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Old Nov 14, 2012, 09:04 AM
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Originally Posted by richard hanson View Post
I have to call you on that -
Past experiences with 72/50/53 mhz show voltage drop is far less of an issue.
None of those will require resetting even if voltages drop below servo operating voltage levels . Servos will slow and operation can become unflyable -but the rx do not stop trying to process.
I used to fly stuff weighing over 40 pounds and I did a lot of checking on battery requirements to keep the huge control surfaces operating.
When 2.4 hit the scene -the power requirements was one of my first questions .
The myth
I know of no myth but factually ALL the 2.4 radios will stop processing info at voltage levels where servos become inoperable . You may see a few tenths volt differences between brands but all of the rx stop and must reset at some point around 3 volts.
When I made similar experiments on a Fasst RX, I found out that my servos stopped around 3V, but the RX at 2.7V. This means, that the servos cannot draw the voltage below 3V, and thus cannot produce brownouts.
And even if they did, a Fasst RX has always been recovering within one second.

Not so the Spektrum RXes. They suffered from brownouts already at 3.2-3.5V, they synchronized the servo signals making voltage drops much more severe, and in the beginning, they took multiple seconds to respond after power-up or reboot.

This combined lead to the myth that ALL 2.4 systems are in danger of a brownout.

For some strange reason, Fasst, Jeti, FrSky etc. users never had any such problems.

This is because these RXes have a low reboot voltage, they don't synchronize the servo signals, and they reconnect in an instant after reboot.

My buddys and me flew Fasst and Jeti all the time since 2007, did not change anything in our power systems, and we had zero problems.

If our batterys can power our servos, they are also enough to power our recievers.

Some time ago I wrote this:

http://www.rcgroups.com/forums/showt...0#post10855830

Especially interesting is the posting below mine.

A longer explanation:

http://www.rcgroups.com/forums/showt...=4#post7753366
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Old Nov 14, 2012, 11:06 AM
Oxford Panic
AndyOne's Avatar
United Kingdom, Oxford
Joined Feb 2003
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Julez,

I always suspected Futaba knew something about R/C design that others didn't. it's so simple now, this is why you don't hear reports about Futaba brown-outs.
Well done for spotting that one.

A.
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Old Nov 14, 2012, 11:14 AM
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So, has Horizon/Spektrum fixed this horrendous issue or not yet?
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Old Nov 14, 2012, 12:18 PM
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United Kingdom, England, Hitchin
Joined Jan 2004
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Quote:
Originally Posted by AndyOne View Post
I always suspected Futaba knew something about R/C design that others didn't. it's so simple now, this is why you don't hear reports about Futaba brown-outs.
Well done for spotting that one.
Maybe, maybe not. I suspect it's more that being the first (or nearly the first) spread spectrum 2.4 solution meant Spektrum fell victim to the gotchas that always occur when a new technology is introduced to the consumer market. In this case the issues were exascerbated by most people not understanding the physics around 2.4 or the increased power requirements of the RXs, meaning many crashes were blamed on "radio failure" when in fact they were user errors. Either way it meant the likes of Futaba could design improved systems based Spektrums learnings. Just my 2 cents.

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Originally Posted by crvnation View Post
So, has Horizon/Spektrum fixed this horrendous issue or not yet?
I'm not an expert on Spektrum (I use FrSky myself), but I believe they have addressed some of these issues with speedier reboots and lower reboot voltages in their newer receivers, plus of course the full hopping DSMX is a more robust RF solution than DSM2. However if you have one of these older receivers then I guess all the caveats above around brownouts still apply...
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Old Nov 14, 2012, 12:26 PM
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Bowling Green,Ky
Joined Sep 2004
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With DSM2 when you turned on the trannie it scanned for two open channels and locked on. When you turned on the plane the receiver scanned looking for the transmitter and then it locked on. If you had a "brown out" the old receivers had to rescan to find the transmitter. that's what took up the time.
When Spektrum realized this was a issue the first fix was to have the receiver go to the channels it had been using. This was a rewrite of the software in the receiver and any Spektrum user could send their receivers in for the up grade. This improved the reboot time greatly. All the new receivers have this in their programing.
The new X is even faster because it hops and we as users have learned that we need to take care of our power needs better as in all the systems.
I'm still using the first receivers that came out with the modules. Never had them upgraded and have never had a issue. The reason being I use battery's that will handle my needs.
Some day I will upgrade my radio to X when I have to replace the receivers. Dennis
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Old Nov 14, 2012, 12:44 PM
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United States, FL, Miami
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Originally Posted by crvnation View Post
So, has Horizon/Spektrum fixed this horrendous issue or not yet?
No, they havent found a way to power receivers and servos without dc voltage.

As previously stated, other manufacturers sort of got away with inadequete power setups because the servos would stop operating before the receiver.
While better, you still have a situtation where you are losing some control of your model.


And to jasmine2501 disbelief, I've never personally experienced a brownout, just lockouts or lack of signal. I have experienced blackouts though, when the ESC fries in mid-air and everything goes down in a blaze of glory.
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Old Nov 14, 2012, 01:02 PM
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United States, AZ, Mesa
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Originally Posted by pach View Post
And to jasmine2501 disbelief, I've never personally experienced a brownout, just lockouts or lack of signal. I have experienced blackouts though, when the ESC fries in mid-air and everything goes down in a blaze of glory.
Do you have the telemetry record to show that you lost the signal? I believe in loss of signal, I just haven't ever seen it confirmed with measurements. I'm sure it happens, it's a physical law, but I think it is pretty rare when compared to the amount of brown-outs.
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Old Nov 14, 2012, 01:03 PM
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United States, UT, Salt Lake City
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Originally Posted by Julez View Post
When I made similar experiments on a Fasst RX, I found out that my servos stopped around 3V, but the RX at 2.7V. This means, that the servos cannot draw the voltage below 3V, and thus cannot produce brownouts.
And even if they did, a Fasst RX has always been recovering within one second.

