Return-Path: Received: from mtain-di11.r1000.mx.aol.com (mtain-di11.r1000.mx.aol.com [172.29.64.15]) by air-mb03.mail.aol.com (v129.4) with ESMTP id MAILINMB033-a21e4bfce3c65a; Wed, 26 May 2010 05:03:02 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-di11.r1000.mx.aol.com (Internet Inbound) with ESMTP id AEF1E3800009F; Wed, 26 May 2010 05:03:00 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1OHCV2-0002je-I3 for rs_out_1@blacksheep.org; Wed, 26 May 2010 10:02:04 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1OHCV2-0002jV-1G for rsgb_lf_group@blacksheep.org; Wed, 26 May 2010 10:02:04 +0100 Received: from cavuit01.kulnet.kuleuven.be ([134.58.240.43]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1OHCUy-0003Em-QF for rsgb_lf_group@blacksheep.org; Wed, 26 May 2010 10:02:04 +0100 Received: from smtps02.kuleuven.be (smtpshost02.kulnet.kuleuven.be [134.58.240.75]) by cavuit01.kulnet.kuleuven.be (Postfix) with ESMTP id 288587B80DD for ; Wed, 26 May 2010 11:01:43 +0200 (CEST) Received: from ICTS-S-HUB-N4.luna.kuleuven.be (icts-s-hub-n4.luna.kuleuven.be [10.112.9.14]) by smtps02.kuleuven.be (Postfix) with ESMTP id DF6FCF3865 for ; Wed, 26 May 2010 11:01:42 +0200 (CEST) Received: from ICTS-S-EXC2-CA.luna.kuleuven.be ([10.112.11.13]) by ICTS-S-HUB-N4.luna.kuleuven.be ([10.112.9.14]) with mapi; Wed, 26 May 2010 11:01:43 +0200 X-Kuleuven: This mail passed the K.U.Leuven mailcluster From: Rik Strobbe To: "rsgb_lf_group@blacksheep.org" Date: Wed, 26 May 2010 11:01:43 +0200 Thread-Topic: LF: AW: 8.97kHz - Near field and radiated signals? Thread-Index: Acr8sBbpAP4mcABfR7m2usSE3PTu5wAAN/VF Message-ID: References: <38A51B74B884D74083D7950AD0DD85E82A1C00@File-Server-HST.hst.e-technik.tu-darmstadt.de> , In-Reply-To: Accept-Language: nl-NL, nl-BE Content-Language: nl-BE X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: nl-NL, nl-BE MIME-Version: 1.0 X-KULeuven-Information: Katholieke Universiteit Leuven X-KULeuven-Scanned: Found to be clean X-KULeuven-Envelope-From: rik.strobbe@fys.kuleuven.be X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: RE: LF: AW: 8.97kHz - Near field and radiated signals? Content-Type: multipart/alternative; boundary="_000_BF4A524700075746A6467658DFC7102C5106464EEBICTSSEXC2CAlu_" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.8 required=5.0 tests=HTML_30_40,HTML_MESSAGE, TO_ADDRESS_EQ_REAL 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 x-aol-global-disposition: G x-aol-sid: 3039ac1d400f4bfce3c46a0f X-AOL-IP: 193.82.116.20 X-Mailer: Unknown (No Version) --_000_BF4A524700075746A6467658DFC7102C5106464EEBICTSSEXC2CAlu_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Roger, sorry, I made a mistake. in the near field the H field drops 40dB/decade and the E-field drops 60dB= /decade. Assuming the ground antenna acts as a loop (=3D H-field) the signal drop= between 0.4km and 3km will be 35dB. The defintion of near field is vague, depending on the source it goes from= 0.1 wavelength to 1 wavelength. But at 1kHz even 0.1 lambda is 30km, so you are defenitely in the near fie= ld. 73, Rik ON7YD - OR7T ________________________________ Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.or= g] namens Roger Lapthorn [rogerlapthorn@gmail.com] Verzonden: woensdag 26 mei 2010 10:43 Aan: rsgb_lf_group@blacksheep.org Onderwerp: Re: LF: AW: 8.97kHz - Near field and radiated signals? Rick (et al), I am confused by the near field attenuation rates quoted. Some quote 18dB= for doubling distance which would mean an additional path loss of 56dB go= ing from 0.4km to 3km. This makes a lot of difference to what may or may= not be possible. Which is the correct figure? Help! 73s Roger G3XBM On 26 May 2010 09:31, Rik Strobbe > wrote: Roger, the near fiels signal drops with the 3rd power of the distance. So 3km versus 0.4km =3D 422 times weaker =3D -26dB Going from regular CW to QRSS30 will give you a 24dB benefit, so there is= a fair chance to be copied at 3km in this mode. Of course the signal need= s to be very frequency stable, it has to be better than an free running os= cillator. Moving up in frequency would also help. And if you can lay your hands on an old stereo amp it would provide an ext= ra 10dB TX power. Even if your goal is regular CW over a 3km path, starting with QRSS will= most likely give a visible signal at 3km and allow you to watch any progr= ess. 73, Rik ON7YD - OR7T - The best DX targets are quite modest: I would like to exceed 1km initially with the TX power I currently have (around 4W). If I could reac= h G6ALB in the next village 3kms away I would be delighted. If I got any further I would be both amazed and VERY happy! -- http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk http://www.youtube.com/user/g3xbm G3XBM GQRP 1678 ISWL G11088 --_000_BF4A524700075746A6467658DFC7102C5106464EEBICTSSEXC2CAlu_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Roger,
 
