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-bounces@contesting.com] On Behalf Of Paul
Mclaren
Sent: 21 September 2018 20:24
To: wa5rtg@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, <wa5rtg@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.mcl@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
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>>
>
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