Trevor,
You haven't really provided enough information to solve your problem. If you
want to use a shunt coil then I suggest that you consider measuring the R-jX at
your frequency of interest and then designing an L-network using purposeful
shortening of the antenna to create a capacitive reactance and then shunting the
feedpoint with an inductance. For example, if the frequency is 1.82 MHz and R
remained 18 ohm (it probably won't) then shortening the antenna to make the
feedpoint 18 -j25, a shunt inductor of 3.3 uH will yield an SWR of 1.05:1
This is in effect an unbalanced version of a hairpin match on a Yagi DE.
Wes N7WS
On 11/1/2017 9:54 AM, MR TREVOR DUNNE wrote:
Hi All
I finally got the vertical up and running, problem I have now is I can't find a
low SWR on the coil, the best I can get is about 2.8:1 no matter where I tap
the coil that's the best SWR, I can move that point up and down the band by
moving the tap but the SWR stays the same,
My current set up is about 55ft vertical I have 2 loading wires in a T shape,
wires are 50ft either side of the vertical and the are pretty level and in line,
I have 38 radials averaging about 45-60ft long, I will add more when time
allows but don't the make the SWR worse ??
With no coil I get resonance at 2.12mhz with R=16 X=2 on my MFJ269,
The coil is 25ft of 5mm copper brake pipe in a 4" diameter, the coil is
attached to base of the vertical and the other end is grounded,
Any pointers on what I can do to get a better match,
Thanks
Trevor
EI2GLB
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