omnidirectional antenna using 4 biquads

Dumb question perhaps, but here goes. If you arrange 4 biquads in a
rectangular formation and used a power combiner, would you get a
decent omnidirectional antenna? Looking at the biquad pattern
http://martybugs.net/wireless/biquad...ad_azimuth.jpg
the antenna is good for about +-45 degrees. Seems to me you would get
an omnidirectional antenna without too squished of a donut. The
disadvantage is the combiner loss of 6db (ideal).

On Sat, 2 Feb 2008 22:26:54 -0800 (PST), miso@sushi.com wrote in
<bb019663-7b79-41c6-a2a5-65f69c959e44@s19g2000prg.googlegroups.com>:

>Dumb question perhaps, but here goes. If you arrange 4 biquads in a
>rectangular formation and used a power combiner, would you get a
>decent omnidirectional antenna? Looking at the biquad pattern
>http://martybugs.net/wireless/biquad...ad_azimuth.jpg
>the antenna is good for about +-45 degrees. Seems to me you would get
>an omnidirectional antenna without too squished of a donut. The
>disadvantage is the combiner loss of 6db (ideal).

What would be the point?

--
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On Feb 2, 11:15 pm, John Navas <spamfilt...@navasgroup.com> wrote:
> On Sat, 2 Feb 2008 22:26:54 -0800 (PST), m...@sushi.com wrote in
> <bb019663-7b79-41c6-a2a5-65f69c959...@s19g2000prg.googlegroups.com>:
>
> >Dumb question perhaps, but here goes. If you arrange 4 biquads in a
> >rectangular formation and used a power combiner, would you get a
> >decent omnidirectional antenna? Looking at the biquad pattern
> >http://martybugs.net/wireless/biquad...ad_azimuth.jpg
> >the antenna is good for about +-45 degrees. Seems to me you would get
> >an omnidirectional antenna without too squished of a donut. The
> >disadvantage is the combiner loss of 6db (ideal).
>
> What would be the point?
>
> --
> Best regards, FAQ for Wireless Internet: <http://Wireless.wikia.com>
> John Navas FAQ for Wi-Fi: <http://wireless.wikia.com/wiki/Wi-Fi>
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Like I already stated, high gain without a squished donut, i.e.
compared to a colinear.

On Sat, 2 Feb 2008 23:57:24 -0800 (PST), miso@sushi.com wrote in
<3ade6810-a747-4c41-938d-9740eeb77d85@1g2000hsl.googlegroups.com>:

>On Feb 2, 11:15 pm, John Navas <spamfilt...@navasgroup.com> wrote:
>> On Sat, 2 Feb 2008 22:26:54 -0800 (PST), m...@sushi.com wrote in
>> <bb019663-7b79-41c6-a2a5-65f69c959...@s19g2000prg.googlegroups.com>:
>>
>> >Dumb question perhaps, but here goes. If you arrange 4 biquads in a
>> >rectangular formation and used a power combiner, would you get a
>> >decent omnidirectional antenna? Looking at the biquad pattern
>> >http://martybugs.net/wireless/biquad...ad_azimuth.jpg
>> >the antenna is good for about +-45 degrees. Seems to me you would get
>> >an omnidirectional antenna without too squished of a donut. The
>> >disadvantage is the combiner loss of 6db (ideal).
>>
>> What would be the point?

>Like I already stated, high gain without a squished donut, i.e.
>compared to a colinear.

What makes you think it won't be a squished donut, albeit a crude one
(due to uneven horizontal gain pattern)? The coverage of a biquad is
more like 45° than 90°.

--
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<miso@sushi.com> wrote in message
news:bb019663-7b79-41c6-a2a5-65f69c959e44@s19g2000prg.googlegroups.com...
> Dumb question perhaps, but here goes. If you arrange 4 biquads in a
> rectangular formation and used a power combiner, would you get a
> decent omnidirectional antenna? Looking at the biquad pattern
> http://martybugs.net/wireless/biquad...ad_azimuth.jpg
> the antenna is good for about +-45 degrees. Seems to me you would get
> an omnidirectional antenna without too squished of a donut. The
> disadvantage is the combiner loss of 6db (ideal).

The other problem I see is if you use some sort of combiner or phasing
harness the loss associated with such a device would be more or equal to the
gain of any one antenna.

