I believe only large and expensive installations on posh ocean liners. had
rotary spark gaps. The trouble with a static gap is that the voltage
necessary to strike a spark is more than the voltage required to keep it
going. Hence instead of a short spark one got a long one of varying
intensity. This gave a broadband signal and what my father described to me
once as a wet dribble of a note - illustrating this by blowing what brits
call a raspberry
. . He certainly described to me how they regularly used to have to get out
a file to sharpen the points and improve the note.
My mother (who was 'courting' my father at the time and took the operators
sandwiches and coffee in the middle of the night-shift ] told me the noise
and the flickering spark in the wire mesh cage which surrounded the
spark-gap were quite terrifying if you opened the door of that room.
The RSG was intended to move the points together just long enough to strike
the spark but separate them again before the spark deteriorated. Thus one
got a very short high intensity spark no "wet dribble" and a clean pleasant
sounding note and [I assume] a spectrum cleaner sig. Ths is in contrast to
VE2CV's experiment in which he used a gap between two spheres and ,
incidentally, produced what I would call 595c signals
BTW I realise I have no idea of the length of the spark gap...anybody
know?
Bryan G3GVB
----- Original Message -----
From: <[email protected]>
To: <[email protected]>
Sent: 28 June 2006 03:47
Subject: Re: LF: RSGB seeks 501-504 kHz for Expermintal license
> Probably 20 years ago or so, some old-timer brought a recording
> of a few different spark transmissions to the local ham-club meeting.
> It's nothing I'd ever care to have to deal with in an actual QSO.
> I suppose the original recording must have been on a magnetic-wire
> recorder, at that time, which probably didn't help the sound any, either.
>
> As I recall, the most maddening effect was the change in pitch over
> a period of a couple of seconds or so; not sure of the cause of that.
> Maybe somebody can comment: I am supposing that most spark-
> gap xmitters were of the "rotarty spark gap" type? Maybe the
> RSG slowed down under the load of xmitting....?
>
> Again, I have no knowledge of spark-gap xmitters, but I've read
> the thoughts of some prominent tesla-coil builders that seem quite
> sure that their rigs are "reasonably" spectrally clean, i.e. the Q of
> the resonant circuit ensures fairly clean oscillations. Perhaps somebody
> can put it in more correct terms than I can. In other words, fairly
> clean due to it *having* a tuned circuit, rather than hooking up a
> Model T coil to a long wire.
>
> While there *are* HF tesla coils, they use tubes, transistors, etc.
> For whatever reason, the traditional spark-gap TC just won't fly
> above a few hundred KHz, IIRC.
>
> 73,
> Randy
> KZ4RV
>
> On 27 Jun 2006 at 13:17, captbrian wrote:
>
> > You would have to be about 86 [and I assume a M0 is just a lad ;-) ] to
> > have heard at age 10, the last coast stations working spark. Smaller
> > stations , GRL at Fishguard for example, were concentrated at
> > Burnham-on-Sea/portishead with all-singing-all-dancing thermionic stuff
> > around 1930..
> >
> > I have never heard of spark being used at other than MF ...does anyone
know
> > of HF operations?
> >
> > Bryan - G3GVB
> >
> >
> >
> >
> > I wouldn't know if these sound like the
> > > real thing, being a bit too young... (not often I get to say that
these
> > > days!)
> > >
> > >
> > > Cheers, Jim Moritz
> > > 73 de M0BMU
> > >
> > >
> > >
> > >
> > >
> > >
> > >
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>
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