BuschBarber

My Feedback: (2)

I recently switched my H9 P47-150 from 72Mhz to 2.4. I have Dual Elev, Dual Ail, Dual Flap, Dual Retract servos, Throttle, Rudder, and Fiber Optic Kill. Fuji32ei gas motor. When I moved the Elevator stick, the Elevator servos would become erratic and the Rx would Reboot. I thought it was the 5v regulator, so I switched to a CC BEC Pro. Same problem. I finally traced the problem to the extensions going To and From the Rx battery Switch Harness.

I have had to deal with problems like this for years, with 72Mhz, but this is the first time I have had this happen with 2.4. I do not blame the radio. The aircraft is 5 years old and even though the extensions seem in good shape, things happen. The aircraft has never been crashed. The Rx is new, however, I tried an older Rx and got the same results before I changed the extensions.

I even changed transmitters to see if that had any effect.

stoneenforcer

My Feedback: (23)

really sounds like a 2.4 lock out. how many satelites are you runnning? ive had and seen this same issue. 20' off the ground hovering, cockpit facing me, plane 25' in front of me. bam! lock out!! had it happen twice. ALL 2.4 systems have blinds spots. You might have found one due to the orientation of your rx. Do you check your rx after you turn it on to make sure you have a full connection and not a parial aka blinking light?

from your descriptions, inputs and volt feed. I just dont see anything else being an issue.

rgburrill

An electronic engineer, you are?

Noise rarely affects the RF portion of the system - it usually affects the IF and final demod. Spread spectrum gives you the ability to haphazardly turn on your radio without thinking about anyone else out there.

I have seen several gassers get wiped out by ignition noise on take-off due to the higher engine speed.

dirtybird

My Feedback: (5)

Yes
I wrote the ground test procedures for the Irridum satellite system control. It was similar to a spread spectrum system at 3ghz. The only difference was it used a generated key for code synchronization instead of a pseudo random number generator.

All Day Dan

My Feedback: (5)

Scota, here's Futabas' advice that they have listed on their website;
Guidelines for setting up gasoline engine models.
All ignition equipment, including an electronic kill switch, must be mounted at least 12", and preferably 14", away from all radio equipment, including throttle servos, etc. Ignition kill switch should always be on opposite side of fuselage from radio kill switch. All pushrods going to anything related to the engine must be non-conductive (just nonmetal clevises is not sufficient).

Please listen to their advice the next time you set up your models. Remove that $20 piece of Chinese cr*p you are using as a BEC and use a seperate battery for the ignition. Yes, they will work sometimes. It's not worth the risk as you have found out. Sorry about the plane. Dan.

raptureboy

Oh, I just can't help myself. Airtronics 2.4 FHSS for 3 yrs not even a twitch or nervous moment, 2000 MaH NmH 6v NOBSBATTERIES sub C cell on Rec, 2000 MaH 4.8 AA on ignition on a 1/5 Stearman and a 1/4 Ryan. But really it's all a crap shoot, and I'm glad you didn't suffer a total loss and that it may have been something as simple as reverse controls. The key to NmH batteries is not just capacity but also impedence of the cells. Suggest you check out this site for excellent batteries andexcellent advice. www.hangtimes.com Thats my 5 cents.

eddieC

My Feedback: (2)

Never. Ever.  +1

I don't know about a switching regulator, but I've seen 2.4 get swamped (a lockout) by ignition noise. PCM also. Anything can be swamped by a strong enough signal.

Rgb, he gotcha good.   