Adair

miso@sushi.com wrote:
> On Feb 2, 11:15 pm, John Navas <spamfilt...@navasgroup.com> wrote:
>> On Sat, 2 Feb 2008 22:26:54 -0800 (PST), m...@sushi.com wrote in
>> <bb019663-7b79-41c6-a2a5-65f69c959...@s19g2000prg.googlegroups.com>:
>>
>>> Dumb question perhaps, but here goes. If you arrange 4 biquads in a
>>> rectangular formation and used a power combiner, would you get a
>>> decent omnidirectional antenna? Looking at the biquad pattern
>>> http://martybugs.net/wireless/biquad...ad_azimuth.jpg
>>> the antenna is good for about +-45 degrees. Seems to me you would
>>> get an omnidirectional antenna without too squished of a donut. The
>>> disadvantage is the combiner loss of 6db (ideal).
>>
>> What would be the point?
>>
>> --
>> Best regards, FAQ for Wireless Internet:
>> <http://Wireless.wikia.com> John Navas FAQ for Wi-Fi:
>> <http://wireless.wikia.com/wiki/Wi-Fi> Wi-Fi How To:
>> <http://wireless.wikia.com/wiki/Wi-Fi_HowTo>
>> Fixes to Wi-Fi Problems:
>> <http://wireless.wikia.com/wiki/Wi-Fi_Fixes>
>
> Like I already stated, high gain without a squished donut, i.e.
> compared to a colinear.

huh - just a random google search yielded this typical construction ?
http://www.larsen-b.com/Article/201.html

On Feb 3, 7:57 am, "Adair Winter" <ada...@swbell.net> wrote:
> <m...@sushi.com> wrote in message
>
> news:bb019663-7b79-41c6-a2a5-65f69c959e44@s19g2000prg.googlegroups.com...
>
> > Dumb question perhaps, but here goes. If you arrange 4 biquads in a
> > rectangular formation and used a power combiner, would you get a
> > decent omnidirectional antenna? Looking at the biquad pattern
> >http://martybugs.net/wireless/biquad...ad_azimuth.jpg
> > the antenna is good for about +-45 degrees. Seems to me you would get
> > an omnidirectional antenna without too squished of a donut. The
> > disadvantage is the combiner loss of 6db (ideal).
>
> The other problem I see is if you use some sort of combiner or phasing
> harness the loss associated with such a device would be more or equal to the
> gain of any one antenna.
>
> Adair

No, the loss is very close to 6dB. Gain should be around 14db prior to
loss. What might make a difference is the aperture.

On Feb 3, 12:24 am, John Navas <spamfilt...@navasgroup.com> wrote:
> On Sat, 2 Feb 2008 23:57:24 -0800 (PST), m...@sushi.com wrote in
> <3ade6810-a747-4c41-938d-9740eeb77...@1g2000hsl.googlegroups.com>:
>
> >On Feb 2, 11:15 pm, John Navas <spamfilt...@navasgroup.com> wrote:
> >> On Sat, 2 Feb 2008 22:26:54 -0800 (PST), m...@sushi.com wrote in
> >> <bb019663-7b79-41c6-a2a5-65f69c959...@s19g2000prg.googlegroups.com>:
>
> >> >Dumb question perhaps, but here goes. If you arrange 4 biquads in a
> >> >rectangular formation and used a power combiner, would you get a
> >> >decent omnidirectional antenna? Looking at the biquad pattern
> >> >http://martybugs.net/wireless/biquad...ad_azimuth.jpg
> >> >the antenna is good for about +-45 degrees. Seems to me you would get
> >> >an omnidirectional antenna without too squished of a donut. The
> >> >disadvantage is the combiner loss of 6db (ideal).
>
> >> What would be the point?
> >Like I already stated, high gain without a squished donut, i.e.
> >compared to a colinear.
>
> What makes you think it won't be a squished donut, albeit a crude one
> (due to uneven horizontal gain pattern)? The coverage of a biquad is
> more like 45° than 90°.
>
> --
> Best regards, FAQ for Wireless Internet: <http://Wireless.wikia.com>
> John Navas FAQ for Wi-Fi: <http://wireless.wikia.com/wiki/Wi-Fi>
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The vertical response should be that of the biquad itself.

