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+--- Thread: Propagation... why do I miss some signals? (/showthread.php?tid=2749)
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RE: Propagation... why do I miss some signals? - dupreezd - 2018-11-09
(2018-11-09, 18:13)mwaters Wrote: Right or wrong, https://en.m.wikipedia.org/wiki/Skip_zone seems to imply that there is no skip zone at ELF.
We are not receiving detecting RF like in a radio wave.
RE: Propagation... why do I miss some signals? - mwaters - 2018-11-09
(2018-11-09, 18:28)dupreezd Wrote:(2018-11-09, 18:13)mwaters Wrote: Right or wrong, https://en.m.wikipedia.org/wiki/Skip_zone seems to imply that there is no skip zone at ELF.
We are not receiving detecting RF like in a radio wave.
I'm not a physicist, nor do I have any doctorate degrees. I do know some (on ham.stackexchange.com) whom I could ask, but I'd rather not get into this now. I fear that it might just cause hard feelings. :-)
RE: Propagation... why do I miss some signals? - mwaters - 2019-01-21
For some time --and especially in the past few days-- I have noticed that stations on either side of the US-Canada border sometimes pick up many more strokes in South America and far out into the Atlantic Ocean than more southern stations. This is after dark.
There's more to it than described above, but it seemed to me that propagation was also distinctly favoring N-S paths over E-W paths. Anyone else ever notice this?
The documents below confirm that that happens.
http://www.dtic.mil/dtic/tr/fulltext/u2/a267991.pdf
https://apps.dtic.mil/dtic/tr/fulltext/u2/a183261.pdf
Here's a screenshot of one page of the first pdf.
There much more extremely interesting information concerning ELF/VLF propagation there.
See also http://www.tau.ac.il/~colin/courses/AtmosElec/Barr%20Et%20Al%202000%20-%20ELF%20and%20VLF%20radio%20waves.pdf
and
https://www.google.com/search?q=vlf+and+elf+north+and+south+propagation&oq=vlf+and+elf+north+and+south+propagation
RE: Propagation... why do I miss some signals? - mwaters - 2020-03-18
(2018-11-09, 18:28)dupreezd Wrote:(2018-11-09, 18:13)mwaters Wrote: Right or wrong, https://en.m.wikipedia.org/wiki/Skip_zone seems to imply that there is no skip zone at ELF.
We are not receiving detecting RF like in a radio wave.
It finally dawned on me why you believe that, Dries. Audio sound waves from a speaker that are detected by our ears actually overlaps a limited range of radio frequencies. (That was difficult for me (and countless others) to comprehend. After all, ~15 kHz can be heard! It "can't" be RF radio waves!)
Lightning strikes definitely propagate an RF signal that are detected by our BT radio receivers. We are indeed receiving RF radio waves, even though we cannot possibly detect the sound from distant thunderstorms. Think about it: our BT receivers use antennas and probes, not microphones.
There are VLF and LF radio stations whose frequencies are in our VLF or LF band. And some of them continue to be a source of interference to a few stations on our network.
Interestingly, there is a ham band around 137 kHz (2200 meters).
I was wrong when I wrote ELF. The ELF band is either 3 Hz to 30 Hz or 3 Hz to 30 kHz.
RE: Propagation... why do I miss some signals? - cutty - 2020-03-18
(2020-03-18, 03:20)mwaters Wrote:(2018-11-09, 18:28)dupreezd Wrote:(2018-11-09, 18:13)mwaters Wrote: Right or wrong, https://en.m.wikipedia.org/wiki/Skip_zone seems to imply that there is no skip zone at ELF.
We are not receiving detecting RF like in a radio wave.
It finally dawned on me why you believe that, Dries. Audio sound waves from a speaker that are detected by our ears actually overlaps a limited range of radio frequencies. (That was difficult for me (and countless others) to comprehend. After all, ~15 kHz can be heard! It "can't" be RF radio waves!)
Lightning strikes definitely propagate an RF signal that are detected by our BT radio receivers. We are indeed receiving RF radio waves, even though we cannot possibly detect the sound from distant thunderstorms. Think about it: our BT receivers use antennas and probes, not microphones.
