[Antennas] Fluid Motion Antennas

2002年6月28日 16:36:16 -0400 (EDT)

 Dear John:
 Gain is effected by boom length more than anything else. Optimum spacing on 20 meters would call for a boom that is longer than the 16 feet offered by the Fluid Motion beam. However, if the spacing was set at .18 wavelength for 20 meters, it would be too long for a 3 element beam on 15 meters. So by setting the boom length a little shorter, it works on all bands between 20 meters and 6 meters.
 I think the point is that spacing varies from one band to the next, but they have selected what would be somewhat close spacing on 20 meters with greater spacing on each successive band up to 6 meters. Gain is respectable on all bands (not maximium, but not far off either) and the FTB is excellent. Lastly, by tuning each frequency to a 1:1 SWR (or close), you have a very efficient match where ever you use it. I would suspect this antenna (the 3 element model) probably equals or comes very close to a 3 element monobander over all of its operating range.
 Good idea as long as the moving parts keep moving!
Ron W7MRR
 --- On Thu 06/27, John McClain wrote:
From: John McClain [mailto: [email protected]]
To: [email protected],[email protected]
Date: Thu 06/27
Subject: Re: [Antennas] Fluid Motion Antennas
> I read somewhere (maybe Fluid Motion's web page) that the element
> spacing was not critical on these antennas because it can be overcome
> by the fact that the elements are always the proper length no matter
> what the frequency. The article went on to say that it WAS critical
> on multiband trapped beams because there was no one good spacing for
> the elements that was good for all bands but what do I know? If the
> specs that are quoted are accurate, I would say that the performance
> will be pretty good. I currently have a 27 year old TH3-MK3 and I am
> seriously considering replacing it with the 2 element SteppIR but 800ドル
> is a lot of money for a 2-element beam so I am having a difficult time
> making up my mind. Besides the specs, they have some nice features
> especially having the controller interfaced to the rig so that it
> automatically tunes as the VFO is changed. I would be using it on a
> IC-756PRO and a Elecraft K2 but I am not sure if the controller
> supports the K2. Thank you for your thoughts and would really like to
> hear from anyone who has tried the 2-element beam.
>> John
> K7SVV
> K2 #2569
>> ----- Original Message -----
> From: 
> To: ; 
> Sent: Thursday, June 27, 2002 10:28 AM
> Subject: Re: [Antennas] Fluid Motion Antennas
>>> > I think George is totally correct.
> >
> > The antenna design is interesting and we hope you'll keep us
> informed on how
> > it works out.
> >
> > One comment, there was a chap (a W6-??) back in the 1960's that did
> something
> > similar with his own design. He varied the element lengths all over
> the place
> > and as long as the directors were shorter and the reflector was
> longer than
> > the DE, it was pretty hard to screw the gain up to any degree. The F
> to B and
> > bandwidth / SWR varied quite a bit of course. But the one thing that
> really
> > changed the gain significantly was just adding more boom length.
> I've done
> > the same thing with a FS meter and confirmed his results with
> changing fixed
> > tuned elements. But adding more boom made all the difference.
> >
> > It would interesting too if the Fluid Motion antenna had a way
> (probably
> > beyond the cost limits) to vary element spacing as well as element
> length.
> > From what I know of the antenna, you have 3 elements spaced out on a
> boom
> > with no way to move them closer together or farther apart to
> optimize the
> > bands (20M-6M) it covers. If it did, you could then you could really
> change
> > all the parameters.
> >
> > Brian
> > - - -
> >
> > Your moderator for this list is:
> > Larry Wilson KE1HZ [email protected]
> > _______________________________________________
> > Antennas mailing list
> > [email protected]
> > http://mailman.qth.net/mailman/listinfo/antennas
>>> - - - 
>> Your moderator for this list is:
> Larry Wilson KE1HZ [email protected]
> _______________________________________________
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