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Easystar

800mw 1.2GHZ [ esp 1280mhz ] on TX

We plan to use Patch antenna system and maybe oracle diversity.

Antenna tracking is looks so complex and expensive.

Is 2 Patch with different angles is enough ?

And resource for making our Patch antenna's. [ because of high shipment price's to send items to eastern europe]

I read many thing about antenna's but not understand the core.

If DBI increases range increase but covarage angle is decrease.[ is that true ]

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Is 2 Patch with different angles is enough ?

depends on what you want to do, I flew 1 patch for many years, an 8dBi patch has a wide capture angle.

If DBI increases range increase but covarage angle is decrease.[ is that true ]

in a nutshell yes

Terry

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Thanx for the answer.

Forexample any data on capture angle on antennas 8dbi ?

I want to fly 360 degree fly. [ front of me and behind too ]

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Yup, one 8dBi patch is a great place to start.

In practice, you can fly behind them on approach and still get a great picture!

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blog-2_2.gif

Says 70 degree. Two patch covers 140 degree. Without tracking system could you use these systems. Can you fly behind the antennas ?

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blog-2_2.gif

Says 70 degree. Two patch covers 140 degree. Without tracking system could you use these systems. Can you fly behind the antennas ?

Remember that you're point UP then tilting it in the direction of most of your distant flight, so in typical use 'behind' = underground, i.e. don't worry about it.

Remember too that there are plenty of other parameters that will affect range than aerial sensitivity e.g. the direction your transmitter aerial is pointing in (as the aircraft rolls) and what it is transmitting through (from free space to the motor, battery pack etc.), multipath interference etc. So never mind '3dB points', what about the 30dB+ variations as the 'plane moves around the sky?

Sensitivity drops as per the polar diagram, so you will get

- best range when your patch is pointing at the aircraft

- worse range when it is off-centre (including a surprising amount of arc behind it! - but point the patch UP and tilt towards main intended area of flight, so you're only behind it on final approach i.e. close in)

- zero range at certain points - although remember your aircraft will usually keep flying through these, so the picture may vanish for a second... or longer... but that it something you have to get used to flying FPV anyway. It's one of the things that make it exciting. Some try to overcome this with high transmitter power, tracking aerials etc. but occasional drop-outs never completely go away.

So yes you will often get reception from some very odd angles, but on the other hand with an 8dB patch, exact aim isn't what you're after anyway. If you want that go to 14dB or higher, and add tracking. What most of us find is that 8dB pointing straight up, or tilted a bit in the direction you're mainly wanting to fly off in, is fine - and better than a 3dB omni. Although some of us, such as the great VRFlyer, use 3dB omnis to great effect.

(Elsewhere on this forum you'll see discussions about optimum mounting. I have found that, if flying within a mile or so of interference sources (buildings, bluetooth, wifi etc.) sometimes I get the best results by placing a 8dB patch flat on the ground! I guess that a patch aerial on the ground has a great earth plane, and is relatively shielded from distant, low-altitude intereference sources which are effectively 'below the horizon' by this placement, compared to mounted on a tripod)

Start with a single 8dB patch. I eventually moved on to two of these with a diversity switcher, but that's mainly to mitigate multipath interference, rather than to cope with limited beam width from the patch.

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I want to fly 360 degree fly. [ front of me and behind too ]

What power TX and at what range?

Do you fly aerobatics?

Do you need need great video quality to use on a DVD or do you just want to use the down link to point the plane or generally fly about FPV?

The main hole in the coverage is when flying over head but this is as much to do with the plane aerial as the RX aerial.

Doofer seems to have covered most of it tho :)

Terry

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