On Sun, 3 Feb 2008 11:50:53 -0800 (PST), miso@sushi.com wrote in
<4845970a-e4f2-4524-97a7-1d1437fd79d3@d21g2000prf.googlegroups.com>:

>On Feb 3, 12:24 am, John Navas <spamfilt...@navasgroup.com> wrote:
>> On Sat, 2 Feb 2008 23:57:24 -0800 (PST), m...@sushi.com wrote in
>> <3ade6810-a747-4c41-938d-9740eeb77...@1g2000hsl.googlegroups.com>:
>>
>> >On Feb 2, 11:15 pm, John Navas <spamfilt...@navasgroup.com> wrote:
>> >> On Sat, 2 Feb 2008 22:26:54 -0800 (PST), m...@sushi.com wrote in
>> >> <bb019663-7b79-41c6-a2a5-65f69c959...@s19g2000prg.googlegroups.com>:
>>
>> >> >Dumb question perhaps, but here goes. If you arrange 4 biquads in a
>> >> >rectangular formation and used a power combiner, would you get a
>> >> >decent omnidirectional antenna? Looking at the biquad pattern
>> >> >http://martybugs.net/wireless/biquad...ad_azimuth.jpg
>> >> >the antenna is good for about +-45 degrees. Seems to me you would get
>> >> >an omnidirectional antenna without too squished of a donut. The
>> >> >disadvantage is the combiner loss of 6db (ideal).
>>
>> >> What would be the point?
>> >Like I already stated, high gain without a squished donut, i.e.
>> >compared to a colinear.
>>
>> What makes you think it won't be a squished donut, albeit a crude one
>> (due to uneven horizontal gain pattern)? The coverage of a biquad is
>> more like 45° than 90°.

>The vertical response should be that of the biquad itself.

Which will be pretty much a squished donut, albeit a crude one.

--
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On Sun, 3 Feb 2008 11:49:59 -0800 (PST), miso@sushi.com wrote in
<07716fc1-144a-4ae9-b393-638a83bb221c@c23g2000hsa.googlegroups.com>:

>On Feb 3, 7:57 am, "Adair Winter" <ada...@swbell.net> wrote:
>> <m...@sushi.com> wrote in message
>>
>> news:bb019663-7b79-41c6-a2a5-65f69c959e44@s19g2000prg.googlegroups.com...
>>
>> > Dumb question perhaps, but here goes. If you arrange 4 biquads in a
>> > rectangular formation and used a power combiner, would you get a
>> > decent omnidirectional antenna? Looking at the biquad pattern
>> >http://martybugs.net/wireless/biquad...ad_azimuth.jpg
>> > the antenna is good for about +-45 degrees. Seems to me you would get
>> > an omnidirectional antenna without too squished of a donut. The
>> > disadvantage is the combiner loss of 6db (ideal).
>>
>> The other problem I see is if you use some sort of combiner or phasing
>> harness the loss associated with such a device would be more or equal to the
>> gain of any one antenna.

>No, the loss is very close to 6dB. Gain should be around 14db prior to
>loss. What might make a difference is the aperture.

Gain will probably only be 10-12 dB at best, with holes of much worse
gain. A standard hi-gain omni is a much better way to go.

--
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miso@sushi.com wrote:
> Dumb question perhaps, but here goes. If you arrange 4 biquads in a
> rectangular formation and used a power combiner, would you get a
> decent omnidirectional antenna? Looking at the biquad pattern
> http://martybugs.net/wireless/biquad...ad_azimuth.jpg
> the antenna is good for about +-45 degrees. Seems to me you would get
> an omnidirectional antenna without too squished of a donut. The
> disadvantage is the combiner loss of 6db (ideal).

ok... just so we all are reading the same page -
http://martybugs.net/wireless/biquad/

