Return-Path: Received: (qmail 26570 invoked from network); 13 Jul 1999 15:13:32 +0100 Received: from magnus.plus.net.uk (HELO magnus.force9.net) (195.166.128.27) by guiness.force9.net with SMTP; 13 Jul 1999 15:13:32 +0100 Received: (qmail 11354 invoked from network); 13 Jul 1999 14:15:03 -0000 Content-Transfer-Encoding: 8bit Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by magnus.plus.net.uk with SMTP; 13 Jul 1999 14:15:03 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.02 #1) id 11434e-0001xa-00 for rsgb_lf_group-outgoing@blacksheep.org; Tue, 13 Jul 1999 14:58:20 +0100 X-Priority: 3 X-MSMail-Priority: Normal Received: from mailserv.cc.kuleuven.ac.be ([134.58.8.44]) by post.thorcom.com with esmtp (Exim 3.02 #1) id 11434d-0001xV-00 for rsgb_lf_group@blacksheep.org; Tue, 13 Jul 1999 14:58:19 +0100 Received: from LCBD15.fys.kuleuven.ac.be (LCBD15.fys.kuleuven.ac.be [134.58.80.15]) by mailserv.cc.kuleuven.ac.be (8.9.0/8.9.0) with SMTP id QAA18179 for ; Tue, 13 Jul 1999 16:03:59 +0200 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Message-ID: <3.0.1.16.19990713155956.326f5040@mail.cc.kuleuven.ac.be> X-Sender: pb623250@mail.cc.kuleuven.ac.be X-Mailer: Windows Eudora Pro Version 3.0.1 (16) Date: Tue, 13 Jul 1999 15:59:56 To: rsgb_lf_group@blacksheep.org From: "Rik Strobbe" Subject: Re: LF: Re: PA0SE Field Strength Meter In-reply-to: <007001becd2c$1a215600$6397b38f@w8k3f0> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org Sender: At 14:33 13/07/99 +0200, PA0SE wrote: > >There are two factors to be considered, sensitivity and selectivity. > >A dc-receiver can be made as sensitive as a superhet. >... I think that a third factor has te be considered, especially on LF : the intermodulation behavior of the RX. >From my experience with DC-receivers on 80m I know that strong signals near the 'passband' can not only cause 'gost-signals' but also make the RX very insensitive (DC breakthrough). The most critical part (assuming you have a proper designed RF preamp with good IM behavior) is the mixer, this should be a a high-quality DBM. But on 136kHz an almost-perfect DBM is much easier to realise than on HF, I have heard about good results using analog switches as replacement for the diodes. 73, Rik Rik Strobbe ON7YD rik.strobbe@fys.kuleuven.ac.be Villadreef 14 B-3128 Baal BELGIUM (JO20IX)