Raj, it was not a trouble: on the contrary it was a good exercise. I made a QFH some time ago but it was not quite successful. After this reading I will try again. I have an Advantest R3765A vector network analyzer (40MHz - 3GHz) so I can tell if the antenna can work.
On Sat, Jun 9, 2012 at 11:36 AM, Rob Kimberley <robkimber...@btinternet.com>wrote: > I had a go at making one in 1986 for a broken NBS unit (huge two 19" RMK, > single channel GPS), which had been damaged in transit. Used small sections > of semi-rigid coax soldered together. > > It worked well enough to track SVs and get data we needed. > > Rob K > > -----Original Message----- > From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On > Behalf Of Azelio Boriani > Sent: 08 June 2012 21:29 > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Quadrifilar Helix Antenna > > 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 <paulsw...@gmail.com> wrote: > > > Good reads. > > Thanks Raj > > Paul > > WB8TSL > > > > On Fri, Jun 8, 2012 at 8:00 AM, Azelio Boriani > > <azelio.bori...@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_A > > ntenna_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.bori...@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 <vu2...@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 <vu2...@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 > > > >> >> > > > >> > > > >> > > > >> _______________________________________________ > > > >> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go > > > >> to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > > >> and follow the instructions there. > > > >> > > > > > > > > > > > _______________________________________________ > > > time-nuts mailing list -- time-nuts@febo.com > > > To unsubscribe, go to > > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > > and follow the instructions there. > > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.