Return-Path: Received: from rly-dc02.mx.aol.com (rly-dc02.mail.aol.com [172.19.136.31]) by air-dc03.mail.aol.com (v126.13) with ESMTP id MAILINDC034-b064b16b9c9eb; Wed, 02 Dec 2009 14:03:05 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-dc02.mx.aol.com (v125.7) with ESMTP id MAILRELAYINDC022-b064b16b9c9eb; Wed, 02 Dec 2009 14:02:35 -0500 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1NFuSM-0006sb-NX for rs_out_1@blacksheep.org; Wed, 02 Dec 2009 19:01:42 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1NFuSM-0006sQ-36 for rsgb_lf_group@blacksheep.org; Wed, 02 Dec 2009 19:01:42 +0000 Received: from out1.ip03ir2.opaltelecom.net ([62.24.128.239]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1NFuSK-0008Ih-Dj for rsgb_lf_group@blacksheep.org; Wed, 02 Dec 2009 19:01:42 +0000 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AtcEAEVIFktOlANV/2dsb2JhbACCJC2iZbJQhDEE X-IronPort-AV: E=Sophos;i="4.47,329,1257120000"; d="scan'208,217";a="138842373" Received: from unknown (HELO xphd97xgq27nyf) ([78.148.3.85]) by out1.ip03ir2.opaltelecom.net with SMTP; 02 Dec 2009 19:01:34 +0000 Message-ID: <003101ca7381$dcd25df0$0401a8c0@xphd97xgq27nyf> From: "mal hamilton" To: References: <38A51B74B884D74083D7950AD0DD85E828AAF4@File-Server-HST.hst.e-technik.tu-darmstadt.de> Date: Wed, 2 Dec 2009 19:01:31 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 X-Karma: unknown: X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: LF: Re: Results of optimising an active antenna Content-Type: multipart/alternative; boundary="----=_NextPart_000_002E_01CA7381.DC6BD3F0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.6 required=5.0 tests=HTML_40_50, HTML_FONTCOLOR_UNKNOWN,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-IP: 193.82.116.20 ------=_NextPart_000_002E_01CA7381.DC6BD3F0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable This reminds me of the Partridge Joy Stick 50 myears ago !!!!!!!!!!!!!= !!!!!!!1=20 The Wire is doing all the work and the probe is incidental g3kev ----- Original Message -----=20 From: Stefan Sch=E4fer=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Wednesday, December 02, 2009 4:01 PM Subject: LF: Results of optimising an active antenna Hi Mike, Bernd, LF,=20 Thank you very much for your transmission yesterday in the evening!= I could do very useful tests and improve my little rx-antenna signifi= cantly. I'm not sure if anyone who uses a short E-field active antenna as a= rx antenna knows about the dependence of wire length and the height= above ground so I want to give a report of the results of my tests ye= sterday in the dark. Perhaps some others could improve their antenna= by these explanations. (First I tried to sent the pictures into the mail but the mail size= became more than 100kB and so the mail wasn't reflected, as it seems.= So I do modify the mail cancelling the Pictures. I put them on my pag= e at qrz.com and those who are interested in the results of my improve= ments can find them there (at the lower end of the site).) For the first test I tried the active antenna with a wire of 1,4m.= The lower end of the wire was abt 2m above gnd (observed signal of G3= XDV)(Argo without AGC and RX with fast AGC). There was almost nothing= to see. Then, I reduced the wire length to 80cm while the hight above= gnd keeping constant. Results were much better as can be seen.=20 Next: 40cm wire length: even much better!=20 Next: 30cm: signal gets lower but qrm also. SNR slightly better.=20 Next: 25cm is the best, as I think.=20 Next: 20cm Signal becomes worse. So, the optimum seems to be at arou= nd 25.30cm!=20 Next: 20cm in a height of 4m: Signal comes up but noise also. No sig= nificant increase of SNR The signals of Ossi/OE5ODL were audible in all the tests and vy gd= to cpi. But the signal was too strong to see any differences between= the S/N ratios (a Picture is also available). My Conclusion: It seems that a short receiving antenna can bee seen= as a capacitive divider out of the capacity between far field and ant= enna and the capacity between antenna and ground. If the wire length= is to much, the input stage becomes nonlinear/goes into saturation.= If the height above ground is increased the signal comes up, but not= the signal/noise ratio(surely there will be a benefit if such an ante= nna is placed in a region with heavy local qrm. Then, the height shoul= d be increased and the wire length can be decreased). So, one cannot= say "the more the better" talking about the wire length! It's exciting, we can receive our "QRP"-Signals (compared to HF) ove= r a distance of 100s or 1000s of km with a wire that is 1/10000 Lambda= ! In comparison, in the 80m band that would be an antenna of 8mm (!)= ;-) With this improvement I get new hope for receiving anything out of= the city, where my home QTH is. I hope this report isn't nerving because of the long text (and pictu= res) and size. I try to stay always below 100kB. Perhaps some RXs can= be improved or Lowfers gets motivated to try such an antenna. 73, Stefan/DK7FC PS: Mike, what's your locator? I want to check the distance and take= a view to your QTH (on http://f6fvy.free.fr/qthLocator/fullScreen.php= everyone can type the searched QTH-Locator and watch the QTH of the= received stn). So one can see the distance and the wave travelling pa= th and if the stn in directly at the beach or in the mountains and so= on. Vy fine! PPS: I forward this message to Bernd, the constructor of the preamp.= I think he doesn't know that the antenna gets even better when reduci= ng the wire length! (tnx Bernd!)=20 ------=_NextPart_000_002E_01CA7381.DC6BD3F0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
This reminds me of the Partridge Joy= Stick 50=20 myears ago !!!!!!!!!!!!!!!!!!!!1
The Wire is doing all the work and th= e probe is=20 incidental
g3kev
 