On Feb 3, 11:55 am, John Navas <spamfilt...@navasgroup.com> wrote:
> On Sun, 3 Feb 2008 11:49:59 -0800 (PST), m...@sushi.com wrote in
> <07716fc1-144a-4ae9-b393-638a83bb2...@c23g2000hsa.googlegroups.com>:
>
>
>
> >On Feb 3, 7:57 am, "Adair Winter" <ada...@swbell.net> wrote:
> >> <m...@sushi.com> wrote in message
>
> >>news:bb019663-7b79-41c6-a2a5-65f69c959e44@s19g2000prg.googlegroups.com...
>
> >> > Dumb question perhaps, but here goes. If you arrange 4 biquads in a
> >> > rectangular formation and used a power combiner, would you get a
> >> > decent omnidirectional antenna? Looking at the biquad pattern
> >> >http://martybugs.net/wireless/biquad...ad_azimuth.jpg
> >> > the antenna is good for about +-45 degrees. Seems to me you would get
> >> > an omnidirectional antenna without too squished of a donut. The
> >> > disadvantage is the combiner loss of 6db (ideal).
>
> >> The other problem I see is if you use some sort of combiner or phasing
> >> harness the loss associated with such a device would be more or equal to the
> >> gain of any one antenna.
> >No, the loss is very close to 6dB. Gain should be around 14db prior to
> >loss. What might make a difference is the aperture.
>
> Gain will probably only be 10-12 dB at best, with holes of much worse
> gain. A standard hi-gain omni is a much better way to go.
>
> --
> Best regards, FAQ for Wireless Internet: <http://Wireless.wikia.com>
> John Navas FAQ for Wi-Fi: <http://wireless.wikia.com/wiki/Wi-Fi>
> Wi-Fi How To: <http://wireless.wikia.com/wiki/Wi-Fi_HowTo>
> Fixes to Wi-Fi Problems: <http://wireless.wikia.com/wiki/Wi-Fi_Fixes>

Based on what technical analysis?

On Feb 3, 12:28 pm, "P.Schuman" <pschuman_no_spam...@interserv.com>
wrote:
> m...@sushi.com wrote:
> > Dumb question perhaps, but here goes. If you arrange 4 biquads in a
> > rectangular formation and used a power combiner, would you get a
> > decent omnidirectional antenna? Looking at the biquad pattern
> >http://martybugs.net/wireless/biquad...ad_azimuth.jpg
> > the antenna is good for about +-45 degrees. Seems to me you would get
> > an omnidirectional antenna without too squished of a donut. The
> > disadvantage is the combiner loss of 6db (ideal).
>
> ok... just so we all are reading the same page -http://martybugs.net/wireless/biquad/

Yes, that is the right design, though I use loops instead of squares
based on Jeff L's analysis. The loop is much easier to build since the
wire length is the critical issue.
http://www.lazygranch.com/images/wifi/wifi_bq_1.jpg
http://www.lazygranch.com/images/wifi/wifi_bq_2.jpg

When I build another, I think I'll use hardline with a SMA on the end.
The N-connector is really hard to solder to.

On Sun, 3 Feb 2008 15:08:33 -0800 (PST), miso@sushi.com wrote in
<9b782380-2310-43f7-b7c5-7da7e64bd11a@l16g2000hsh.googlegroups.com>:

>On Feb 3, 11:55 am, John Navas <spamfilt...@navasgroup.com> wrote:
>> On Sun, 3 Feb 2008 11:49:59 -0800 (PST), m...@sushi.com wrote in
>> <07716fc1-144a-4ae9-b393-638a83bb2...@c23g2000hsa.googlegroups.com>:
>>
>> >On Feb 3, 7:57 am, "Adair Winter" <ada...@swbell.net> wrote:
>> >> <m...@sushi.com> wrote in message
>>
>> >>news:bb019663-7b79-41c6-a2a5-65f69c959e44@s19g2000prg.googlegroups.com...
>>
>> >> > Dumb question perhaps, but here goes. If you arrange 4 biquads in a
>> >> > rectangular formation and used a power combiner, would you get a
>> >> > decent omnidirectional antenna? Looking at the biquad pattern
>> >> >http://martybugs.net/wireless/biquad...ad_azimuth.jpg
>> >> > the antenna is good for about +-45 degrees. Seems to me you would get
>> >> > an omnidirectional antenna without too squished of a donut. The
>> >> > disadvantage is the combiner loss of 6db (ideal).
>>
>> >> The other problem I see is if you use some sort of combiner or phasing
>> >> harness the loss associated with such a device would be more or equal to the
>> >> gain of any one antenna.
>> >No, the loss is very close to 6dB. Gain should be around 14db prior to
>> >loss. What might make a difference is the aperture.
>>
>> Gain will probably only be 10-12 dB at best, with holes of much worse
>> gain. A standard hi-gain omni is a much better way to go.

>Based on what technical analysis?

