Return-Path: Received: (qmail 13140 invoked from network); 5 Feb 2001 11:25:27 -0000 Received: from unknown (HELO murphys-inbound.servers.plus.net) (212.159.14.225) by excalibur.plus.net with SMTP; 5 Feb 2001 11:25:27 -0000 Received: (qmail 20072 invoked from network); 5 Feb 2001 11:19:27 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by murphys with SMTP; 5 Feb 2001 11:19:27 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.16 #1) id 14PjOV-0005TX-00 for rsgb_lf_group-outgoing@blacksheep.org; Mon, 05 Feb 2001 11:01:15 +0000 X-Priority: 3 X-MSMail-Priority: Normal Received: from [213.2.16.106] (helo=rsgb.org.uk) by post.thorcom.com with esmtp (Exim 3.16 #1) id 14PjOT-0005TS-00 for rsgb_lf_group@blacksheep.org; Mon, 05 Feb 2001 11:01:14 +0000 Received: from miked by rsgb.org.uk with SMTP (MDaemon.v2.8.7.5.R) for ; Mon, 05 Feb 2001 10:57:16 +0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 From: "Mike Dennison" To: rsgb_lf_group@blacksheep.org Date: Mon, 5 Feb 2001 10:57:15 -0000 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 8bit Subject: LF: Earthing the mast Message-ID: <3A7E870B.22556.5402A0@localhost> X-Mailer: Pegasus Mail for Win32 (v3.12c) X-MDaemon-Deliver-To: rsgb_lf_group@blacksheep.org X-Return-Path: miked@mail.rsgbhq Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: A few weeks ago there was a discussion about whether to earth masts, or leave them 'floating'. In the continuous search for more dBs I tried earthing my mast on Saturday. I have a 14m (45ft) mast attached to the brick wall of the house by 'T' and 'K' brackets, standing off about 300mm (1ft). Its base is 600mm (2ft) above ground level. The vertical part of the antenna is about 1m (3ft) away from the mast. I connected the mast to the wire which runs from the Tx to the earth stakes. I expected the capacitance between the mast and the vertical to change the tuning. The change was in fact very small, but the first thing I noticed was the variometer tuning became much more critical. The second thing was a 10 per cent increase in antenna current. Conclusion: the Q of the antenna had increased. I was still prepared to believe that I had simply added a capacitor from the antenna to earth, but when I checked the receive performance the signals improved by 1-2dB (tested by monitoring DCF and detuning until one of the 'S-meter' LCD blobs flickered, then noting that the blob stayed on with the earth connected), and the local noise level reduced at the same time. Another effect, in the short time since I made this change, has been the antenna current has been stable. Before, it would vary by between 10 and 20 percent from one day to the next, depending on the weather, and I assumed this was absorption by trees. It seems that the mast/wall was acting as a resistor to earth, absorbing a different amount of RF from day to day. I also earthed the mast at the far end of my inverted-L and connected the two with a wire, but this had much less effect. This mast is already stuck in the mud at its base so was probably already earthy. What to do next? Mike, G3XDV (IO91VT) http://www.lf.thersgb.net