OT Don't read this (was Re: Altair MBL source)

[Stan Barr]

Hi,

Paul Koning said:
> >>>>> "Geoffrey" == Geoffrey Thomas <geoffreythomas at onetel.com> writes:
> 
>  >> No. Narrow IFs and lack of design attention due to declining
>  >> worthwhile content on AM (plus novelty of FM in the '60s) and
>  >> other factors all conspired to make it sound crappy.
>  >> 
>  Geoffrey> There was a design - in the late 60's?- which used a
>  Geoffrey> detector which demodulted both upper and lower am sidebands
>  Geoffrey> and fed the result to separate speakers. Apparently the
>  Geoffrey> effect during night time fading was exceptional.  Anybody
>  Geoffrey> recall anything about this - Tony ? Sorry if this is ot.
> 
> Don't know about back then, but recently (within the past year) there
> was an article about a receiver using that approach.  It probably was
> in the ham radio publication QEX, and I think that it was by Wes
> Hayward -- or at least he was connected in some way.

Most of the fading is due to phase cancellation between the two sidebands.
The usual technique is to eliminate one sideband and treat the signal
as a single-sideband one, using either the transmitted carrier or a
locally synthesised phase-locked one.  My Racal RA1792 has facilities for
an independent sideband system that would allow seperate demodulation
of the two sidebands, but I've not found the relevant hardware yet...

To get back to computers for a while, this Racal receiver has provision
for remote computer control and I'm currently investigating the SCORE
(Serial Control Of Racal Equipment) protocol it uses, with a view to
writing a remote control program so I can control the receiver from
downstairs and stream the audio over the network. It's even more-or-less
on topic - the radio dates from 1987.

-- 
Cheers,
Stan Barr  stanb at dial.pipex.com

The future was never like this!