Return-Path: Received: (qmail 7750 invoked from network); 14 Nov 1999 23:10:43 +0000 Received: from unknown (HELO magnet.force9.net) (195.166.128.26) by guiness.force9.net with SMTP; 14 Nov 1999 23:10:43 +0000 Received: (qmail 19053 invoked from network); 14 Nov 1999 23:20:31 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by magnet.plus.net.uk with SMTP; 14 Nov 1999 23:20:31 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.02 #1) id 11n8NG-00056n-00 for rsgb_lf_group-outgoing@blacksheep.org; Sun, 14 Nov 1999 22:43:54 +0000 Received: from mailman.zeta.org.au ([203.26.10.16]) by post.thorcom.com with esmtp (Exim 3.02 #1) id 11n8NE-00056h-00 for rsgb_lf_group@blacksheep.org; Sun, 14 Nov 1999 22:43:52 +0000 Received: from steve (beefcake.zeta.org.au [203.26.10.12]) by mailman.zeta.org.au (8.8.7/8.8.7) with ESMTP id JAA22753 for ; Mon, 15 Nov 1999 09:50:12 +1100 Message-ID: <199911142250.JAA22753@mailman.zeta.org.au> X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 From: "Steve Olney" To: rsgb_lf_group@blacksheep.org Subject: LF: Re: Re: RE: CFA Date: Mon, 15 Nov 1999 09:43:38 +1100 X-MSMail-Priority: Normal X-Priority: 3 X-Mailer: Microsoft Internet Mail 4.70.1161 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: G'day All, > > Am I wrong but doesn't the latest coverage map from the IoM site look a lot > smaller than the old one? > Yes I am wrong, it is only a little smaller :-) IMHO the IoM antenna will be deemed to be successful when commissioned. However, the question is, is that an endorsement of the theory. As has been mentioned, already Amateurs are covering large distances on LF (at lower frequencies than 279KHz to boot) without worrying about Div, Grad and Curl. However, they are all using (up until this point) antennae that follow the conventional theories. The question I would like to pose to those with more knowledge and experience than I is; when I can get a signal out to 60km which is readable (using SSB) using a 7m high antenna, with one 2m earth stake and 6mH of lossing tuning coil (small gauge wire wound around PVC pipe) using a power of less than 5-8W, is a coverage of a little over 600Km using kilograms of copper plate, presumably low-loss tuning coils, twice the frequency and half a MEGAWATT so remarkable? I have seen standard loaded short verticals with sizes of the order of a few percent quoted as being almost as good as a full size vertical. I fail to see what is so revolutionary about the CFA (apart from the "theory" expounded for it). Even if the IoM CFA produces a far field signal strength which equals (as expounded by the inventors) the expected field for a full size (270m high) this still will not prove the direct synthesis theory. You would have to prove that it is not working as a conventional antenna by measuring the currents flowing into the elements, thereby measuring the radiation resistance. Conventional short verticals exhibit a low radiation resistance and are made to radiate efficiently by matching to that low Rr while ensuring that losses are a small fraction of the dissipating load. If the CFA exhibits a high radiation resistance (the inventors vaguely mention 377ohms - free space) then this indicates something special, otherwise not. BTW, I have constructed a CFA for 177.4KHz and provided with the correct quadrature drive and swept the antenna through continuous phase and amplitude variations and I can report that it didn't radiate any better than a top-loaded vertical of the same size. I must be stupid. I can say that it is possible to get it to look like 50ohms, i.e. a low SWR. This has been taken by many amateur experimentators to indicate that it is radiating efficiently. I have a dummy load which exhibits the same low SWR, unfortunately it doesn't radiate. Also, there is a narrowcast station on 1665KHz here in Sydney, Australia which uses a CFA commissioned by the inventors. Guess what ? At 60km distance it is about 18dB down on a similar standard stations in the area. I'm sorry, but that makes me doubt a little, whatever the excuses/explanations are. I will be pleased if the IoM CFA works and wait with eagerness for the outcome as long as we get the scientific answers, not the political. All my attempts to get answers from the local BC CFA station has been met with a brick wall so far. Finally, I disagree with the notion that the CFA will fade into the sunset. It will be kept alive by its appeal to our imagination whatever the final outcome is. P.S. Maybe we would be wise to start up a separate CFA email group to avoid raising blood pressures here. Then those who want to subscribe and hear about the latest CFA shenanigans can do so. If there is sufficient response I will setup a CFA group and invite subscribers. 73s Steve Olney (VK2ZTO/AXSO - QF56IK : Lat -33 34 07, Long +150 44 40) ============================================= LowFer URL: http://www.zeta.org.au/~ollaneg/lowfer.htm AXSO LF Experimental Station URL: http://www.zeta.org.au/~ollaneg/axsoextx.htm LF Receiving - FRG-100, CHA antenna LF Transmitting - 177.5/177.4kHz 8W - 7.6m vertical or CHA Modes - AM, SSB, PSK31, SSTV, Hellschreiber, QRSS and a new experimental mode - FDK. See this URL for more: http://www.zeta.org.au/~ollaneg/FDK.htm =============================================