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[195.171.43.25]) by mx.google.com with ESMTP id x6si12194893eew.77.2013.07.07.00.38.04 for ; Sun, 07 Jul 2013 00:38:05 -0700 (PDT) Received-SPF: neutral (google.com: 195.171.43.25 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) client-ip=195.171.43.25; Authentication-Results: mx.google.com; spf=neutral (google.com: 195.171.43.25 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) smtp.mail=owner-rsgb_lf_group@blacksheep.org Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Uvj8x-00085I-5S for rs_out_1@blacksheep.org; Sun, 07 Jul 2013 08:12:23 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Uvj8w-000859-Lt for rsgb_lf_group@blacksheep.org; Sun, 07 Jul 2013 08:12:22 +0100 Received: from mout0.freenet.de ([195.4.92.90]) by relay1.thorcom.net with esmtps (UNKNOWN:AES256-GCM-SHA384:256) (Exim 4.77) (envelope-from ) id 1Uvj8u-0001Bv-T4 for rsgb_lf_group@blacksheep.org; Sun, 07 Jul 2013 08:12:21 +0100 Received: from [195.4.92.142] (helo=mjail2.freenet.de) by mout0.freenet.de with esmtpa (ID dl4yhf@freenet.de) (port 25) (Exim 4.80.1 #4) id 1Uvj8t-0006i5-Ox for rsgb_lf_group@blacksheep.org; Sun, 07 Jul 2013 09:12:19 +0200 Received: from localhost ([::1]:49982 helo=mjail2.freenet.de) by mjail2.freenet.de with esmtpa (ID dl4yhf@freenet.de) (Exim 4.80.1 #4) id 1Uvj8t-0006EH-H3 for rsgb_lf_group@blacksheep.org; Sun, 07 Jul 2013 09:12:19 +0200 Received: from [195.4.92.24] (port=45426 helo=14.mx.freenet.de) by mjail2.freenet.de with esmtpa (ID dl4yhf@freenet.de) (Exim 4.80.1 #4) id 1Uvj6E-0005it-Tc for rsgb_lf_group@blacksheep.org; Sun, 07 Jul 2013 09:09:34 +0200 Received: from blfd-4db0319b.pool.mediaways.net ([77.176.49.155]:1229 helo=[192.168.178.21]) by 14.mx.freenet.de with esmtpsa (ID dl4yhf@freenet.de) (TLSv1:DHE-RSA-CAMELLIA256-SHA:256) (port 465) (Exim 4.80.1 #4) id 1Uvj6E-0000Kq-EC for rsgb_lf_group@blacksheep.org; Sun, 07 Jul 2013 09:09:34 +0200 Message-ID: <51D9142C.90005@freenet.de> Date: Sun, 07 Jul 2013 09:09:32 +0200 From: wolf_dl4yhf User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:17.0) Gecko/20130620 Thunderbird/17.0.7 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <51D498BD.3050007@iup.uni-heidelberg.de> <005b01ce798a$b0476600$6d01a8c0@DELL4> <20130706131640.GG5246@cs.utwente.nl> <51D834D6.9050403@kabelmail.de> <8C9E7EDCA83145B4B00E1D951DC401B1@Clemens0811> <51D89E1D.8060403@virginbroadband.com.au> In-Reply-To: <51D89E1D.8060403@virginbroadband.com.au> X-Spam-Score: -0.3 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has identified this incoming email as possible spam. 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Content preview: Hello everyone, Am 07.07.2013 00:45, schrieb edgar: > Hi Roelof, > > For a test, to isolate the Minwhip, could the signal be re-transmitted > by a small transmitter, battery powered, at a higher frequency to a > local receiver? > > Regards, Edgar > Moonah, Tasmania. > [...] Content analysis details: (-0.3 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [195.4.92.90 listed in list.dnswl.org] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (dl4yhf[at]freenet.de) -0.3 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain X-Scan-Signature: a6b6ffaf48fdddf1ed5c25dc4bf03ee1 Subject: Re: LF: VK1OD's analysis of the MiniWhip antenna Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=none autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false Status: O X-Status: X-Keywords: X-UID: 3128 Hello everyone, Am 07.07.2013 00:45, schrieb edgar: > Hi Roelof, > > For a test, to isolate the Minwhip, could the signal be re-transmitted > by a small transmitter, battery powered, at a higher frequency to a > local receiver? > > Regards, Edgar > Moonah, Tasmania. > My thought, too. An 'isolation' of the feedline would have to be a significantly larger impedance than the input into the amplifier itself (the 50 ohm output into the coax doesn't matter at all). Even most RF transformers won't do because of their capacitance (which is generally larger than the input of a FET, unless one uses an 'Austin transformer'-like design). And a coax choke is useless... even if you could build one with enough inductivity, the stray capacitance will bypass it. The problem with the flea-powered 'FM transistors' (single-transistor design) is their very limited dynamic range; you'd need to filter out the frequency band of interest before the modulator. This makes it a bit complex for a quick test... Miniwhip, filter, demodulator, tiny FM transmitter, all built inside a small case. So you may end up at another solution: A 'Active Differential E-field Antenna' as described at www.vlf.it, which is basically two E-field probes, back-to-back, connected to a differential amplifier with excellent common-mode rejection: http://www.vlf.it/cr/differential_ant.htm All the best, Wolf DL4YHF .