2.4 Ghz SWR Meter
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From: amdx on 24 Jun 2008 11:57 I'm thinking about building a device to measure the input impedance of WiFi antennas. The simplest device I see is shown here http://pe2er.nl/wifiswr/ It's an SWR meter that uses a uses a wifi signal to drive the antenna. Any thoughts or suggestions before I order parts? Mike
From: Jeff Liebermann on 24 Jun 2008 16:16 On Tue, 24 Jun 2008 10:57:17 -0500, "amdx" <amdx(a)knology.net> wrote: > I'm thinking about building a device to measure the input impedance of WiFi >antennas. The simplest device I see is shown here http://pe2er.nl/wifiswr/ >It's an SWR meter that uses a uses a wifi signal to drive the antenna. I use a sweep generator HP8620a or Wiltron something, a directional coupler or reflection coefficient bridge, and a scope. Without a sweep generator or network analyzer, the VSWR bridge is kinda wasted. For antennas, you want to know the VSWR across the entire 2400-2583.5MHz band, and then some. > Any thoughts or suggestions before I order parts? > Mike Nope. It works. I've built two. Adjusting the balance cap is a problem as it changes when I move the bridge, install the cover, and move things around. Build it solidly and inside a case so you won't lose the null. I didn't use a meter. The output went to a scope. If you can find scrap polysulfone PCB material, use it instead of G10/FR4. Less lossy. If using a Wi-Fi router for a signal source, you'll have problems seeing anything on the meter without the peak detector circuit. There's VSWR bridge in the middle of this page, somewhere, maybe: <http://yves.maguer.free.fr/WiFi/page_wifi_yves.html> Also: <http://www.qsl.net/n9zia/wireless/appendixF.html> The commercial Wiltron versions: <http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=120270695813> <http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220162346759> -- 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
From: msg on 24 Jun 2008 17:11 Jeff Liebermann wrote: <snip> > > If using a Wi-Fi router for a signal source, you'll have problems > seeing anything on the meter without the peak detector circuit. <snip> Once again Jeff, are you ready to help the cause by acquiring (by hook or crook) the airsleuth stuff? They have code to do a sweep generator using the Proxim HomeRF stuff as well as their spectrum analyzer. Since there is more hardware out and about unmarried to their s/w, it would be nice to know what may be necessary to induce nuptials. Michael
From: amdx on 24 Jun 2008 17:39 "Jeff Liebermann" <jeffl(a)cruzio.com> wrote in message news:cpj26413pr26h3aq44oujf52ishfab8s09(a)4ax.com... > On Tue, 24 Jun 2008 10:57:17 -0500, "amdx" <amdx(a)knology.net> wrote: > >> I'm thinking about building a device to measure the input impedance of >> WiFi >>antennas. The simplest device I see is shown here http://pe2er.nl/wifiswr/ >>It's an SWR meter that uses a uses a wifi signal to drive the antenna. > > I use a sweep generator HP8620a or Wiltron something, a directional > coupler or reflection coefficient bridge, and a scope. Without a > sweep generator or network analyzer, the VSWR bridge is kinda wasted. > For antennas, you want to know the VSWR across the entire > 2400-2583.5MHz band, and then some. Thanks for the input Jeff, I don't have any Ghz equipment so when I build an antenna I don't really know what I hav other than it works. I've compared signal strengths on the computers wireless utility so I know which is better, but not what makes an antenna match better. >> Any thoughts or suggestions before I order parts? >> >> Mike > > Nope. It works. I've built two. Adjusting the balance cap is a > problem as it changes when I move the bridge, install the cover, and > move things around. Build it solidly and inside a case so you won't > lose the null. > When you mention balance cap, do you mean the cu foil that you trim or add. If so? I think you adjust this with a 50 ohm dummy load, to zero the output? I don't really see this? I think we're adjusting the 49.9 ohm resistors capacitance to ground. Tell me what you can, I'll have to study it more. Are you recommending a case on the head unit? PCB material ok? > I didn't use a meter. The output went to a scope. You monitor the dc level with your scope? Never mind, I see that is a pulse coming out of the head unit. > If you can find scrap polysulfone PCB material, use it instead of > G10/FR4. Less lossy. I have some Rogers Duroid .031", 5880 I think > If using a Wi-Fi router for a signal source, you'll have problems > seeing anything on the meter without the peak detector circuit. Interesting, why do you think the author says it (the peak hold switch) is not needed? I think we're talking about the same thing! Did you use the BAT 62-03W diode? If not what did you use? Some one recommended the BAT 62-02W it's smaller so should be ok, and I can get it. Thanks again, Mike
From: Jeff Liebermann on 24 Jun 2008 20:06
On Tue, 24 Jun 2008 16:11:33 -0500, msg <msg@_cybertheque.org_> wrote: >Jeff Liebermann wrote: > ><snip> >> >> If using a Wi-Fi router for a signal source, you'll have problems >> seeing anything on the meter without the peak detector circuit. > ><snip> > >Once again Jeff, are you ready to help the cause by acquiring >(by hook or crook) the airsleuth stuff? They have code to >do a sweep generator using the Proxim HomeRF stuff as well >as their spectrum analyzer. Since there is more hardware >out and about unmarried to their s/w, it would be nice to >know what may be necessary to induce nuptials. Nope. Not interested, too busy, too lazy, it's summer, I got better things to do, no money in it, no fun, I hate grinding code, HomeRF is dead, etc. -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 jeffl(a)comix.santa-cruz.ca.us # http://802.11junk.com jeffl(a)cruzio.com # http://www.LearnByDestroying.com AE6KS |