There are VLF and LF radio stations whose frequencies are in our VLF or LF band. And some of them continue to be a source of interference to a few stations on our network.
Interestingly, there is a ham band around 137 kHz (2200 meters).
I was wrong when I wrote ELF. The ELF band is either 3 Hz to 30 Hz or 3 Hz to 30 kHz.
Let's try this approach: to oversimplify quite a bit.... .and see how much trouble I can get in...
Radio Frequency refers to the "Rate of Oscillation" of an electromagnetic wave. A radio wave consists of a Magnetic Field, and an Electric Field, neither can exist without the other, and they are self propogating and reinforcing. They are produced by and represent 'alternating current' / Voltage.
Lightning does NOT produce a repetitive, 'oscillatiing' signal...it has 'no frequency' ... it produces an 'impulse' or series of impulses, of energy that is seen at frequenciy 'locations' well up into the megahertz... but they aren't oscillating...the 'amplitude' of extremely short 'field changes' simulates an oscillating signal, but the polarity normally doesn't change, as in AC... lightning is virtually DC, not AC It will have little or no Electric "plane component", just a pulse, beyond a "relatively" short distance, is not self propagating, and fades out rapidly with distance, since it's concertated in the 'magnetic field" realm, but this magnetic field can be sensed a very long way because of the original strength..
The step leader DC Currents can produce instanteous current flow, generating magnetic fields, of shorter duration, and amplitude..
The Discharge DC Current produces a very intense magnetic field.. Our loops follow that magnetic surge which does not "Oscillate".
etc...
BOTH vary in amplitude over time as they occur, which may appear as a 'wave' visually, especially in the case of 'sombrero' signals....
The E probe does NOT detect RF at all... in a manner of speaking, it is a capacitor that lives inside a capacitor. It mimics the charge, and change of charge, within that atmosphere / earth capacitor, and as those charged particles build up and decay, the changing potentials manifest as 'voltage' changes. Hence "E Field". Again, those changes can be so rapid, that they can be said to manifest in the 'RF' spectrum, but they are not 'oscillating' and have no relevant magnetic field... in fact, the E probe should be immune to magnetic effects!
We do not detect, with our system, 'radio frequency waves" ... we detect impulse' energy magnetic effects and charge state changes which must exist" SOMEWHERE" in the energy specturm... but that does NOT mean they are 'Radio Waves". And yes, any Radio Transmitter or device that produces a magnetic field in our band pass will cause interference... any 'spark gap' can cause interference in the E field. And a spark discharge may also be detected in the H field loops;.
It's easy to 'mix theories', and term usages. It's also pretty much human to have our pet theories, indeed I have mine.
And if you think you can't hear lightning, it' only because of the extremely short duration of the pulse presence. ... you can hear it 'down-mixed' manifesting as 'thunder' since air responds so slowly.... sort of 'lengthing the pulse width"...
RE: Propagation... why do I miss some signals? - AlixNevison - 2021-07-21
The more energy we save, the healthier our future will be. This doesn't mean that we should stop working. Saving energy is part of the process of life, and we need the power to run our bodies and to do the things that keep us feeling full. But let's not let our efforts be wasted on activities that won't do much to support our well-being in the future. For example, I make an outstanding contribution by using intelligent meters that are helping me to save a lot of energy and money. You can read about these things on https://www.simplyswitch.com/energy/guides/prepayment-gas-and-electricity-meters/. I think that this is one of the best solutions.
RE: Propagation... why do I miss some signals? - cutty - 2021-07-21
(2021-07-21, 09:37)AlixNevison Wrote: Honestly, I didn't know about these theories. But now I looked and believed. Although some things seem odd to me ...They've been slow coming to my consciousness, also. Things are odd because they may differ radically from our experience, background, expections, etc... but look here:
https://frankfortweather.us/blitzblitz/SplitCoil/Cuttys_Split-Coil_Build_Addenda_Vshort.pdf