Published data on biquad antennas, both gain and antenna pattern; e.g.,
<http://www.nec2.org/wlan.htm>

The BiQuad also makes a useful stand-alone antenna, with wide
bandwidth and about 11dBi gain ...

Gain pattern: http://www.nec2.org/biquad.gif

--
Best regards, FAQ for Wireless Internet: <http://Wireless.wikia.com>
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On Sun, 03 Feb 2008 23:39:26 GMT, John Navas
<spamfilter1@navasgroup.com> wrote in
<mhjcq39fm597mljb3nlikpppjq2stngkra@4ax.com>:

>On Sun, 3 Feb 2008 15:08:33 -0800 (PST), miso@sushi.com wrote in
><9b782380-2310-43f7-b7c5-7da7e64bd11a@l16g2000hsh.googlegroups.com>:
>
>>On Feb 3, 11:55 am, John Navas <spamfilt...@navasgroup.com> wrote:
>>> On Sun, 3 Feb 2008 11:49:59 -0800 (PST), m...@sushi.com wrote in
>>> <07716fc1-144a-4ae9-b393-638a83bb2...@c23g2000hsa.googlegroups.com>:
>>>
>>> >On Feb 3, 7:57 am, "Adair Winter" <ada...@swbell.net> wrote:
>>> >> <m...@sushi.com> wrote in message
>>>
>>> >>news:bb019663-7b79-41c6-a2a5-65f69c959e44@s19g2000prg.googlegroups.com...
>>>
>>> >> > Dumb question perhaps, but here goes. If you arrange 4 biquads in a
>>> >> > rectangular formation and used a power combiner, would you get a
>>> >> > decent omnidirectional antenna? Looking at the biquad pattern
>>> >> >http://martybugs.net/wireless/biquad...ad_azimuth.jpg
>>> >> > the antenna is good for about +-45 degrees. Seems to me you would get
>>> >> > an omnidirectional antenna without too squished of a donut. The
>>> >> > disadvantage is the combiner loss of 6db (ideal).
>>>
>>> >> The other problem I see is if you use some sort of combiner or phasing
>>> >> harness the loss associated with such a device would be more or equal to the
>>> >> gain of any one antenna.
>>> >No, the loss is very close to 6dB. Gain should be around 14db prior to
>>> >loss. What might make a difference is the aperture.
>>>
>>> Gain will probably only be 10-12 dB at best, with holes of much worse
>>> gain. A standard hi-gain omni is a much better way to go.
>
>>Based on what technical analysis?
>
>Published data on biquad antennas, both gain and antenna pattern; e.g.,
><http://www.nec2.org/wlan.htm>
>
> The BiQuad also makes a useful stand-alone antenna, with wide
> bandwidth and about 11dBi gain ...
>
> Gain pattern: http://www.nec2.org/biquad.gif

See also <http://www.lecad.uni-lj.si/~leon/other/wlan/biquad/>

--
Best regards, FAQ for Wireless Internet: <http://Wireless.wikia.com>
John Navas FAQ for Wi-Fi: <http://wireless.wikia.com/wiki/Wi-Fi>
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Fixes to Wi-Fi Problems: <http://wireless.wikia.com/wiki/Wi-Fi_Fixes>

