C@gnat>
From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <20150108220755.GA20377@cs.utwente.nl> <54AF0F8C.8030106@virginbroadband.com.au> <20150110211701.GN29958@cs.utwente.nl> <FD91181D329143B38573246548F8F478@gnat> <20150111123406.GA20063@cs.utwente.nl>
Date: Sun, 11 Jan 2015 13:33:52 -0000
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Subject: Re: LF: Eb/N0 values for amateur modes
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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" <ptdeboer@cs.utwente.nl>
To: <rsgb_lf_group@blacksheep.org>
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
>
>