Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=5.0 tests=FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,HTML_MESSAGE,RCVD_IN_DNSWL_MED, SPF_PASS,T_DKIM_INVALID,T_KAM_HTML_FONT_INVALID autolearn=ham autolearn_force=no version=3.4.0 X-Spam-DCC: : mailn 1480; Body=2 Fuz1=2 Fuz2=2 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by lipkowski.org (8.14.4/8.14.4/Debian-8+deb8u1) with ESMTP id v33MbNkZ018216 for ; Tue, 4 Apr 2017 00:37:24 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1cvAVn-0007qs-Mf for rs_out_1@blacksheep.org; Mon, 03 Apr 2017 23:31:47 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1cvAVm-0007qj-HJ for rsgb_lf_group@blacksheep.org; Mon, 03 Apr 2017 23:31:46 +0100 Received: from resqmta-ch2-01v.sys.comcast.net ([2001:558:fe21:29:69:252:207:33]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1cvAVg-0005Uz-0j for rsgb_lf_group@blacksheep.org; Mon, 03 Apr 2017 23:31:45 +0100 Received: from resomta-ch2-06v.sys.comcast.net ([69.252.207.102]) by resqmta-ch2-01v.sys.comcast.net with SMTP id vAUOccchRO3QovAVbcfJqj; Mon, 03 Apr 2017 22:31:35 +0000 X-DKIM-Result: Domain=comcast.net Result=Signature OK DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=comcast.net; s=q20161114; t=1491258695; bh=j9zbg/agso/lfsZxm5jxo01lKRni8/7ljSeBemI8zdQ=; h=Received:Received:From:To:Subject:Date:Message-ID:MIME-Version: Content-Type; b=d4hBbEuIY4wGl4DemThQ7BJXDmk6PpJbwYuCQoPY/N72fGN0yRlOi9fr0ML7pVndn ugpoDN3N54GI0Vi+HeVr6o79J/pjITGokFNLsQG0olIVF2/+b51uslxY3qIt6Li/n/ rYA0V//yY84NXoRrKMgyGoOyJdSiyuoOUZFxtAsY0y1Ov2J/cQ89Q7UhHFgwsgvWy4 4zkNGvUi2mmo5SRJb4glUnA/Lw42XXe59OMWILF6iKnp+eumZFty6zh+cTBTf+kkZc Bp8IVui5PehG1LksdEo2RcR/25ToO3RLTSBsCNcvKbKkoNoomi5QuzIDSJU/ggmE9E qIfYX9KWVFogw== Received: from Owner ([IPv6:2601:140:8500:7f9f:f505:f220:93b9:41b5]) by resomta-ch2-06v.sys.comcast.net with SMTP id vAVZcBU9reyvGvAVacMQ5M; Mon, 03 Apr 2017 22:31:34 +0000 From: To: References: <5872C893.80807@abelian.org> <58755576.6000702@posteo.de> <58E2383D.9040206@posteo.de> In-Reply-To: <58E2383D.9040206@posteo.de> Date: Mon, 3 Apr 2017 18:30:49 -0400 Message-ID: <032a01d2acca$09680930$1c381b90$@comcast.net> MIME-Version: 1.0 X-Mailer: Microsoft Outlook 14.0 Thread-Index: AQH/WG6HdSYzf25Z+mzXJ05L2KR3RANKfGNdAsYsalYBMQ+OFaEgrXLw Content-Language: en-us X-CMAE-Envelope: MS4wfClQc8ERsXaIaqmYCmvoA8iE/UxjQv9jsWiVsC0x3r7HjTeesQs39NJ3BcUnCyk21NaXkseDJW/Aff5tSVsKOCfqaF5HzjK8XbJaLNffnHz7MabbRCtV 0m1Yja/+lkTrp154fPqpe/xTpV6woZLYMWk= X-Scan-Signature: d649dfc0db196e6c4945f3b0d88e548d Subject: LF: RE: A new distance record on 970 Hz / 309 km band Content-Type: multipart/alternative; boundary="----=_NextPart_000_032B_01D2ACA8.82566930" 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 X-Scanned-By: MIMEDefang 2.75 Status: RO X-Status: X-Keywords: X-UID: 11104 This is a multipart message in MIME format. ------=_NextPart_000_032B_01D2ACA8.82566930 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Stefan, =20 Congratulations! A new record of 30 dB SNR in 424 uHz at 7.2 km, 970 Hz = is great news! =20 Your 10.01.2017 22:43 message did not reach my e-mail server so I am = glad that you attached it below; you mentioned: =20 =E2=80=9CAnd who knows the advantages of this part of the spectrum for = our purposes?=E2=80=9D =20 I imagine that your experiments will help to answer that intriguing = question. =20 Some likely advantages: 1) Propagation should be much more predictable at 970 Hz than at = 2970 Hz*, especially at ranges less than 2000 km, perhaps making = experiments easier to design with reasonable confidence 2) Propagation should be significantly more stable over minutes, = hours, and day-to-day at 970 Hz than at 2.9 kHz - 30 kHz, especially at = ranges less than 2000 km** 3) Path loss at 970 Hz may be ~ 2/3 of path loss at 2970 Hz (in = dB/m); still high compared to 9 kHz (but natural noise attenuation is = correspondingly high) 4) Rock, fresh water and even seawater penetration at 970 Hz is = good compared to 2970 Hz and very good compared to 10kHz. At 970Hz: = roughly 10dB loss at 10 meters in sea water, 10dB loss at 100 meters in = some common types of rock and fresh water. The rock and water examples = are more interesting when considering that natural and some cultural = noises attenuate about as much as the desired signal at depth, so at = depth a very sensitive receiver could be fully effective even with = little or no electronic cancellation of natural and cultural noises. = With a 1 fT/rt-Hz receiver, a signal barely detectable on the surface = without natural noise cancellation might still be detectable at 100 to = 200 meters penetration (or depth) in caverns, valleys, canyons etc. =20 =20 =20 *2970 Hz is theoretically in a less-complicated, more stable, = below-high-order-cutoff part of the spectrum; but practically speaking = 2970 Hz is close enough to cutoff to be highly sensitive to modal = interference effects with changes in the ionosphere for paths 100km = =E2=80=93 1000 km. 970 Hz is well outside this region of sensitivity = to changes in the ionosphere for paths 100km =E2=80=93 1000 km. =20 =20 ** At 970 Hz basically no modal interference effects when ionospheric = disturbances occur. =20 =20 73, =20 Jim AA5BW =20 =20 From: owner-rsgb_lf_group@blacksheep.org = [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of DK7FC Sent: Monday, April 3, 2017 7:56 AM To: rsgb_lf_group@blacksheep.org Subject: ULF: A new distance record on 970 Hz / 309 km band =20 Hi ULF friends, Saturday night i build an active E field receiver optimised for ULF. It = is using a BF862 front-end as a source follower and a LT1028 with 20 dB = gain. There are 3 RC filter stages cutting off at 10 kHz. Furthermore = there are two isolation transformers in series, 4:1=3D>1:10. In the = center they are parallel resonated. This gives a further good low pass = filtering and some additional gain below 3 kHz. It was a quick = construction without thinking to much, soldered at night, 02 AM local = time. The antenna probe is a 1m long steel rod (for welding) with 2 mm = diameter. The antenna height above ground was just 2m. There were no = trees in a radius of 20 m. For transmitting i'm again using the modified 5 kV mains transformer. At = 970 Hz, the antenna impedance is 342 kOhm! So i can just run 15 mA = antenna current which means 3 nW ERP. The new ALC build inside SpecLab = holds the 15 mA accurately and protects the transformer that way! = SpecLab is a very well usable tool for transmitting on VLF/ULF, thanks = to DL4YHF!! The transmit frequency was 970.005 Hz. I didn't expect much, thought that this distance may be to optimistic. = The last signals were very weak on my tree grabber in 3.5 km distance. = But that tree grabber is using loop antennas and they are not sensitive = in that frequency range. So there was a certain chance to see a trace, = maybe in 212 uHz??? I drove to JN49JL00EB and built up the receiver there because it is a = quiet location, a nice region for a walk and, there is a good restaurant = not to far!!!!!! So it was easy to spend some time there and let the = Raspi (using a GPS module on the right soundcard channel, with PPS+NMEA) = record for nearly 3 hours at 24 kS/s. This is the path between TX and RX: = http://no.nonsense.ee/qth/map.html?qth=3DJN49JL00EB = = &from=3Djn49ik00wd A distance of 7.2 km, or 0.023 wavelengths or 14% of = the distance to the far field border. So it is still a near field = experiment. It is about twice the distance i've managed in the last test. Now i'm back in the shack, analysing the recording and to my surprise i = can see a strong trace of 30 dB SNR in 424 uHz!!! See attachments in 424 = uHz and 3.8 mHz. All this makes me much more optimistic to reach farer distances. I tell = you i will crack the far field border on that 309 km band! That would be = a distance of 49.3 km. There must have been some local thunderstorms not to far away, because = there was QRN in the observed spectrum. So the SNR can be improved a bit = by doing the next test in the late morning hours. Also the resonance of = the transformers seem to be a bit to low, so maybe i can reach a bit = more sensitivity when optimising that resonance. It could further help = to rise the effective height of the antenna. Flat fields rather than the = deep forest is the region to select now.... 73, Stefan Am 10.01.2017 22:43, schrieb DK7FC:=20 Hi ULF,=20 Since a few hours i'm running 15 mA antenna current on 970 Hz, the 309 = km band. This requires to apply 5 kV to the antenna. You can see a very = faint trace on the lower image at = http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html=20 Just about 10 dB SNR in 424 uHz in 3.5 km distance, or in 0.011 lambda = distance. The receive antenna is a H field antenna that is not even = pointing to the transmitter. Also the preamp noise is dominating the = background noise on that frequency. So the RX is deaf on that band. = Anyway, there is something.=20 The ALC into SpecLab does a very good job, it holds the antenna current = stable during all the changes and working point drifts. The plot can be = seen at http://www.iup.uni-heidelberg.de/schaefer_vlf/VLF/TX.png=20 15 mA results in an ERP of 3 nW.=20 My new preamp circuit is waiting for a first test together with the = large loop. I hope to pick up the signal in at least 5 km distance with = that preamp which is really low noise down to the lower Hz range.=20 An E field reeiver would be a better choise for the reception from that = E field Tx antenna, at least in the lower near field. Maybe that will = give another test then.=20 With 30 kV i could reach 0.3 uW. Not sure where this could be detected? = And who knows the advantages of this part of the spectrum for our = purposes!?!=20 Since 21:20 UTC, a 2 character EbNaut message is running. It will take = 2h, 2min, 40s. Hopefully the tree grabber is available until the message = ends. It will shut down in a few hours due to lack of solar energy in = these days (an improvement of this system has already been prepared and = waits for the installation).=20 73, Stefan=20 ------=_NextPart_000_032B_01D2ACA8.82566930 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable

Stefan,

 

Congratulations! A new record of 30 dB SNR in 424 uHz = at 7.2 km, 970 Hz is great news!

 

Your = 10.01.2017 22:43 message did not reach my e-mail server so I am glad = that you attached it below; you mentioned:

 

=E2=80=9CAnd = who knows the advantages of this part of the spectrum for our = purposes?=E2=80=9D

 

I imagine = that your experiments will help to answer that intriguing = question.

 

Some likely advantages:

1)      = Propagation should be much more predictable at = 970 Hz than at 2970 Hz*, especially at ranges less than 2000 km, perhaps = making experiments easier to design with reasonable = confidence

2)      = Propagation should be significantly more stable = over minutes, hours, and day-to-day at 970 Hz than at 2.9 kHz - 30 kHz, = especially at ranges less than 2000 km**

3)      = Path loss at 970 Hz may be ~ 2/3 of path loss at = 2970 Hz (in dB/m); still high compared to 9 kHz (but natural noise = attenuation is correspondingly high)

4)      = Rock, fresh water and even seawater penetration = at 970 Hz is good compared to 2970 Hz and very good compared to 10kHz. = =C2=A0=C2=A0At 970Hz: roughly 10dB loss at 10 meters in sea water, 10dB = loss at 100 meters in some common types of rock and fresh water. The = rock and water examples are more interesting when considering that = natural and some cultural noises attenuate about as much as the desired = signal at depth, so at depth a very sensitive receiver could be fully = effective even with little or no electronic cancellation of natural and = cultural noises. =C2=A0With a 1 fT/rt-Hz receiver, a signal barely = detectable on the surface without natural noise cancellation might still = be detectable at 100 to 200 meters penetration (or depth) in caverns, = valleys, canyons etc. =C2=A0=C2=A0=C2=A0=C2=A0

 

 

*2970 Hz is = theoretically in a less-complicated, more stable, = below-high-order-cutoff part of the spectrum; but practically speaking = 2970 Hz is close enough to cutoff to be highly sensitive to modal = interference effects with changes in the ionosphere for paths 100km = =E2=80=93 1000 km. =C2=A0=C2=A0970 Hz is well outside this region of = sensitivity to changes in the ionosphere for paths 100km =E2=80=93 1000 = km. =C2=A0=C2=A0

 

** At 970 Hz = basically no modal interference effects when ionospheric disturbances = occur.

 

 

73,

 

Jim = AA5BW

 

 

From: owner-rsgb_lf_group@blacksheep.org = [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of = DK7FC
Sent: Monday, April 3, 2017 7:56 AM
To: = rsgb_lf_group@blacksheep.org
Subject: ULF: A new distance = record on 970 Hz / 309 km band

 

Hi ULF = friends,

Saturday night i build an active E field receiver = optimised for ULF. It is using a BF862 front-end as a source follower = and a LT1028 with 20 dB gain. There are 3 RC filter stages cutting off = at 10 kHz. Furthermore there are two isolation transformers in series, = 4:1=3D>1:10. In the center they are parallel resonated. This gives a = further good low pass filtering and some additional gain below 3 kHz. It = was a quick construction without thinking to much, soldered at night, 02 = AM local time. The antenna probe is a 1m long steel rod (for welding) = with 2 mm diameter. The antenna height above ground was just 2m. There = were no trees in a radius of 20 m.

For transmitting i'm again = using the modified 5 kV mains transformer. At 970 Hz, the antenna = impedance is 342 kOhm! So i can just run 15 mA antenna current which = means 3 nW ERP. The new ALC build inside SpecLab holds the 15 mA = accurately and protects the transformer that way! SpecLab is a very well = usable tool for transmitting on VLF/ULF, thanks to DL4YHF!!
The = transmit frequency was 970.005 Hz.

I didn't expect much, thought = that this distance may be to optimistic. The last signals were very weak = on my tree grabber in 3.5 km distance. But that tree grabber is using = loop antennas and they are not sensitive in that frequency range. So = there was a certain chance to see a trace, maybe in 212 uHz???
I = drove to JN49JL00EB and built up the receiver there because it is a = quiet location, a nice region for a walk and, there is a good restaurant = not to far!!!!!! So it was easy to spend some time there and let the = Raspi (using a GPS module on the right soundcard channel, with PPS+NMEA) = record for nearly 3 hours at 24 kS/s.
This is the path between TX and = RX: http://no.nonsense.ee/qth/map.html?qth=3DJN49JL00EB&from=3D= jn49ik00wd  A distance of 7.2 km, or 0.023 = wavelengths or 14% of the distance to the far field border. So it is = still a near field experiment.
It is about twice the distance i've = managed in the last test.

Now i'm back in the shack, analysing = the recording and to my surprise i can see a strong trace of 30 dB SNR = in 424 uHz!!! See attachments in 424 uHz and 3.8 mHz.

All this = makes me much more optimistic to reach farer distances. I tell you i = will crack the far field border on that 309 km band! That would be a = distance of 49.3 km.

There must have been some local = thunderstorms not to far away, because there was QRN in the observed = spectrum. So the SNR can be improved a bit by doing the next test in the = late morning hours. Also the resonance of the transformers seem to be a = bit to low, so maybe i can reach a bit more sensitivity when optimising = that resonance. It could further help to rise the effective height of = the antenna. Flat fields rather than the deep forest is the region to = select now....

73, Stefan



Am 10.01.2017 22:43, = schrieb DK7FC:

Hi ULF,

Since a few hours i'm = running 15 mA antenna current on 970 Hz, the 309 km band. This requires = to apply 5 kV to the antenna. You can see a very faint trace on the = lower image at http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.ht= ml

Just about 10 dB SNR in 424 uHz in 3.5 km distance, or in = 0.011 lambda distance. The receive antenna is a H field antenna that is = not even pointing to the transmitter. Also the preamp noise is = dominating the background noise on that frequency. So the RX is deaf on = that band. Anyway, there is something.

The ALC into SpecLab does = a very good job, it holds the antenna current stable during all the = changes and working point drifts. The plot can be seen at http://= www.iup.uni-heidelberg.de/schaefer_vlf/VLF/TX.png
15 mA results = in an ERP of  3 nW.

My new preamp circuit is waiting for a = first test together with the large loop. I hope to pick up the signal in = at least 5 km distance with that preamp which is really low noise down = to the lower Hz range.
An E field reeiver would be a better choise = for the reception from that E field Tx antenna, at least in the lower = near field. Maybe that will give another test then.

With 30 kV i = could reach 0.3 uW. Not sure where this could be detected? And who knows = the advantages of this part of the spectrum for our purposes!?! =

Since 21:20 UTC, a 2 character EbNaut message is running. It = will take 2h, 2min, 40s. Hopefully the tree grabber is available until = the message ends. It will shut down in a few hours due to lack of solar = energy in these days (an improvement of this system has already been = prepared and waits for the installation).


73, Stefan =


------=_NextPart_000_032B_01D2ACA8.82566930--