Multi 8dbi patches...or kinda like that

[ob1]

This may have already been covered somewhere else...if so, I apologize.

I currently use the 4.5" square 8dbi patch from BWAV, and basically mounted it to a 10" square coroplast chest-plate with a neck-strap, along with all of my other associated FPV stuff, so that as I fly, if necessary I can re-point my body to insure the patch stays focused in the general direction of the plane. This allows me (and my goggles, rx, batts, antenna, etc) to be mobile...ie not tied to a table or chair or tripod.

What I have been wondering is could several patch antennas be arranged in some sort of circular pattern and fed into a single rx to achieve a full 360-degree coverage? The best description I can offer to get you to visualize this is to imagine cutting a basketball in half, so that you have two hemispheres. If you took one of the hemispheres and set it on the flat side you would then have a domed structure. If you placed 6 of the 8dbi patches around the circumference of the dome, you would cover a full 360-degrees of peripheral "antenna vision" (if each antenna is capable of 60 degrees coverage via 30 degrees on either side of center). Each patch antenna could be angled slightly upward so that coverage would be provided from slightly above the ground to 60 degrees up-angle. I know this sounds like a dumb design, but it is simply my layman's method of explaining the need. I believe something like this would cover most all areas except for a narrow column that extends upward directly over the dome. I suppose to save money a person could build each patch (like the design from rc-cam projects) instead of shelling out $44 for each one from BWAV or RangeVideo. How can several patches be connected to a single rx? Is there already a way to do this inexpensively? Are there antennas that already provide this "dome-like" coverage? Essentially this design retains the "directional" capabilities of each patch, it simply means that as the plane moves around the sky the video tx signal is picked up more strongly by one patch than the others....or at least that is the goal. It would be nice to not have to worry about keeping a single patch (or yagi) pointed in the general direction of the plane. Any ideas or suggestions are welcome.
Thx...
ob1

[PeteSchug]

It's not quite as good as what you are hoping for, but BWAV sells a diversity rx and a dual 11 dBi patch to go with it.

There are two patch ant's in one enclosure with two leads coming out. each lead goes to one of the rx's in the diversity rx. The circuitry reads the strength level of each signal and switches to the stronger one. The switch is done during video retrace so you never see it or record it.

I've flown with mine a couple of times and generally got a very good signal. You can see some degradation when I am _WAY_ off to the side. It didn't work all that well in Vermont when I laid the dual patch flat on wet ground! I guess I should be happy I got a signal at all. I was flying by visual contact and my friend Bob had the goggles on. I usually bring a tripod, but we had two airplanes, the video gear and the tx to carry and it was a bit of a hike to where we flew.

At our field I usually hang my antenna on the snow fence that marks our flight line. I angle it a bit up and that has worked fine for me both with the standard rx with the 8 dBi patch or the diversity with the 11 dBi patch. Hearing the diversity rx chirp every time it switches is sort of encouraging, you know the thing is working.

As stated elsewhere, at our flying field I can't get too far away, (except up!) but I also pick up a strong signal even when flying pretty low. The approach is parallel to the flight line and edge on to the patch and I still get mostly good coverage.

Pete

[AndrésMtnez]

There´s a thread on Rc-Cam with a very similar idea, might be useful

http://www.rc-cam.com/forum/index.php?showtopic=1528&st=0

[JackBauer]

Would it work to hook the patch up to a motor and spin it at high speed to cover most directions? Of course the antenna wire would have to have a rotating joint type of connection. And maybe the motor should be remotely located but the force transmitted to the antenna's location, to avoid causing RF interference. This idea is similar to a rotating radar antenna but since we want video with no gaps, the rotation speed should be fast.

[Kilrah]

This (http://www.rc-cam.com/forum/index.php?showtopic=15) or other equivalents would be better.

[PeteSchug]

If you have three antennas aimed in a triangular pattern, pointing a little out from the center the entire array can be aimed. What you have to do is move the array towards the strongest antenna until two antennas have equal strength, then move the array towards the two strong ones until all three are equal.

This can be done continuously as you fly.

