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

[Colin Wilson]

Hi

Well just to let you all know that the usual Police will no doubt be on the 
band this coming week-end and don't forget you could get a speeding ticket 
if your not careful and get points on your licence!  Now you would not want 
that now would you?

73 es enjoy

Colin G3VCQ/J38CW


----- Original Message ----- 
From: "David, G3YYD" <g3yyd at btinternet.com>
To: <uk-contest at contesting.com>
Sent: Thursday, November 26, 2009 2:33 PM
Subject: Re: [UK-CONTEST] Re 1 CW Sending speed & Bandwidth


> 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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