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Tuning trim/add to EFHW antenna?

Jul 10th, 08:51

USAF_VET

Joined: Aug 22nd 2017, 16:21
Total Topics: 0
Total Posts: 0
I have a 40m EFHW antenna that works well considering all things. It's routed up a cedar pole, over a roof (w/18" stand-off), and over to a cherry tree ... the HOA cops haven't spotted it yet!

The SWR min is coming in lower than the design (the route and proximity issues detune the antenna). I'm just using the built in SWR meter in my ICOM IC-7100, FYI. Close 'nuf.

Is there a way to calculate how much antenna wire I need to add or subtract if I know the difference in frequency and what direction the SWR minimum needs to go to be optimal?

Thanks ... been around for awhile but still a newb..

Brian
Jul 12th, 08:51

W1VT

Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
You could could use antenna modeling software to figure out what it does in an idealized situation and extrapolate that to your installation, but the most practical solution is to get an an Antenna Analyzer to do SWR sweeps of the antenna to speed up the cut and try.

Zak W1VT
ARRL Senior Lab Engineer

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