Return-Path: X-Spam-DCC: paranoid 1356; 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=1.7 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, FORGED_MUA_OUTLOOK 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 tA7MxOQ3008391 for ; Sat, 7 Nov 2015 23:59:24 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ZvCOx-00011t-1d for rs_out_1@blacksheep.org; Sat, 07 Nov 2015 22:56:03 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ZvCOw-00011k-MA for rsgb_lf_group@blacksheep.org; Sat, 07 Nov 2015 22:56:02 +0000 Received: from rgout0505.bt.lon5.cpcloud.co.uk ([65.20.0.226]) by relay1.thorcom.net with esmtp (Exim 4.86) (envelope-from ) id 1ZvCNs-0004ax-Gb for rsgb_lf_group@blacksheep.org; Sat, 07 Nov 2015 22:56:01 +0000 X-OWM-Source-IP: 86.136.57.57 (GB) X-OWM-Env-Sender: alan.melia@btinternet.com X-CTCH-RefID: str=0001.0A090204.563E8130.000E,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0 X-Junkmail-Premium-Raw: score=38/50,refid=2.7.2:2015.11.7.211217:17:38.936,ip=86.136.57.57,rules=__HAS_MSGID, __SANE_MSGID, MSGID_32HEX_LC, INVALID_MSGID_NO_FQDN, __MSGID_32HEX, __HAS_FROM, __PHISH_FROM2, __FRAUD_WEBMAIL_FROM, __TO_MALFORMED_2, __TO_NO_NAME, __BOUNCE_CHALLENGE_SUBJ, __BOUNCE_NDR_SUBJ_EXEMPT, __SUBJ_ALPHA_END, __MIME_VERSION, __CT, __CT_TEXT_PLAIN, __CTE, __HAS_X_PRIORITY, __HAS_MSMAIL_PRI, __HAS_X_MAILER, USER_AGENT_OE, __OUTLOOK_MUA_1, __USER_AGENT_MS_GENERIC, __ANY_URI, __FRAUD_BODY_WEBMAIL, __URI_NO_WWW, __URI_NO_PATH, __SUBJ_ALPHA_NEGATE, __INT_PROD_TV, __FORWARDED_MSG, __MIME_TEXT_ONLY, RDNS_GENERIC_POOLED, __URI_NS, SXL_IP_DYNAMIC[57.57.136.86.fur], HTML_00_01, HTML_00_10, RDNS_SUSP_GENERIC, __PHISH_FROM, __OUTLOOK_MUA, __PHISH_SPEAR_STRUCTURE_1, RDNS_SUSP, __FRAUD_WEBMAIL, FORGED_MUA_OUTLOOK, NO_URI_HTTPS X-CTCH-Spam: Unknown Received: from gnat (86.136.57.57) by rgout05.bt.lon5.cpcloud.co.uk (8.6.122.06) (authenticated as alan.melia@btinternet.com) id 563A0A1000622B94 for rsgb_lf_group@blacksheep.org; Sat, 7 Nov 2015 22:54:31 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=btinternet.com; s=btcpcloud; t=1446936887; bh=QXW60Zs34FRRqb+RIsB+m+w8TmOtMbwoxTW4YPFtBrg=; h=Message-ID:From:To:References:Subject:Date:MIME-Version:X-Mailer; b=qlfvqekFwyb60giuvWnmxzSrIoqxULqXzJK8X0T9TdqQMcGGO53ZJEMKnQYb9yLBNqIde3m7dzwbyEvpcrZz6GA/EqFGMMBss5Zb2o7CqT9NuUO9s/IF/mzvp9E8XOYN1K4Vt289yPDM2ojk5Zna2X70nUOgzZbw47Pqu+QVw7U= Message-ID: From: "Alan Melia" 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> Date: Sat, 7 Nov 2015 22:54:32 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5931 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157 X-Scan-Signature: cbf9d9751ac5f32708197d03fa6d8d74 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: 4893 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 > >