Message-ID: <3D4EA15D.3A1D682D@usa.net>
Date: Mon, 05 Aug 2002 18:01:33 +0200
From: "Alberto di Bene" <dibene@usa.net>
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To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: Confused over Jason coding
References: <7D653C9C42F5D411A27C00508BF8803DCB9B63@mail.dstl.gov.uk>
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Talbot Andrew wrote:

> I'm sure this was all explained last year when the mode was being developed
> but can't find any reference to it now.  And the Tech Notes that come with
> V0.94 don't cover this aspect.

>From the TechNote :

> The frequency deltas can assume one of 16 different values. After sending one tone,
> the next one is shifted by the appropriate amount, up or down depending on the
> setting of the USB/LSB switch. With 16 deltas we need 17 slots, and any overflow
> causes a wraparound.

Maybe I haven't been much clear there. What I meant is that the direction of the frequency
shift depends on the setting of the USB / LSB switch in the Option menu of the
program. If the amount of the shift is such that we go over the highest (or the lowest)
slot, then a wraparound occurs, and we re-enter from the opposite side.

In its first incarnation Jason was sideband-insensitive, but it had a greater band occupancy.
I asked for opinions, and the general consensus was that the need to specify the USB / LSB
mode was a small price to pay for a reduction in bandwidth.

> A thought has just occurred while writing this - does the direction of
> frequency shift matter, which can then be taken modulo 16, giving 16
> possible shifts from 17 tones?  Which means the sideband in use is
> sensitive.  Have I answered my own question ?

Yes, you did.

73  Alberto  I2PHD