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Old Feb 13, 2011, 07:36 AM
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I posted mine in the SPW antenna thread, but here it is again next to a 1280 SPW. Not hard to build..
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Old Feb 13, 2011, 10:58 AM
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I just flew a sort of head-to-head of my SPW vs CL. For me I found the SPW to perform slightly better. This of course might be a build quality difference as my CL is a revised former SPW. It seemed as though the CL started dropping quality at 1.5 miles a little, where the SPW hit 2 before a noticeable degradation. But this is still very limited testing... needs more flights.

But, as you say, the CP sure maintains nice video. I was flying very low today around buildings and had no multipath probs. Now I need a better camera than my 380tvl one... Very over-exposed/contrast and it shows down low.
FPV 110213 EZ CP SPW Low Alt Testing (1 min 31 sec)
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Old Feb 13, 2011, 11:09 AM
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Quote:
Originally Posted by IBCrazy View Post
I will try to answer questions here:

Q: Will you build this for me?
A: Yes. These are part of my "new system" of FPV antennas. As much as I'd like people here to build it themselves, I understand that it is not easy and intimidating.

-Alex
KJ4RIV
How much for 910mhz? and if I get 2 of these I can use one on the VRX and VTX?

Thanks

Mike
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Old Feb 13, 2011, 03:37 PM
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Alex,

I'm pleased to see you championing Circularly Polarised omni directional antennas for FPV purposes.
I had been banging on about CP for some time and only when I found the Skew-Planar, was I happy that there was something not too difficult to make for our purposes.

Until then, OMM's CPOD was perhaps the only other realistic CP omni directional antenna and he will admit it is not easy to fabricate.

Now you are re-inventing the cloverleaf with CP to boot.

I wish I had more time and half your energy !

Keep up the good work.

Nigel.
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Old Feb 13, 2011, 06:24 PM
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Quote:
Originally Posted by Derek_S View Post
I just flew a sort of head-to-head of my SPW vs CL. For me I found the SPW to perform slightly better. This of course might be a build quality difference as my CL is a revised former SPW. It seemed as though the CL started dropping quality at 1.5 miles a little, where the SPW hit 2 before a noticeable degradation. But this is still very limited testing... needs more flights.
I just did 1 mile on two cloverleaf antennas on the BoB system. 1 mile on omnis is unheard of. Especially when you consider that I was surrounded by metal. I couldn't believe it. I still can't believe it...

My observation of the SPW vs Cloverleaf:

SPW has better multipath rejection.
Cloverleaf has longer ultimate range
Clover leaf is far easier to build
Cloverleaf can get perfect 1.0 SWR and maintain circularity where the skew planar wheel can only get 1.3.
The skew planar wheel does better as an RX antenna where the cloverleaf does better as a TX antenna.

-Alex
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Old Feb 13, 2011, 06:26 PM
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Originally Posted by Derek_S View Post
But, as you say, the CP sure maintains nice video. I was flying very low today around buildings and had no multipath probs. Now I need a better camera than my 380tvl one... Very over-exposed/contrast and it shows down low.
Didn't I tell you that once you go CP you'll never go back to linear? It solved you video problems, didn't it? Try the SPW on the RX and CL on the TX for a 1+ mile omni solution.

-Alex
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Old Feb 13, 2011, 06:36 PM
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It really is fantastic so far. I still want to do some linear head-to-head just 'cause so i have a good inventory of 'proof' videos.
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Old Feb 13, 2011, 06:37 PM
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Upgrade to CP

This thread has got me excited about circular polarization, especially since I'm rebuilding my TS2 (again).

I have 2.4 ghz gear and my rx has diversity. If I did a cloverleaf for my plane and did a cloverleaf (or a skew planar) as well as a helical for the RX would I have long range directional distance and short-range omni? Would this be approaching the best configuration without going to large antennae? My constrain is that I carry all of my gear in a belly pack around my waist for portability. I need to mount all my gear right in front of my stomach (and for obvious reasons I'd want to limit the length of my helix so I don't start looking like Dilbert...)
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Old Feb 13, 2011, 06:42 PM
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A 5 turn helix at 2.4 GHz is only 6" long.

And short range omni? There is no such thing anymore. If I can do 1 mile on the BoB system flying from my back porch with two cloverleafs, everyone should be able to get this.

If I were you, I'd build two 5 turn helicals and aim them 50-60 degrees apart. Fly a cloverleaf or SPW on the plane. This will get you 3 miles or more. Use the tapered microstrip match fr the helical. Also, keep the feedpoint as close to the ground plane as possible. This is the key to perfect SWR.

-Alex
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Old Feb 13, 2011, 07:08 PM
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Do you know how narrow the frequency range would be on a skew planar wheel or clover leaf @ ~ 5.8ghz? I'm curious if we will need these to be tuned to a particular channel or if "5.8ghz" is close enough? These sure sound fantastic!
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Old Feb 13, 2011, 07:20 PM
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Alex, for longer range I am thinking about another helix. What would be a good next step? 6 turn maybe? I have diversity so I might use my 4 turn plus a longer range one.
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Old Feb 13, 2011, 07:33 PM
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A 6 turn is pretty good for moderate range. However if you want long range, the only option that I know of is a dish feed. If you have an old satellite dish or know where there is one that is being thrown out, use that with a 3 turn helix in the reverse polarization direction (polarization reverses upon reflection). This will get you farther out than you could imagine. Probably further than your LRS...

-Alex
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Old Feb 13, 2011, 07:34 PM
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Quote:
Originally Posted by Mikey-flies View Post
Do you know how narrow the frequency range would be on a skew planar wheel or clover leaf @ ~ 5.8ghz? I'm curious if we will need these to be tuned to a particular channel or if "5.8ghz" is close enough? These sure sound fantastic!
5.8GHz is close enough.

-Alex
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Old Feb 13, 2011, 08:10 PM
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I live in an apartment so I can get those all the time when people move out. They just get discarded. Of course hauling that around will be a job, but I have a truck so it would be fun to play with if it is weather proof enough to just leave in the bed

Is it built the same otherwise? Also you do mean a dish like direct tv, dish network, etc?


edit: oh, and what is the gain on such a dish?
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Old Feb 13, 2011, 09:59 PM
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Gain? Who knows? That's why I said keep it 3 turns on the helix. The gain is likely upwards of 15db. So if you consider that a 3 turn helix is 7.5 db, add in the 15db and you have a 23dbic antenna. Play with the aim angle a bit. Just attach the base right where the old recievers were. Aim it approximately where the old elements were aimed. You can play with it a little bit by putting your plane on one side of the building and your RX antenna on the other side and adjust for best RSSI through the building. The signal should get through just barely strong enough to get a decent signal.

-Alex
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