[amsat-bb] Re: quadrafilar helix for 70cm- ambiguous design specs
domenico.i8cvs at tin.it
Wed Sep 30 05:34:36 PDT 2009
Hi Frank, KB1QZH
The best starting point is the original article of the inventor of QHA i.e
Walter Maxell, W2DU
In a separate email I have attached the above fundamental article.
----- Original Message -----
From: "Franklyn A. Ballentine, jr" <art.ballentine at gmail.com>
To: "i8cvs" <domenico.i8cvs at tin.it>
Cc: "AMSAT-BB" <amsat-bb at amsat.org>
Sent: Tuesday, September 29, 2009 6:45 PM
Subject: Re: [amsat-bb] Re: quadrafilar helix for 70cm- ambiguous design
I have a question along the same line. Is the QHA in the ARRL
Satellite Handbook \ Antenna handbook, a good starting place?
On Tue, Sep 29, 2009 at 11:17 AM, i8cvs <domenico.i8cvs at tin.it> wrote:
> ----- Original Message -----
> From: "Tim Goodrich" <tim at timgoodrich.net>
> To: <amsat-bb at amsat.org>
> Sent: Monday, September 28, 2009 9:45 PM
> Subject: [amsat-bb] quadrafilar helix for 70cm- ambiguous design specs
>> Hi All,
>> The house I just bought precludes me from even using my arrow inside as
>> there must be something un-RF friendly in the walls. Therefore, I was
>> looking for a roof antenna and the October QST article on the QFH
>> me to build one. However, after doing some research, I have come up with
>> sets of design specs and I'm unsure which one is correct.
>> I converted everything from you're the 146Mhz QST model to 436Mhz.
>> when I plug that info into http://www.jcoppens.com/ant/qfh/calc.en.php
>> The values it puts out are different in the "compensated length" field.
>> only difference is this model calculates for a full turn as opposed to a
>> half turn, but the lengths shouldn't be as different as it says. Under
>> QST model, I get a wavelength of 688mm, but under the website's model, it
>> gives me a "compensated wavelength" of 729mm.
>> The values I used to calculate are:
>> Can anyone tell me which specs to use and/or explain this compensated
>> wavelength issue?
>> Thank you,
> Hi Tim, KI6VBY
> Read please the book "REFLECTION" Transmission Lines and Antennas by
> M. Walter Maxwell, W2DU Chapter 22 The Quadrifilar Helix Antenna pages
> 22-1 to 22-23 and also
> "Experimental Investigation of Quadrifilar Helix Antennas for 2400 MHz"
> AMSAT Journal May/June 2004
> In a separate email I have sent to you both articles as an attachement.
> 73" de
> i8CVS Domenico
> Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
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