On Feb 3, 3:40 pm, John Navas <spamfilt...@navasgroup.com> wrote:
> On Sun, 03 Feb 2008 23:39:26 GMT, John Navas
> <spamfilt...@navasgroup.com> wrote in
> <mhjcq39fm597mljb3nlikpppjq2stng...@4ax.com>:
>
>
>
> >On Sun, 3 Feb 2008 15:08:33 -0800 (PST), m...@sushi.com wrote in
> ><9b782380-2310-43f7-b7c5-7da7e64bd...@l16g2000hsh.googlegroups.com>:
>
> >>On Feb 3, 11:55 am, John Navas <spamfilt...@navasgroup.com> wrote:
> >>> On Sun, 3 Feb 2008 11:49:59 -0800 (PST), m...@sushi.com wrote in
> >>> <07716fc1-144a-4ae9-b393-638a83bb2...@c23g2000hsa.googlegroups.com>:
>
> >>> >On Feb 3, 7:57 am, "Adair Winter" <ada...@swbell.net> wrote:
> >>> >> <m...@sushi.com> wrote in message
>
> >>> >>news:bb019663-7b79-41c6-a2a5-65f69c959e44@s19g2000prg.googlegroups.com...
>
> >>> >> > Dumb question perhaps, but here goes. If you arrange 4 biquads in a
> >>> >> > rectangular formation and used a power combiner, would you get a
> >>> >> > decent omnidirectional antenna? Looking at the biquad pattern
> >>> >> >http://martybugs.net/wireless/biquad...ad_azimuth.jpg
> >>> >> > the antenna is good for about +-45 degrees. Seems to me you would get
> >>> >> > an omnidirectional antenna without too squished of a donut. The
> >>> >> > disadvantage is the combiner loss of 6db (ideal).
>
> >>> >> The other problem I see is if you use some sort of combiner or phasing
> >>> >> harness the loss associated with such a device would be more or equal to the
> >>> >> gain of any one antenna.
> >>> >No, the loss is very close to 6dB. Gain should be around 14db prior to
> >>> >loss. What might make a difference is the aperture.
>
> >>> Gain will probably only be 10-12 dB at best, with holes of much worse
> >>> gain. A standard hi-gain omni is a much better way to go.
>
> >>Based on what technical analysis?
>
> >Published data on biquad antennas, both gain and antenna pattern; e.g.,
> ><http://www.nec2.org/wlan.htm>
>
> > The BiQuad also makes a useful stand-alone antenna, with wide
> > bandwidth and about 11dBi gain ...
>
> > Gain pattern:http://www.nec2.org/biquad.gif
>
> See also <http://www.lecad.uni-lj.si/~leon/other/wlan/biquad/>
>
> --
> Best regards, FAQ for Wireless Internet: <http://Wireless.wikia.com>
> John Navas FAQ for Wi-Fi: <http://wireless.wikia.com/wiki/Wi-Fi>
> Wi-Fi How To: <http://wireless.wikia.com/wiki/Wi-Fi_HowTo>
> Fixes to Wi-Fi Problems: <http://wireless.wikia.com/wiki/Wi-Fi_Fixes>

I'm familiar with both of those websites. At the 45 degree point, the
antennas would be in phase, boosting the signal 3dB. It would dip, but
nothing is perfect. For instance, the omni is only at full gain over a
narrow portion of the donut.

As you know, some sector antenna omni schemes use a similar design,
though they use individual transceivers per sector.

miso@sushi.com hath wroth:

>Dumb question perhaps, but here goes.

Well, yes... it's kinda dumb the way you presented it, unless it's a
theoretical question. What's missing are:
1. What problem are you trying to solve?
2. What do you have to work with?

>If you arrange 4 biquads in a
>rectangular formation and used a power combiner, would you get a
>decent omnidirectional antenna?

Actually, yes. That's roughly what would happen. The roughly 60
degree horizontal beamwidth would not yield a continuous
omnidirectional pattern. There would be some holes every 90 degrees,
where the pattern of two of the antennas meet. See patterns at:
<http://802.11junk.com/jeffl/antennas/Biquad/>
<http://www.lecad.uni-lj.si/~leon/other/wlan/biquad/index.html>

However, there's a rather nasty power divider/combiner effect you need
to consider. In order to get gain, you have to feed it with a 180
degree power splitter (Wilkinson Combiner). A 90 degree splitter will
result in a rather ugly pattern. Let's assume for a moment that there
are no combiner losses, and that the power splits equally (-3dB) per 2
ports.

In transmit, 1/4 th of the power goes to each antenna, resulting in a
-6dB loss in gain. In receive, all the signal received by any antenna
goes to the receiver, so there's no receive loss. Therefore, if a
single biquad has a gain of about +10dBi, the array will have a gain
of +4dBi in transmit, and +10dBi in receive.

>Looking at the biquad pattern
>http://martybugs.net/wireless/biquad...ad_azimuth.jpg
>the antenna is good for about +-45 degrees. Seems to me you would get
>an omnidirectional antenna without too squished of a donut.

The -3dB bandwidth of a biquad is about 60 degress, not 90 degrees. At
+/-45 degress, that pattern appears to be -8dB down from the peak.
That means you'll have a -5dB hole in the pattern every 90 degrees if
you use a power splitter/combiner.

>The
>disadvantage is the combiner loss of 6db (ideal).

