"John S" wrote in message ...

On 11/23/2014 11:17 AM, Wayne wrote:


"John S" wrote in message ...

I like antennas that are short-circuited DC-wise. Mainly because, at
one time I had a radio on a vertical and lightning struck about a mile
away and blocked my receiver for several seconds. Of course, not all
radios have a floating input, but, it impressed me.

So, I "invented" the folded unipole which would match to a 50 ohm feed.

Any interest?

Yes.

# By the way, Wayne, my interests in antennas have recently been in the
# 70cm band (specifically 434MHz) where there are numerous cheap modules
# to play with. They have only 1 or so mW output and are illegal in the US
# for unlicensed operation except under strict limitations. However, with
# a license, I can do what I wish as long as I comply with the
# regulations. My software always sends my call letters at each
# transmission, for example.

# As for the folded unipole, first imagine a normal unipole. Remember that
# the feed resistance is about 30 or so ohms, yes? So, the recommendation
# is to droop the radials to about -45 degrees. This raises the feed
# resistance to about 50 ohms.

# Now, the folded unipole has a higher feed resistance than we want.
# Hmmmm.. what if we RAISE the radials to compensate? Yeah, stupid, right?

# It works, and I have a model here which exhibits SWR so low I cannot
# measure it except with a vector voltmeter.

# I am not recommending this for the average amateur because tuning the
# antenna is a bit troublesome for many. It is a bit easier to adjust a
# normal unipole's length than a folded unipole's length. That's why I
# haven't pushed it.

Interesting.
But, I would expect the folded unipole to have a feedpoint of about 150 ish
ohms over perfect ground.

Is that the antenna that you have built and tested?