Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dd01.r1000.mx.aol.com (Internet Inbound) with ESMTP id 17B6D3800008E; Mon, 21 Jan 2013 17:40:02 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1TxQ1E-0008N4-1L for rs_out_1@blacksheep.org; Mon, 21 Jan 2013 22:39:08 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1TxQ1D-0008Mv-Dr for rsgb_lf_group@blacksheep.org; Mon, 21 Jan 2013 22:39:07 +0000 Received: from relay2.uni-heidelberg.de ([129.206.210.211]) by relay1.thorcom.net with esmtps (TLSv1:AES256-SHA:256) (Exim 4.77) (envelope-from ) id 1TxQ19-0004jj-OL for rsgb_lf_group@blacksheep.org; Mon, 21 Jan 2013 22:39:06 +0000 Received: from freitag.iup.uni-heidelberg.de (freitag.iup.uni-heidelberg.de [129.206.29.204]) by relay2.uni-heidelberg.de (8.13.8/8.13.8) with ESMTP id r0LMd3Lq015286 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Mon, 21 Jan 2013 23:39:03 +0100 Received: from [129.206.22.206] (pc206.iup.uni-heidelberg.de [129.206.22.206]) by freitag.iup.uni-heidelberg.de (8.12.11.20060308/8.11.2) with ESMTP id r0LMd2Gd012899 for ; Mon, 21 Jan 2013 23:39:03 +0100 Message-ID: <50FDC381.3020503@iup.uni-heidelberg.de> Date: Mon, 21 Jan 2013 23:38:57 +0100 From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: In-Reply-To: X-Spam-Score: -2.3 (--) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Maybe you can show your location and the locations of the RX stations in a map. Then add the calculated ERP. Maybe you can find some more RX stations and you will see a directional pattern from the antenna. Maybe it acts like a loop? Or a mixture of a loop, a dipole on the ground and measurement errors. Furthermore people may have different noise background levels, as you say. [...] Content analysis details: (-2.3 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at http://www.dnswl.org/, medium trust [129.206.210.211 listed in list.dnswl.org] -0.0 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain 0.0 HTML_MESSAGE BODY: HTML included in message X-Scan-Signature: 3df6620ae1cf83b986cf2fc02407da16 Subject: Re: LF: 472kHz ERP calculations based on WSPR results Content-Type: multipart/alternative; boundary="------------060007060306070701090309" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=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 x-aol-global-disposition: G x-aol-sid: 3039ac1d408d50fdc3c24875 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. --------------060007060306070701090309 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Maybe you can show your location and the locations of the RX stations in a map. Then add the calculated ERP. Maybe you can find some more RX stations and you will see a directional pattern from the antenna. Maybe it acts like a loop? Or a mixture of a loop, a dipole on the ground and measurement errors. Furthermore people may have different noise background levels, as you say. When will you try a full size dipole on the ground? You have a notebook, a QRP PA, a battery, a compact PA and some forest not to far from the house. And you will need not more than 280m of wire for that test :-) It may become the best MF antenna that you ever had! :-) 73, Stefan/DK7FC Am 21.01.2013 23:05, schrieb Roger Lapthorn: > With several repeatable ground wave reports on 472kHz WSPR using my > 20m baseline earth-electrode antenna today, I decided it was time for > a recalculation of my ERP based on a formula (for 500kHz) supplied > some years ago by *Jim M0BMU*. The assumption (from M0BMU, that I am > now unsure is right) is that the noise floor is around 3uV/m in a > 2500Hz (WSPR) bandwidth. So, based on the WSPR S/N ratio the field > strength when using the earth-electrodes can be calculated. > > *G3ZJO* at 79km gets me at around -19dB giving my field strength > around 355nV/m. > *G3XDV* at 61km he gets me around -12dB S/N giving my field strength > around 810nV/m. > *M0BMU* at 69km he gets me around -30dB S/N giving a field strength > around 100nV/m > > _*ERP Calculations*_ (NB the earth-electrode antenna behaves like a > loop so has directionality that has not been considered) > > ERP using G3ZJO's results = (E*d)^2/49; with E = 355nV, d = 79km _*ERP > = 16uW*_ > ERP using G3XDV's results = (E*d)^2/49; with E = 810nV, d = 61km* > *_*ERP = 49uW*_ > ERP using M0BMU's results = (E*d)^2/49; with E =100nV, d = 69km* > *_*ERP = 1uW*_ > > Now, to me these figures seem /far/ too low, so perhaps the noise > level is much higher than 3uV/m or my maths are wrong? > > Certainly the noise floor here is S4- S8 due to SMPSUs and other noise > sources, so higher than 3uV/m. > > I think these ERP numbers can be doubled based on ground wave losses > but, even so, the figures appear to be /extremely/ low. My Marconi > antenna is some 8dB (average) better than the earth-electrode antenna > and I am sure the ERP is well above 1mW using this antenna. My RF > /into/ the earth electrodes is 10W. > > *_Conclusions_* > I am totally puzzled: measuring antenna current on the Marconi I get > ERPs that are an order of magnitude higher yet measured results with > the earth-electrode antenna average just 8dB down on the Marconi. This > suggests ERPs for the earth-electrode antenna in the low mW region, > which I find much more believable. My maths has never been good, so it > is possible I have made mistakes, so I would welcome any corrections. > > For now, I am of the view that the ERP is around 5mW for the > earth-electrode antenna and around 30mW with the Marconi, yet measured > results suggest much less. > > Any thoughts please? > > 73s > Roger G3XBM > > -- > http://g3xbm-qrp.blogspot.com/ > http://www.g3xbm.co.uk > https://sites.google.com/site/sub9khz/ > http://qss2.blogspot.com/ > http://www.youtube.com/user/G3XBM > --------------060007060306070701090309 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Maybe you can show your location and the locations of the RX stations in a map. Then add the calculated ERP. Maybe you can find some more RX stations and you will see a directional pattern from the antenna. Maybe it acts like a loop? Or a mixture of a loop, a dipole on the ground and measurement errors. Furthermore people may have different noise background levels, as you say.

