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Old Oct 16, 2011, 03:58 PM
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Austin, TX
Joined Jan 2009
743 Posts
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2.4GHz patch versus Stock Spektrum Ant

I wonder if anyone else had has the same experience as I....I tried to increase my control range for my Spektrum setup from its current limit of about 1 mile by replacing the stock (1/4 wave?) antenna on my tx module with a 7dbi patch antenna which is actually sold for use with an 2.4G FRsky module by Rangevideo...

I found it actually performed worse than my stock antenna...

My configuration:
Skysurfer with RVOSD
5.8G 200mw Foxtech video link
Spektrum AR7 RX with satellite...main RX ant in same plane with wing...satellite mounted 90deg to main with 45 deg vertical rotation to give some vertical polarization

JR with Spektrum module...antenna vertical (although most of the time its really horizontal because I fly sitting down with the xmitter in my lap)

here is a video from this morning's range testing in the air....I fiddled with the patch elevation and horizontal/vertical orientation a bit a time trying to get optimum rc link..I was careful to point it directly at the plane..but stock wins hands down..anybody think they know why?...a 2.4ghz patch is hard to manufacture wrong...and +DBs is always better, as they say..
http://www.youtube.com/watch?v=RUpyGDwv0t0

PS when I got back home and ran some on the ground range check comparisons and found the same results...the patch was directional and had excellent front to back, but gave no better range than my stock 1/4wave...perhaps even worse...

PPS yes I did make sure that the connectors weren't RP-SMA vs SMA and not making center pin connection on the patch...
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Old Oct 16, 2011, 04:18 PM
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Italia, Piemonte, Torino
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Video was private
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Old Oct 16, 2011, 04:52 PM
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Austin, TX
Joined Jan 2009
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Originally Posted by Neo360 View Post
Video was private
sorry, meant to make it unlisted on my channel...should be fixed now
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Old Oct 17, 2011, 02:26 AM
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Romania, Dolj, Craiova
Joined Sep 2007
14,281 Posts
The patch should permanently aim to the model, it is not good for close proximity around flying.
Worse, having the patch horizontally means that the active beam is aiming the sky overhead, either the ground. The lateral (thin) side of the patch radiation is almost null.
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Old Oct 17, 2011, 07:21 AM
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Austin, TX
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Originally Posted by RENATOA View Post
The patch should permanently aim to the model, it is not good for close proximity around flying.
Worse, having the patch horizontally means that the active beam is aiming the sky overhead, either the ground. The lateral (thin) side of the patch radiation is almost null.
it was always pointed directly at the model....never sideways as you suggest, which is a deep null in the pattern ....so the H-plane max lobe was always directly at the model...I varied the E(or V) plane slightly and also changed from vertical to horizontal polarization orientation, in various combinations to try to get the pattern's maximum lobe directly at the plane in the distance...no luck...or rather once I got it maximized, it was still poor....

and it works fine close as long as you are in front in the 50-60deg beamwidth and not behind or overhead....as the theoretical pattern suggests....it does have directivity and good front to back ratio as I noted above...

the max gain just doesn't come close to 7dbi....its more like isotropic...

as I said, its hard to screw up a patch design...this one is PCB, I am sure, and should be very repeatable...I am just wondering what other variable could be affecting its performance...
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Old Oct 17, 2011, 12:20 PM
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Joined Oct 2007
1,310 Posts
Check the polarity of the connectors. I had make this mistake, plugging RP female SMA to non RP male SMA there is no connection on the center plug.
Like you say, the PCB patch is very repeatable. This is why I told Rangevideo to sell that type. I tested the other ones and they were crap.
But are you sure you have the correct one?
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Old Oct 17, 2011, 12:23 PM
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Austin, TX
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Originally Posted by Elcheapo View Post
Check the polarity of the connectors. I had make this mistake, plugging RP female SMA to non RP male SMA there is no connection on the center plug.
Like you say, the PCB patch is very repeatable. This is why I told Rangevideo to sell that type. I tested the other ones and they were crap.
But are you sure you have the correct one?
thanks...as I stated...I checked that....BTW if they weren't connected I would have never gotten 3/4 of mile....without an antenna(ie RP-SMA attached to SMA) you will get about 10ft..

and I got mine from RangeVideo...in the FRSky section...
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Old Oct 17, 2011, 12:24 PM
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Lakewood, Colorado
Joined Aug 2002
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And since the Spektrum tx doesn't actually have an SMA connector, how exactly
are you hooking up the patch? I'd look there first.

ian
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Old Oct 17, 2011, 12:27 PM
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Austin, TX
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Originally Posted by Daemon View Post
And since the Spektrum tx doesn't actually have an SMA connector, how exactly
are you hooking up the patch? I'd look there first.

ian
my DSM1 Spektrum JR TX module does have an RP-SMA connector
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Old Oct 17, 2011, 12:39 PM
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BTW if they weren't connected I would have never gotten 3/4 of mile
I flew 1.5Km away when I made this mistake, but I was using the 1W booster. The output of the FRsky does match the patch connector, so no way to have this issue without adapter. I made the mistake because I had two types of adapters mixed.
The other thing you have to check is that you aim the correct side of the patch to the plane. Being a patch this is a critical issue.
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