X-GM-THRID: 1205303726009860196 X-Gmail-Labels: rsgb lf X-Gmail-Received: 4f61cac8b007ef3fe660d5ded3fa86bd8b1846ce Delivered-To: daveyxm@gmail.com Received: by 10.54.127.17 with SMTP id z17cs24141wrc; Mon, 5 Jun 2006 05:46:56 -0700 (PDT) Received: by 10.78.69.7 with SMTP id r7mr708878hua; Mon, 05 Jun 2006 05:46:55 -0700 (PDT) Return-Path: Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mx.gmail.com with ESMTP id 3si915986huc.2006.06.05.05.46.51; Mon, 05 Jun 2006 05:46:55 -0700 (PDT) Received-SPF: neutral (gmail.com: 193.82.116.20 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1FnEOZ-0007vU-B8 for rs_out_1@blacksheep.org; Mon, 05 Jun 2006 13:41:23 +0100 Received: from [193.82.59.130] (helo=relay2.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1FnEOY-0007vL-ON for rsgb_lf_group@blacksheep.org; Mon, 05 Jun 2006 13:41:22 +0100 Received: from mailout10.sul.t-online.com ([194.25.134.21]) by relay2.thorcom.net with esmtp (Exim 4.51) id 1FnEOU-00057z-FE for rsgb_lf_group@blacksheep.org; Mon, 05 Jun 2006 13:41:22 +0100 Received: from fwd34.aul.t-online.de by mailout10.sul.t-online.com with smtp id 1FnENV-000743-05; Mon, 05 Jun 2006 14:40:17 +0200 Received: from 127.0.0.1 (ZBoG6rZdweu+3rEmvArB1tCA6BjpZ6b0h6Nsr6-UrjuQUEnFeT1DQ6@[84.145.231.103]) by fwd34.sul.t-online.de with smtp id 1FnENP-0dqAKm0; Mon, 5 Jun 2006 14:40:11 +0200 MIME-Version: 1.0 From: hajo.brandt.dj1zb@t-online.de (Hans-Joachim Brandt) To: X-Mailer: T-Online eMail 5.00.0036 Date: 05 Jun 2006 12:39 GMT Message-ID: <1FnENP-0dqAKm0@fwd34.sul.t-online.de> X-ID: ZBoG6rZdweu+3rEmvArB1tCA6BjpZ6b0h6Nsr6-UrjuQUEnFeT1DQ6 X-TOI-MSGID: b5f931fe-a638-4c74-a87c-3dc630d3ea07 X-Spam-Score: -0.8 (/) X-Spam-Report: autolearn=disabled,AWL=-0.878,HTML_60_70=0.027,HTML_MESSAGE=0.001 Subject: Re: LF: QRP RF Ammeter Content-Type: Multipart/Alternative; Boundary="__Next_1149511193_Part196__" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.2 required=5.0 tests=HTML_50_60,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 Status: O X-Status: X-Keywords: X-UID: 5453 --__Next_1149511193_Part196__ Content-Type: Text/Plain; Charset="ISO-8859-1" Content-Transfer-Encoding: Quoted-Printable Dear Weazle, the general rule for current transformers is that for frequency independan= t operation the inductive reactance of the secondary coil should be at leas= t five times the parallel resistor. The other aim ist to employ a ferrite t= oroid giving the highest inductance with the least number of turns. Therefo= re the Amidon material -75 should give best results (from those materials I= know, there may be even newer toroids with even higher AL values, for swit= ch-mode power supplies). Optimum choice of the parallel resistor will depen= d on the sensitivity of the meter available and its internal resistance. OKP 73 Ha-Jo, DJ1ZB=20 =20 "J. B. Weazle McCreath" schrieb:=20 Hi Guys, I'm in need of the details on how to build an RF ammeter for the L= owfer freqs.Surfing the web has yielded plenty of info for the 137 band uni= ts, but they'remeant for much higher power. I expect that I'll need a lot = more turns on thesecondary of the current transformer, and likely a more se= nsitive movementfor the indicator. Any and all help is appreciated. 73, J.= B., VE3EAR - VE3WZL Solar and wind powered EN93dr --__Next_1149511193_Part196__ Content-Type: Text/HTML; Charset="ISO-8859-1" Content-Transfer-Encoding: Quoted-Printable T-Online eMail
Dear Weazle,
 
the general rule for = current=20 transformers is that for frequency independant operation the inductive= =20 reactance of the secondary coil should be at least five times the parallel= =20 resistor. The other aim ist to employ a ferrite toroid giving the high= est=20 inductance with the least number of turns. Therefore the Amidon material -7= 5=20 should give best results (from those materials I know, there may be even ne= wer=20 toroids with even higher AL values, for switch-mode power supplies). Optimu= m=20 choice of the parallel resistor will depend on the sensitivity of the meter= =20 available and its internal resistance.
 
OKP
 
73 Ha-Jo,=20 DJ1ZB 
 
 
  "J. B. Weazle McCreath" <weazle@hurontel.on.ca&= gt;=20 schrieb:
=20
Hi Guys,
 
I'm in need of the details on how to build= an RF=20 ammeter for the Lowfer freqs.
Surfing the web has yielded plenty of info= for the=20 137 band units, but they're
meant for much higher power.  I expec= t that=20 I'll need a lot more turns on the
secondary of the current transformer, = ;and=20 likely a more sensitive movement
for the indicator.  Any and all help = is=20 appreciated.
 
73, J.B., VE3EAR - VE3WZL
Solar and win= d=20 powered
EN93dr
 
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