Yep. -6dB per port for a 4 port splitter plus whatever internal loss
the combiner adds. Typically about 0.5dB per port. See specs on a
typical combiner at:
<http://www.hyperlinktech.com/web/signal_splitters.php>

Did you ever even look at the Amos/Franklin antennas I've often
suggested?
<http://pe2er.nl/wifisector/>
<http://yu1aw.ba-karlsruhe.de/vhf_ant.htm>
<http://www.brest-wireless.net/wiki/materiel:amos>
<http://www.qsl.net/yu1aw/vhf_ant.htm>
<http://www.brest-wireless.net/gallery/AntenneAmos>
Note that there are several photos showing back to back antennas to
form an omni pattern.

Incidentally, I blundered across this "curtain quad" antenna, which
looks interesting:
<http://home.comcast.net/~ross_anderson/2400MHzAntenna.htm>

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Feb 3, 11:37 pm, Jeff Liebermann <je...@cruzio.com> wrote:
> m...@sushi.com hath wroth:
>
> >Dumb question perhaps, but here goes.
>
> Well, yes... it's kinda dumb the way you presented it, unless it's a
> theoretical question. What's missing are:
> 1. What problem are you trying to solve?
> 2. What do you have to work with?
>
> >If you arrange 4 biquads in a
> >rectangular formation and used a power combiner, would you get a
> >decent omnidirectional antenna?
>
> Actually, yes. That's roughly what would happen. The roughly 60
> degree horizontal beamwidth would not yield a continuous
> omnidirectional pattern. There would be some holes every 90 degrees,
> where the pattern of two of the antennas meet. See patterns at:
> <http://802.11junk.com/jeffl/antennas/Biquad/>
> <http://www.lecad.uni-lj.si/~leon/other/wlan/biquad/index.html>
>
> However, there's a rather nasty power divider/combiner effect you need
> to consider. In order to get gain, you have to feed it with a 180
> degree power splitter (Wilkinson Combiner). A 90 degree splitter will
> result in a rather ugly pattern. Let's assume for a moment that there
> are no combiner losses, and that the power splits equally (-3dB) per 2
> ports.
>
> In transmit, 1/4 th of the power goes to each antenna, resulting in a
> -6dB loss in gain. In receive, all the signal received by any antenna
> goes to the receiver, so there's no receive loss. Therefore, if a
> single biquad has a gain of about +10dBi, the array will have a gain
> of +4dBi in transmit, and +10dBi in receive.
>
> >Looking at the biquad pattern
> >http://martybugs.net/wireless/biquad...ad_azimuth.jpg
> >the antenna is good for about +-45 degrees. Seems to me you would get
> >an omnidirectional antenna without too squished of a donut.
>
> The -3dB bandwidth of a biquad is about 60 degress, not 90 degrees. At
> +/-45 degress, that pattern appears to be -8dB down from the peak.
> That means you'll have a -5dB hole in the pattern every 90 degrees if
> you use a power splitter/combiner.
>
> >The
> >disadvantage is the combiner loss of 6db (ideal).
>
> Yep. -6dB per port for a 4 port splitter plus whatever internal loss
> the combiner adds. Typically about 0.5dB per port. See specs on a
> typical combiner at:
> <http://www.hyperlinktech.com/web/signal_splitters.php>
>
> Did you ever even look at the Amos/Franklin antennas I've often
> suggested?
> <http://pe2er.nl/wifisector/>
> <http://yu1aw.ba-karlsruhe.de/vhf_ant.htm>
> <http://www.brest-wireless.net/wiki/materiel:amos>
> <http://www.qsl.net/yu1aw/vhf_ant.htm>
> <http://www.brest-wireless.net/gallery/AntenneAmos>
> Note that there are several photos showing back to back antennas to
> form an omni pattern.
>
> Incidentally, I blundered across this "curtain quad" antenna, which
> looks interesting:
> <http://home.comcast.net/~ross_anderson/2400MHzAntenna.htm>
>
> --
> Jeff Liebermann je...@cruzio.com
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558

It was mostly a thinking outside the box exercise. Also, I have need
for a high gain vertically polarized L-band antenna, and have seen
enough poorly made coax colinears that I figured something else should
be examined.

I will look into that "curtain" for wifi, but I need an omni. Nothing
COTS exists for my other project. L band is an odd place to be. Too
low in frequency for some designs and to high in frequency for others
(J-poles for instance).