Quad Double quad ?

Quad Double quad ?

Postby mr_wlan » Sat Aug 03, 2002 5:29 am

Hi,

I've just written up the quad double quad which funnily enough gives around four times the gain of the single double quad.

the article is located at http://www.frars.org.uk/cgi-bin/render.pl?pageid=1162

regards,

mr_wlan
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Postby lincomatic » Sat Aug 03, 2002 6:01 am

very nice, mr_wlan, thank you for sharing it with us. i will surely build one in the not-too-distant future.

btw, do you have any idea if this design is any good?
i got it from:
http://patraswireless.net/antennas.html

also, do you use software to model your antennae? and if so what is it?
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the quad antenna

Postby mr_wlan » Mon Aug 05, 2002 1:35 pm

Hi Linco,

well that antenna you provide a link to has an impedance by it's nature of 25 ohms, this means that the simplest way to match it to 50 ohms is to use a pair of them, phased up. Using a 3/4 wave transformer will take 25 ohms and give you 100 ohms, 2 100 ohms in parallel will give you 50 ohms, and your feed point.

as for the antenna modelling software - that's a secret!

cheers,

mr_wlan.
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Postby ew123 » Tue Aug 06, 2002 5:18 am

Hello mr_wlan

I have been searching for a phased array antenna for weeks without success. So your antenna is a real hit.

You use UT 141 coax for the phasing assembly. I suppose the exact length of the assembly is important (is this so?). If I want to use different coax (RG 58), what are the parameters I have to pay attention to?

Thanks in advance
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Postby ted » Tue Aug 06, 2002 9:42 am

I am not a microwave expert, but for my knowledge RG58 is a bad choice for these frequences.

And, yes, because these pieces of cable are impedance transformers, the exact (electrical) length is critical. So, if you replace the UT 141 with anything else, there is a fair chance that some adjustment is needed.
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Postby ew123 » Thu Aug 08, 2002 12:49 am

I'm searching for information about the calculation of these phasing assemblies. Does anybody have some information about these matching lines?
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Postby ppp1 » Thu Aug 08, 2002 11:34 pm

Hi there,

I was searching myself for low-profile high-gain atnennas and I came through with the attached file. Matching impedance of this double-eight design is highly dependent of the gap (spacing) between the reflector plane and the actual radiating element.

Although I dont have a VSWR meter for 2.4GHz, practical measurements (against Lucent 24dBi parabolic grid) shown that making the gap 15mm results with the best performance (approx. 14dBi). Someone can safely say that this gap provides the construction with a impedance match somewhat near 50 Ohm.

Another interesting antenna design is the one the following link reffered to: f5ad.free.fr/ANT-QSP_F1AIA_Sextuple_Quad_2310.htm

In the near future, I will attach my USB client on the back of the reflector plane, thus making some short of embedded antenna. The only cable run to my desktop PC will be the USB cable itself. No RF cable, maximum EIRP. Check patraswireless.net/devices.html for more.

Regards

Kostas with PatrasWirelessNetwork

PS: Three more postes will be commited in order to send the pictures.
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Postby ppp1 » Thu Aug 08, 2002 11:35 pm

Post number 2
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Postby ppp1 » Thu Aug 08, 2002 11:35 pm

Post number 3
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Postby ppp1 » Thu Aug 08, 2002 11:36 pm

Final post
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For dipoles phased array

Postby Pow » Tue Aug 20, 2002 12:02 am

The same can be done with four dipoles. Will give you about 15 dBi gain.

http://pow.za.net/panel.html
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double doublequad problem here

Postby Pow » Tue Aug 20, 2002 1:15 am

ppp1, lincomatic:

the problem with double doublequiad (double eight) is that its cool for horizontal polarization but not so cool for vertical polarization.
In your pictures it is horizontal polarization. Turn 90 degrees to get vertical polarization.

This design is used as tv antenna where horizontal polarization is common.

When using vert polariz double doublequad, azimuth half power beamwidth is way smaller than elevation.

(correct me if i'm wrong)
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