FlyingGiants Exclusive! Introducing The Futaba 12FG, Modules & More!

[Hammbone]

What about the fact that 2.4Ghz can't see through carbon fiber, metal, fuel tanks, people, trees, etc.? How is this an improvement?

Jim

[bodywerks]

I think that is a misleading statement. 72Mhz has a hard time getting a signal through carbon fiber, too. Glider guys with 100% CF airframes have to run their antennas outside the fuse to get sufficient performance.
I saw the Xlink operate with the receiver covered by a cast iron sink, so I would say that "can't pass through metal" might not be entirely true.
2.4 passes through fuel tanks just dandy, even full of fuel. Now, if you fill it with water, that's a different story - but why would you do that?
I have deliberately put a person in between myself and my plane to test that theory and maintained full control. Others have done the same with the same results.
I never tried trees, but why would I need to? Besides, all my planes are made of wood (just like trees) and the 2.4 receiver is inside it and has been working fine.

The only honest fault I have seen, and experienced, is the looooooong reboot time in the event of a receiver power drop/loss (Spektrum's deal). I have learned not to trust an ESC's BEC to four high-powered micro servos on a 3 pound plane - simple as that.

[Hammbone]

A misleading statement? This comes from the manufacturers themselves.

I think you are correct in saying that 72Mhz can't see through carbon fiber either, but 72Mhz has the ability to go around the carbon fiber as long as the rx isn't completely surrounded by the carbon fiber. 2.4Ghz is line of sight and cannot go around something.
At least that's my understanding.

I just don't see this as an improvement.

Jim

[toprudder]

	Quote: Originally Posted by Hammbone
	2.4Ghz is line of sight and cannot go around something. At least that's my understanding.

Not entirely true.

I have done shielding performance tests of large chambers (faraday cages) at 1ghz and 10ghz. It amazes me how you can aim a transmitting horn antenna at the outside of the chamber and if there is a tiny hole somewhere, the signal will leak in even if the hole is on the other side of the chamber. Granted, it may be highly attenuated (depends on the size of the hole) but it still leaks in. In fact, a 1 or 10 ghz signal will leak in where a 100 mhz signal may not. The shorter wavelengths can squeeze through a smaller hole.

Now, if you want to talk "light", that is another story.

Bob R.

[Hammbone]

Look guys, I don't want to argue with you about this stuff, but the info I am talking about comes straight from the manufacturers of 2.4Ghz systems. They are the ones that say 2.4Ghz is "line of sight", they are the ones that say it has problems going through solid objects.

I don't understand why any of you would risk your planes with 2.4Ghz when this is what the manufacturers are telling you.

It seems like you are just ignoring this info, or thinking it is O.K. because now you don't have to worry about frequencies.

I'll take frequencies over that any day!

EDIT: Then you have the problem of 2.4Ghz rx's locking out if the voltage goes below a certain level................ I've never heard of 72Mhz rx's doing that.

You are free to fly what you want though, as am I.

Take care, Jim

[JEFFRO503]

well..i can't put in my 2 cents on this because i don't own and 2.4 stuff yet.........but i wanted to visit this thread and see if there was any updated info towards the release of the Moduels and so forth. I have a 9Z which is eagerly waiting the release of the fasst moduel.......any news at all? I'm about to just go buy a spektrum moduel i think.

[DR10044]

Just curious, where do we fly our planes that line of site is an issue? During range checks I have put objects such as metal buildings between my transmitter and plane and could not get the signal to drop. In practice, I will never do this while flying!

[Hammbone]

	Quote: Originally Posted by DR10044
	Just curious, where do we fly our planes that line of site is an issue? During range checks I have put objects such as metal buildings between my transmitter and plane and could not get the signal to drop. In practice, I will never do this while flying!

Does your engine ever get between your tx and your rx? Do any of your planes have carbon fiber on them? If they do, would the carbon fiber sometimes get between your tx and your rx? Do your servos sometimes get between your tx and your rx? Does metal or carbon fiber landing gear ever get between your tx and your rx?

The manufacturer has said that this may be a problem. I didn't say this, the manufacturer did.

Happy flying.

Jim

[toprudder]

Well, any signal has a problem going "through" something. It is just that the wavelengths involved make the size of the objects necessary to attenuate the signal different for 72mhz and 2.4ghz. 72mhz is line-of-sight as well, when you get down to it.

Radio waves will also bend around objects to some extent. They also reflect. Reflections can cause a signal to be cancelled out, when a reflected signal arrives 180 degrees out of phase with the incident signal.

This is why there are two antennas on the different receivers, and why the Spektrum systems lock onto two frequencies. Mount them according to the directions and you should not have a problem.

The reboot issue has nothing to do with 2.4ghz, it has to do with the way the Spektrum receiver boots up and acquires the signal. A momentary dropout in the voltage causes this, and careful attention to the voltage supply can mitigate this problem. This is not as much of an issue with the Futaba FASST system, the voltage must drop much lower and also takes less than a second to return to operation if/when it does happen.

I, too, am interested in when the 12FG and the FASST modules for the older radios will be available. I will splurge on a 12FG once they have been out a few months, I already have 4 6ch receivers that will work with it. Alas, they won't work with the modules for the older radios.

The nice thing about this hobby is that you can use whatever you want.

Bob R.

[Hammbone]

72Mhz is not line of sight. It will go around objects and still get to the rx.
Manufacturers of 72Mhz systems do not warn you that the signal may get blocked by solid objects which get in the way.

Jim

[magicswanson]

JEFFRO503:

http://www2.towerhobbies.com/cgi-bin...?&I=LNRTU7&P=G

It says "Late Sep", which means Oct-Nov. Pretty much the end of the season here.

Doug

[toprudder]

	Quote: Originally Posted by Hammbone
	72Mhz is not line of sight. It will go around objects and still get to the rx. Manufacturers of 72Mhz systems do not warn you that the signal may get blocked by solid objects which get in the way. Jim

http://en.wikipedia.org/wiki/Line-of-sight

In particular, look at the section "how do cell phones work".

Bob R.