[time-nuts] Quadrifilar Helix Antenna

Azelio Boriani azelio.boriani at screen.it
Fri Jun 8 23:06:20 UTC 2012


Here the antenna top detail is very very clear (fig.2) on page 2:

http://ap-s.ei.tuat.ac.jp/isapx/2009/pdf/1149.pdf



On Fri, Jun 8, 2012 at 10:29 PM, Azelio Boriani <azelio.boriani at screen.it>wrote:

> OK here a summary of the IV3QBN article (original in Italian) on QFH:
>
>
>
> This article suggests that instead of buying one, you can make your GPS
> antenna. After two
> antenna examples (fig.1 an Amsat plane spiral antenna and fig.2 a 9GHz
> array of patches)
> the author suggests to use a backfire quadrifilar helix, directly fed by a
> 50OHM coax cable.
> The helix is only half a turn, but the pitch is much greater than the
> classic helix.
> The result can be seen in fig.3 and 4. The turn diameter must be an
> integer fraction of the
> lambda, as suggested by Kilgus [C. Kilgus: Resonant Quadrifilar Helix-IEEE
> Transactions on
> Antenna and Propagation. Vol AP-17, May 1969] and the length of the turn
> must be 0.28 times
> the lambda. To compensate for the reactive part of the antenna impedance,
> the trick is to
> make the wire pairs one longer and one shorter than the computed length so
> that one is
> seen as capacitive and the other inductive compensating each other. The 4
> wires are soldered
> on the outer conductor of the coax cable (bottom of the helix, GND) and on
> top of the cable
> two wires (one from each pair) on the center conductor and the other two
> on the outer
> conductor. This way the helix will radiate/receive from the top and the
> gain will be
> maximum in the 40degrees direction (radiation pattern in fig.3). You need
> a piece of UT141
> coax cable and 4 enamelled copper wires 1.5 upto 1.8mm in diameter. The
> longer pair is
> 103mm in length and the shorter is 99mm, the diameter of the helix will be
> 30mm. See fig.5
> for a detail of the helix. At the bottom the distance between the two
> pairs is 5mm and the
> length is 69mm (the shorter) and 73mm (the longer). In fig.6 you can see
> how to solder the
> top of the cable [but the detail is not so clear, IMHO]. The length [69
> and 73? He doesn't
> say explicitly] can be adjusted to trim the return loss but a network
> analyzer or a sweep
> is needed to check the result. The antenna is wound anticlockwise as seen
> from the top. In
> fig.4 you can see the HP8714ES analyzer result for the antenna [that the
> author claims to
> have seen after the first try, without adjusting anything]. To use this
> antenna directly,
> don't forget to put a DC blocking capacitor in order not to short the
> antenna supply from
> the GPS receiver or use a MMIC (MAR3, INA,ERA, MSA) [and a filter would be
> best] to have
> an active antenna.
>
>
>
>
> On Fri, Jun 8, 2012 at 4:05 PM, paul swed <paulswedb at gmail.com> wrote:
>
>> Good reads.
>> Thanks Raj
>> Paul
>> WB8TSL
>>
>> On Fri, Jun 8, 2012 at 8:00 AM, Azelio Boriani <azelio.boriani at screen.it
>> >wrote:
>>
>> > Meanwhile take a look at these:
>> >
>> > http://www.kunstmanen.net/WKfiles/Techdocs/RQHA/RQHA1999-1eng.pdf
>> >
>> > http://w2du.com/r2ch22.pdf
>> >
>> >
>> >
>> http://www.rish.kyoto-u.ac.jp/digitalbeacon/information/Building_QFH_Antenna_Guide.pdf
>> >
>> > http://ap-s.ei.tuat.ac.jp/isapx/2006/pdf/1E2a-5.pdf
>> >
>> > On Fri, Jun 8, 2012 at 1:04 PM, Azelio Boriani <
>> azelio.boriani at screen.it
>> > >wrote:
>> >
>> > > I have made a QFH but then found a Procomm GPS4 in Germany for a good
>> > > price...
>> > >
>> > >
>> > > On Fri, Jun 8, 2012 at 12:49 PM, Raj <vu2zap at gmail.com> wrote:
>> > >
>> > >> Not to worry Azelio, if you could tell us the gist of it. I thought
>> > maybe
>> > >> I could
>> > >> try and brew one for my tbolt.
>> > >>
>> > >> At 08-06-2012, you wrote:
>> > >> >I have tried to translate with Google (yes, I'm Italian but need
>> time
>> > to
>> > >> >translate the whole PDF) but the result is very poor. If you can
>> wait I
>> > >> can
>> > >> >prepare a short summary or a complete traslation (more time).
>> > >> >
>> > >> >On Fri, Jun 8, 2012 at 10:31 AM, Raj <vu2zap at gmail.com> wrote:
>> > >> >
>> > >> >>
>> > >> >> I came across this article. I dont understand Italian!
>> > >> >>  From RadioKit Elettronica 2003-03
>> > >> >>
>> > >> >> https://dl.dropbox.com/u/10377704/IV3QBN%20QuadHelix.pdf
>> > >> >>
>> > >>
>> > >>
>> > >> _______________________________________________
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>> > >
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>
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