[time-nuts] Loran, GPS, Lightning, Timing

paul swed paulswedb at gmail.com
Wed Jun 25 17:42:01 EDT 2014

I am currently using a 12AX7 as a ELF preamp and have for years.
A note in the coldest part of winter preheat the tube low filament voltage.
They tend to fracture.
It sits 200 ft from the house as far away in the woods as possible.
That said and back to the thread. At these frequencies tubes do work. The
12AX7 can be found on vlf.it and numbers of tubes will work. They run 12 V
on the plate. They also stand up to nearby lightning very well.
So Diddier now you have no excuse. I can't wait to implement your design on
one of my stm boards. Not sure how to get this back on time-nuts topics

On Wed, Jun 25, 2014 at 4:44 PM, Poul-Henning Kamp <phk at phk.freebsd.dk>

> In message <16957e54-f6d5-4c0a-9068-6f0c772d2082 at email.android.com>,
> Didier Jug
> es writes:
> >I think it would be perfectly appropriate to design an LF amplifier
> >with 12AU7s considering the high signal levels when the storm does
> >get close.
> Somewhere, sometime, I saw an homebrew article for a lightning detector
> which was based on some obscure valve/tube that had grid on the top
> terminal.
> A wire from the grid electrode ran to a porcelain isolator and from
> there to the wire antenna, in order to get the highest possible
> imput impedance.
> I have no idea where I saw that article, but some HAM magazine or
> possibly Elector about 10-20 years back is a good guess.
> --
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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