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twinturbostang

RC Control range issues

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Branching off the discussion of my poor rc range into a separate thread. The issue here is I appear to be suffering from reduced RC range. For a long time I've felt that there was reduced range with my planes. Various glitching, lack luster range checks, etc. The final straw was a crash of my FPV plane last weekend at 0.35 mile range (complete receiver lockout). I was flying my TwinStar with a Futaba 9C transmitter and a Berg7P receiver, which is supposed to be one of the best receivers out there. I was flying with a buddy, who also has a FPV Twinstar. He has almost an identical setup... Futaba 9C Super, Berg7P, etc. And he has been twice as far down range without any control issues, at this particular field. He even is running a 1Watt video transmitter just inches away from his Berg, whereas I'm running a 500mW transmitter.

Here is a quote from Mr.RC-Cam that I would like to reply to...

That is a reasonable range for a clean RF environment. But when you install switching regulators, video gear, ESC's, motors, and so on, the localized RF noise can be substantial. It can be a challenge to get everything to play nice together. Two identical models, with what looks like identical equipment, can have vastly different personalities when it comes to RF noise. So, don't get distracted by your buddy's success.

I refuse to believe it's some sort of black magic. There seems to be something severely limiting the range of my system. And I don't believe (although I could be wrong) that it has to do with switching regulators. I'm running a ParkBEC. My buddy is running the SportBEC, which is even larger.

My best guess at this point is that there may be something wrong with my frequency module. I've got another module on another channel that I am going to try and see if that makes a difference. However, if anyone has any other suggestions, please let me know.

BTW, I've had a receiver lockout before. Totally different setup. Different plane, built in BEC, FMA M5II receiver, different field, and at close range. The RC transmitter was the same though.

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If you believe it is a R/C system problem, then try this:

Perform a ground range test with everything powered on (video gear, accessories, etc.). Vary the motor's RPM to see if there is a worse case throttle position. Use the ground range test criteria suggested by your R/C maker.

Then, turn off EVERYTHING but the R/C gear. Compare the ground range under that situation. If the reliable range is the same, then you have eliminated motor and video equipment problems, which will reduce the troubleshooting work by a huge factor. To eliminate the switching BEC as a cause, unplug it and run the R/C Rx from a common 4-cell NiCD (or use the linear BEC in your ESC for the test).

Many times a range reduction is caused by more than one thing (EMI/RFI is additive). Each will contribute to the broken camel's back. The goal is to find a practical compromise in your installation that results in range performance that is acceptable. Sometimes it is as simple as moving the Rx or its antenna. Sometimes not.

Let's assume for now that it is EMI/RFI. Basically, you start out with what is called the Rx gain budget. Noise sources erode it. We can screw it up a lot and not notice that it has been compromised. But, each added noise source takes away the budget's safety margin. The perfect storm is when things are marginal, but not noticed, until something new comes along (external interference, poor R/C Tx antenna orientation, goofy Tx, servo motor that is getting noisier, bad karma, etc). Then the house of cards comes down.

But maybe it's not EMI/RFI. It will be very sweet if your problem is simply a bad Tx or Rx. I've never been so lucky, but hopefully that is all you need to deal with.

I doubt anything I've mentioned is new news to you. But, it might be good info for the newcomers.

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I have had problems with switching regulators in the past so I don't touch them now. I know someone will chime in and say they use them all the time with no problems but 'I' play it safe, once bitten twice shy.

I have also had range issues when running a 500mW TX so I stick to 100mW or 10mW TX's.

I find most range limiting effects come from the local area I fly though, sometimes the range is 1 mile with no glitches and other times it down to 1/4 mile with the same set up.

One thing I learned is that you can't be too carefull, everything in the quote you posted has at some time caused me to loose sleep !

I would test your gear one item at a time. Start with a basic plane running separate batteries for everything and a low power video TX of 100mW and see what range you can get. If all is well you can change one thing towards your ideal setup and retest, go on this way until you hit the wall. If all is not well on the first test then you know you have a basic problem like the speed controller or receiver.

Terry

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I forgot to say ...

I've got another module on another channel that I am going to try and see if that makes a difference.

It may very well help. But maybe not because the old Tx module was defective. Although the EMI/RFI we usually experience is broadband noise, the strongest harmonics are at mulitple fixed frequencies. So, moving to another channel might put you in a better place in the RF spectrum. But, the noise will still be there (and might bite you another day).

These are the sort of curve balls that make the troubleshooting task so much fun. :)

I have had problems with switching regulators in the past so I don't touch them now.

