Return-Path: Received: (qmail 22433 invoked from network); 22 Jun 2001 06:23:49 -0000 Received: from unknown (HELO murphys-inbound.servers.plus.net) (212.159.14.225) by excalibur.plus.net with SMTP; 22 Jun 2001 06:23:49 -0000 Received: (qmail 6820 invoked from network); 22 Jun 2001 06:23:30 -0000 Content-Transfer-Encoding: 8bit Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by murphys with SMTP; 22 Jun 2001 06:23:30 -0000 X-Priority: 3 X-MSMail-Priority: Normal Received: from majordom by post.thorcom.com with local (Exim 3.16 #2) id 15DKGi-0001aJ-00 for rsgb_lf_group-outgoing@blacksheep.org; Fri, 22 Jun 2001 07:18:12 +0100 Received: from ns3.swh.sk ([192.108.125.37]) by post.thorcom.com with esmtp (Exim 3.16 #2) id 15DKGf-0001aE-00 for rsgb_lf_group@blacksheep.org; Fri, 22 Jun 2001 07:18:09 +0100 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from hermes.swh.sk (hermes [192.108.125.60]) by ns3.swh.sk (8.11.0/8.11.0) with ESMTP id f5M6O9S32337 for ; Fri, 22 Jun 2001 08:24:09 +0200 Received: from btss101a.swh.sk (btss.swh.sk [139.24.136.15]) by hermes.swh.sk (8.9.3/8.9.2) with ESMTP id IAA03220 for ; Fri, 22 Jun 2001 08:17:19 +0200 (MET DST) Received: by btss.swh.sk with Internet Mail Service (5.5.2653.19) id ; Fri, 22 Jun 2001 08:17:16 +0200 Message-ID: <29BDD4F529FCD311B631009027357C4E0225878C@btss103a.swh.sk> From: "Gasparik Richard" To: rsgb_lf_group@blacksheep.org Subject: RE: LF: Loop antenna by DF3LP... Date: Fri, 22 Jun 2001 08:17:15 +0200 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2653.19) Content-Type: text/plain; charset=iso-8859-2; format=flowed Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Hello Peter and LF-group... That's OK. Sorry for my mistake, tuning cap is parallel. For the frame I'm using RG58 coax, so not very good one. With my radio IC-761 is an preamp needed...so, thank you very much for your information...best regards and I hope to see you sometimes on 136... 73 de Rich OM2TW -----Original Message----- From: Peter W. Schnoor [mailto:pwsch@nephro.uni-kiel.de] Sent: Thursday, June 21, 2001 6:31 PM To: rsgb_lf_group@blacksheep.org Subject: Re: LF: Loop antenna by DF3LP... Hello Richard, Gasparik Richard wrote: > I have build an loop antenna (project of DF3LP). I find that the > sensitivity of the loop with preamp is very low. DFC39 is normaly 50-60dB > over S9 on my LW antenna, but with loop antenna it's 30dB less. The "gain" of this antenna is approx. -60 dB, approx. 30 dB down compared to my vertical. So the simple preamp as described *plus* a Dual-Gate MosFet in front of my first mixer stage are sufficient for hearing/seeing reasonable background noise levels even on "quiet" winter mornings. > I tuned it for the maximu with serial caps. Hmm... I remember using *parallel* caps so that the loop acts as parallel tuned circuit! Do you apply rigid Flexwell cable or similar for the frame? I found a significant difference using rugged air insulated cable compared to thin coax (60 Ohms) of unknown origin at the same geometry. RG213 or better are recommended. Compared to other loop designs the bandwidth is *broad* and it was difficult tuning the mid frequency right on the amateur band by fixed caps. > Directivity is very good (more than 40dB at > 90 degrees). It's normal or not ? Yes, I found more than 50 dB of directivity at ground wave (!) propagation. The main goal for building this loop was (i) nulling out the LORAN splatter from SYLT as sharp as possible and (ii) shielding the E-field as much as possible. 73 es gl de DF3LP Peter