Path: ...!news.mixmin.net!weretis.net!feeder8.news.weretis.net!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail From: liz@poppyrecords.invalid.invalid (Liz Tuddenham) Newsgroups: sci.electronics.design Subject: Re: Sleeve dipoles Date: Sun, 22 Dec 2024 10:46:03 +0000 Organization: Poppy Records Lines: 47 Message-ID: <1r4yps7.tln6011jcvupsN%liz@poppyrecords.invalid.invalid> References: <1r4wu7h.59lomx16sv7eoN%liz@poppyrecords.invalid.invalid> <1r4xqqh.qpknh71bcv5n8N%liz@poppyrecords.invalid.invalid> X-Trace: individual.net e3ijm2ALzh8BP/9IZpULegvLSsTy/LnRb3iWyd3AfpLGpZ38LM X-Orig-Path: liz Cancel-Lock: sha1:7K1YL07Fq+ovjaIqCX+Vv73lDbU= sha256:67CbyNL2Ib9q5J1rZMnz7r9Al06NYOsROKRUoKsanC4= User-Agent: MacSOUP/2.4.6 Bytes: 2573 Dave Platt wrote: [...] > Can you point me to a picture or article which shows this sort of > construction? https://kv5r.com > Ham Radio > 2-meter sleeve dipole My reasoning is as follows: 1) The co-ax is inside the bottom dipole element and close to the actual radiating conductor, so the sleeve of the co-ax must be at about the same potential as the corresponding position on the bottom element. There is no attempt to separate them as there would be with a large-diameter bottom element or 45-degree Discone rods. 2) That dipole is floating on approximately 7ft of insulating plastic pipe and it appears that the length of the supporting pipe is not critical. 3) The feed co-ax comes vertically downwards, not at right-angles to the dipole. If the length of the mounting pole is not critical, it follows that the length of the co-ax is not critical. 4) Therefore the coax sleeve does not carry standing waves and must be at earth potential up to the point where it enters the bottom element. 5) Therefore the bottom of the bottom element of the dipole is at earth potential. 6) If all the co-ax sleeve below the dipole is at earth potential, there is no reason why it could not be encased in a metallic supporting pole. 7) If the bottom of the dipole is at earth potential, there is no reason why it should not be electrically in contact with the earthed supporting pole - or even form a continuation of it. The end result could be regarded as a quarter-wave whip above a folded-back ground plane of indeterminate size. -- ~ Liz Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk