Return-Path: Received: from mtain-md02.r1000.mx.aol.com (mtain-md02.r1000.mx.aol.com [172.29.96.86]) by air-da10.mail.aol.com (v126.13) with ESMTP id MAILINDA104-86944b681f39343; Tue, 02 Feb 2010 07:48:57 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-md02.r1000.mx.aol.com (Internet Inbound) with ESMTP id E7C653800010E; Tue, 2 Feb 2010 07:48:55 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1NcIAU-0005So-9T for rs_out_1@blacksheep.org; Tue, 02 Feb 2010 12:47:46 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1NcIAT-0005Sf-Mf for rsgb_lf_group@blacksheep.org; Tue, 02 Feb 2010 12:47:45 +0000 Received: from mail-fx0-f210.google.com ([209.85.220.210]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1NcIAR-00078n-2T for rsgb_lf_group@blacksheep.org; Tue, 02 Feb 2010 12:47:45 +0000 Received: by fxm2 with SMTP id 2so1283868fxm.29 for ; Tue, 02 Feb 2010 04:47:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type; bh=Z8IAkWoMWKJ4QKuM35C4utdYyLObvuNUNX1RNmQATOk=; b=vB902XmIVGWZLJhQjRhiBPDw78dxwjCuBootsd0xrTxlCf38D4V3cDL50V7JUXWxrw 6F+Rsmh9GTY2ZGnOI7Weqj6CCsjmn0FM1RYF4ssooyw/Q1HH+PaJIzGYJV9cCBKQpMir w1HTSGSjqUmESctVb/VVGZnAbeQG8s6tvrOT8= DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=mF04LW/cANSOtBoHE38pN5KYfIxpWJgz+kN6jALy+AG867oiPaB4Sb3b64XlSCbVIL TBopn7J0RV3MPxbvTh2HipGiZCU91dxIXRbX2YSOago0+HVZH7RlLIbi2vWwEfZxMjIk tWPDwQKaM/8OG5LuUFXX/epS0IhSursGe52Mg= MIME-Version: 1.0 Received: by 10.239.150.79 with SMTP id m15mr949494hbb.32.1265114856076; Tue, 02 Feb 2010 04:47:36 -0800 (PST) In-Reply-To: <02E3EF3F48994AB88A1489042CE7EA02@JimPC> References: <12077821.1264946261487.JavaMail.root@wamui-cynical.atl.sa.earthlink.net> <38A51B74B884D74083D7950AD0DD85E82A1ACF@File-Server-HST.hst.e-technik.tu-darmstadt.de> <4C25D51A6FE646D5B8D9D37C87EA6BBC@lindavideo> <02E3EF3F48994AB88A1489042CE7EA02@JimPC> Date: Tue, 2 Feb 2010 12:47:36 +0000 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org DomainKey-Status: good (testing) X-Spam-Score: 0.9 (/) X-Spam-Report: autolearn=disabled,HTML_10_20=0.945,HTML_MESSAGE=0.001 Subject: Re: LF: Loop preamp with the BF862 / optical link Content-Type: multipart/alternative; boundary=001485f9a72c98b6b8047e9d8114 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: 3039ac1d60564b681f376800 X-AOL-IP: 193.82.116.20 X-Mailer: Unknown (No Version) --001485f9a72c98b6b8047e9d8114 Content-Type: text/plain; charset=ISO-8859-1 An experimental system I tested for work a few years ago used the low cost optical components from RS, the HBR2404 and 1404 devices with polymer cable. This was for a remote wide band antenna with full galvanic isolation. Measurements suggested 60dB dynamic range was feasible and an anlogue bandwidth in excess of 200MHz from a discrete drive and the optiacl recevers own internal preamp. Noise figure wasn't a problem, but I do recall it being the the 'sub 10dB' region, adequate for hight HF through VHF. The 60dB dynamic range was not good enough for our HF bands requirements, so another route was taken , but when used with a high Q antenna over a limited band, should be quite adequate. The old analogue cable TV systems used fibre (to the street corner where it was turned directly into RF for the coax final run. Based on a few back-of-envelope calculations, at the bandwidth needed of 2GHz or so, must have had a total effective dynamic range in the 80dB region to avoid visible degradation on nearly 100 analogue TV signals. Andy www.g4jnt.com This email has been scanned for damaging side-effects by the health and safety police, is guaranteed to contain no substances hazardous to health, but may contribute to dissolving the nether and polar regions On 2 February 2010 11:57, James Moritz wrote: > Dear Ken, Stefan, LF Group, > > If I remember correctly, the components Stefan is discussing use a polymer > fibre and are intended for short-distance optical links of a few metres, > rather than telecomms-type applications with miles of fibre, so fibre loss > is not really an issue. The ones I encountered some years ago used visible > red LEDs, although I think there were infra-red ones too. The plastic fibre > could be simply cut with a sharp knife, and clamped into the > emitter/detector components with reasonable results, rather than requiring > precision optical connectors. There is an overview at > http://www.avagotech.com/docs/AV00-0143EN > > Of course, since the optical link is effectively a signal-frequency gain > component in the receiver front end, its noise figure will contribute > towards the receiver noise figure. Since the overall efficiency of the > electrical/optical/electrical conversion is rather low, with the loss of the > fibre in addition, there will be much less signal power coming out of the > detector than going in to the emitter. Also the detector and emitter will > contribute their own noise. So the noise figure of the optical link by > itself is probably rather high. But the FET voltage-to-current input stage > driving the emitter will have a high power gain due to the very high input > impedance, which would greatly reduce the impact of noise in the optical > link - clearly the overall noise level in Stefan's system is reasonably low. > > Most optical links are used with digital signals, so this analogue optical > link is quite unusual - as well as noise, distortion products will also be > produced by the optical link. But DK7FC's antenna obviously works, so the > principle is viable. > > Cheers, Jim Moritz > 73 de M0BMU > > > ----- Original Message ----- From: "Ken" > To: > Sent: Monday, February 01, 2010 5:56 PM > Subject: Re: LF: 2nd try of sending the pic of my loop preamp with the > BF862 > > > Hi Stefan. >> 150dB/km, is a very high loss for modern fibre, even thhe early 850nm >> multimode fibre was only 1 or 2dB /km... >> > > > --001485f9a72c98b6b8047e9d8114 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
An experimental system I tested for work a few years ago used the low= cost optical components from RS, the HBR2404 and 1404 devices with polyme= r cable.=A0 This was for a remote wide band antenna with full galvanic iso= lation.=A0=A0 Measurements suggested 60dB dynamic range was feasible and= an anlogue bandwidth in excess of 200MHz from a discrete drive and the op= tiacl recevers own internal preamp.=A0=A0=A0 Noise figure wasn't a pro= blem, but I do recall it being the the 'sub 10dB' region, adequate= for hight HF through VHF.
=A0
The 60dB dynamic range was not good enough for our HF bands requireme= nts, so another route was taken , but when used with a high Q antenna over= a limited band, should be quite adequate.=A0
=A0
The old analogue cable TV systems used fibre (to the street corner wh= ere it was turned directly into RF for the coax final=A0run.=A0=A0Based on= a few back-of-envelope calculations, at the bandwidth needed=A0of 2GHz or= so, must have had a total effective dynamic range in the 80dB region to= avoid visible degradation on nearly 100 analogue TV signals.
=A0
=A0
Andy
www.g4jnt.com

