Instructor

My Feedback: (16)

Skidman,

I don't mean after the link-up has been established, I mean the first time you turn on the transmitter and then the receiver. Try it and you will see what I mean. The Futaba 2.4 links up much faster than the Spektrum. I know, I have tried it....

Larry

JPMacG

My Feedback: (2)

I don't believe that 2.4 GHz is significantly worse or better than 72 MHz with regard to absorption or multipath. However, the path loss at 2.4 GHz is much, much worse than 72 MHz. Path loss (free space attenuation) is proportional to frequency squared. So 2400 MHz is a whole bunch worse than 72 MHz - about 1000 times worse. One would have to transmit about 1000 times more power at 2400 MHz than at 72 MHz in order to get same power delivered at the receive antenna terminals. http://en.wikipedia.org/wiki/Path_loss

rmh

" Nobody here would understand a component-by-component signal path explanation. Think of my explanation as a block diagram. (i.e. overall correct with a lot of details intentionally omitted.)" END QUOTE
2.4 users really don't need a signal path explanation. Nor can 99% use one."
Unfortunately for many , the expectation of 2.4 radios is that they should act like a current cell phone . turn on and go - Plug n Play.
read thru some of the explanations/opinions posted here - they simply are not plausible
A basic understanding of power requirements -is also desirable when using 2.4-
Tests which can clarify and prove power , signal strength and reception capability ARE available from all the manufacturers.
As shown in some comments - these are ignored or replaced with other 'tests" which may not be relevant .
Add to this, tests which may be true for one type device may be meaningless on other brands.
I have seen these approaches over the years and expect to see the same type approaches as an ongoing state of misunderstanding .
it is inevitable

H5487

I started to explain atmospheric signal attenuation but then saw that JPMacG did a very good job of it.

Bob, you're thinking more of antenna design. In your analogy 'stream' would be a highly focused directional antenna and 'spray' would be less directional. All of our little 2.4 Gig wire antennas are essentially omnidirectional in two dimensions but when two are mounted at different orientations, they are addressing the low signal strength in that third dimension.

Harvey

ira d

The simple answer is Spectrum felt that was what they needed to do to receive the best signal and other brands feel they dont need to go that route. It seems that not using the remote
receivers is working just fine for the brands that dont.

snir2001

My Feedback: (1)

Thanks god....

chuckk2

Back in the dark ages (1970's and before) the RC flyer preferred to use wood rod and metal linkage, or plastic
tubes with a plastic tube inside. Why? the plastic tubes were flexible, and when secured properly, worked quite well.
Both types resulted in metal rod lengths short enough to not be much of a problem at 72 Mhz
Something about parasitic antennas and altering the radiation patterns of received signals.
Today, the metal rod lengths are much longer than the 2.4 GHZ 1/4wave antennas and thus have less effect.
BUT, 2.4ghz can be absorbed or reflected more easily that 72mhz. It only make sense to use multiple antennas, and to have them oriented in different planes.
Spacing out the receivers also makes sense from a noise level standpoint.

Cobra1

My Feedback: (42)

I will just say that with some of the poor installations I have seen, it is a testament to all 2.4 radio manufacturers that they work very well under some very bad situations. I use spektrum because they made a cheap module for my futaba 9c. It has worked flawlessly but is DSM2 only. I like the remote receivers personally as it is just like the handheld radios system we use at work. The base station has many antennas placed around the building due to dead spots. I am sure our aircraft has dead spots as well but because it is moving the rcvr gets a good digital packet after a few milliseconds and all is well - and the pilot never notices. Do the remotes eliminate this, no as the data monitor shows, but I can move a rcvr that is consistently showing missed data and that gives me peace. At my age I need a little peace now and then.

rgburrill

This proves our patent office has no idea what technology is. So much stuff gets patented that shouldn't be. In 1972 my X-Band transponder system was subject to bad multipath that would kill the receiver input on a shipborne navigation system. To solve this I put a second receiver mounted several wavelengts away from the first, just enough so that if one receiver lost signal the ohter would take over. This is one of the reasons Spektrum uses 2 receivers, not just that the antennae are oriented 90 degrees from each other.

Andy, if someone really wanted to challenge your patent they would find so much prior art it would be funny.

Rob2160

Thanks for your comment Dave, Can you suggest a practical test that a layperson can use to determine that his Transmitter and Receiver are operating correctly?

