[SECC] Balloons and antennas

[K4SB]

In my experience, and I've run half waves with balloons many times,
you should get a larger size balloon of at least 4 feet and preferably
5. You don't need anything above that. Reason is that helium can
actually escape through the walls of a container made of any of our
hardest steels or materials. Granted, it take a while, but it will do
it. By using the larger balloon, you keep the thickness of the balloon
when inflated to carry the weight below that it would be if you used a
smaller one; hence more wall thickness.

Feed at the bottom should be through a parallel LC network. If I
remember correctly,
you need an inductance of about 23, and around 300 pf of capacitance.
I usually use RG8 which is about 30 pf per foot. Tape about 4 turns
from the bottom of the coil, and keep on until you have a 1:1 match.

One word of caution, keep the bottom end of the raised vertical at
ground potential
until you have attached it to the top of the coil/cap combo. Or, if
you're curious as to why, try touching the end after it's been up for
about 5 minutes.

One other thing I've always done is to stretch a small rope or heavy
twine between 2 trees or other supports as high as I can and use that
to support the bottom xxxx length of the vertical. I use #16 for this
as weight is not a consequence, and then #18 for the rest.

Be SURE you use a piece of string at least 12 inches long between the
top of the vertical and the balloon tie off.

Lastly, pray for a calm night  

73
Ed

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