Thi= s email has been scanned for damaging side-effects by the health and safet= y police, is guaranteed to contain no substances hazardous to health, but= may contribute to dissolving the nether and polar regions


On 2 February 2010 11:57, James Moritz <james.moritz= @btopenworld.com> wrote:
Dear Ken, Stefan, LF Group,
If I remember correctly, the components Stefan is discussing use a= polymer fibre and are intended for short-distance optical links of a few= metres, rather than telecomms-type applications with miles of fibre, so= fibre loss is not really an issue. The ones I encountered some years ago= used visible red LEDs, although I think there were infra-red ones too. Th= e plastic fibre could be simply cut with a sharp knife, and clamped into= the emitter/detector components with reasonable results, rather than requ= iring precision optical connectors. There is an overview at http://www.avago= tech.com/docs/AV00-0143EN

Of course, since the optical link is effectively a signal-frequency ga= in component in the receiver front end, its noise figure will contribute= towards the receiver noise figure. Since the overall efficiency of the el= ectrical/optical/electrical conversion is rather low, with the loss of the= fibre in addition, there will be much less signal power coming out of the= detector than going in to the emitter. Also the detector and emitter will= contribute their own noise. So the noise figure of the optical link by it= self is probably rather high. But the FET voltage-to-current input stage= driving the emitter will have a high power gain due to the very high inpu= t impedance, which would greatly reduce the impact of noise in the optical= link - clearly the overall noise level in Stefan's system is reasonab= ly low.

Most optical links are used with digital signals, so this analogue opt= ical link is quite unusual - as well as noise, distortion products will al= so be produced by the optical link. But DK7FC's antenna obviously work= s, so the principle is viable.

Cheers, Jim Moritz
73 de M0BMU


----- Original Message --= --- From: "Ken" <ken.h.wright@btinternet.com>
To: <rsgb_lf_group@= blacksheep.org>
Sent: Monday, February 01, 2010 5:56 PM
Subject: Re: LF: 2nd try of sen= ding the pic of my loop preamp with the BF862


Hi Stefan.
150dB/km, is a= very high loss for modern fibre, even thhe early 850nm multimode fibre wa= s only 1 or 2dB /km...



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