When will you try a full size dipole on the ground? You have a notebook, a QRP PA, a battery, a compact PA and some forest not to far from the house. And you will need not more than 280m of wire for that test :-) It may become the best MF antenna that you ever had! :-)

73, Stefan/DK7FC


Am 21.01.2013 23:05, schrieb Roger Lapthorn:
With several repeatable ground wave reports on 472kHz WSPR using my 20m baseline earth-electrode antenna today, I decided it was time for a recalculation of my ERP based on a formula (for 500kHz) supplied some years ago by Jim M0BMU.  The assumption (from M0BMU, that I am now unsure is right) is that the noise floor is around 3uV/m in a 2500Hz (WSPR) bandwidth. So, based on the WSPR S/N ratio the field strength when using the earth-electrodes can be calculated.

G3ZJO at 79km gets me at around -19dB giving my field strength around 355nV/m. 
G3XDV at 61km he gets me around -12dB S/N giving my field strength around 810nV/m.  
M0BMU at 69km he gets me around -30dB S/N giving a field strength around 100nV/m

ERP Calculations  (NB the earth-electrode antenna behaves like a loop so has directionality that has not been considered)

ERP using G3ZJO's results = (E*d)^2/49; with E = 355nV, d = 79km   ERP = 16uW
ERP using G3XDV's results = (E*d)^2/49; with E = 810nV, d = 61km  ERP  = 49uW
ERP using M0BMU's results =  (E*d)^2/49; with E =100nV, d = 69km  ERP = 1uW

Now, to me these figures seem far too low, so perhaps the noise level is much higher than 3uV/m or my maths are wrong?

Certainly the noise floor here is S4- S8 due to SMPSUs and other noise sources, so higher than 3uV/m. 

I think these ERP numbers can be doubled based on ground wave losses but, even so, the figures appear to be extremely low.  My Marconi antenna is some 8dB (average) better than the earth-electrode antenna and I am sure the ERP is well above 1mW using this antenna. My RF into the earth electrodes is 10W.

Conclusions
I am totally puzzled: measuring antenna current on the Marconi I get ERPs that are an order of magnitude higher yet measured results with the earth-electrode antenna average just 8dB down on the Marconi. This suggests ERPs for the earth-electrode antenna in the low mW region, which I find much more believable. My maths has never been good, so it is possible I have made mistakes, so I would welcome any corrections.

For now, I am of the view that the ERP is around 5mW for the earth-electrode antenna and around 30mW with the Marconi, yet measured results suggest much less.

Any thoughts please?

73s
Roger G3XBM
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