DB, I enjoy your posts, but have seen many problems running ignition from the Rx pack(s). Glitching, lockouts, etc. When FM was popular and we got glitches running gassers, 'PCM' was the answer. When PCM had the same issues, '2.4' was the answer. The real answer many times is get rid of the RF noise - better shielding, isolation, etc.  Props to your expertise, but I'll not run ignition from the RX battery. It just eliminates one more worry.

raptureboy

That is ancient advise from the 72mhz days. Have you really tried to mount any equipment related to ignition 12-14 inchs away from your radio gear? Look at all the small 60 size planes being flown on gas. It's not an issue for 2.4 I have been using 4-40 metal rods with bolt on nylon ball links on all my gassers and not once has it been an issue. My receiver even sits under the throttle rod. A modern electronic ignition properly installed and grounded is not a problem for 2.4 Battery issues on the other hand are responsible for most of all the issues being blamed on the radio, and I am still amazed at how guys at my field still think it can't be the battery because they charged it last night and it's 2000 maH, or brag on how little they paid for their radio batteries in their $1000 plane I'm not saying the op has or uses cheap batteries it's just that this always keeps coming up thatwe have to use lipos or A123 or whatever when the current tech is still a reliable option and safe and easy to maintain IF the operator would educate themselves about the proper selection, care, and use of their equipment. O.k I'm done. Next.

dirtybird

My Feedback: (5)

We have all been spooked by the sensitivity of our old systems to RFI.
I remember when digital AM systems appeared I was surprised it even worked. FM systems were an improvement but even so it required careful shielding of the components.
Spread Spectrum systems are a different animal though. The information is spread over a band of frequencies at least 1 mhz wide. Even if part of that band is wiped out the receiver can reconstruct the missing data from the little data it has received.
Your ear does the same thing. If you get in a high noise environment, and you are talking to your buddy, you can hear what he says even though the noise is much higher than his voice.
The only real problem with SS is it demands a stable DC source because it uses a microprocessor.
Ignition noises are just simply not in the 2.4 frequency domain. Ignition noise, however can bypass the receiver and couple directly to the servo leads if they(the RFI) are strong enough. So it make sense to shield the ignition system. The manufacturers do that for us if you follow their direction.
Mainly make sure the cap is on the spark plug securely.

dwaynenancy

My Feedback: (62)

Rich, could you tell me whether or not your extensions had gold plated pins/sockets?

rgburrill

Cool. Then you certainly will understand that FM, PCM and the various SS technologies are used to get the signal from the transmitter to the receiver. And you'll understand that the servos are independent of whcih broadcast method is used. So you must know that these receives downconvert the input to one or more IF frequencies that ultimately carry a pretty much similar signal that is output to the servos. I haven't studied SS since it's been a while since I worked RF systems but PCM, FM (both single and double conversion) and the much older AM ultimately 455KHz as the final IF frequency. And there is where the noise really can hurt, no matter what kind of broadcast system you use. As someone else pointed out, gas engine ignition problems have been blamed on RF interference for years with the new technologies promissing to fix it. But they didn't because the problem is not a broadcast RF technology problem.

So, did you also write the EMI/EMC test procedures for the satellite? Have you done Tempest testing or anything like it? Do you remember that the number one problem in nearly all EMI/EMC issues is the power leads?

eddieC

My Feedback: (2)

BuschBarber

My Feedback: (2)

I only buy extensions with Gold Plated pins and 20-22ga wire.

erik valdez

My Feedback: (80)

You guy's apparently need to refer to my work, I wrote the test procedures for the Turbo Encabulator.

[link=http://www.youtube.com/watch?v=lVZ8Ko-nss4]http://www.youtube.com/watch?v=lVZ8Ko-nss4[/link]

dirtybird

My Feedback: (5)

I haven't looked at the schematic of a 2.4 receiver but I am fairly confident there are no IF circuits in there. At least I don't see any IF cans. Remember IF circuits are used to provide selectivity. With SS we need broadband capability. I have an XPS receiver thats about the size of a postage stamp. If there is any down converting done its done on chip.
I have not done any EMI/EMC OR TEMPEST testing. It was always a concern with our circuit design when I did circuit design. BTW TEMPEST testing is done on military systems to make sure the cryptography key is not available via RFI. Its not done on non-military systems.
You appear to be hung up on hetrodyne circuits. There are other ways to do it.
Hetrodyne systems normally mix two signals together to down convert a signal. There is a system used for a radar speed detection that uses only one transmitted signal. The transmitted signal is mixed with the received signal. Due to Doppler shift the resultant signal will be an indication of the speed of the detected target. Do you know what the official name of such a receiver is? Its called a homodyne receiver.

