[Boatanchors] Making Stable Inductors for 2 MHz

[J. Forster]

>
> John -
>
>
> Why is shaping required?  Does it have to do with some property of the
> signal that determines the ability of the LORAN receiver to provide
> location information, or is shaping used in an attempt to reduce the
> occupied bandwidth of the transmitted signal?  If it is the latter, then
> shaping would not be important to the demonstration project, assuming
> there is no intent to actually radiate a signal.

It is for both. The receiver circuits expect to see the shaped pulse and I
want the signal on the display, which will be visible to the public, to
look authentic (complete with noise).

> Since LORAN signals were repetitive pulses, which by their very nature
> occupy very wide bandwidths, then  shaping would have been  an absolute
> requirement if the service was not to interfere with the top end of the
> standard AM broadcast band, as well as the nearby 2-MHz marine channels,
> the distress channel at 2182 kHz being an obvious example.

Yes.

> Among other things, the bandwidth of the antennas in use would have some
> narrowing effect, not unlike the very earliest days of spark
> transmissions, where the natural resonance of the antennas used was
> often the only  tuning available.  These antenna limitations would have
> provided some pulse shaping.

Not much. They were not resonant AFAIK. The receiver is tens of KHz wide.

> As an interesting aside, this is the
> reason that ELF and VLF signals, such as those used to contact submerged
> submarines,  have severe limitations on the keying speeds that can be
> used - the antennas, particularly for ELF, simply cannot be "started"
> and "stopped" very quickly.  I read somewhere that it can take several
> tens of seconds to send a single character at ELF.  I have no direct
> experience with this last item.   The actual facts may be a bit
> different.  Perhaps someone here can offer additional information.
>
>
> - Jim, KL7CC

The sub signals are likely BPSK.