Return-Path: X-Spam-DCC: paranoid 1290; Body=2 Fuz1=2 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-2.4 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id tA8EJhgf009705 for ; Sun, 8 Nov 2015 15:19:44 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ZvQl0-0005LQ-03 for rs_out_1@blacksheep.org; Sun, 08 Nov 2015 14:15:46 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ZvQkz-0005LH-KJ for rsgb_lf_group@blacksheep.org; Sun, 08 Nov 2015 14:15:45 +0000 Received: from smtpout3.wanadoo.co.uk ([80.12.242.59] helo=smtpout.wanadoo.co.uk) by relay1.thorcom.net with esmtp (Exim 4.86) (envelope-from ) id 1ZvQjq-0006R0-GF for rsgb_lf_group@blacksheep.org; Sun, 08 Nov 2015 14:15:44 +0000 Received: from AGB ([95.150.81.97]) by mwinf5d33 with ME id f2EF1r00625yy13032EFfa; Sun, 08 Nov 2015 15:14:18 +0100 X-ME-Helo: AGB X-ME-Date: Sun, 08 Nov 2015 15:14:18 +0100 X-ME-IP: 95.150.81.97 Message-ID: From: "Graham" To: References: <1843908200.20151104162925@chriswilson.tv>, , <8E31BC8EB75546E59F99E35AFAAA0DEE@AGB> <563DD93A.22662.37C4EA@mike.dennison.ntlworld.com> <514333482.20151107111905@chriswilson.tv> <79AAC450664E4A62AE4F7F72331E43BC@gnat> <9E37EAD7DC7A43E08EFF3EAF82788F58@gnat> <957601B31AB3407BB82F82515E15A9F1@AGB> <676EC95B2D174FF79B59FC2718AE9C5F@gnat> <78E3B72A3F604C6A9A7B44236A343EEA@AGB> In-Reply-To: Date: Sun, 8 Nov 2015 14:14:15 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8117.416 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8117.416 X-Scan-Signature: 913d7a7c91a460d176c89ad756da16f9 Subject: Re: Re[2]: LF: Capacitive top hat question Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=response Content-Transfer-Encoding: 7bit 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 X-Scanned-By: MIMEDefang 2.56 on 10.1.3.10 Status: O X-Status: X-Keywords: X-UID: 4903 Lets call it 'parametric re-distribution' Google gives ''About 1,010,000 results (0.18 seconds)'' for the phrase 'apparent capacitance' , just gives a way of quantifying 'thing's , besides , just because you can measure it , doesn't necessarily mean it actually exists.. Any good Ae is result of a little 'If it looks right , probably is right ' engineering ''theory'' , what works is all that really counts Which is where we came in ... how to improve the signal from Chris's Ae system ? 73-G,) -------------------------------------------------- From: "Alan Melia" Sent: Saturday, November 07, 2015 10:54 PM To: Subject: Re: Re[2]: LF: Capacitive top hat question > Not really ! and I dont have a text book that defines "apparent > capacitance". :-)) > > If there is no environmental loss the elevated loading coil makes little > difference, it does increase Rrad by up to about 10% (J. of Canadian BC > Engineers from memory)......every little helps as they say. It doesnt > produce the size of effect on Rloss though. > > Re-read the Alan and Finbar articles on spiral loads, there was some > effect due to the increased capacitance of the spiral (elevated load) but > the loss was greatly reduced by putting capacitive load above it, There > was nothing "apparent" about it as the parameters were measured and a plot > of several different configurations produced a plot of top capacitive > loading against ground loss. The big problem is windage those who tried > it, like Gary and Finbar, lost their aerials to gales. > > Do the calculation properly and there is little extra current in the > top-load, In fact with a meander of wires it is less. The reduced loss > effect is due to the area of the ground "plate" you are using and > reduction of the 2D loss resistance. > > Alan > G3NYK > > ----- Original Message ----- > From: "Graham" > To: > Sent: Saturday, November 07, 2015 9:16 PM > Subject: Re: Re[2]: LF: Capacitive top hat question > > >> 'elevated coil merely reduces the voltage in the section below it'. >> >> 'load the best point for the ground rods was under the remote end' >> >> Quite so , what go's up must come down, lower voltage at the tuner , >> more amps in the vertical , higher voltage >> at the top/end .. same capacity , but more voltage , more power >> transfer to ground >> >> Which was my point , adding additional top wires, more capacity , has >> the same effect as adding a top loading coil, which in turn >> increases the apparent capacity to ground , same result ? >> >> G, .. >> >> -------------------------------------------------- >> From: "Alan Melia" >> Sent: Saturday, November 07, 2015 4:23 PM >> To: >> Subject: Re: Re[2]: LF: Capacitive top hat question >> >>> I think you are waving your arms around G :-)) There is no >>> "transformation" the elevated coil merely reduces the voltage in the >>> section below it. This reduces the current forced into lossy environment >>> near the feed and verticle (as Mike found) The top section has a remote >>> end with is the high voltage point, that point drives most displacement >>> current through the "load capacitance" to ground. The capacitance is a >>> physical thing.....two plates....it does not vary with frequency !! At >>> the feed point the elevated coil cancels some of the capacitance so the >>> capacitance must be measured well below the resonant