Me too. But I have not given up on them (their ability to work with high cell voltages is too compelling to ignore.). But, I am VERY careful to test for their impact to the system (obsessively so). Each installation is different, so it doesn't do any good to observe another modeler's success or failure. And, the mfg's claims are not a reliable guarantee the switcher is truly noise free.

Edited by Mr.RC-Cam

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It's not unreasonable to say that you also may have a problem with your transmitter. I sent mine in every few years for a checkup. At the least it's piece of mind, and at best it can save alot of frustration.

If your not going to be able to fly for a while anyway because of a business trip, consider sending your radio to either Radiosouth

http://www.radiosouthrc.com/radio_repair.htm

or the Futaba service center

http://www.futaba-rc.com/service.html

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It's not unreasonable to say that you also may have a problem with your transmitter. I sent mine in every few years for a checkup. At the least it's piece of mind, and at best it can save alot of frustration.

If your not going to be able to fly for a while anyway because of a business trip, consider sending your radio to either Radiosouth

http://www.radiosouthrc.com/radio_repair.htm

or the Futaba service center

http://www.futaba-rc.com/service.html

What do they suppose to do with the transmitter? To fine "retune" the transmitter?. Maybe it could help you I don´t know, in my case after brainstorming I found that my too little aileron servos where causing huge glitches (Hitec HS-55), I replaced them and the improvement was a lot. I´ve also found that my old futaba 6 channel ppm receiver is the best that behaves with my setup, compared with what were supossed to be better ones. But I have convinced that the mayor problem here is that we´re using small electric planes that don´t permit to separate the components enough.

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Could be your transmitter. Mine wasnt working very well for a few hours then it went complete nuts and the module died. Perhaps you can borrow your mate's module from his 9c and see if it works better with your gear on range test or not.

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Thanks for the suggestions guys. Not exactly what I wanted to hear of course (having to test EVERYTHING)! :) But ya know, that's the way it goes I guess. :)

Well, I definitely will be checking the switching regulators as possible sources of interference. I have two on the plane... external BEC, and a switch regulator that powers the video gear. It's possible that either of those could be causing problems.

It's interesting that two of you mentioned servos. I did notice that the rudder seems to behave strangely sometimes, no matter what channel on the receiver I plug it in to. I thought maybe it was because of the servo lead length, but I have the elevator servo almost identically matched. Yet it seems fine. So perhaps there's a problem with the rudder servo. It's an HS-55 btw.

BTW, have you guys checked out the ExtremeLink system? It sounds VERY promising. Five mile range, bi-directional communication, error checking, works with existing transmitters, etc. etc. Unfortunately, it so far looks like vaporware. I guess some people have been testing it. But no products to sell yet. There's also the possible interference issue with 2.4GHz video systems, although it's not clear if their technology will get around the problems or not. But even so, if it works as they claim, it would be a VERY VERY good reason to go with 900MHz video equipment.

edit: Holy #%$! It looks like they are selling them now! Check it out... http://www.xtremepowersystems.net/products.php?cat=11 Although most are out of stock already! lol

Edited by twinturbostang

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edit: Holy #%$! It looks like they are selling them now! Check it out... http://www.xtremepowersystems.net/products.php?cat=11 Although most are out of stock already! lol

I'm more for the "We added the products to the site so that appears to move but they've never been in stock and won't before some more time" approach, no "Wow" for me yet ;)

And yes, I've already had defective servos cause problems too, but it was more of them overloading the BEC for some internal short / overconsumption.

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I'm more for the "We added the products to the site so that appears to move but they've never been in stock and won't before some more time" approach, no "Wow" for me yet ;)

lol Yeah, I guess that's possible! :) It does look like they are moving forward though. The receiver modules look legit. They have FCC #'s as well on the transmitter modules. I don't know... could those numbers be checked somehow to make sure those are legit as well?

And yes, I've already had defective servos cause problems too, but it was more of them overloading the BEC for some internal short / overconsumption.

I will definitely check that servo then.

Edited by twinturbostang

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Here's a question... what happens when you put two linear regulators in parallel? Do they share the load, effectively doubling the possible current rating? Reason I ask is because if that's the case, then I could probably remove the external BEC I am running on the Twinstar. It uses two ESC's tied together, which means the linear regulators are also tied together in parallel. With 6 servos, that would mean each ESC is only driving the power of 3, which is definitely ok to do using a 3 cell lipo supply pack. I can probably remove the other regulator and run the video gear directly off a 4 cell NiMH pack.

Of course, this could do nothing at all, if the problem exists elsewhere. But it's at least something to test.

