Re: SSTC As a transmitter.

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Gary Peterson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <glpeterson-at-tfcbooks-dot-com>

Yes, I would have to upgrade to General as well.  I hope the shared
allocation is given the go ahead.  As for legality, I'd like to know for
sure.  I suppose it would be okay as long as the transmitter produced
undamped waves and it had proper bandwidth characteristics.  From the FCC's
Notice of Proposed Rule Making
<http://hraunfoss.fcc.gov/edocs_public/attachmatch/FCC-02-136A1.txt>,

"We propose to require that amateur stations in the 135.7-137.8 kHz band
meet the technical limits suggested by Canada in the WRC-03 preparatory
process, noted above.  As provided in the Canadian proposal, we believe that
sharing of this spectrum would be facilitated if the amateur station is
limited to an EIRP of 1 W and the transmission bandwidth is limited to 100
Hz. Because of possible difficulty in measuring the EIRP of the amateur
station in this frequency range, as noted by ComEd, we additionally propose
to limit amateur output power in this band to 100 W PEP. "

Assuming it's legal, and if Tesla is to be believed, our signals would
propagate by conduction rather than electromagnetic radiation so a really
good ground connection would be very important.  According to Tesla 136 kHz
would be a little high for optimum performance--35 kHz and below would
apparently work better.  (At 500 kHz EM radiation would have begun to
predominate.)  A very stable square-wave generator would also be a must.
The proposed band is only 2100 Hz wide so resonator tuning could be handled
by varying the height of the elevated capacitance by just a few feet.

As for the receiver, Tesla said,

 ". . . That circuit, and that, and that one must be attuned; this is an
indispensable condition for economic transmission; but it is not essential
to tune this fourth circuit [the receiver secondary].  As a matter of fact,
in certain instances I have obtained a better result without tuning the
fourth circuit than when I tuned it. . . .
     If you take this fourth circuit entirely away, and leave only that
circuit here, the antenna and the ground connection, then that is the ideal
condition for the flow of the current in this receiving circuit.  Any other
circuit you bring near to that excited circuit with the antenna will draw
energy from it and tend to pull down the oscillation in the latter circuit
and diminish the resonant rise.  No matter what you link to the antenna
circuit, and how you link it, the energy you take away from that circuit
will always tend, being frictional, to diminish the resonant rise.  Now the
art consists in reducing as much as possible the energy necessary for the
signal, and in that regard the evolution of detectors as the audion of Dr.
De Forest, and of other such devices, is in the proper direction, rational,
and good.  But the ideal condition requires that you should have here a
device which only requires pressure and no current; and once you have a
device which does not need any current but merely acts by pressure and has
no internal capacity, so that there will be no capacity current in the
circuit, then that is the ideal receiver. . . ."

A good receiver might consist of a well grounded helical resonator with an
elevated isotropic capacitance--what Tesla called the antenna circuit--with
an e-field probe in the near vicinity of the vertical conductor  linking the
coil and isotropic cap.  Lyle Koehler, KØLR has posted a suitable e-field
probe circuit at  http://www-dot-computerpro-dot-com/~lyle/preamp/preamp.htm.  Any
standard  communications receiver that tunes the band might do the job, even
without a preamp.  For initial tuning very close in, a sensitive AC
voltmeter would work.  A grounded voltmeter with an elevated conductor would
also be a good instrument for transmitter peaking.

Gary, KB0DEB



----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, July 22, 2002 9:36 PM
Subject: SSTC As a transmitter.


>
> Original poster: "Mike Panetta by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<ahuitzot-at-mindspring-dot-com>
>
> Now that would be cool!  I had actually had a similar thought, working a
> ham band with an SSTC, but I was not sure of the legality of it.  I am a
> ham (KG4TTU is my call), but I do not have privlages on such a low band
> (yet :).  I still think it would be a really cool thing, atleast to
> listen :)
>
> Mike
>
>
>
> On Mon, 2002-07-22 at 10:46, Tesla list wrote:
> > Original poster: "Gary Peterson by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <glpeterson-at-tfcbooks-dot-com>
> >
> >  > I shudder to think how off-topic this may become . . .
> >
> > I agree.  Would rather discuss the possibility of working other SSTC
> > builders on the proposed 135.7 - 137.8 kHz ham band.
> >
> > Gary
> >
>
>
>
>