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Re: LF: 4X OP32 report

To: <[email protected]>
Subject: Re: LF: 4X OP32 report
From: "Graham" <[email protected]>
Date: Wed, 25 Jul 2012 23:57:17 +0100
Importance: Normal
In-reply-to: <004f01cd6a8c$7566a7c0$0401a8c0@xphd97xgq27nyf>
References: <CAK59VFNOneVPmCEjVc1kK3FpvfmCX5qp_gZo5-AFy58Hmiq-6g@mail.gmail.com> <[email protected]> <DEF0879101734958AE61D0D590E070DF@AGB> <[email protected]> <16CA55FCF4C44B789AA114D2CCB51D1B@AGB> <004f01cd6a8c$7566a7c0$0401a8c0@xphd97xgq27nyf>
Reply-to: [email protected]
Sender: [email protected]

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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