Not so the Spektrum RXes. They suffered from brownouts already at 3.2-3.5V, they synchronized the servo signals making voltage drops much more severe, and in the beginning, they took multiple seconds to respond after power-up or reboot.

This combined lead to the myth that ALL 2.4 systems are in danger of a brownout.

For some strange reason, Fasst, Jeti, FrSky etc. users never had any such problems.

This is because these RXes have a low reboot voltage, they don't synchronize the servo signals, and they reconnect in an instant after reboot.

My buddys and me flew Fasst and Jeti all the time since 2007, did not change anything in our power systems, and we had zero problems.

If our batterys can power our servos, they are also enough to power our recievers.

Some time ago I wrote this:

http://www.rcgroups.com/forums/showt...0#post10855830

Especially interesting is the posting below mine.

A longer explanation:

http://www.rcgroups.com/forums/showt...=4#post7753366
I don't agree - - In actual pactice a battery which is depleted ( o ralmost depleted ) goes thu the under 4 to under 3 volts - in a fairly short time period - Failure of either rx or servo being of little importance as things have stopped responding.
The reasoning of "you had no failures " means little as honestly I have flown 2.4 Spektrum from initial issueing of early DSM DX6 tx and rx- never a failure in the air.
amongst the many Spektrum users here - the experience has been the same .
Most of the early on users I know, flew small electrics and were aware of how bad batteries could be.-(capacity only, no tbeing an indicator of how they responded under loads .) They simply made sure they used enough battery POWER.
The Horror issues are simply BS.
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Old Nov 14, 2012, 01:35 PM
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Bowling Green,Ky
Joined Sep 2004
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As I said in my last post. My receivers are the ones that came with module before they even had radios.
I did take the time to try and understand the system and when i flew the first time everybody at my club thought I was crazy (some still think I am) They to a man said they'd never change. Well guess what, don't see a card on the board anymore.
The first year Spekrum sold the module and receiver I took a chance and took 8 to our jet meet. Sold them within a half hour. the guys put them in their jets did a range check and took off. Not one failure.
I can still remember all the griping when we had to upgrade our radios to narrow band. And yes some blamed crashes on the radio. Dennis
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Old Nov 14, 2012, 02:00 PM
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Quote:
Originally Posted by jasmine2501 View Post
Do you have the telemetry record to show that you lost the signal? I believe in loss of signal, I just haven't ever seen it confirmed with measurements. I'm sure it happens, it's a physical law, but I think it is pretty rare when compared to the amount of brown-outs.
You really dont need that when you are flying level with 2 micro servos and absolutely no load and control is only lost in certain orientations of the plane.

Or when signal failsafe hits and suddenly the plane is doing the loops set for failsafe.
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Old Nov 14, 2012, 02:38 PM
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United States, UT, Salt Lake City
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Quote:
Originally Posted by pach View Post
You really dont need that when you are flying level with 2 micro servos and absolutely no load and control is only lost in certain orientations of the plane.

Or when signal failsafe hits and suddenly the plane is doing the loops set for failsafe.
I do believe in signal loss- seen it - also have seen WHY signal loss occurred.
The last times involved the most expensive Futaba systems on the market.
The problem?
antenna orientation and correcting this issue, fixed the problem
Why would good flyers flying good equipment have this issue?
Does it happen on low cost stuf
- saw it last month - when the plane was flown behind the pilot - in a line which blocked the tx (held against the chest).
If the plane failsafes in certain positions - is that a receiver Problem?
Or simply incorrect antenna placement (or using short range setup in long range app.) issue. Also - I have setup tests which show certian battery failures can and will result in servos driving or staying full over .
The condition occurs when power drops below threshold- servos stop - power moves back above threshold , again powering the servos - etc., etc,
If you have never tested for this it is hard to accept - but it will and can happen.
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Old Nov 14, 2012, 02:43 PM
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Originally Posted by richard hanson View Post
- saw it last month - when the plane was flown behind the pilot - in a line which blocked the tx (held against the chest).
And? I saw a video of 1st place winner at iHobby, Patrick H., fly an entire routine with his Blade 130 X...with the TX behind his back. Obviously, it was Spektrum. He didn't seem to have any problems.
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Old Nov 14, 2012, 02:49 PM
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Originally Posted by crvnation View Post
And? I saw a video of 1st place winner at iHobby, Patrick H., fly an entire routine with his Blade 130 X...with the TX behind his back. Obviously, it was Spektrum. He didn't seem to have any problems.
That was not a tiny Bind n Fly which has minimal antenna.
You can block the signal in many cases by placing a body between tx and the model - this test is easily done using a system which has telemetry that shows losses
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Old Nov 14, 2012, 03:06 PM
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You can block the signal in many cases by placing a body between tx and the model - this test is easily done using a system which has telemetry that shows losses
Whatever... I just said *he* didn't see to have any problems flying an entire routine with his body in between his TX and, yes, that tiny BNF heli with an extremely minimal antenna. If anything, that would be a much worse scenario than with bigger stuff that has longer antennae, satellites, etc.
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Old Nov 14, 2012, 03:12 PM
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Originally Posted by pach View Post
You really dont need that when you are flying level with 2 micro servos and absolutely no load and control is only lost in certain orientations of the plane.

Or when signal failsafe hits and suddenly the plane is doing the loops set for failsafe.
Yeah sure, there's nothing other than signal lost to explain that.
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