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Sunday, December 30, 2012

A homemade antenna for marine freqs! The Bad A Boatenna!

Many Have ask me about various antennas in the past for other things besides amateur radio. Upon occasion I do build one from time to time for other uses but one thing always remains the same no matter what part of the spectrum you are creating an antenna for......Math. I have also had a few friends in the past ask me to push them a detailed plan on how to build antennas for thier use. So here is an attempt at giving some instructions for making a decent antenna for the marine band. Since the marine band is only a few mhz from the amateur radio portion of VHF its pretty easy so lets look at a tried and true design and break down some measurements to make it simple. Most of the VHF freqs are from 156-158 Mhz or so so we will do the math for 157.

1/4 wave =  1ft. 5 - 29/32in. or 0.454 M
1/2 wave =  2ft. 11 - 25/32in. or 0.909 M

So using these calculations lets throw is on a collinear!


Now when your done stick it inside PVC pipe for a radome and have fun. Use a smaller former for the coil if you want the antenna slimmer and add in a common mode choke with about 2 feet of coax if it gives you tuning issues! Not happy with 2 half waves? add a coil and another half wave! you can keep on stacking until you are out of wire. Other than that good luck!