[Towertalk] LPDAs (vs. SteppIR vs. F12 XR5)

[n4kg@juno.com]

While the SteppIR does have a fixed 16 ft boom length,
that is NO WORSE than any of the popular 3L tribanders
such as the A3, TA33, TH3, HG Explorer on 14 ft booms
or the CL33 on an 18 ft boom.  The .35WL 'optimum' is
also a compromise between gain and F/B and is somewhat
forgiving.  One needs to go to 5 elements on a 0.75 WL boom
to realize a significant improvement over a good 3L Yagi.

On 10M, the SteppIR suffers from lower than optimum F/B.
On 20M, the gain is maybe 1 dB below a 24 ft boom.
These are NOT severe compromises for continuous coverage
from 14 to 30 MHz (actually 50 MHz where the compromises
are more severe).

The Force 12 XR5 is a VERY GOOD  5 Band antenna with
2 primary active elements on each band (10, 12, 15, 17, 20M)
and good bandwidth.

The Cushcraft X7 is another good triband Yagi on an 18 ft boom
utilizing a 4 element Log Cell DE and parasitic reflectors and
director with heavy duty construction at an attractive price.

Small LP antennas offer comparable gain and F/B over a
continuous spectrum from 14 through 30 MHz.

ANY of the above are  GOOD  CHOICES, allowing the consumer
to pick the best compromise for HIS situation.

We should be glad we have such nice choises available to us !

Tom  N4KG

On Thu, 14 Nov 2002 "EUGENE  SMAR" <spelunk.sueno@prodigy.net> writes:
> TT:
> 
>      It seems to me that the main advantage of the SteppIR concept 
> is that
> the operator gets a warm-and-fuzzy feeling about SWR everywhere he 
> decides
> to operate. Other than that, it seems like it's a compromise across 
> the
> bands except for the narrow frequency range where F/B or forward 
> gain is
> optimal.
> 
>      The LPDA, OTOH, is also a compromise - in gain vs boom length.  
> One
> gets the same warm-and-fuzzy feeling about SWR, but with no moving 
> parts to
> worry about, and with somewhat more consistent F/B and forward gain 
> across
> its design range.
> 
>      Nothing's ever easy, is it?
> 
> 73 de
> Gene Smar  AD3F
> 
> -----Original Message-----
> From: Jon Ogden <na9d@speakeasy.net>
> To: Jim@ShawResources.com <Jim@ShawResources.com>; Dino Darling
> <k6rix@arrl.net>; towertalk@contesting.com 
> <towertalk@contesting.com>
> Date: Thursday, November 14, 2002 2:01 PM
> Subject: Re: [Towertalk] LPDAs...
> 
> 
> >on 11/14/02 10:51 AM, Jim Shaw at Jim@ShawResources.com wrote:
> >
> >> QUESTION:  Instead of an LPDA, why not use a 3 element SteppIR 
> antenna?
> >> Don't they cover all frequencies continuously from 13.9 to 30 
> MHz?  Isn't
> >> that similar to the design goal of an LPDA?  Seems like a SteppIR 
> should
> >> easily cover MARS frequencies in that range.  Just asking cause I 
> have no first hand experience with either and LPDA or a SteppIR.
> >
> >The SteppIR antenna has been discussed here ad nauseum.  My main 
> issues with the SteppIR:
> >
> >1.) Mechanical.  How reliable is it?  What about condensation 
> inside the
> >motor, etc. and then what about when all that moisture freezes?  It 
> would
> >just suck the royal you know what to have your antenna freeze up in 
> the
> >middle of January when chasing that rare DX.
> >
> >2.) Only 3 elements.
> >
> >3.) As others have said, the element spacing is only optimized for 
> one band.
> >
> >4.) It's expensive for just 3 elements.
> >
> >While the SteppIR I would think certainly have a lot going for it 
> over a 3
> >element Yagi, I don't think its performance can compare with some 
> of the bigger multiband Yagis.
> >
> >It's an interesting antenna and for some people and some 
> installations,perhaps quite a good one.
> >
> >73,
> >
> >Jon
> >NA9D
> >
> >-------------------------------------
> >Jon Ogden
> >NA9D (ex: KE9NA)
> >

________________________________________________________________
Sign Up for Juno Platinum Internet Access Today
Only $9.95 per month!
Visit www.juno.com