Paul this was covered a few days ago. Aim to resonate the L at approx. 1.9mhz then put a hairpin coil across the feed point, somewhere in the region of 2.5 microhenries. Then if needed adjust the horizontal part of the L and the coil. I used a variable inductance to get the needed value here with a 20m vertical and two top loading wires. Then replaced the correct adjusted coil value with a fixed coil. If you have room for a T even if its inverted that would be better to save unwanted horizontal polarisation from your L. If you need further info send me an email off ref' 73 Clive GM3POI
-----Original Message----- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Paul Mclaren Sent: 21 September 2018 20:24 To: wa5...@gmail.com; Topband Subject: Re: Topband: 160m antenna help Stan, Thanks and another daft question.....what sort of wire would recommend for the coil? Regards Paul MM0ZBH On Fri, 21 Sep 2018, 21:20 Stan Stockton, <wa5...@gmail.com> wrote: > Paul, > > The antenna is too short since you want to operate at 1825. Make it > longer by about four feet. > > Then wind a coil that will probably have 20-30 turns of wire and maybe 3 > inches diameter and connect one end to the bottom of the antenna and the > other end to your radials. > > You will have to experiment with the number if turns on this hairpin but > you are trying to bring the R up to about 50 where you will see a nearly > perfect match. > > 73...Stan, K5GO/ZF9CW > > On Fri, Sep 21, 2018, 3:07 PM Paul Mclaren <paul....@gmail.com> wrote: > >> Looking for the advice of the experienced hams for what if anything I >> should do to make my 160m inverted L more efficient. Being realistic I >> am >> limited as I have a postage stamp garden so can't really lay more radials >> or change much beyond the inverted L. I guess the question is would some >> sort of match at the base help? >> >> Antenna is inverted L with 18m vertical section >> >> Radials are approx 40 x 10m lengths and a layer of copper mesh out to >> about >> 5 metres from the base as well. >> >> Using my RigExpert AA30 analyser the readings are: >> >> Usual TX frequency: >> >> Freq 1825khz: SWR: 2.6, R33ohm, X 31ohm, Z 44ohm, L: 2700nH >> >> >> Lowest SWR is: >> >> Freq 1882kHz: SWR 1.7, R72.5ohm, X20.5ohm, Z77ohm, L: 1900nH >> >> I'll be honest and confess I don't fully understand how to best optimise >> the antenna and what "good" looks like particularly on the low bands. >> >> Help please and thanks in advance. >> >> Regards >> >> Paul MM0ZBH >> >> The antenna works but no >> _________________ >> Topband Reflector Archives - http://www.contesting.com/_topband >> > _________________ Topband Reflector Archives - http://www.contesting.com/_topband --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus _________________ Topband Reflector Archives - http://www.contesting.com/_topband