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Old Nov 29, 2009, 08:28 AM
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is Hitec 2.4 GHZ Single Antenna (BODA) is as Good as Dual Antenna system ?

is Hitec 2.4 GHZ Single Antenna (BODA) is as Good as Dual Antenna system ?

Guys, I am curious about the Hitec's New Technology BODA (Boosted Omni-Directional Antenna system) , Hitec have claimed that this BODA system is as Good as Dual Antenna system.

By just looking at its Picture.....it look like just a single Antenna with additional Ground Plane system.....its like a regular antenna with a Higher gain due to additional Ground Plane......that Bigger diameter look like a ground plane.

While the Dual Antenna system.....uses a Polarization concept...Horizontal and Vertical Polarization.....that's the reason why they recommend to arrange the 2 antenna wire should be 90 degree.

look like the Hitec 9 channel Dual Antenna is the best receiver, cause its usede both system. its BODA and its Dual Antenna.

Can someone post a link about the studies of BODA system.
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Old Nov 29, 2009, 09:30 AM
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I love it when companys use fancy buzzwords for stuff that is downright normal.


This BODA whatever antenna is nothing like more than an ordinary dipole with a "Sperrtopf". The english word is "tuning sleeve" or something like that. It is commonly found in normal antennas:
http://www.vallstedt-networks.de/For.../dipol_784.jpg
http://www.mikrocontroller.net/attac...AN-Antenne.JPG
It somehow increases the antenna sensivity a bit, but in no way makes it omni-directional. Jim Drew has the patent on those antennas, you know

Antenna diversity is always better than having a single antenna in challenging environments.
But normally, one can also get away with using a single antenna.
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Old Nov 29, 2009, 11:36 AM
Xtreme Power Systems
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This is a tuned ground plane, which DOES make its radiation pattern omin-directional.
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Old Nov 29, 2009, 11:36 AM
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The big question is does it work with no issues. The answer is yes.

Dual antennas are installed on the Optima 9 for redundancy and piece of mind. All testing and consumer usage has been done with a single "BODA" antenna in aircraft up to 42% with zero issues.

Don't be confused by Spektrum that attaches a receiver to every antenna. Dual antennas give you two channels to use. I guess that's why the giant scale guys use up to 8 antennas so they have more channels?

The Hitec AFHSS uses 20 channels and hops continuously and one antenna works just fine! In fact, The $50 Optima 6 is perfectly suitable for any giant scale plane!

Julez- The marketing guys have to have something to do!

Mike
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Old Nov 29, 2009, 04:26 PM
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"This is a tuned ground plane, which DOES make its radiation pattern omin-directional."

If you live in a two dimensional world - well, someone had to say it
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Old Nov 29, 2009, 09:45 PM
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Quote:
Originally Posted by MikeMayberry View Post
The Hitec AFHSS uses 20 channels and hops continuously and one antenna works just fine! In fact, The $50 Optima 6 is perfectly suitable for any giant scale plane!

Mike
What's the width of 1 of your channels? And does the hops happen while in normal mode or just the scan mode? Or please explain the explanation in the spectra confuses me a bit It makes me think that it just hops while in scan mode.
Thanks.
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Old Nov 29, 2009, 11:40 PM
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The Hitec antenna is a sleeve dipole.

These antennas do exhibit a more symmetric radiation pattern than many others which also means that they are closer to an isotropic gain (of 1.0). Remember that any antenna which claims to have a gain over isotropic does *not* have a spherical radiation pattern because the only way to obtain gain is to take power radiated from one direction and add it to the power radiated in another.

Their biggest advantage aside from the more symmetric radiation pattern (note: not *fully* symmetric but better than any other practical antenna) is that they also exhibit very low SWR -- which is the ratio of the power you put into the antenna to the power that gets reflected back by any mis-match of impedance.

I suspect Hitec had taken this route to reduce the chances of null-spots in the radiation pattern from causing momentary dropouts in the signal and also because they're transmitting through that antenna as well.

When an antenna (such as those on Futaba, Spektrum, Corona, etc) are used only for receiving, the requirements to be a well matched to the circuitry inside are much less critical than when you're using them to transmit.

A poorly matched antenna hooked up to a transmitter causes that trasmitter to get hot and can produce unnecessarily high (potentially destructive) voltages in the circuitry.

Hitec's antenna therefore, provides a reliable link under a wider range of attitudes and aspects than would do a 1/4-wave antenna with an irregular groundplane (ie: XPS and similar) while also ensuring that a much of the telemetry transmission power is actually converted into a broadcast radio signal as possible.

The only other manufacturer I've seen using a coaxial sleeve-dipole type antenna on their 2.4GHz receivers is the Chinese company WFly.