You are correct, I don't fully understand the characteristics and environmental effects on the 2.4 Ghz frequency.

I know what I have read, that 2.4Ghz is essentially line of sight and it can be easily blocked by physical objects..

Before you claim my testing is "Meaningless" you must view it from my perspective. because I assure you, it was not meaningless to me.

Case in point.

1. I operated FM RC equipment for over 20 years and know that the average range (of my equipment) was about 1000 meters. Beyond that the Servos started to glitch severely.

This was never an issue because I rarely if ever flew beyond 300-400 meters. I knew the distances I was flying were less than the range of the radio - therefore I felt confident while flying.

2. Just over 3 Years ago, I purchased a 2.4Ghz radio.. I read about that frequency being easily blocked by physical objects. I wanted to know what I was working with..

I had NO idea what range to expect.. Was it 200 meters? Was it 1000 meters? How can you determine it as a layperson?

Answer - Turn on the Transmitter, power up a receiver, with a servo connected and a fail safe set on the throttle channel and start walking..

I used a small GPS to measure straightline distance and ensure I had line of sight - I also checked periodically by placing myself and other items (a plastic box) between the receiver and the transmitter to see if it made a difference at different ranges (and yes it did)

My first two radios were a Spektrum DX6i and a Futaba 6EX.

I did this testing with both of them. (results here - ( actually my first posts on RCU 3 years ago)

My simple test proved (to ME only) that I could reasonably expect the equipment to work fine at my normal flying distances inside a foam or balsa airframe with clear line of sight (max 300-400 meters)

If this testing had resulted in a lost connection at only 100 or 200 meters, I would have never used the equipment in my aircraft.

Perhaps from a scientific viewpoint, your comment is correct, but from an empirical testing viewpoint, it works for me.

There is another valid reason why I do this to all my new equipment.

Having tested several new 2.4Ghz radios, and achieving solid connection at over 3500 meters line of sight range, I have established for myself, a reasonable baseline of performance.

When I buy a new transmitter or receiver, I test it.. expecting it to perform similarly.. IE about 3500 meters line of sight range.. This has proven to be the case. I therefore know that my new equipment is functioning correctly (at least on par with the average)

I did purchase 3 Spektrum receivers on Ebay, they were park flyer receivers so I only expected 600 meters range.. in reality one of them lost contact at 150 meters, the other two at around 300 meters (line of sight) I wasn't happy with this so I threw them away (never used) and stuck to full range receivers from that point forwards.

Imagine if I bought a new radio and did NO range testing, perhaps it would bind correctly, perhaps it would appear to range check ok on low power mode.. but what if it was faulty and only gave about 500 meters range on full power? How would I know this without doing any practical testing?

My tests were not trying to prove one brand is better than the other..

Nor was I trying to establish scientifically the precise range of 2.4GHZ RC equipment.

My testing was for my own personal confidence in the new equipment initially and subsequently to ensure new products were performing to the same standard as my proven equipment.

If you can suggest a better way for the layman to test the approximate range of his radio equipment then please share and I will glady adopt your techniques.

Tony Iannucelli

My Feedback: (193)

Thanks Rob. Your post was great, exactly what a forum should be all about, facts. My experience, although not as extensive as yours in the number of flights, has been identical otherwise. Everything seems to work. I favor JR because of the programming ease. There are only a handful of pilots that I've observed capable of discerning the .001 difference in signal strength, servo speed, or any other technical specs. They work or they don't for most sport pilots. Heck, most sport pilots don't even use rates, expo, or other basic radio features from what I've observed. Not sure why they would worry about antenna diversity.

rmh

Patents are categorized
there are patents which cover a new/innovative device/item
Also patents concerning the use of an already existing device.
The patent wording will show what the patent covers.
I had assigned patents in both areas-
all expired.

eddieC

My Feedback: (2)

I experienced a signal loss on a Futaba 2.4 receiver when one of the antennas came loose from its tape mooring, allowing both antennas to lie in the same plane (no pun). It was like the receiver was turned off, nothing worked, and the plane sieved thru a tree.

We also had a fellow using Spektrum (DMS2 IIRC) in a Fun Cub have his airplane almost fly off by itself! He flew it, parked it on the flight line without disconnecting the battery or turning off the arming switch. Another fellow turned on his Spektrum and the Fun Cub engine started, and the plane taxied quickly across the runway and fortunately hit the hedge before it could get airborne. The thinking was the #2 Spektrum transmitter saw an 'open' freq and used it, as the Fun Cub's transmitter was off, and the open freq must have been one the Cub had been using. Almost had a flyaway as a result.