----- Original Message -----
Sent: Wednesday, December 02,= 2009 4:01=20 PM
Subject: LF: Results of optim= ising an=20 active antenna

Hi Mike, Bernd, LF, =

Thank you very much for your trans= mission yesterday in=20 the evening! I could do very useful tests and improve my little rx-a= ntenna=20 significantly.

I'm not sure if anyone who uses a= short E-field active=20 antenna as a rx antenna knows about the dependence of wire length an= d the=20 height above ground so I want to give a report of the results of my= tests=20 yesterday in the dark. Perhaps some others could improve their anten= na by=20 these explanations=85

(First I tried to=20 sent the pictures into the mail but the mail size became more than= 100kB and=20 so the mail wasn=92t reflected, as it seems. So I do modify the mail= cancelling=20 the Pictures. I put them on my page at qrz.com and those who are int= erested in=20 the results of my improvements can find them there (at the lower end= of the=20 site)=85)

For the first test I tried the act= ive antenna with a=20 wire of 1,4m. The lower end of the wire was abt 2m above gnd (observ= ed signal=20 of G3XDV)(Argo without AGC and RX with fast AGC). There was almost= nothing to=20 see. Then, I reduced the wire length to 80cm while the hight above= gnd keeping=20 constant. Results were much better as can be seen.

Next: 40cm wire length: even much= better!=20

Next: 30cm: signal gets lower but= qrm also. SNR=20 slightly better.

Next: 25cm is the best, as I think= .

Next: 20cm Signal becomes worse.= So, the optimum seems=20 to be at around 25=8530cm!

Next: 20cm in a height of 4m: Sign= al comes up but=20 noise also. No significant increase of SNR

The signals of Ossi/OE5ODL were au= dible in all the=20 tests and vy gd to cpi. But the signal was too strong to see any dif= ferences=20 between the S/N ratios (a Picture is also available).<= /P>

 =

My Conclusion: It seems that a sho= rt receiving antenna=20 can bee seen as a capacitive divider out of the capacity between far= field and=20 antenna and the capacity between antenna and ground. If the wire len= gth is to=20 much, the input stage becomes nonlinear/goes into saturation. If the= height=20 above ground is increased the signal comes up, but not the signal/no= ise ratio(surely there will be=20 a benefit if such an antenna is placed in a region with heavy local= qrm. Then,=20 the height should be increased and the wire length can be decreased)= . So, one cannot sa= y =93the more the better=94=20 talking about the wire length!

It=92s exciting, we can receive ou= r =93QRP=94-Signals=20 (compared to HF) over a distance of 100s or 1000s of km with a wire= that is=20 1/10000 Lambda! In co= mparison, in=20 the 80m band that would be an antenna of 8mm (!)=20 ;-)

With this improvement I get new ho= pe for receiving=20 anything out of the city, where my home QTH is=85

I hope this report isn=92t nerving= because of the long=20 text (a= nd=20 pictures) and size. I=20 try to stay always below 100kB. Perhaps some RXs can be improved or= Lowfers=20 gets motivated to try such an antenna=85

73, Stefan/DK7FC

PS: Mike, what's your locator? I= want to check the=20 distance and take a view to your QTH (on http://f6fvy.free.fr/qthLocator/fullScreen.php<= /SPAN>=20 everyone can type the searched QTH-Locator and watch the QTH of the= received=20 stn). So one can see the distance and the wave travelling path and= if the stn=20 in directly at the beach or in the mountains and so on. Vy=20 fine!

PPS: I forward this message to Ber= nd, the constructor=20 of the preamp. I think he doesn=92t know that the antenna gets even= better when=20 reducing the wire length! (tnx Bernd!)

 

 

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