I'll be going more deeply into this in my 2.4GHz shootout and my review of the Hitec AFHSS system at RCModelReviews.com which (due to my wife's failing health) have been delayed a little longer than I'd hoped.
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Old Nov 29, 2009, 11:58 PM
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guys, Thanks for all your reply.....Hope somebody can make the actual Measurement of the Antenna Gain of BODA and a non-BODA antenna.....I am very interested about the Actual Measurement.

look like its already been proven that The Single Antenna can work, there already lots of products such as XPS , Spectrum 2.4 GHZ Single Antenna, ASSAN , Esky , Corona 2.4 GHZ..........look like the chance of successful is 99.9 %

here is my opinion of change of successful

2.4 GHZ Single Antenna is 99.9 %
2.4 GHZ Dual Antenna is 99.99 %
2.4 GHZ Tripple Antenna is 99.999 %

In 3 Dimensional World there are 3 Plane, X, Y, Z......if you are using a RC Car, Single Antenna is Good enought, cause can run in Single Plane .......... in Airplane and Helicopter, it use 3 Plane.........its the same reason, I use Tripple Antenna on all my Scale/Gasser Helicopter.

One Thing I like about the Hitec's 2.4 GHZ is its Built-in Telemetry....Hope, Hitec has an option to send the Quality of Data Link, such as Signal Strength, and percentage of Successful packet send.
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Old Nov 30, 2009, 02:02 AM
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I think the gain of the antenna is not the germane talking point.

a 2 antenna setup is using those 2 antennae not only to compensate for polarization and achieve all aspect signal reception, but also to have multiple sampling sources to filter out multipathing and to reduce the likelihood of the signal being shadowed.

the 'BODA' antenna helps the all aspect reception issue, but it does nothing to address multipathing and shadowing.

I do however think that it realistically is a '99.90%' vs '99.99%' type problem, and one way of looking at that is to say that both systems are very reliable. but the other way of looking at it is that the first system would experience 10x the failures, so...

if you keep the single antenna far from the engine/rx battery, and you are flying a mostly wood/foam radio transparent aircraft, you're minimizing risk to what any sane person would call an acceptable level, but a 2nd antenna would still provide a safer solution, and one can consider more challenging installs that would make a stronger argument for multiple receiving elements.

mind you, one has to keep in mind that the 9ch hitec RX with 2 antennae is quite inexpensive, slightly more than a 7ch unit from fut/spektrum, while the 7ch unit is a dose cheaper, so a prospective purchaser can choose to have similar security by paying similar prices, or they can decide themselves that they'd rather not pay for the extra reception performance if they feel it unnecessary, so there's not really a downside to the hitec system when looked at in this way.
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Old Nov 30, 2009, 02:51 AM
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Quote:
Originally Posted by DannyZRC View Post
the 'BODA' antenna helps the all aspect reception issue, but it does nothing to address multipathing and shadowing.
That is true -- but hopping over 80MHz of the band does do a lot to help multi-pathing by shifting the null-points created by the intersection of the primary signal and the reflections.

As has been stated -- it's a 99% solution and if you lose one frame in 100 then you'll never notice it.

I must admit though that I would be happier using two antennae in a large model with significant metal or carbon components that might produce a lot of shadowing.

It's a good move on Hitec's part to offer dual antennae on their 9-channel receiver -- because that's the one most likely to be used in very large models with big motors and carbon wing-tubes, etc.
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Old Nov 30, 2009, 01:21 PM
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FYI: The samples of the Optima 6 's I've been testing have two antenna connectors and the Optima 7's have a place for second connection but it is not installed. It could be added in the future if needed. But again... we have not needed it, big motor (DA170,) carbon-fiber wing tube (AeroWorks 42%Yak) and all.

XJet- Sorry to hear about your wife's health... I hope she feels better soon. I will be interested to see your analysis of the Hitec 2.4 system vs. the others.

Mike.
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Old Nov 30, 2009, 06:21 PM
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Quote:
Originally Posted by MikeMayberry View Post
FYI: The samples of the Optima 6 's I've been testing have two antenna connectors and the Optima 7's have a place for second connection but it is not installed. It could be added in the future if needed. But again... we have not needed it, big motor (DA170,) carbon-fiber wing tube (od42%Yak) and all.
Mike.
Thats very interesting to know........this means I can just purchase the Optima 7 with Single Antenna and add my own 2.4 GHZ Antenna......I can easily purchase a WIFI 2.4 GHZ antenna.

Mike, When the Hitec 2.4 GHZ Telemetry will be available ?
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Old Nov 30, 2009, 07:25 PM
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Not exactly... The current Optima 7's do not have the second connector soldered to the board, but there is a spot for it.

Telemetry add on items are due sometime in the first quarter '10. That's all the info I have at this time.

Note: Please keep this thread on topic... if you want to discuss Aurora stuff other than the antenna, post in that thread.

Mike.
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Old Nov 30, 2009, 07:42 PM
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you know, my ar6200 which has the satellite rx is my most reliable, 100% idiot proof and my overall favorite rx. I've never had a problem with it, and its taken some abuse. I can't say that about the single rx or single antenna units. I would really like to see an aurora rx and play around with it doing range checks and stuff, to see what happens.

Lucas
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Old Dec 01, 2009, 12:03 AM
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You're still talking apples and oranges between AFHSS & DSM-2.

We did a power down range check to 1320' (1/4 mile!) with the Optima 7. What do you get with the AR6200?

Mike.
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