Helix antenna
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From: jimmie68 on 1 Aug 2008 16:33 On Jul 31, 1:12 am, m...(a)sushi.com wrote: > On Jul 30, 1:57 pm, jimmi...(a)gmail.com wrote: > > > > > > > On Jul 29, 11:47 pm, m...(a)sushi.com wrote: > > > > On Jul 29, 1:52 pm, jimmi...(a)gmail.com wrote: > > > > > In WiFi is there any standard convention for the polarity of a helical > > > > antenna. I am building a 40 turn unit and wanted to know whether I > > > > should build it right or left handed. > > > > > Yes I know this will only matter when trying to connect with other > > > > systems that use circular polarity. > > > > > Jimmie > > > > Please post how it works out. Also, have you considered building a 4 > > > 10 turn helix (heli?) and run in parallel. That gets around the > > > matching issue. > > > Yes, I thought about that but I have plans for the 40 turn unit > > including the matching device. Also I have access to a Network > > Analyzer and S pararamter test set for tuning it up. I think building > > the matching network may be easier than build a phasing harness for 4 > > Helix antennas. However I have never done this before so plans may > > change. Who knows, if things work out OK I may build a 4 X 40 turn > > device. > > > Jimmie > > My guess is paralleling the 4 helix antennas would have a broader > bandwidth than the impedance matched solution. Broadband is good in > the sense that it allows for more error in the construction.- Hide quoted text - > > - Show quoted text - Usually paralelling(stacking) antennas means a narrower bandwidth. This statement assumes all the stacked antennas are identical. Jimmie
From: jimmie68 on 1 Aug 2008 20:09 On Aug 1, 4:33 pm, jimmi...(a)gmail.com wrote: > On Jul 31, 1:12 am, m...(a)sushi.com wrote: > > > > > > > On Jul 30, 1:57 pm, jimmi...(a)gmail.com wrote: > > > > On Jul 29, 11:47 pm, m...(a)sushi.com wrote: > > > > > On Jul 29, 1:52 pm, jimmi...(a)gmail.com wrote: > > > > > > In WiFi is there any standard convention for the polarity of a helical > > > > > antenna. I am building a 40 turn unit and wanted to know whether I > > > > > should build it right or left handed. > > > > > > Yes I know this will only matter when trying to connect with other > > > > > systems that use circular polarity. > > > > > > Jimmie > > > > > Please post how it works out. Also, have you considered building a 4 > > > > 10 turn helix (heli?) and run in parallel. That gets around the > > > > matching issue. > > > > Yes, I thought about that but I have plans for the 40 turn unit > > > including the matching device. Also I have access to a Network > > > Analyzer and S pararamter test set for tuning it up. I think building > > > the matching network may be easier than build a phasing harness for 4 > > > Helix antennas. However I have never done this before so plans may > > > change. Who knows, if things work out OK I may build a 4 X 40 turn > > > device. > > > > Jimmie > > > My guess is paralleling the 4 helix antennas would have a broader > > bandwidth than the impedance matched solution. Broadband is good in > > the sense that it allows for more error in the construction.- Hide quoted text - > > > - Show quoted text - > > Usually paralelling(stacking) antennas means a narrower bandwidth. > This statement assumes all the stacked antennas are identical. > > Jimmie- Hide quoted text - > > - Show quoted text - This should be of interest to anyo one wanting to build a helix antena. http://www.qsl.net/ve3cvg/antennas/2400/ Jimmie
From: miso on 2 Aug 2008 02:18 On Aug 1, 1:33 pm, jimmi...(a)gmail.com wrote: > On Jul 31, 1:12 am, m...(a)sushi.com wrote: > > > > > On Jul 30, 1:57 pm, jimmi...(a)gmail.com wrote: > > > > On Jul 29, 11:47 pm, m...(a)sushi.com wrote: > > > > > On Jul 29, 1:52 pm, jimmi...(a)gmail.com wrote: > > > > > > In WiFi is there any standard convention for the polarity of a helical > > > > > antenna. I am building a 40 turn unit and wanted to know whether I > > > > > should build it right or left handed. > > > > > > Yes I know this will only matter when trying to connect with other > > > > > systems that use circular polarity. > > > > > > Jimmie > > > > > Please post how it works out. Also, have you considered building a 4 > > > > 10 turn helix (heli?) and run in parallel. That gets around the > > > > matching issue. > > > > Yes, I thought about that but I have plans for the 40 turn unit > > > including the matching device. Also I have access to a Network > > > Analyzer and S pararamter test set for tuning it up. I think building > > > the matching network may be easier than build a phasing harness for 4 > > > Helix antennas. However I have never done this before so plans may > > > change. Who knows, if things work out OK I may build a 4 X 40 turn > > > device. > > > > Jimmie > > > My guess is paralleling the 4 helix antennas would have a broader > > bandwidth than the impedance matched solution. Broadband is good in > > the sense that it allows for more error in the construction.- Hide quoted text - > > > - Show quoted text - > > Usually paralelling(stacking) antennas means a narrower bandwidth. > This statement assumes all the stacked antennas are identical. > > Jimmie I see no reason for stacked antennas to have a narrower bandwidth. Can you elaborate?
