The SteppIR is catching on and seems to have a loyal following, so it's a
success.
However, here are the LPDA advantages that I find, as a user:
-No moving parts to wear out or fail
-Maintains excellent F/B over its entire range of frequencies
-Zero time required to change bands, not even a second
-More bang for the buck, e.g., lower cost for equivalent performance
-VSWR satisfactory everywhere, over the >1 octave range
Drawbacks to the LPDA? Wind loading and turning radius, for sure, as back
end elements are huge, typically >0.6-wavelength or longer for the lowest
frequency. And the booms are hot, so must be well insulated from its
support. And, for a given boomlength, not as much gain as a single-band
Yagi, for sure. Then, trapped multiband antennas don't, either...nor does
the SteppIR, since it's optimum spaced for only one band. The SteppIR can
obviously be adjusted to make a beam pattern over an octave or more, and to
create a good match to its feedline, by infinitely varying all the element
length combinations; but it will never be optimized on more than one band
because of the fixed element spacing.
Can't comment on SteppIR wind/WX survivability, etc, since I don't think any
have been up long enough yet. In a few years, we'll know more on that one!
-WB2WIK/6
"If everything seems under control, you're just not going fast enough." -
Mario Andretti
> -----Original Message-----
> From: Jim Shaw [SMTP:Jim@shawresources.com]
> Sent: Thursday, November 14, 2002 8:52 AM
> To: Jon Ogden; Dino Darling; towertalk@contesting.com
> Subject: RE: [Towertalk] LPDAs...
>
> 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.
>
>
> 73 de Jim WA6PX
> JGShaw@Alumni.HAAS.org
>
> -----Original Message-----
> From: towertalk-admin@contesting.com
> [mailto:towertalk-admin@contesting.com]On Behalf Of Jon Ogden
> Sent: Thursday, November 14, 2002 6:41 AM
> To: Dino Darling; towertalk@contesting.com
> Subject: Re: [Towertalk] LPDAs...
>
>
> on 11/14/02 12:17 AM, Dino Darling at k6rix@arrl.net wrote:
>
> > I learned more about LPDA's from this article than anything I've read to
> > date! I will have to re-read the article myself, but I remember talk
> about
> > front-to-back figures that were BETTER than a small yagi.
>
> I could believe they have better F/B than a small Yagi. I also believe
> that
> a good sized LPDA would outperform a small beam. However, I am not
> completely sold on the idea of absolutely better performance.
>
> I'll have to look into it since I am currently perusing what sort of
> antenna
> to get to replace my TA-33.
>
> 73,
>
> Jon
> NA9D
>
> -------------------------------------
> Jon Ogden
> NA9D (ex: KE9NA)
>
> Citizen of the People's Democratic Republik of Illinois
>
> Life Member: ARRL, NRA
> Member: AMSAT, DXCC
>
> http://www.qsl.net/na9d
>
> "A life lived in fear is a life half lived."
>
>
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