Paul,
It would be nice to have a few more data points. The two you supplied when
mapped onto the Smith Chart don't give much evidence of a resonant point and the
second one doesn't make sense. With these limited data I suggest that your
loading wire is too long. I would try shortening it to bring X down to zero.
Alternatively, a series capacitor of 2800 pf would give you resonance at 1.825
with SWR= 1.5. By serendipity the SWR at 1.882 is also 1.5, but on the opposite
(wrong) side of the Smith Chart
None of this improves the ground loss situation.
Bottom line, I suspect your data is flawed, which seems to be an epidemic with
the numbers being posted lately from RigExpert equipment. This is curious as I
have an AA-55 which, except for tacking on one bogus data point in exported
files, agrees closely with data taken on the same inverted L with my DG8SAQ
VNWA. It also overlays modeled data quite nicely.
Wes N7WS
On 9/21/2018 1:06 PM, Paul Mclaren 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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