Hello Alex,
In your case, the "dry" soil state make the antenna impedance about 30ohms.
In the "wet" soil state, the ground conductivity improves minimizing the
losses. The antenna impedancebecomes about 17ohms, much closer to the ideal
11ohms (in your case).
Solution:
Minimize ground losses.
How?
With an RF current meter (such:
http://www.w8ji.com/building_a_current_meter.htm) start from the scratch to
re-arrange the radials for less ground loss.
Anyhow, keep in mind that the "wet" soil state antenna impedance is better then
the initial one.
I know you should use an impedance adapter but this is the way it works.
Good luck.
73 de YO3FFF
Cristi
________________________________
From: ALEXEY OGORODOV <ua4wae@mail.ru>
To: topband@contesting.com
Sent: Thursday, January 31, 2013 4:37 AM
Subject: Topband: inverted L issues
Hello,
Right to the point. At HD2A we installed an Inverted L with the following
dimensions:
vertical portion 16m
horizontal portion 26m.
The horizontal wire goes with slightly upward with with its end at 19m above
the gound.
The ground system - 4 x 6ft ground rods at the base
- 34 x 42odd m radials on the ground
No matching device is used. Fed directly with RG8 coax.
The SWR was at 1.5 to 1.8 on 1.832 now it is 3:1 at the same frequency with no
visible alterations to the antenna except the rain season.
The question: what could cause the SWR increment? any suggestions to bring it
down and keep it relatively stable.
Thanks in advance,
Alberto, Alex
HD2A Team
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Topband Reflector
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