This assumes starting with the antennas pointing in the right general direction. I don't know what would happen if the plane were behind the array. It would probably turn around completely, but it would depend on if the antennas had any kind of reception from behind.

Personally I think it is overkill for what we do, but I don't think it is much more difficult than making a radio controlled airplane.

People have rigged telescopes to track stars by similar means, and they can keep a scope pointed as accurately as the most careful human operator.

Unless you are going for a low wattage distance record a normal patch aimed pretty close to the airplane is all you should ever need.

On the other hand, if I had AnthonyRC's couch potato flying setup, (again, WOW, I'm envious) an antenna rig like that on the roof might be the best thing I could have to assure myself a strong signal.

Pete

[typicalaimster]

Hmm I know the diversity RX you could use multiple antennas with. There are antenna splitters out there you can buy.

Just to give you an idea there is a 180 degree 'sector' antenna out there. The problem is it's 180x10 degrees..

http://www.hyperlinktech.com/web/copyrighted_images/pattern_hg2415p_180.gif

The other problem is the price. It's not cheap at $480! I can buy the diversity RX for that price!

I noticed a 2 way splitter is about $40. I'm curious if your signal would be cut in half, or be doubled at that point.

[PeteSchug]

Any idea what the chart looks like for a BWAV 8dBi patch?

I have the Diversity and the dual patch and I'd love to see what that looks like too, and what angle the pair has.

I've gotten mostly very nice looking video out of it, but I only recorded two flights so far. Edge on to the ant. there were some squiggly line artifacts near the edges of the image, but considering how far off axis that is I think of it as pretty good.

I did an unrecorded flight (too many devices and buttons, I forgot to hit record!) video pilotage flight and had a very good image the entire time. The antenna is stationary in all of my flights. Note the wormy artifacts on the left edge of the image.

Pete

Edit:

Here is the worst single video frame from the first flight of my E*. This is on final, almost edge on to the dual patch and about 200 yards out.

The flight line is between the two widely spaced trees on the left and I am the closer vertical blob. The antenna is on a plastic snow fence half way between the metal fence posts. (I don't trust them not to affect the antenna.) I used to put my antenna on a tripod, but experience has shown that even the 8 dBi patch works well over most of the area and acceptably even when almost edge on. I guess I am about 80° off axis in this picture.

Remeber, this is the WORST frame.

Pete

[typicalaimster]

This is what the single 8 looks like

http://www.hyperlinktech.com/web/copyrighted_images/pattern_hg2409pc.gif

If the diversity is the one I think it is.. This is the pattern for that one..

http://www.hyperlinktech.com/web/copyrighted_images/pattern_hg2411dp.gif

[PeteSchug]

Thanks typicalaimster,

Any idea how wide the angular separation between the horizontal lobes are on the dual? In my limited experience I think it works pretty good.

Pete

[AndrésMtnez]

If the diversity is the one I think it is.. This is the pattern for that one..

Does the pattern change if the antenna is used with a Diversity? :confused:

[PeteSchug]

Does the pattern change if the antenna is used with a Diversity? :confused:

It shouldn't matter at all.

What always worries me is nearby reflectors or stuff like that. For an example look at a yagi antenna. Only one element is actually connected to the receiver, but all the rest affect the width of the lobe. I always worry that my antenna (whatever it is) will be affected by things like nearby metal rods etc, so I am careful where I place it.

My worst reception came recently when I laid my antenna (dual patch, diversity rx) on damp ground. It was half convenience and half a test. I was flying by visual contact while my friend wore the goggles, so it was safe, and sure enough the video was very poor. My friend was amazed none the less.

Pete

[PeteSchug]

Looking at the lobe pattern of the second patch antenna it seems to have reasonable reception edge on, but has a dip to almost zero seventy degrees off axis. Considering that there are two antennas aimed a bit differently and the diversity rx knows which one to listen to, effectively you have a pretty good signal at any angle in front of the antenna, including edge on.

Pete

[typicalaimster]

Does the pattern change if the antenna is used with a Diversity? :confused:

No the pattern will not change. The diversity rx is looking at the signal coming in. It then switches to the more powerful signal. What you can do, however, is aim the antenna a few degrees the other direction. This would give you a larger flying area.

