The thing is Mal , that its CW but not as 'you know it , to miss
quote CapJTK , Yes the slow qrss 'did' paint CW on the screen or
paper tape , but with the narrow frequency shift keying , with
equal mark / space ratio , with a vari-code ie Morse , which needs to
be interpreted by the operator , its neither CW or Data transmission
Seeing traces , is the $64,000 question , yes we can see , and yes we
can Guess , but if you where a RO working on BP tankers , with
everything sent in 5 figure code groups , or other users of this
system, 1 wrong letter and you could loose the whole message .. which
takes the story full circle .. unless there is a full trace, q5 copy
or a decode , the message has not been successfully transmitted
With time hopping , Ala FEC , data modes are able to decode , after
loosing a substantial % of the signal , upto 50% in the case of Opera
, the fec and data coding are designed to provide maximum efficiency
in qrm , static impulses are met by a non linear routine, that seeks
to reduce the dynamic range , also the noise impulse / Tx 'ON'
time ratio is very low , adding a second layer of 'limiting' , ( there
is no need to pre-process the audio signal)
73-G..
--------------------------------------------------
From: "mal hamilton" <[email protected]>
Sent: Wednesday, July 25, 2012 6:39 PM
To: <[email protected]>
Subject: Re: LF: 4X OP32 report
Graham es Co
While Opera es other data modes are an alternative to CW for a change they
need another level of demodulation and cannot really compete with the
basic
CW mode or QRSS CW.
I often see traces of all data modes that could easily be identified in
QRSS
but they do not decode therefore the purpose of the transmission is lost.
de mal/g3kev
----- Original Message -----
From: "Graham" <[email protected]>
To: <[email protected]>
Sent: Wednesday, July 25, 2012 4:07 PM
Subject: Re: LF: 4X OP32 report
schrieb Stefan, :)
Why do you think so?
Its linked to the DSP engine in Op , there is a timing issue , if
other applications lock the sound card at a different rate , due
to
the % tolerances , low level decodes can be lost , noting, Op is a
'data mode , so the overheads in the transmission are much higher
,
as are the DSP engine requirements , as can be seen with 'older'
pc's
cpu loading can be a issue , as is a one-pass system , all the
processing is taking place in real time
But on with the show ,
73 -G..
-76 dB in 28 mHz b/w , what is that when translated to 2.5Khz
B/w ?
--------------------------------------------------
From: "Stefan Schäfer" <[email protected]>
Sent: Wednesday, July 25, 2012 3:08 PM
To: <[email protected]>
Subject: Re: LF: 4X OP32 report
>
> Am 25.07.2012 15:51, schrieb Graham:
>>
>> Pity nothing decoded in the US last night , but signal 's in 1500
>> /2000 mile range where quite substantial ...
>> from this , it seems that propagation on 136 is really linked to
the
>> seasons ?
>
> Yes (of course) and no. W1VD received me quite well a few weeks ago,
> see
> https://dl.dropbox.com/u/19882028/LF/07_July2012.jpg
> Not to forget W1TAG:
> https://dl.dropbox.com/u/19882028/LF/DK7FC_Juli2012.jpg
>
> So there is some propagation in summer but of course it depends on the
> solar activity. Don't know how the condx have been yesterday.
>
>> One point from previous trials , If Spec-lab is used with
>> Opera
>> , then SL must be set to 48Khz sample rate , or OP can loose
low
>> level decode sensitivity.
> Why do you think so? As long as the frequency range of a SSB bandwidth
at
> audio levels passes through the SL filter, then it should be fine. So 8
> kHz SR should be fine. Of course it depends on which shift frequency
> you
> have to use. I have to use 11 kHz shift and so i choosed a SR of 30
> kHz.
>
>
> 73, Stefan
>
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