Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-me01.r1000.mx.aol.com (Internet Inbound) with ESMTP id 7740A38000081; Thu, 23 Jun 2011 05:31:54 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QZgFW-0007Wx-Ve for rs_out_1@blacksheep.org; Thu, 23 Jun 2011 10:30:58 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QZgFW-0007Wo-Bv for rsgb_lf_group@blacksheep.org; Thu, 23 Jun 2011 10:30:58 +0100 Received: from outbound-queue-2.mail.thdo.gradwell.net ([212.11.70.35]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QZgFV-0008VP-RK for rsgb_lf_group@blacksheep.org; Thu, 23 Jun 2011 10:30:58 +0100 Received: from outbound-edge-2.mail.thdo.gradwell.net (bonnie.gradwell.net [212.11.70.2]) by outbound-queue-2.mail.thdo.gradwell.net (Postfix) with ESMTP id D1A3E21FE7 for ; Thu, 23 Jun 2011 10:30:55 +0100 (BST) Received: from ctuash.plus.com (HELO Hugh) (212.159.90.113) (smtp-auth username ashford, mechanism login) by outbound-edge-2.mail.thdo.gradwell.net (qpsmtpd/0.83) with ESMTPA; Thu, 23 Jun 2011 10:30:55 +0100 Message-ID: <8E5A99F295084A29A0CD37A4CC7BCF0B@Hugh> From: "Hugh_m0wye" To: References: <000c01cb5a7a$44cfcc50$0401a8c0@xphd97xgq27nyf> <4C1A271605FB0B62@smtp208.alice.it> <4C9A8CC5.30305@gmx.com> <4C9B3FCE.5080700@gmx.com> <7C83B6E4275F422A83872B7E0134B689@Hugh> <4E01E9B8.6020001@iup.uni-heidelberg.de> Date: Thu, 23 Jun 2011 10:30:49 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5931 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5994 X-Gradwell-MongoId: 4e0307cf.bb64-3c52-2 X-Gradwell-Auth-Method: smtpauth X-Gradwell-Auth-Credentials: ashford X-Spam-Score: 3.4 (+++) X-Spam-Report: autolearn=disabled,FORGED_MUA_OUTLOOK=3.36,HTML_MESSAGE=0.001 Subject: Re: LF: PA0RDT polarisation Content-Type: multipart/alternative; boundary="----=_NextPart_000_0030_01CC3190.9E8FD620" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.6 required=5.0 tests=FORGED_MUA_OUTLOOK, 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-SCOLL-SCORE: 0:2:503251936:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d60894e03080913a7 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. ------=_NextPart_000_0030_01CC3190.9E8FD620 Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable Thankyou very much to those who answered my questions. When I have used an E-field probe to explore unwanted radiation from = circuit boards, the orientation of the probe had an effect on the signal = strength. But now I can see that on this larger scale, the plate of the = probe will generally be above the counterpoise, so vertically polarised = signals will always be favoured, whatever the orientation of the probe. I feel I have a better understanding of how it works now. thanks once again. 73, Hugh M0WYE ----- Original Message -----=20 From: Stefan Sch=E4fer=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Wednesday, June 22, 2011 2:10 PM Subject: Re: LF: PA0RDT polarisation Hello Hugh, The model i have in my mind is a capacitive divider that is within an = E=20 field (TX signals and noise). There are 2 plates, the probe and the=20 counterpoise. The counterpoise has a C against ground that is several=20 orders higher as the probe, normally. If the antenna is in a fixed=20 position, you may vary the way the feed cable runs, and change its=20 capacity against ground from say 1 nF to 2 nF. But the plate has just=20 about 3 pF and so the voltage across the gate and source of the amp=20 input does not change significantly. However, if you place the probe near a tree or a high building, the=20 signal usually drops significantly, since the E fields becomes much=20 lower near lossy and conductive things. So this directly affects the=20 input voltage and thus mostly the SNR. Rising the antenna much above ground is usually useful. But if you = would=20 be outside in a flat landscape without trees and local noise, is would = be totally appropriate to put it on the roof of a car. Good luck with your works. What do you plan? :-) 73, Stefan/DK7FC Am 21.06.2011 17:23, schrieb Roelof Bakker: > Hello Hugh, > > Though it may not make sense, mounting orientation is irrelevant. > And the feed line does not need to run vertical either. > > I have tested the antenna at the same "position in space" with two=20 > ways of mounting. > The first one was the normal way with a vertical mast in the garden. > The second way was using the same mast and cable length, but this = time=20 > extended horizontal from an upstairs window. > The receiver was a battery operated selective level meter, which = could=20 > be read to 0.5 dB. > > The test was carried out receiving the vertical polarized signal of=20 > NDB ONO on 399.5 kHz, 59 km away. > The measured levels agreed within 1 dB! > > So the good news is when the need arises, the antenna can be mounted = > on a pole and pushed out of the window! > > Best regards, > Roelof Bakker, pa0rdt ------=_NextPart_000_0030_01CC3190.9E8FD620 Content-Type: text/html; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable
Thankyou very much to those who answered my=20 questions.
When I have used an E-field probe to explore = unwanted=20 radiation from circuit boards, the orientation of the probe had an = effect on the=20 signal strength. But now I can see that on this larger scale, the plate = of the=20 probe will generally be above the counterpoise, so vertically polarised = signals=20 will always be favoured, whatever the orientation of the = probe.
I feel I have a better understanding of how it = works=20 now.
thanks once again.
73, Hugh M0WYE
----- Original Message -----
From:=20 Stefan = Sch=E4fer
Sent: Wednesday, June 22, 2011 = 2:10=20 PM
Subject: Re: LF: PA0RDT=20 polarisation

Hello Hugh,

The model i have in my mind is a = capacitive=20 divider that is within an E
field (TX signals and noise). There = are 2=20 plates, the probe and the
counterpoise. The counterpoise has a C = against=20 ground that is several
orders higher as the probe, normally. If = the=20 antenna is in a fixed
position, you may vary the way the feed = cable runs,=20 and change its
capacity against ground from say 1 nF to 2 nF. But = the=20 plate has just
about 3 pF and so the voltage across the gate and = source of=20 the amp
input does not change significantly.
However, if you = place the=20 probe near a tree or a high building, the
signal usually drops=20 significantly, since the E fields becomes much
lower near lossy = and=20 conductive things. So this directly affects the
input voltage and = thus=20 mostly the SNR.
Rising the antenna much above ground is usually = useful. But=20 if you would
be outside in a flat landscape without trees and = local noise,=20 is would
be totally appropriate to put it on the roof of a = car.
Good=20 luck with your works. What do you plan? :-)


73,=20 Stefan/DK7FC


Am 21.06.2011 17:23, schrieb Roelof = Bakker:
>=20 Hello Hugh,
>
> Though it may not make sense, mounting = orientation=20 is irrelevant.
> And the feed line does not need to run vertical = either.
>
> I have tested the antenna at the same = "position in=20 space" with two
> ways of mounting.
> The first one was = the=20 normal way with a vertical mast in the garden.
> The second way = was=20 using the same mast and cable length, but this time
> extended=20 horizontal from an upstairs window.
> The receiver was a battery = operated selective level meter, which could
> be read to 0.5=20 dB.
>
> The test was carried out receiving the vertical = polarized=20 signal of
> NDB ONO on 399.5 kHz, 59 km away.
> The = measured=20 levels agreed within 1 dB!
>
> So the good news is when = the need=20 arises, the antenna can be mounted
> on a pole and pushed out = of the=20 window!
>
> Best regards,
> Roelof Bakker,=20 pa0rdt
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