Message-ID: <2BD00AC139914C138F0FB6FE5FB00F4D@AGB>
From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
To: <rsgb_lf_group@blacksheep.org>
References: <281222.921.qm@web26004.mail.ukl.yahoo.com> <001301c901e6$917c2d30$2201a8c0@PC2> <731EB49F88B309428FFDDD2423F810E441C128@HERMES4.ds.leeds.ac.uk> <48AADCE5.7070602@virgin.net> <034D836CD37D497C80547813F78DE240@AGB> <48AB191F.2070100@w1tag.com>
Date: Wed, 20 Aug 2008 00:58:02 +0100
MIME-Version: 1.0
Importance: Normal
Subject: Re: LF: Keyboard Modes for 600 Meters
Content-Type: text/plain;
	format=flowed;
	charset="iso-8859-1";
	reply-type=response
Content-Transfer-Encoding: 7bit
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org


John,

I think you will find , olivia  runs more than one tone at any one time and 
produces a 'two tone test' envelope , simple check, view the sound card o/p 
on a scope ? I had a conversation with Simon (dm780)  at the hf convention 
last  year, you can use none linear, but at the expense of  s/n ratio and 
side band splatter .. the ultra low conduction angle  D and E set-ups  can 
be observed to  generate 'gray noise' close in when handling pseudo linear 
transmissions , I assume as they loose 'phase linearity'  due to the abrupt 
change of sate ?   the systems look to  be defined in terms of 'stats' ie 
side band / noise levels as maximum predicted  levels, which presumably are 
deemed acceptable when pulse shaping data streams ... may not be ideal for 
close in analogue work ?

There is defiantly a play off between data transmissions generated by 
conventional analogue  mixing  / amplification and digital  systems  in 
terms of close in noise, but as to the effect on the readability / decode of 
the signal, ive not had the chance to  compare , though interestingly, the 
JT65 test on 500 , showed the K1JT software to  give a constant +3 dB 
improvement in the reported s/n   over multipsk (at the time) , I was 
sending the two systems on alternate time slots, via the same soundcard 
through the same transmitter path , AWE64  isa sound card ,Racal MA1723 
exciter  and 20 Watt Class A solid state Racal 24v drive amplifier, ALC was 
'on'

As to the reason, I can only assume there was/is some compromise in the 
generation code ?

G ..


--------------------------------------------------
From: "John Andrews" <w1tag@w1tag.com>
Sent: Tuesday, August 19, 2008 8:03 PM
To: <rsgb_lf_group@blacksheep.org>
Subject: Re: LF: Keyboard Modes for 600 Meters

> Dear ++ (Graham), <g>
>
> I think that Olivia uses sequential FSK, not simultaneous tones. I don't 
> believe that Jay and I evaluated any simultaneous systems. We did use 
> linear PA's during the tests, but that was more for convenience in 
> switching back and forth between PSK and FSK systems. The claim is 
> generally made that the various FSK modes do not require amplitude 
> linearity. It would make an interesting experiment to compare bandwidths 
> and perhaps audible keying artifacts between linear and switching amps 
> while driving the fairly high Q antennas we use at LF and MF. I'm always 
> amazed at how click-free the hard-keyed CW signals are down here.
>
> John A.
>
> Graham wrote:
>> Interesting list of modes and tests ,
>
>
>
> No virus found in this incoming message.
> Checked by AVG - http://www.avg.com Version: 8.0.138 / Virus Database: 
> 270.6.5/1620 - Release Date: 8/19/2008 06:04
>
>
>