The point being, 2.4 is not the simple, bulletproof technology some would have us believe. We still must pay attention to installation, battery voltage, digital servo loads, etc., and after all that, Murphy still has his say.

harve28

I was a spektrum user and way too many problems
With these systems where we fly. I have now switched to futaba 8fgh super with no issues this far!

rmh

I frankly do not see this as actually happening

lopflyers

My Feedback: (12)

Oh wow, Rob, you are more meticulous and careful than most of us. I enjoyed your experiments

1UGLYPUG

If Futaba was so great and reliable, why won't they back up their equipment when someone loses a plane with a radio they know and admit was at fault? I lost 3 planes with a bad 6EX Futaba transmitter. After the second lost plane, I figured out it was the Transmitter since I had two transmitters, and bound the plane to the other TX and the problem followed the bad TX. I sent it in, and they "repaired" it,,, after I asked for a new TX. I lost another plane, sent the TX back again,and this time they replaced it. No problems since proving it was a bad TX. Still they told me to go pound sand about the loss of my 3 planes. Spektrum on the other hand, will sometimes replace a lost plane if they know their equipment is bad. They replaced 2 of my friends planes due to their bad transmitter. Now, I fly only Spektrum and have no problems and have not lost another plane. I will never buy another Futaba product due to poor customer service. Spektrum has a superior product and backs it up with superior customer service. I would not buy Futaba based on their poor customer support. Futaba stinks....

Rob2160

Thanks, I had lots of spare time while living in Perth, around 25 days free per month... not much else to do... This hobby kept me sane.

branded

My Feedback: (9)

Well, ok I'll clarify. Let's imagine the hose outputting a narrowly focused stream in a 360 degree (Omni-directional) and primarily line of sight. Similarly, lower frequencies are also emitted at 360 degrees but tend to spread out and follow the curvature of the earth and atmosphere.

[email protected]

My Feedback: (34)

This may be the most intelligent response that I have ever seen to this type question. I do not get the bashers of one or the other at all. There are lots of fine radio systems out there. As suggested, if new to the hobby, a wise decision might be to use what others use in your area. I know it worked to my advantage.. Thank you Paul...

(This was in response to post #3 by Paul. I hit quote, but it didn't work as I expected)

Luchnia

My Feedback: (21)

I am neither a Spektrum, JR, Futaba or any radio fanatic really. I have had Futaba, Spektrum and JR and mostly because I picked up some bargains. Right now I am flying a dreaded Spektrum DX7 and JR9503 which I picked up cheap. I supposed they were blackout/brownout whatever radios. I never had a glitch with either one since day one. Ignorance of others have provided great savings on many of these radios. I think there are a number of good radios out there today.

Antenna technology is amazing and in some cases has many variables. I don't have a big problem with satelite receivers, yet gets kind of crazy when you have them strung all over the place. At some point redundancy gets way overkill.

One thing I observed in the last couple of years at a club I frequent some is that many of the guys I know that were die-hard Futaba fans have switched to the newer Spektrum stuff. Mostly the 8 channel radio though. I think it is DX8 or something like that. I am wondering if that is because of the price break or maybe the features the radio has? Spektrum would not be any better than Futaba of comparible price, but model match is a sweet feature if you ask me. That is one of my favorite things about the JR/Spektrum raidos.

MinnSpin

My Feedback: (40)

Reminds me of the chicken vs. egg question.
Who was first?

Spektrum is a good system, but without the satellite - range and consistent performance are greatly affected.
Futaba does not exhibit this behavior, whether because of circuit integration or length of implementation and customer feedback.

rmh

These opinions are revealing ----and pretty much as one could expect.

1UGLYPUG

I don't care about whether you have a satellite receiver or not, all I know is that I have not lost a single plane with my Spekturm radios, and have lost 3 with Futaba, and they admitted it was there fault and sent me a new transmitter,,,, After that, it is customer service that makes the difference to me, and Spektrum has better customer service...

Luchnia

My Feedback: (21)

Good point - customer service could weigh into this. I do think most get excellent CS from Futaba though. Each experience can vary. As the old saying goes, "Your mileage may vary."