Return-Path: Received: (qmail 12141 invoked from network); 30 May 2001 12:05:50 -0000 Received: from unknown (HELO warrior-inbound.servers.plus.net) (212.159.14.227) by excalibur.plus.net with SMTP; 30 May 2001 12:05:50 -0000 Received: (qmail 18507 invoked from network); 30 May 2001 12:05:10 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by warrior with SMTP; 30 May 2001 12:05:10 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.16 #2) id 1554cR-0006XD-00 for rsgb_lf_group-outgoing@blacksheep.org; Wed, 30 May 2001 12:58:31 +0100 Received: from rubellite.lion-access.net ([212.19.217.4]) by post.thorcom.com with esmtp (Exim 3.16 #2) id 1554cH-0006X8-00 for rsgb_lf_group@blacksheep.org; Wed, 30 May 2001 12:58:21 +0100 Received: from w8k3f0 (1Cust191.tnt2.rtm1.nl.uu.net [213.116.98.191]) by rubellite.lion-access.net (I-Lab) with SMTP id DCCD32923; Wed, 30 May 2001 11:56:43 +0000 (GMT) Message-ID: <007b01c0e900$35e8e0a0$bf6274d5@w8k3f0> From: "Dick Rollema" To: "LF-Group" Cc: "Jules Moraal" Subject: LF: Filed effect versus bipolar transistors Date: Wed, 30 May 2001 13:59:57 +0200 MIME-Version: 1.0 Content-Type: text/html; charset=windows-1252 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.00.2314.1300 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Content-transfer-encoding: 8bit

To All from PA0SE

Many thanks to those who gave me their views on the matter of FETs versus bipolar transistors in LF transmitters.

I now understand why at unpredictable moments one of the four HEXFETs IRF520 in my TX fails, though they are operated within their maximum ratings. It must be the class B operation for which the FETs were not designed.

I will turn down the supply voltage down to 30V again at which I started on LF. The FETs seemed to accept that over prolonged transmission times.

73, Dick, PA0SE