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 <[email protected]>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 <[email protected]> wrote: > >> Good reads. >> Thanks Raj >> Paul >> WB8TSL >> >> On Fri, Jun 8, 2012 at 8:00 AM, Azelio Boriani <[email protected] >> >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 < >> [email protected] >> > >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 <[email protected]> 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 <[email protected]> wrote: >> > >> > >> > >> >> >> > >> >> I came across this article. I dont understand Italian! >> > >> >> From RadioKit Elettronica 2003-03 >> > >> >> >> > >> >> https://dl.dropbox.com/u/10377704/IV3QBN%20QuadHelix.pdf >> > >> >> >> > >> >> > >> >> > >> _______________________________________________ >> > >> time-nuts mailing list -- [email protected] >> > >> To unsubscribe, go to >> > >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> > >> and follow the instructions there. >> > >> >> > > >> > > >> > _______________________________________________ >> > time-nuts mailing list -- [email protected] >> > To unsubscribe, go to >> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> > and follow the instructions there. >> > >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
