Loran, GPS, Lightning, Timing
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.
I have been thinking of building a system myself since I already have an STMicro Discovery board and several GPS receivers I could use.
One potential problem is that the preamps obviously must remain connected to the antennas when the storm gets close, while my ham radio gear is normally disconnected when not in use. I have had so much lightning damage over here (North West Florida) over the years that I am concerned about pissing off the Gods for good...
Didier KO4BB
On June 25, 2014 1:54:19 PM CDT, paul swed paulswedb@gmail.com wrote:
I have been watching the blitzortung system in the US for a few days
now
and really like the clean and simple display. Very nicely done.
Also downloaded the information package.
Oddly it does not use any 12AU7s in the design.
Regards
Paul
WB8TSL
On Wed, Jun 25, 2014 at 2:24 AM, nuts nuts@lazygranch.com wrote:
This one is/was run by the Neveda Test Site. I don't know if NOAA
took
it over. When you get strikes, it give the lat/lon.
At the moment, all is quiet on the western front.
However, I have to say that near real time website is more
impressive.
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In message 16957e54-f6d5-4c0a-9068-6f0c772d2082@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@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.
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
Regards
Paul
WB8TSL
On Wed, Jun 25, 2014 at 4:44 PM, Poul-Henning Kamp phk@phk.freebsd.dk
wrote:
In message 16957e54-f6d5-4c0a-9068-6f0c772d2082@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@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.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
On Wed, Jun 25, 2014 at 1:24 PM, Didier Juges shalimr9@gmail.com wrote:
One potential problem is that the preamps obviously must remain connected
to the antennas when the storm gets close, while my ham radio gear is
normally disconnected when not in use. I have had so much lightning damage
over here (North West Florida) over the years that I am concerned about
pissing off the Gods for good...
It could be 100% safe if there were no wires leading back to the house. A
battery powered receiver that connected back to the house over WiFi would
be safe. Use a solar panel and a lead/acid battery for power. The only
trouble is the added cost and a direct hit would still cost you a few
hundred $$. Less risk is to expose only some minimum portion of the
system to lightening then run fiber optic cable back to the house.
--
Chris Albertson
Redondo Beach, California
The Boonton (later HP) model 260A Q meter used such a tube for a 100
megohm VTVM.
The tube was specially made for Boonton as the 535-A.
There are also references to the 1659/535-A.
If you search for it, use "Boonton 535-A" to avoid the Tektronix 535
scope.
The Q meter manual has a picture of it.
Bill Hawkins
-----Original Message-----
From: Poul-Henning Kamp
Sent: Wednesday, June 25, 2014 3:45 PM
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.
A couple of other things about dealing with lightning:
There is a cone of protection starting at the highest grounded point
around for about 100 feet.
These were developed to protect explosives bunkers from direct hits.
The angle of the cone (between a vertical line to the tip and the edge
of the cone) is 30 to 45 degrees.
Exceptions have been reported, of course. That should save you from most
direct hits.
Then you have to deal with the electric field that builds up from
passing charged clouds.
Some kind of high-value resistor in parallel with a small glass sealed
spark gap from antenna to ground would help.
It doesn't have to deal with a direct hit, just keep the grid from
arcing in the tube.
Some of the sealed spark gaps also contain inert gas. You don't want a
triggered spark gap, just a surge suppressor.
Old radios with octal sockets had tubes in the RF and IF amplifiers with
grid caps, like the 6K7.
Should be a lot more available than the Boonton 535-A.
Bill Hawkins
On Wed, Jun 25, 2014 at 4:42 PM, paul swed paulswedb@gmail.com wrote:
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
Regards
Try a 6DJ8 instead of the 12AX7. It has a higher GM and a LOT more
bandwidth. What kind of risetime are we talking about for a lightning
strike? And why not a loop antenna? That should provide plenty of signal
but not destructive voltages.
I know you are talking about measuring lightning strikes but if you get the
impedance high enough, you can actually measure the earth's electric field.
(It is about 200V/m if I recall properly.) Interestingly it is affected by
the solar flux and solar wind.
--
Brian Lloyd
Lloyd Aviation
706 Flightline Drive
Spring Branch, TX 78070
brian@lloyd.com
+1.916.877.5067
Is anyone using a field mill?
I have always been going to make one.
It consists of a horizontal metal plane with a conducting button on the surface
which is insulated from the ground plane.
A metallic maltese cross driven by a motor alternately covers and uncovers the electrode
exposing/not exposing it to the sky.
The electrode button has capacitance to ground which drops its impedance,
but across that impedance is an AC voltage proportional to the ambient static field.
A typical field in fine weather is 300 Volts/metre so the signal is not trivial.
You should be able to make a field mill that works continuously except when
actually shorted by rain.
This is not a very high impedance device, and should show many marvellous things
as the clouds float over you.
You can calibrate it with a metal plate, say 12 inches above it with 50 volts on it.
That should produce a uniform field on the mill.
cheers,
Neville Michie
I know you are talking about measuring lightning strikes but if you get the
impedance high enough, you can actually measure the earth's electric field.
(It is about 200V/m if I recall properly.) Interestingly it is affected by
the solar flux and solar wind.
--
Brian Lloyd
Lloyd Aviation
706 Flightline Drive
Spring Branch, TX 78070
brian@lloyd.com
+1.916.877.5067
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As I recall, the Boonton 535A isn't specially made at all,
but rather a selected 2A6 triode/twin diode. The tube is
selected for having an especially clean vacuum, and being
capable of running with a really high grid leak resistor (100M).
-Chuck Harris
Bill Hawkins wrote:
A couple of other things about dealing with lightning:
There is a cone of protection starting at the highest grounded point
around for about 100 feet.
These were developed to protect explosives bunkers from direct hits.
The angle of the cone (between a vertical line to the tip and the edge
of the cone) is 30 to 45 degrees.
Exceptions have been reported, of course. That should save you from most
direct hits.
Then you have to deal with the electric field that builds up from
passing charged clouds.
Some kind of high-value resistor in parallel with a small glass sealed
spark gap from antenna to ground would help.
It doesn't have to deal with a direct hit, just keep the grid from
arcing in the tube.
Some of the sealed spark gaps also contain inert gas. You don't want a
triggered spark gap, just a surge suppressor.
Old radios with octal sockets had tubes in the RF and IF amplifiers with
grid caps, like the 6K7.
Should be a lot more available than the Boonton 535-A.
Bill Hawkins
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Charley Wenzel made it very safe: here is
http://www.techlib.com/electronics/lightning.html,
I used cross-correlation to identify the "right electrical noise"
Alex
On 6/25/2014 8:22 PM, Brian Lloyd wrote:
On Wed, Jun 25, 2014 at 4:42 PM, paul swed paulswedb@gmail.com wrote:
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
Regards
Try a 6DJ8 instead of the 12AX7. It has a higher GM and a LOT more
bandwidth. What kind of risetime are we talking about for a lightning
strike? And why not a loop antenna? That should provide plenty of signal
but not destructive voltages.
I know you are talking about measuring lightning strikes but if you get the
impedance high enough, you can actually measure the earth's electric field.
(It is about 200V/m if I recall properly.) Interestingly it is affected by
the solar flux and solar wind.