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The original message has been attached to this so you can view it or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Hello Markus, But then, where are the increased levels coming from? You can see on the map that there were no lightnings in a range < 180 km during the observed time... 73, Stefan [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain 0.0 HTML_MESSAGE BODY: HTML included in message X-Scan-Signature: 7ee575a0a6578bbbbe5ea7af32688fd5 Subject: Re: VLF: Using resonance effects of earth-ionosphere for radio experiments Content-Type: multipart/alternative; boundary="------------020207050703080701040806" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,HTML_MESSAGE autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false This is a multi-part message in MIME format. --------------020207050703080701040806 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hello Markus, But then, where are the increased levels coming from? You can see on the map that there were no lightnings in a range < 180 km during the observed time... 73, Stefan Am 23.10.2017 21:08, schrieb Markus Vester: > Hi Stefan, VLF enthusiasts, > > in July 2015, I attempted a temporal correlation of "Tweek-mode" > resonances in Heidelberg and Nürnberg against Blitzortung data from a > passing storm front: > http://df6nm.bplaced.net/VLF/spherics/tweek_resonances_dk7fc_df6nm_Blitzortung_150725_0700.jpg > > It seems that the vertical resonances between earth and > ionosphere extend only to a lateral range of about 90 km, and they > have died down at ~ 180 km. Horizontal currents (e.g. cloud-to-cloud > lightning or loop antennas with upward radiation) are required to > excite and receive them. > > Respective emails with further details are at > https://uk.groups.yahoo.com/neo/groups/rsgb_lf_group/conversations/topics/4924 > https://uk.groups.yahoo.com/neo/groups/rsgb_lf_group/conversations/messages/4976 > > Best regards, > Markus (DF6NM) > > > -----Ursprüngliche Mitteilung----- > Von: DK7FC > An: rsgb_lf_group > Verschickt: Mo, 23. Okt 2017 13:17 > Betreff: VLF: Using resonance effects of earth-ionosphere for radio > experiments > > Paul, Markus, VLF, > > Some days ago there have been local thunderstorms near DL0AO in JN59. > Two images in attachemnt. > The distance is about 225 km. The thunderstorms were on a small spot only. > > The sferics are clearly pronounced with an SNR increase of 10 dB and > more, quite a sharp peak/trace. That's not a new observation but now we > are operating just in that frequency range! > The effect seems to appear in integer multiples of about 1.7 kHz, which > is roughly a wavelength of a 180 km, and the earth-ionosphere height is > just lambda/2. > > It would be most interesting to see how a similar spectrogram looks from > Pauls site (time and date given in the images). Is the effect still > there in 881 km? How strong is it expressed. Are the frequencies the same? > If so, we should try to find that region of enhanced propagation, by > using a 2-tone or 3-tone carrier signal. No problem to provide that from > here. > > The effect is less expressed on 3.4 kHz in this event. Recently we > discussed about a geometric single-hop path difference between DK7FC and > DL0AO (Markus calculated 63.3 km difference between groundwave and > skywave). 5.17 is at a 1.09 lambda difference on that path, so > groundwave and skywave will add constructively. The 3rd order trace of > the sferic resonance effect is also at 5.1 kHz! > 3.4 kHz, or the 88.2 km wave, is then at 1.4 lambda difference, so > skyway and groundwave do not add so constructive. Maybe this explains > the lower expressed resonance effect? > > It looks like there can be SNR difference of several dB when changing > the frequency by just a few 10 Hz, at least arround 5.1 kHz and on the > path to DL0AO. We should try to check that! > > Could there be a frequency with an advantage on the way to RN3AUS? On a > 2000 km path the effects will be less expressed. But worth to think > about... > > 73, Stefan > > > --------------020207050703080701040806 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: 8bit Hello Markus,

But then, where are the increased levels coming from? You can see on the map that there were no lightnings in a range < 180 km during the observed time...

73, Stefan

Am 23.10.2017 21:08, schrieb Markus Vester:
Hi Stefan, VLF enthusiasts,

in July 2015, I attempted a temporal correlation of "Tweek-mode" resonances in Heidelberg and Nürnberg against Blitzortung data from a passing storm front:
http://df6nm.bplaced.net/VLF/spherics/tweek_resonances_dk7fc_df6nm_Blitzortung_150725_0700.jpg

It seems that the vertical resonances between earth and ionosphere extend only to a lateral range of about 90 km, and they have died down at ~ 180 km. Horizontal currents (e.g. cloud-to-cloud lightning or loop antennas with upward radiation) are required to excite and receive them.

Respective emails with further details are at 
https://uk.groups.yahoo.com/neo/groups/rsgb_lf_group/conversations/topics/4924
https://uk.groups.yahoo.com/neo/groups/rsgb_lf_group/conversations/messages/4976

Best regards,
Markus (DF6NM)
 

-----Ursprüngliche Mitteilung-----
Von: DK7FC <selberdenken@posteo.de>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Mo, 23. Okt 2017 13:17
Betreff: VLF: Using resonance effects of earth-ionosphere for radio experiments

Paul, Markus, VLF,

Some days ago there have been local thunderstorms near DL0AO in JN59.
Two images in attachemnt.
The distance is about 225 km. The thunderstorms were on a small spot only.

The sferics are clearly pronounced with an SNR increase of 10 dB and
more, quite a sharp peak/trace. That's not a new observation but now we
are operating just in that frequency range!
The effect seems to appear in integer multiples of about 1.7 kHz, which
is roughly a wavelength of a 180 km, and the earth-ionosphere height is
just lambda/2.

It would be most interesting to see how a similar spectrogram looks from
Pauls site (time and date given in the images). Is the effect still
there in 881 km? How strong is it expressed. Are the frequencies the same?
If so, we should try to find that region of enhanced propagation, by
using a 2-tone or 3-tone carrier signal. No problem to provide that from
here.

The effect is less expressed on 3.4 kHz in this event. Recently we
discussed about a geometric single-hop path difference between DK7FC and
DL0AO (Markus calculated 63.3 km difference between groundwave and
skywave). 5.17 is at a 1.09 lambda difference on that path, so
groundwave and skywave will add constructively. The 3rd order trace of
the sferic resonance effect is also at 5.1 kHz!
3.4 kHz, or the 88.2 km wave, is then at 1.4 lambda difference, so
skyway and groundwave do not add so constructive. Maybe this explains
the lower expressed resonance effect?

It looks like there can be SNR difference of several dB when changing
the frequency by just a few 10 Hz, at least arround 5.1 kHz and on the
path to DL0AO. We should try to check that!

Could there be a frequency with an advantage on the way to RN3AUS? On a
2000 km path the effects will be less expressed. But worth to think about...

73, Stefan



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