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 How Many 2.4 systems can we have operating at once
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aeajr

476 Posts

Posted - 06/12/2009 :  05:29:54 AM  Show Profile
A typical ESL contest has between 20 and 40 pilots. Today between 10% and 20% of the pilots are using 2.4 GHz systems. However over time I would expect that to increase. So I have been working the forums to see what experience people are having at large events.

Seems we have little to be concerned about when it comes to 2.4 at ESL events, at least for Spektrum or Futaba. There have been quite a number of events where there have been hundreds of 2.4 systems with no frequency control of any kind. I will post some links at the end of this note.

It is important to note that estimates are that as high as 80% of the 2.4 systems have been Spektrum/JR type. So, much of the discussion is specific to Spektrum.

Of particular interest is this page from one of those discussions. There is a report of a conversation with Spektrum Engineers and several posts from Spektrum and Horizon people that may be of interest. They discuss the kinds of tests they have done and what they have observed at these events.

Spektrum comments about large events and testing with large numbers of radios.
http://www.rcgroups.com/forums/showthread.php?p=12227164#post12227164

I have not found similar discussions of this length or depth around the other 2.4 GHz brands so it is not clear how they handle these large radio populations but so far it would seem at least Spektrum and Futaba are handling them just fine.

Note that there is an expanding crop of 2.4 system brands. Are they all equally good at dealing with large numbers of radios on at one time? Frankly we don't know. But for the moment, it would seem unlikely that we will ever have enough radios/pilots at an ESL contest to be concerned.

http://www.rcgroups.com/forums/showthread.php?t=1047652&page=32#post12437986



Best regards,
Ed Anderson
Long Island Silent Flyers
ESL Newsletter Editor

Edited by - aeajr on 06/12/2009 06:02:03 AM

aeajr

476 Posts

Posted - 06/12/2009 :  05:31:31 AM  Show Profile
This is a copy of a post contained in the thread referenced above.

From Spektrum

--------------------------------------------------------------------------------

Gentleman, My name is John Adams and I’m the Technical Director for Spektrum/ Horizon Hobby. I’ve been reading this post with great interest. Our engineers have attended most of these mega R/C events including IRCHA (heli event with over 700 pilots), E-Feast (Indoor electric event with 300 plus pilots) Joe Nall (the largest airplane event in the world), and the AMA US Nationals, not to mention all the R/C car events that we attend with hundreds of drivers. In all cases Spektrum represent over 80% of the 2.4 GHz radios at these events and we’ve had minimal reports of radio issues. The few issues that were reported were investigated and 98% of those were discovered to be secondary cause (like battery system failures, faulty connectors, airframe failures, etc.) During development our staff conducted an enormous amount of testing including simultaneously operating 66 Spektrum transmitters, purchased 40 Futaba FASST transmitters and simultaneously operating them, obtained a high output 2.4GHz frequency generator to create interfering signals, Forced multiple transmitters on the same frequency, done tons of field testing in all types of aircraft, etc, etc, etc. I’m positive that we’ve done more testing than any other 2.4GHz radio brand because I am the guy that is responsible for this testing! Early on we discovered that a high percentage of the problems that pilots were experiencing were loss of control due to momentary power loss/ interruptions. When the voltage of any receiver (Futaba, XPS, etc) drops below 3.2 volts the system ceases to function. With our early Spektrum systems the receiver would take 3 to 7 seconds to reboot if a power loss occurred. We have since initiated new programming that causes the system to reconnect immediately after a power interruption and furthermore an LED on the receiver will flash indicating that the interruption occurred. The six staff members that Horizon sent to SEFF this year included product engineers, radio technicians, product managers and product developers. These folks are technical experts capable of diagnosing any type of issues that may occur with any Horizon product including radios. With an estimated 6000 plus flights, our staff received minimal radio issues reported by customers at the event. This included replacing a suspect AR7000 receiver, replacing a frayed remote receiver extension and replacing a suspect DX7 that a customer had issues with previously (not at this event). This morning I contacted JFetter (the original poster) by phone and had a great discussion. Fetter said his research has made him aware of 6 pilots that experienced loss of control at SEFF. Horizon sends staff members to these events to support our products which include trouble shooting and diagnosing problems in the field. In the future if you are at an event and have an issue with any Horizon product, please bring this to the attention of Horizon staff members at the event.
Thanks
John Adams Technical Director Spektrum

Best regards,
Ed Anderson
Long Island Silent Flyers
ESL Newsletter Editor
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cluft

14 Posts

Posted - 07/19/2009 :  11:13:30 PM  Show Profile
You will have a problem with people flying the wrong plane and crashing or colliding with other planes long before you overload the 2.4 band with too many radios.

Carl
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dean

9 Posts

Posted - 11/07/2014 :  01:07:19 AM  Show Profile
The last one to the right feeds power to the "load" - in this case a relay of 100 ohms winding resistance. And again, resistors lead to various transistor elements, as required for their particular performances.

http://www.rctophobby.com/

Edited by - dean on 11/07/2014 01:07:41 AM
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