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I've paralleled linear BECs loads of times and never had a problem.

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what happens when you put two linear regulators in parallel? Do they share the load, effectively doubling the possible current rating?

For them to share 50/50 you need to add a small resistance in series with the output of each that is equal on both. The easy way is to add a long 'Y' lead, this will balance the current. I've been doing this for years with no problems :)

Terry

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Thanks for the suggestions guys. Not exactly what I wanted to hear of course (having to test EVERYTHING)! :) But ya know, that's the way it goes I guess. :)

Well, I definitely will be checking the switching regulators as possible sources of interference. I have two on the plane... external BEC, and a switch regulator that powers the video gear. It's possible that either of those could be causing problems.

It's interesting that two of you mentioned servos. I did notice that the rudder seems to behave strangely sometimes, no matter what channel on the receiver I plug it in to. I thought maybe it was because of the servo lead length, but I have the elevator servo almost identically matched. Yet it seems fine. So perhaps there's a problem with the rudder servo. It's an HS-55 btw.

BTW, have you guys checked out the ExtremeLink system? It sounds VERY promising. Five mile range, bi-directional communication, error checking, works with existing transmitters, etc. etc. Unfortunately, it so far looks like vaporware. I guess some people have been testing it. But no products to sell yet. There's also the possible interference issue with 2.4GHz video systems, although it's not clear if their technology will get around the problems or not. But even so, if it works as they claim, it would be a VERY VERY good reason to go with 900MHz video equipment.

edit: Holy #%$! It looks like they are selling them now! Check it out... http://www.xtremepowersystems.net/products.php?cat=11 Although most are out of stock already! lol

Check out the FCC ID!!! Its a:

http://www.maxstream.net/products/xbee/xbe...dule-zigbee.php

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For them to share 50/50 you need to add a small resistance in series with the output of each that is equal on both. The easy way is to add a long 'Y' lead, this will balance the current. I've been doing this for years with no problems :)

Terry

Well, the servo leads Y together anyways, before going to the receiver. So hopefully that will do the trick. Thanks!

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Interesting, so MaxStream quotes the 100mW EIRP version at 1 mile range, and the ExtremeLink guys claim 5 miles.

Is this really the module used?

I noticed that too. But does MaxStream quote range as far as ground to ground? Or ground to air? Because ExtremeLink even states 1 mile ground to ground, and 5 miles ground to air.

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And -at least so says extremelink from what I've read- they use a customised version Maxstream has made for them.

I guess it's mostly software stuff to improve the real-time character, but that might also mean they're always using a low bitrate which results in better RX sensitivity and thus range...

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If you look at MaxStream's specs, they claim -100dB receiver sensitivity!! And 250kbps data rate. I'm starting to believe this is the real deal. It sounds very promising. Full digital bi-directional communication with error checking. What could be better! :)

Oh, and Mark... great job finding the module XPS is using! You can actually see the XBee-Pro in the clear packaged park flyer receiver module here... http://www.xtremepowersystems.net/proddeta...hp?prod=XPS-RX6 And now I see why that one is rated at only 1000 feet. It is using the "chip" antenna, whereas the other receivers are using the whip antenna.

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If you look at MaxStream's specs, they claim -100dB receiver sensitivity!! And 250kbps data rate. I'm starting to believe this is the real deal. It sounds very promising. Full digital bi-directional communication with error checking. What could be better! :)

Oh, and Mark... great job finding the module XPS is using! You can actually see the XBee-Pro in the clear packaged park flyer receiver module here... http://www.xtremepowersystems.net/proddeta...hp?prod=XPS-RX6 And now I see why that one is rated at only 1000 feet. It is using the "chip" antenna, whereas the other receivers are using the whip antenna.

This stuff is interesting, but of little use to models with a video feed outside of the US.

The move in the USA appears to be 2.4GHz for uplink, and 900MHz for video downlink. Since 900MHz is strictly 'verboten' for video work in Europe (and many other places), this isn't a very 'global' solution.

Seems to make more sense to use 2.4GHz for the video downlink, in Europe use 868MHz for the uplink, and in the USA use 900MHz for the uplink. The 868/900MHz modules are generally interchangable and can handly the telemetry downlink also.

As soon as the PCBs come back from Olimex we'll see how this works in practice :)

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A guy on rcgroups mentioned that they may be working on a 900MHz version. So if you guys are allowed to use that frequency band for RC control, then that would be your ticket.

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Seems to make more sense to use 2.4GHz for the video downlink, in Europe use 868MHz for the uplink

In the UK we can use 459Mhz for the up link.

Terry

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