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Jan 25, 2013, 02:16 PM
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Michael V's Avatar
A few more points:
- FM signal always selects the strongest, so while antenna direction in close proximity may not be an issue of range, it still is a factor in resistance to noise pollution.
- Diversity units with multiple antennas is a good solution (chooses the best signal out of multiple antennas) that is typical on some FPV receiving stations. It may that Rx with two antennas use diversity, but I'm not sure. In which case put one wire horizontal, the other vertical, or at 90deg of each other, each has its advantages (except parallel is not as good)
- What I meant thus is that you may have one plane or one flying session for which horizontal is best and another for which vertical is best. There is no perfect for all. Or one can just choose one and make it the best compromise.
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Jan 25, 2013, 05:41 PM
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Teambarger's Avatar
subd
Jan 25, 2013, 07:33 PM
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tignmeg's Avatar
Michael V
Thank you for your effort. It was very informative.
The key bits I got out of that was that you should 'try' to optimize orientation but most users would not notice the improvement and diversity is well worth the effort/cost. This explains why some high end receivers have multiple antennae / satellites.


A pity some in this forum would much prefer to flog us off saying it is far too complicated for posting in a forum. When it is more likely that they themselves don't understand it.
Jan 25, 2013, 07:35 PM
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Atomic Skull's Avatar
Quote:
Originally Posted by Fly2High View Post

Now, if I am up such that I am in a thermal turn and the carbon fuse blocks one antenna, couold you not have the other receiver antenna pointing straight at the transmitter causing it to reeiver the worst possible signal?
I'm starting to prefer FRP to CF in my helicopter frames. Only a few grams weight difference, more durable in a crash and it won't shadow the radio. Less expensive too.

And you can get them in colors other than boring black.
Last edited by Atomic Skull; Jan 25, 2013 at 07:41 PM.
Jan 26, 2013, 03:41 AM
Registered User
All this talk of antennae position makes me wonder why we can't have diversity on our tx as well as on out rx.
I have my antennae horizontal as more likely that I will fly high over my head then far away out to the side, but on occasion if I am laying down with plane thermaling I have to think about the orientation a bit to be safe.
Is there a reason we don't have 2 tx antennas?
Jan 26, 2013, 04:37 AM
Suspended Account
Quote:
Originally Posted by Atomic Skull View Post
more durable in a crash and it won't shadow the radio.
I disagree

Quote:
Originally Posted by nigelsheffield View Post
Is there a reason we don't have 2 tx antennas?


Jan 26, 2013, 04:48 AM
Bleriot's R Us
xairflyer's Avatar
Quote:
Originally Posted by nigelsheffield View Post
All this talk of antennae position makes me wonder why we can't have diversity on our tx as well as on out rx.
I have my antennae horizontal as more likely that I will fly high over my head then far away out to the side, but on occasion if I am laying down with plane thermaling I have to think about the orientation a bit to be safe.
Is there a reason we don't have 2 tx antennas?
Multiplex do
Jan 26, 2013, 12:31 PM
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Michael V's Avatar
Quote:
Originally Posted by nigelsheffield View Post
All this talk of antennae position makes me wonder why we can't have diversity on our tx as well as on out rx.
I have my antennae horizontal as more likely that I will fly high over my head then far away out to the side, but on occasion if I am laying down with plane thermaling I have to think about the orientation a bit to be safe.
Is there a reason we don't have 2 tx antennas?
This is my theory, but it could be wrong:
One can only have one antenna active at the time. That's what diversity does, pick the one with the strongest signal.
So you cannot have two antenna active, and while it's easy to pick the strongest signal when receiving, when transmitting there is no reason why one would be stronger than the other unless you get feedback from the receiver (and constantly pulses both) or you know where the receiver is at least. That is why.
Now I don't know what the 2 antennas purpose is on the transmitters pictured below, but I'm curious. Anyone knows?
Jan 26, 2013, 12:40 PM
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WimH's Avatar
Quote:
Originally Posted by Michael V View Post
Now I don't know what the 2 antennas purpose is on the transmitters pictured below, but I'm curious. Anyone knows?
Transmitter diversity...
Jan 26, 2013, 12:58 PM
Registered User
The transmitters using two antennas use them switched, not simultaneously.
Using both in the same time will make multipath even worse.

When you see two or more antennas in professional tower, those are antenna arrays, and the placement is uber critical to make hem work as only one.
Jan 26, 2013, 08:25 PM
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Quote:
Originally Posted by tignmeg View Post
A pity some in this forum would much prefer to flog us off saying it is far too complicated for posting in a forum. When it is more likely that they themselves don't understand it.
Whats a pity, is people want to be spoon fed on a forum, without doing the research themselves, and actually learning!!

Regardless, everything Ren and I have stated still holds true!!

Even when considering Rx diversity, and the way most people fly, if the antennae are placed at 90deg., the average position of the two, with an acceptable receiving pattern will be vertical. Even if one is pointed down, its still vertically polarized. There are some cases where the average will be horizontal, but that should only apply if you were careless in you Rx antenna placement.
Jan 26, 2013, 08:54 PM
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tignmeg's Avatar
Quote:
Originally Posted by KKUSA View Post
Regardless, everything Ren and I have stated still holds true!!
.
Maybe that would have been true if there had actually been anything said that was actually constructive.

Luckily, most who have posted here are smarter than me and just ignored the rhetoric and arrogance.
Jan 26, 2013, 09:13 PM
Registered User
Maybe KKUSA you're talking about Rx with two antennas. Mine only have one.
Jan 26, 2013, 09:52 PM
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Quote:
Originally Posted by xairflyer View Post
Multiplex do
As does the Futaba 8J and the Spektrum DX18.
Jan 27, 2013, 03:30 AM
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Atomic Skull's Avatar
Quote:
Originally Posted by Mikarro View Post
I disagree
CF's greater stiffness actually makes it more likely to shatter in a crash than an FG or plastic frame.


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