[typicalaimster]

Looking at the lobe pattern of the second patch antenna it seems to have reasonable reception edge on, but has a dip to almost zero seventy degrees off axis. Considering that there are two antennas aimed a bit differently and the diversity rx knows which one to listen to, effectively you have a pretty good signal at any angle in front of the antenna, including edge on.


Actually what would concern me is the 30 degree beam view on the vertical. I guess this would be fine if you were flying out and not up. On my tripod I usually angle the antenna so it's 'looking' at my flying area.

[twinturbostang]

My worst reception came recently when I laid my antenna (dual patch, diversity rx) on damp ground. It was half convenience and half a test.
I had a case where putting the antenna on the ground actually improved the signal. However, this was with a regular whip antenna, hooked to a rather cheap receiver (before I got my BlackWidow stuff). Elevating the receiver/antenna 3 to 4 feet off the ground seriously degraded the video quality. I believe that the antenna was not a true dipole. And so the ground was actually acting as a ground plane for the antenna.

[ijustwant]

Why don't you just order one of this ?
http://www.wimo.com/cgi-bin/verteiler.pl?url=wlan_splitter_e.htm

[PeteSchug]

No the pattern will not change. The diversity rx is looking at the signal coming in. It then switches to the more powerful signal. What you can do, however, is aim the antenna a few degrees the other direction. This would give you a larger flying area.

I don't know for sure, but I think that the antennas are not aimed down the central axis, but slightly out.

If they are aimed exactly the same it's almost pointless to use a dual patch when you can stick two separate patches on and aim them outward deliberately.

As far as the vertical goes, I usually drape my antenna over a plastic snow fence so that it is aimed a bit up. (less than 45°, probably about 30°) That would put the null in the vertical plane close to overhead. Flying overhead is something I generally avoid at my club, though out in the boonies in Vermont I might do it. (Overhead equals flying down the flight line or crossing it, neither is a good idea.)

Pete

[AndrésMtnez]

No the pattern will not change. The diversity rx is looking at the signal coming in. It then switches to the more powerful signal. What you can do, however, is aim the antenna a few degrees the other direction. This would give you a larger flying area.



I´m missing something... :confused:


What´s the second pattern you´ve showed us?

[ob1]

Why don't you just order one of this ?
http://www.wimo.com/cgi-bin/verteiler.pl?url=wlan_splitter_e.htm
Thanks for the link...all of the discussions were worthwhile because there is some good info being exchanged. However, based on the vendor's descriptions, I believe this "splitter" will do exactly what I want and is resonably priced as well. All I need to do now is make a few of the rc-cam "goof-proof" patches and figure a way to hook them together with this vendor's splitter (using sma connector instead of "n" connector), and give it a try. If the rc-cam gp antennas cover approximately 60 degrees beamwidth (30 degrees on either side of center), then I assume building an array of 3 antennas should cover about 180 degrees. so I should be able to fly from extreme left to extreme right of my field without losing the signal or encountering any significant signal degradation....and without re-pointing the antenna array.

[typicalaimster]

What´s the second pattern you´ve showed us?

Going back to Pete's commment..

I have the Diversity and the dual patch and I'd love to see what that looks like too, and what angle the pair has.

The Second pattern in post #7 is for an antenna called the "Diversity Antenna". This is an antenna with dual outputs built in.

http://www.hyperlinktech.com/web/copyrighted_images/re11dp_400.jpg

You could use this patch antenna and plug both inputs into your Diversity receiver. This would cut down one antenna. The problem is the antenna is a bit more focused than the standard 8db patches. If you were flying within the 'AMA suggested field boundary' this would not be a problem. If you were going beyond that it's another story.

[AndrésMtnez]

Ok, sorry I misunderstood Pete

I thought he was using two equal 8dBi patches, sometimes my bad english combined with my short knowledge of this stuff put me in a tight spot :rolleyes:


Many thanks :)
Andres

[typicalaimster]

Heh more I look at it I think it was a break down on my part