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Author Topic: Is there a base HF vertical antenna that telescope  (Read 708 times)

Posts: 14

« on: June 08, 2002, 04:03:01 PM »

I would like to install a base HF (40 -10 meters)antenna that would be small when collapsed, but tall when extended.  Is there a base station vertical that does this?  It seems like it would be perfect for "stealthy" antennas, but I haven't seen any so far except the High Sierra and they only collapse 1-1.5 feet...any ideas?  It seems to me that if we can rotate them, we can make then go up and down...thanks, John

Posts: 3585

« Reply #1 on: June 08, 2002, 05:25:14 PM »

Hmm - that would be an interesting project. My first thought would be an extendable conductive tape like the Fluidmotion Yagi's. But that would requre a fixed tube to extend into.

I 'spect that something like the compressed air or pressurized oil operated towers, with a matching network at the base, would get the job done. Several sections of polished stainless steel, with wiping contacts and seals between sections, a means of extending just the right amount of tower, and an air compressor or an oil pump to extend the tower. Pretty complex and by no means cheap - but it could be done.

73  Pete Allen  AC5E

Posts: 36

« Reply #2 on: June 08, 2002, 08:54:49 PM »

Only masts you can strap the vertical to and those go up and down clumsily by hand.  There are big ones that do it but those are hardly stealth.  They also require guys at a certain height or they begin to look like upside down letter "J"s -- the original J-pole. Nice product  idea, though.  Crank it up at night and then pull it down and the neighbors are none the wiser.

Posts: 2080

« Reply #3 on: June 10, 2002, 10:30:16 AM »

Hello John,

I am currently experimenting with the very lightweight MFJ fibergalsss telescoping mast ($79.95).  You can attach a wire to the tip and run it up quite easily (manually) to 33 feet.  With a few radials at the base and a tuner I have a 10-40 vertical that is easy to put up and take down and pretty stealthy too.  For more info on my idea for a (FluidMotion) SteppIR-type tunable vertical, see my post from a few weeks back.  (I would extend the fiberglass tube all the way up and leave it there, then run the radiating wire up and down the inside of the tube with a motor to tune for the desired frequency)  I'd be interested in hearing any successes anyone has with this approach.  More here:

Good luck and have fun!

73, Terry, WØFM

Posts: 61

« Reply #4 on: June 10, 2002, 12:22:45 PM »

Check out the Sommer web site and particularly their T-25 vertical. I don't know if it is designed to be repeatedly expanded and contracted, but it is shipped in the contracted position.

Good luck in your search!

73s de KC7CRR

Posts: 17284

« Reply #5 on: June 10, 2002, 03:41:51 PM »

The biggest problem probably would be getting good electrical
contact between the sections.  I think a tilt-over would be much
easier: you could do it with a home-brew whip made from aluminum
tubing or a commercial antenna such as a 14AVQ.

If you take a  cross connector and screw a length of pipe into
each end you will have two arms that can be used as a pivot,
one for mounting the base of the antenna, and one to attach to
a counterweight (perhaps a plastic dishpan filled with concrete -
stick one end of the pipe in it while it hardens.)  Then you just need
a pair of sawhorses or similar to set the pivot arms on.  With the
right counterweight (and arm length) you could easily pull the
antenna down to horizontal during the day, then swing it up to
vertical at night.  A coat of black paint might help, too.

A low-tech version would be an old tire filled with concrete as is
often used for portable tetherball posts, etc.  Put about a 2' stub
of pipe in the concrete while it sets and mount your antenna on
that.  Then the whole thing can be tipped over to hide the antenna.
You may have to experiment with the amount of weight required to
hold the antenna upright - it will depend on the size of the antenna
and the expected winds.
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