I was in a bit of a rush with my previous response; here¹s a little background. The (Stoddart) 94455-1 was a response to the biconical design presented in MIL-STD-461A, back in 1968. That design used the tunable dipole T1 balun (30 200 MHz) but substituting the biconical elements for the tunable dipole elements.
That approach had some problems, because the T1 balun obviously was designed to convert 73 balanced to 50 unbalanced, and the biconical cage design is closer to 180 200 balanced. Later designs tried to be a better match to the biconical characteristic impedance. But none are good at the very low end, where the cage elements are simply too short to achieve the characteristic impedance and instead look capacitive. Hence the crummy low-frequency vswr of all 137 cm tip-to-tip biconicals used from 30 200 MHz. Ken Javor Phone: (256) 650-5261 From: Ken Javor <[email protected]> Reply-To: Ken Javor <[email protected]> Date: Fri, 9 Apr 2021 09:09:52 -0500 To: <[email protected]> Subject: Re: [PSES] Replacement Antenna [General Use] Any biconical with a 137 cm tip-to-tip length suffices, as that is the only criterion set. There have been improvements in balun technology made since the 94455-1. The antenna factor should be smoother and more accurate. Ken Javor Phone: (256) 650-5261 From: "Price, Andrew (Leonardo, UK)" <[email protected]> Reply-To: "Price, Andrew (Leonardo, UK)" <[email protected]> Date: Fri, 9 Apr 2021 09:50:28 +0000 To: <[email protected]> Subject: [PSES] Replacement Antenna [General Use] Hi All Looking to replace a 94455-1 Bicon Antenna, does anyone know of a preferred replacement? Regards Andy Andrew Price Integrated Sensing & Protection (ISP) Prinicpal Environmental Engineer (EMC) Leonardo UK Sigma House, Christopher Martin Rd, Basildon SS14 3EL, UK Tel EMC LAB : +44 (0)1268 883308 Mobile: +44 (0)7507 854888 [email protected] <mailto:[email protected]> leonardocomapany.com HELICOPTERS / AERONAUTICS / ELECTRONICS, DEFENCE AND SECURITY SYSTEMS / SPACE P Please consider the environment before printing this email. Leonardo UK Ltd Registered Office: 1 Eagle Place, St James¹s, London SW1Y 6AF A company registered in England & Wales. 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To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) <http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