sorry, I made a mistake.
in the near field the H field drops= 40dB/decade and the E-field drops 60dB/decade.
Assuming the ground antenna acts as= a loop (=3D H-field) the signal drop between 0.4km and 3km will be 35dB.<= /font>
The defintion of near field is vague= , depending on the source it goes from 0.1 wavelength to 1 wavelength.
But at 1kHz even 0.1 lambda is 30km,= so you are defenitely in the near field.
 
73, Rik  ON7YD - OR7T
 
Van: owner-rsgb_= lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens Roger= Lapthorn [rogerlapthorn@gmail.com]
Verzonden: woensdag 26 mei 2010 10:43
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: Re: LF: AW: 8.97kHz - Near field and radiated signals?
Rick (et al),

I am confused by the near field attenuation rates quoted. Some quote 18= dB for doubling distance which would mean an additional path loss of= 56dB going from 0.4km to 3km. This makes a lot of difference to what may= or may not be possible.

Which is the correct figure? Help!

73s
Roger G3XBM


On 26 May 2010 09:31, Rik Strobbe <Rik.Strobbe@fys.ku= leuven.be> wrote:

Roger,

 

the near fiels signal drops with the= 3rd power of the distance.

So 3km versus 0.4km =3D 422 times weak= er =3D -26dB

Going from regular CW to QRSS30 will= give you a 24dB benefit, so there is a fair chance to be copied at 3km in= this mode. Of course the signal needs to be very frequency stable, it has= to be better than an free running oscillator.

Moving up in frequency would also help= .

And if you can lay your hands on an ol= d stereo amp it would provide an extra 10dB TX power.

 

Even if your goal is regular CW over&n= bsp;a 3km path, starting with QRSS will most likely give a visible signal= at 3km and allow you to watch any progress.

 

73, Rik  ON7YD - OR7T

 

 - The best DX targets are quite modest: I would like to exceed 1k= m


 initially with the TX power I currently have (around 4W). If I could= reach
 G6ALB in the next village 3kms away I would be delighted. If I got= any
 further I would be both amazed and VERY happy!



--
http://g3xbm-= qrp.blogspot.com/
http://www.g3xbm.co.u= k
http://www= .youtube.com/user/g3xbm
G3XBM    GQRP 1678      ISWL G11088
--_000_BF4A524700075746A6467658DFC7102C5106464EEBICTSSEXC2CAlu_--