Update The XBEE-PRO chip has been used in xps recaivers. The following link gives the spec sheet for that chip.
http://www.digi.com/products/wireles...odule#overview

dirtybird

My Feedback: (5)

Can that be used for a colonospy?

dbacque

My Feedback: (3)

Wow, tempest testing! I haven't done that since the 80's when I was working on military flight simulators. Tempest was amazing stuff. Before we built a specialized computer room, they could pull the tempest test vehicle up outside our building and bring us hardcopies of what was up on our CRTs inside our computer room. All I could ever say was How the Heck??? Building a tempest room was expensive but stopped all emissions. Those spooks knew what they were doing.

Gee, was that off topic or what?

Dave

AndyKunz

That is what allowed me to meet VP George Bush when I worked in defense back in the 80's.

Andy

chuckk2

A little shielding of the monitor leads might have solved the RF radiation.
Think of putting a whole Navy ship through tempest testing! Been there, etc.
(1967-8) Or a whole large aircraft such as a B1.
In the 70s and 80s, HP terminals were some of the "nosiest", due to no shielding on the cables.


One of the problems with civil aircraft was the overhaul system that replaced whole sections at a time.
cabling was tested for resistance, etc., but the integrity of the shields was not checked. Hence the concern about
interference from calculators, computers, and cell phones, even when a calculator is FAA approved for use on aircraft.
With certain military aircraft, it was not unknown to use a spectrum analyzer on the ramp, checking for undesired emissions
before a mission. We also checked some aircraft using active RF sources.
I hope past lessons learned eventually resulted in better susceptibility testing.

chuckk2

[quote]ORIGINAL: rgburrill


An electronic engineer, you are?

Noise rarely affects the RF portion of the system - it usually affects the IF and final demod. Spread spectrum gives you the ability to haphazardly turn on your radio without thinking about anyone else out there.

I have seen several gassers get wiped out by ignition noise on take-off due to the higher engine speed."


That aside, unsuppressed spark noise can cause RF related problems by increasing the noise that the receiver "front end" sees, thus reducing the receiver's ability to deal with a weak signal. As to noise amplified in the various parts of a superhetrodyne receiver, Collins Radio and/ or Drake had an interesting patented
method that used a wide band IF to detect noise, then mix the inverted noise with the signal from a narrow band IF. One of the more successful applications was, of all things, use in some citizen's band transceivers. There also was a circuit developed for use in helicopters to knock out rotor and ignition noise, using hot carrier diodes.

dirtybird

My Feedback: (5)

I think this thread has ran its course. Bye!
A tutorial on spread spectrum systems for those that are interested is located here:
http://www.maxim-ic.com/app-notes/index.mvp/id/1890

pmerritt

My Feedback: (118)

I hear only the heli guys are allowed educated enough to wear the title of "Certified Colonoscopists"?
A hobby shop owner told me KISS. The more crap one throws into their plane, the more can go wrong.
It amazes me that without a $1,000,000.00 flight recorder than anyone can go over to a pile of mangled balsa, monokote, plastic and batteries and diagnose what broke first, last or even contributed to a crash.
A sudden movement like that should indicate some electronic malfunction but could also be a physical issue with rod set up, clevises, servo mounting, fatigue, faulty factory production,yada yada yada. Just because they fly good one time, doesn't mean that something didn't get tweaked or torqued or work itself loose.
It's almost like 15 minutes of flying requires one hour of preflight and how can one pre-determine the failure of an a piece of electronics that probably cost the Chinese $0.75 cents to make? KISS them now or kiss them goodbye.

Scota4570

Back to my Kaos..............

The following weekend it was all patched up. I took off and made a circuit of the pattern. On my return leg the wing departed the airplane. The wing fluttered to earth with no damage. The fuse landed like a lawn dart.

Obviously there was undetected damage. It was cursed!

RIP

AndyKunz

Bummer I'd really be bummed if my Kaos lost a wing. I saw it happen on a trainer tonight - pretty spectacular.

Andy

eddieC

My Feedback: (2)

Sorry to hear it. Around here tho, we call that an 'upgrade opportunity'.