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2.4 Receiver Antenna Types - Now I'm Confused ?

Old 07-27-2007, 12:50 PM
  #26  
d_wheel
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Default RE: 2.4 Receiver Antenna Types - Now I'm Confused ?


ORIGINAL: dirtybird

Xtreme's technique is not new.
The 2-way communications feature is new as far as I know.

The way I see it and extra receiver amounts to redundancy and is not needed.
I guess this is where we will have to disagree. Take a look at message 11 and tell what is wrong with the analogy I refer to.

Later;

D.W.
Old 07-27-2007, 06:54 PM
  #27  
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Default RE: 2.4 Receiver Antenna Types - Now I'm Confused ?

ORIGINAL: d_wheel


I guess this is where we will have to disagree. Take a look at message 11 and tell what is wrong with the analogy I refer to.

Later;

D.W.
There is nothing wrong with your analogy. Its just that if you fly PPM you have been living with it for a long time. All RF transmissions have null spots. You can't get rid of them. I see no reason to get concerned just because the wavelength is shorter. An airplane transitions thru them so quickly most of the time you never notice them.
I think in the interest of economy the other receiver in the Spectrum system will disappear. Maybe not the extra antenna of Futaba. Wire is cheap.
Old 07-28-2007, 07:16 AM
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Default RE: 2.4 Receiver Antenna Types - Now I'm Confused ?


ORIGINAL: dirtybird


There is nothing wrong with your analogy. Its just that if you fly PPM you have been living with it for a long time. All RF transmissions have null spots. You can't get rid of them. I see no reason to get concerned just because the wavelength is shorter. An airplane transitions thru them so quickly most of the time you never notice them.
I think in the interest of economy the other receiver in the Spectrum system will disappear. Maybe not the extra antenna of Futaba. Wire is cheap.
Ah yes. Now I understand what you are saying. I agree that most of us have been living with short losses of signal for years, and never knew they were occurring. Dual antenna systems were not designed to eliminate these very short losses of signal (although they do help minimize them). Shading, caused by large metal items like engines, are much longer in duration and are definitely noticeable in flight. This is exacerbated by the short wave length (small objects are easier to hide behind objects than larger ones) and is why dual antennas are needed with 2.4ghz. While some may opt for the cheaper one antenna designs, others will look at the small additional price as cheap insurance against the loss of expensive aircraft and equipment. Dual receiver/antenna designs are most likely here to stay in full range equipment. Single antennas work fine for park fliers and will most likely remain dominant in that area.

Later;

D.W.
Old 07-28-2007, 10:27 AM
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Default RE: 2.4 Receiver Antenna Types - Now I'm Confused ?


ORIGINAL: d_wheel


ORIGINAL: dirtybird


There is nothing wrong with your analogy. Its just that if you fly PPM you have been living with it for a long time. All RF transmissions have null spots. You can't get rid of them. I see no reason to get concerned just because the wavelength is shorter. An airplane transitions thru them so quickly most of the time you never notice them.
I think in the interest of economy the other receiver in the Spectrum system will disappear. Maybe not the extra antenna of Futaba. Wire is cheap.
Ah yes. Now I understand what you are saying. I agree that most of us have been living with short losses of signal for years, and never knew they were occurring. Dual antenna systems were not designed to eliminate these very short losses of signal (although they do help minimize them). Shading, caused by large metal items like engines, are much longer in duration and are definitely noticeable in flight. This is exacerbated by the short wave length (small objects are easier to hide behind objects than larger ones) and is why dual antennas are needed with 2.4ghz. While some may opt for the cheaper one antenna designs, others will look at the small additional price as cheap insurance against the loss of expensive aircraft and equipment. Dual receiver/antenna designs are most likely here to stay in full range equipment. Single antennas work fine for park fliers and will most likely remain dominant in that area.

Later;

D.W.
I have an xtreme system with three receivers. One is in a 72" weeks special with a G-62, one is in a 62" Lazy Ace, and one is in a 77" Weeks special with a BME 102. The one in the Lazy Ace is in a tight space so I ignored the 2" rule. There are servos, throttle cable and servo cables very close. I have several flights on all airplanes and have not yet had a glitch.
Now I know that this is a small sample,but there has been thousands of the xtreme systems sold and I don't hear anybody complaining.
As Jim Drew says, if people want extra receivers he will be happy to sell them to them.
As I see it an extra receiver is nothing more than redundancy. Once you start along that path you soon will find the receiver is very low on the failure chart. Things like switches, connectors, batteries and even servos are much more likely to fail. They are not wrapped in foam and protected like the receiver is.
In the beginning people thought the short wavelength might be a problem for the reason you pointed out. Thats why Spectrum came out for park fliers only. I think xtreme has proven its not a problem. If you are not convinced you should take a look at xtremes' kitchen sink demo.
Old 07-28-2007, 10:52 AM
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Default RE: 2.4 Receiver Antenna Types - Now I'm Confused ?


ORIGINAL: dirtybird
If you are not convinced you should take a look at xtremes' kitchen sink demo.
I can see this discussion is akin to politics and religion. Neither of us are going to convince the other of anything, so perhaps the only thing we can agree on is to disagree.

As for the kitchen sink demo, I have seen many references to it, but on the other hand I have also seen magicians make elephants appear out of thin air.

I am happy for your good experience with XPS and hope it continues to go well for you. Can't remember if I mentioned it before or not, but I understand they will be offering dual receiver options in the future. With their 2-way communication AND dual receives, they will be hard to beat in the reliability department.

Later;

D.W.
Old 07-28-2007, 02:41 PM
  #31  
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Default RE: 2.4 Receiver Antenna Types - Now I'm Confused ?

Two things about the famed "Sink Demo".

1 - RF can enter the sink by diffraction (bending) at the sink opening. And moving a single servo in a static environment is worlds different than moving all your servos in the dynamic environment of a plane in flight.

2 - The thickness of the metal in the sink is only a tiny percentage of the thickness of, say a DA150.

The whole thing reminded me of the auto wax demos where they set the car on "fire", using lighter fluid. Impressive, but totally meaningless.
Old 07-28-2007, 08:18 PM
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Default RE: 2.4 Receiver Antenna Types - Now I'm Confused ?


ORIGINAL: Silent-AV8R

Two things about the famed "Sink Demo".

1 - RF can enter the sink by diffraction (bending) at the sink opening. And moving a single servo in a static environment is worlds different than moving all your servos in the dynamic environment of a plane in flight.

2 - The thickness of the metal in the sink is only a tiny percentage of the thickness of, say a DA150.

The whole thing reminded me of the auto wax demos where they set the car on "fire", using lighter fluid. Impressive, but totally meaningless.
1. Obviously the RF is getting in there somehow. The detected frame is the same no matter how many servos are connected and the load imposed on them.
2. Thickness has no bearing on screening. It depends on the integrety of the screening- not its thickness. Did you ever hear of a screen room? They are used in lab testing environments and they use thin aluminum screening to stop RF. The holes in the screen just have to be smaller than the wavelength of the RF you are screening.
3. I don't think this is meaningless. And it sure is impressive.
3.

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