X-GM-THRID: 1214483372695040095 X-Gmail-Labels: rsgb lf X-Gmail-Received: fc5b7c138123bfdedbdc25006a18bffac5af229b Delivered-To: daveyxm@gmail.com Received: by 10.64.250.20 with SMTP id x20cs923340qbh; Thu, 14 Sep 2006 01:13:20 -0700 (PDT) Received: by 10.48.202.19 with SMTP id z19mr11821975nff; Thu, 14 Sep 2006 01:13:19 -0700 (PDT) Return-Path: Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mx.gmail.com with ESMTP id d2si18874499nfe.2006.09.14.01.13.15; Thu, 14 Sep 2006 01:13:19 -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 1GNmHL-0000eV-Ae for rs_out_1@blacksheep.org; Thu, 14 Sep 2006 09:08:59 +0100 Received: from [193.82.59.130] (helo=relay2.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1GNmHK-0000eM-Ol for rsgb_lf_group@blacksheep.org; Thu, 14 Sep 2006 09:08:58 +0100 Received: from relay.dera.gov.uk ([192.5.29.49] helo=relay.dstl.gov.uk) by relay2.thorcom.net with smtp (Exim 4.51) id 1GNmHG-0004fU-Mt for rsgb_lf_group@blacksheep.org; Thu, 14 Sep 2006 09:08:58 +0100 Received: (qmail 7552 invoked from network); 14 Sep 2006 09:08:44 +0100 Received: from warlock.dstl.gov.uk (192.5.29.10) by relay.dera.gov.uk with SMTP; 14 Sep 2006 09:08:44 +0100 Message-ID: <7D653C9C42F5D411A27C00508BF8803D06D4E490@mail.dstl.gov.uk> From: Talbot Andrew To: ukmicrowaves@yahoogroups.com, rsgb_lf_group@blacksheep.org Cc: Paul Phillips Date: Thu, 14 Sep 2006 09:08:42 +0100 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2653.19) X-Spam-Score: -0.9 (/) X-Spam-Report: autolearn=disabled,AWL=-1.028,FORGED_RCVD_HELO=0.05,HTML_40_50=0.086,HTML_MESSAGE=0.001 Subject: LF: RF Ferrite - off topic for LF and Micro waves Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C6D7D4.FE61D1E0" 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_20_30,HTML_FONTCOLOR_BLUE, 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: 4313 This message is in MIME format. Since your mail reader does not understand this format, some or all of this message may not be legible. ------_=_NextPart_001_01C6D7D4.FE61D1E0 Content-Type: text/plain Not really microwaves and certainly not LF, but hopefully someone can help... I've been reminded that I promised to finish a 200 Watt 70MHz solid state PA, a project started some time ago and got put on hold. I'm stuck for a suitable ferrite core for the output transformer. It needs to match approx 3 ohms load resistance to 50 ohm output. The windings will be made using either conventional wire as in HF PAs, or made from semirigid coax with shunt outer, series inner. The latter will need a physiacally larger core to accomodate the wire thickness. Some cores I did have that 'ought' to have worked taken from a 35 watt broadband PA (0.5 to 1000MHz) failed miserably and got seriously hot no matter what winding configuration was used. In that original PA they were acting only as common mode chokes and presumably didn't have to carry nearly so much flux. Does anyone have details of a suitable core/material, or better still have a core going spare :-) The PA uses an MRF 141G Mosfet device rated for 300 Watts out with 14dB gain. The circuit itself is quite simple - see the data sheet for teh MRF141G - and would have been finished a long time ago but for the output transformer. Andy G4JNT "This e-mail is intended for the recipient only. If you are not the intended recipient you must not use, disclose, distribute, copy, print, or rely upon this e-mail. If an addressing or transmission error has misdirected this e-mail, please notify the author by replying to this e-mail." "Recipients should note that all e-mail traffic on MOD systems is subject to monitoring and auditing." ------_=_NextPart_001_01C6D7D4.FE61D1E0 Content-Type: text/html

Not really microwaves and certainly not LF, but hopefully someone can help...

I've been reminded that I promised to finish a 200 Watt 70MHz solid state PA, a project started some time ago and got put on hold.  I'm stuck for a suitable ferrite core for the output transformer.   It needs to match approx 3 ohms load resistance to 50 ohm output.  The windings will be made using either conventional wire as in HF PAs, or made from semirigid coax with shunt outer, series inner.  The latter will need a physiacally larger core to accomodate the wire thickness.

Some cores I did have that 'ought' to have worked taken from a 35 watt broadband PA (0.5 to 1000MHz) failed miserably and got seriously hot no matter what winding configuration was used.  In that original PA they were acting only as common mode chokes and presumably didn't have to carry nearly so much flux.

Does anyone have details of a suitable core/material, or better still have a core going spare   :-)

The PA uses an MRF 141G Mosfet device rated for 300 Watts out with 14dB gain.  The circuit  itself is quite simple - see the data sheet for teh MRF141G -  and would have been finished a long time ago but for the output transformer.

Andy  G4JNT

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