[UK-CONTEST] Re 1 CW Sending speed & Bandwidth

[David, G3YYD]

Bandwidth occupied of course depends on how "hard" the keying is.

12WPM using the "PARIS" speed system equates to dots of 100milliseconds 
length. Sending a stream of dots will, assuming minimal bandwidth for 
the information (i.e very soft keying), require a baseband bandwidth of 
5Hz. Modulating this onto a carrier occupies 10Hz. 36WPM would need 
30Hz. However an excellent low click rig uses raised cosine modulation 
with 5 milliseconds from zero to full power. This is equivalent to a 
full cycle of 20milliseconds and thus the bandwidth occupied once 
modulated onto a carrier is 100Hz. Very few rigs achieve this sort of TX 
bandwidth performance probably the K3 and Orion get near it.

Incidentally for machine reading of Morse then ideally the modulation 
would be very soft to ensure all the sideband power is within the 
minimum bandwidth required along with a matching filter at the RX end. 
This would provide the best signal to noise ratio for machine reading. 
Humans require a harder edge to be able to distinguish individual 
symbols and hence a wider bandwidth than the minimal is required.

I find I can copy mid-20s WPM in 50Hz bandwidth on the K3 although it is 
a bit soft, which indicates I need about twice the minimum bandwidth for 
good copy on a reasonable signal. 30+ WPM then 50Hz is too narrow for me 
and have to use 100Hz or wider.

David G3YYD

Chris Tran GM3WOJ wrote:
> Hello Andy et al
>
> Sorry Andy but this G8 vs G3 thing is completely irrelevant to the 
> discussion - in the 160m contest last weekend there were several UK stations 
> who sounded as if they were keying with their left foot, but it made no 
> difference to me if they were G3, G8, M5 etc I just wanted to make the QSO. 
> It's also not helpful to describe operators who choose to operate at higher 
> speed as 'snobs'. In the CQ WW contest this coming weekend I'm going to be 
> sending as fast as possible to maintain a high QSO rate, slowing down only 
> if I think my sending speed will stop stations calling me or lose mults 
> calling me or make the logged QSO information wrong - this is the norm in CQ 
> WW and is the way it should be.
>
> I found that an hour here and there over the winter with Morserunner or RUFZ 
> software helped my copying speed a lot, but a real pile-up is a different 
> matter - at first stressful but eventually great fun to work. I found the 
> Wyboston pile-up test the most stressful of all - give me a real pile-up any 
> day !!
>
> 160m sending speed - interesting point about bandwidth vs data rate - 
> correct me if I'm wrong but 35wpm = 175 letters/min = 525 morse 
> characters/min = 8.75 Hz therefore it should still be possible to send at 
> 35wpm and it will be within a narrow receive filter bandwidth ?  I am not 
> advocating that everyone speeds up on 160m, just pointing out that slower is 
> not necessarily best.
>
> 73
> Chris   GM3WOJ / ZL1CT 
>
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