From: miso on 2 Aug 2008 02:28 On Aug 1, 5:09 pm, jimmi...(a)gmail.com wrote: > On Aug 1, 4:33 pm, jimmi...(a)gmail.com wrote: > > > > > On Jul 31, 1:12 am, m...(a)sushi.com wrote: > > > > On Jul 30, 1:57 pm, jimmi...(a)gmail.com wrote: > > > > > On Jul 29, 11:47 pm, m...(a)sushi.com wrote: > > > > > > On Jul 29, 1:52 pm, jimmi...(a)gmail.com wrote: > > > > > > > In WiFi is there any standard convention for the polarity of a helical > > > > > > antenna. I am building a 40 turn unit and wanted to know whether I > > > > > > should build it right or left handed. > > > > > > > Yes I know this will only matter when trying to connect with other > > > > > > systems that use circular polarity. > > > > > > > Jimmie > > > > > > Please post how it works out. Also, have you considered building a 4 > > > > > 10 turn helix (heli?) and run in parallel. That gets around the > > > > > matching issue. > > > > > Yes, I thought about that but I have plans for the 40 turn unit > > > > including the matching device. Also I have access to a Network > > > > Analyzer and S pararamter test set for tuning it up. I think building > > > > the matching network may be easier than build a phasing harness for 4 > > > > Helix antennas. However I have never done this before so plans may > > > > change. Who knows, if things work out OK I may build a 4 X 40 turn > > > > device. > > > > > Jimmie > > > > My guess is paralleling the 4 helix antennas would have a broader > > > bandwidth than the impedance matched solution. Broadband is good in > > > the sense that it allows for more error in the construction.- Hide quoted text - > > > > - Show quoted text - > > > Usually paralelling(stacking) antennas means a narrower bandwidth. > > This statement assumes all the stacked antennas are identical. > > > Jimmie- Hide quoted text - > > > - Show quoted text - > > This should be of interest to anyo one wanting to build a helix > antena. > > http://www.qsl.net/ve3cvg/antennas/2400/ > > Jimmie When I build antennas, I try to use all copper if I can. Otherwise, you get a battery connecting Al to copper. I'm not sure about connecting copper to galvanized. I've built a few log periodics (VHF/ UHF) and used that gunk (OK, not a technical term) used with Al wiring. Still, it deteriorates with time. Consider using copper wire. Have you considered the biquad? Unless you have circular polarization on both ends, you will lose 3db when interfacing with linear polarized antennas, so 16db becomes 13db, which is close to the biquad. I guess a long helix would be better for snooping purposes since not everyone is vertically polarized.
From: Jeff Liebermann on 2 Aug 2008 11:58 On Fri, 1 Aug 2008 23:18:03 -0700 (PDT), miso(a)sushi.com wrote: >On Aug 1, 1:33�pm, jimmi...(a)gmail.com wrote: >> Usually paralelling(stacking) antennas means a narrower bandwidth. >> This statement assumes all the stacked antennas are identical. >> Jimmie >I see no reason for stacked antennas to have a narrower bandwidth. Can >you elaborate? If your definition of bandwidth is the frequency between the -3dB points, stacking two isolated resonant antennas together results in exactly the same bandwidth as one antenna. An easier way to see this is if the two antennas were simple parallel tuned circuits acting as a bandpass filter. If you connect them together, using some means of coupling that is critically coupled (i.e. maximum power tranfer), the resultant circuit has exactly the same bandwidth. If you plot it on a piece of graph paper, you could stack a dozen critically coupled tuned circuits together and get exactly the same -3dB bandwidth. Obviously the skirt factor and bandwidth at other refrence points will be narrower as you add sections. Of course, such things fall apart when dealing with real world devices and antennas. Two stacked antennas will couple to each other, causing difficulties with such simplistic explanations. The traditional 2x2 array of helixes heavily couple to each other, especially since they're the same sense. Anyway, the only way to get it right is to fire up your favorite NEC antenna modeling program, which takes such things into consideration. 4NEC2 includes a helix generator. Specifically for a helix, the approximate -3dB bandwidth for a single helix is roughly equal to the center frequency. In other words, if you cut a helix for 2.4GHz, it will be usable from 1.2 to 3.6Ghz. Stacking 4 of these together will theoretically not reduce this bandwidth, but in reality, will reduce it somewhat. I don't think operation in an 83.5MHz band is going to be affected with an antenna with a 1 or 2Ghz bandwidth. -- Jeff Liebermann jeffl(a)cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
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