frequuency, or the >>> inductance allowed for. This can all be calculated easily. This is why I >>> always recommend measring the parameters of an untuned aerial . You dont >>> then get confused by the tuning elements, it is a simple capacitance in >>> series with a resistance (which is predominantly loss) >>> >>> If you have a copy of the old Peter Dodd LF experimenters Sourcebook >>> there is an interesting reprint of an article from 1926 about the Nauen >>> VLF aerial system.. Short of money they couldnt afford unlimited amounts >>> of copper so they had to use what they could afford efficiently. The >>> found with a top load the best point for the ground rods was under the >>> remote end not under the feed point!! >>> >>> Alan >>> G3NYK >>> >>> ----- Original Message ----- >>> From: "Graham" >>> To: >>> Sent: Saturday, November 07, 2015 3:53 PM >>> Subject: Re: Re[2]: LF: Capacitive top hat question >>> >>> >>>> Im thinking of transformation, caused by a top loading coil . That >>>> would appear to offer a higher ground capacity from the top wires >>>> , after the coil , lowering the feed z at one side and higher at >>>> the other ? >>>> >>>> G, >>>> >>>> -------------------------------------------------- >>>> From: "Alan Melia" >>>> Sent: Saturday, November 07, 2015 3:24 PM >>>> To: >>>> Subject: Re: Re[2]: LF: Capacitive top hat question >>>> >>>>> Measured ....the only type that matters :-)) >>>>> Alan >>>>> ----- Original Message ----- >>>>> From: "Graham" >>>>> To: >>>>> Sent: Saturday, November 07, 2015 2:31 PM >>>>> Subject: Re: Re[2]: LF: Capacitive top hat question >>>>> >>>>> >>>>>> doubling the capacity ofan aerial halves the ground loss >>>>>> >>>>>> Actual or effective capacity ? >>>>>> >>>>>> G, >>>>>> >>>>>> -------------------------------------------------- >>>>>> From: "Alan Melia" >>>>>> Sent: Saturday, November 07, 2015 12:32 PM >>>>>> To: >>>>>> Subject: Re: Re[2]: LF: Capacitive top hat question >>>>>> >>>>>>> I think that maybe too much emphasis is placed on specific >>>>>>> structures. At these frequencies any structure of conductors can be >>>>>>> resolved into an equivalent vertical and horizontal >>>>>>> arrangement......even a continuously sloping wire!. As Mike says the >>>>>>> horizonal portion does not radiate appreciably because of the >>>>>>> reflection in the close-by ground. >>>>>>> >>>>>>> Predominantly horizontal conductors will inrease the capacitance of >>>>>>> the aerial to ground and an extra run of wire will have most effect >>>>>>> if separated by around a metre to reduce interaction between to two. >>>>>>> Ball-park figure an extra 6pF per metre. The actual configuration of >>>>>>> connection is unimportant for the horizonals form a "skeleton" >>>>>>> plate. Note whereas Rugby LF station had originally caged wires >>>>>>> between the 850 foot masts to increase the capacity, after the >>>>>>> rebuild the internal area with the masts was "laced" with straight >>>>>>> single wires. This produced more capacity and was easier to maintain >>>>>>> the the high windage cages. >>>>>>> >>>>>>> Then the more horizontal wire the higher the aerial capacity, so the >>>>>>> smaller the inductance needed to resonate it ......and lower coil >>>>>>> loss. However another effect not well modelledin aerial synthesis >>>>>>> programs isthat doubling the capacity ofan aerial halves the ground >>>>>>> loss. There are mesurements on my web site confirming this, under >>>>>>> spiral aerials. Halving ground loss is very difficult to achieve >>>>>>> with extra groundrods or "radials" at LF/MF unless it is poor to >>>>>>> start with. The only casewhere this is not useful is over very good >>>>>>> ground, a high water-table or possibly sea water. >>>>>>> >>>>>>> As to feeding Chris's loop as a loop..... the size is much less than >>>>>>> a wavelength and is too low compared with the wavelenth to radiate >>>>>>> efficiently. Any uncancelled radiation will probably be vertically >>>>>>> upwards, much of which will escape the ionosphere never to return. >>>>>>> Its performance at HF where distance above ground is of the same >>>>>>> order as a wavelength will be totally different. Phase difference >>>>>>> round the loop will lead to a totally different pattern of >>>>>>> radiation. >>>>>>> >>>>>>> Alan >>>>>>> G3NYK >>>>>>> >>>>>>> >>>>>>> ----- Original Message ----- >>>>>>> From: "Chris Wilson" >>>>>>> To: "Mike Dennison" >>>>>>> Sent: Saturday, November 07, 2015 11:19 AM >>>>>>> Subject: Re[2]: LF: Capacitive top hat question >>>>>>> >>>>>>> >>>>>>>> Hello Mike, >>>>>>>> >>>>>>>> Saturday, November 7, 2015 >>>>>>>> >>>>>>>> >>>>>>>> Thanks for the info Mike, as always! Is there any real benefit in >>>>>>>> having the vertical section centralised within the top hat >>>>>>>> capacitive >>>>>>>> array, be it a horizontal loop, random horizontal wires, or a plain >>>>>>>> single wire? >>>>>>>> >>>>>>>> And is there much point in struggling to get one corner or side of >>>>>>>> a >>>>>>>> horizontal top hat loop higher than the rest, or the same for a >>>>>>>> single >>>>>>>> wire? I have some tall trees, but unfortunately not two tall trees >>>>>>>> opposite one another a >> >> > >