[TowerTalk] 160 meter shunt fed tower

[Dan Schaaf]

ALso, X= 637 means that the antenna is short and the X is capacitive reactance. So you need base loading inductance in series from the coax center conductor to teh feed point.
Then the SWR will come down.
So if you use the inductive  reactance formula XL = 2*PI*F*L and solve for L then you will know how much inductance to use.
Keep in mind that short antennas are high RF voltage at the feedpoint so you will need to make a beefy coil, on a T300A-2 Toroid form. That is the starting point. Then you may have to tweak teh inductance by spreading or squishing together the turns to get the correct resonant point.
Then after you have it tweaked for the frequency you want to use, then coat teh coil with Corona Dope to prevent it from arcing across turns at high power transmitted. I use 14 ga Romex house wire in my coil which is good for 600 volts breakdown. Then coat it with 3 layers of the dope.

Best Regards
Dan Schaaf
K3ZXL www.k3zxl.com
NOBSKA www.nobska.net
Cape Cod Instruments www.gnm-inc.com
Tel: 941-766-0706
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