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Author Topic: CRANKIR antenna  (Read 3241 times)
AE5EK
Member

Posts: 53




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« on: April 02, 2013, 12:33:02 PM »

See steppir.com for pictures of this new antenna.  The active portion of the antenna seems to change in either length or position or both.
Notice the gap in the antenna wire in the top left.
Apparently it can be tuned over multiple bands. 
Any thoughts other can share about this antenna and how a folded vertical works? they claim it is within .3 dB of a normal vertical.
Has any one ever modeled a folded vertical?

tks

Dennis
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WB6BYU
Member

Posts: 13026




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« Reply #1 on: April 02, 2013, 12:51:33 PM »

There isn't anything out of the ordinary about the antenna.  Lots of hams
have put up a vertical wire (or a dipole for that matter) and bent the ends
around to fit when they ran out of space.  That's all this does (at least on
40m and the other bands where the antenna is less than 1/4 wave tall.)

I modeled a similar antenna, but with less horizontal width to it.  In my case
I used a single wire that went around two pulleys with an insulator between
the ends:  by feeding it through the bottom pulley (and assuming good
contact) both sides of the wire would act as verticals, so it could be designed
to operate on two different bands at a single setting.

Generally your radiation resistance drops as the antenna is shortened and the
wire end gets closer to the ground, but even with 1/3 of the wire folded over
there is little loss of signals strength.  SteppIR improved 40m performance by
making the antenna wider so that, for a given wire length, the far end is further
off the ground.

You still need an effective ground system, just as with any other quarter wave
vertical.

No magic, and no reason to suggest that it doesn't work as they claim.  It's
certainly consistent with the modeling results I've had for similar antennas,
though I haven't actually tried building one yet.
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KH6DC
Member

Posts: 634




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« Reply #2 on: April 03, 2013, 12:32:03 AM »

Looks like a vertical Moxon.  I may be interested in buying the 6-80m version when released.
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73 and Aloha,
de Delwyn, KH6DC
WB6BYU
Member

Posts: 13026




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« Reply #3 on: April 03, 2013, 07:07:06 AM »

It may look like a Moxon, but there is no directivity to the pattern.
It is just a quarter wave vertical wire bent over at the top to reduce
the required height on 40m and 30m.
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