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Member postings for Peter Christy

Here is a list of all the postings Peter Christy has made in our forums. Click on a thread name to jump to the thread.

Thread: Hurricane/ do they need rudder/aileron mix?
24/05/2019 08:56:25
Posted by Jon - Laser Engines on 24/05/2019 08:25:36:
You have two sticks and two hands, that is how you do your mixing

Exactly! laugh



Thread: Glitches and crashes
21/05/2019 19:54:50

Posted by Tim Kearsley on 21/05/2019 19:43:53:

It could of course be nothing to do with the Tx, but how can you tell?


Not easy with 2.4 GHz gear! In days of yore (35MHz and 27MHz) dodgy transmitters were quite easy to spot with a simple monitor. Because 2.4 GHz gear does not transmit continuously, spotting a dodgy Tx is not easy.

I suspect the service agents will simply change the RF board as a precaution, as well as checking for obvious things like dodgy stick pots or frayed wires. A service engineer capable of fault finding a 2.4 GHz RF board at component level - and fixing it - will be expensive. Much cheaper just to change the board!

One thing you could try is moving the sticks *very slowly* from one extreme to the other. Most people just bang the sticks from end to end while checking, and assume everything in between will be OK. T'ain't necessarily so! A noisy stick pot (or servo for that matter) will only be revealed if you move slowly from one end to the other. If it jitters at any point, you've found a problem!



Thread: Pontefract Single Channel and Retro Meet
21/05/2019 11:49:18

For anyone who missed this cracking event, here's a video - courtesy of Phil - of all the weird and wonderful models and radio gear of yesteryear.....

Thread: CAA registration consulation
17/05/2019 08:35:34

Exactly right, C8! I shall be taking a break this winter and will see what happens when the "170,000" figure fails to materialise.



16/05/2019 16:15:30

They obviously got their blurb from here: **LINK**

Some of you seem to have had more luck with your MP than I have. Repeated letters - and copies of letters sent to DfT, CAA, etc - have just produced vacuous replies pointing me to government statements. Mind, you, I think she knows her days are numbered.

I see Grayling is in the news again, with yet another of his flagship policies being over-turned after costing the taxpayer millions. How on earth does he manage to keep his job? He must know where some skeletons are buried!

This does make me hark back to a question I asked earlier. What about writing to the Public Accounts Committee pointing out the financial flaws in this proposal?



15/05/2019 07:26:20

Percy: I've never believed that this came from the CAA, and Andy's post above seems to confirm this. I think it can be laid firmly at the door of the Minister for Transport. He has a substantial record of failing to heed expert advice, with disastrous consequences - privatisation of the probation service and the Christmas rail timetables to name but two.

The one glimmer of hope on the horizon is that, given the present political situation, he may be out of his job before this is ever implemented.

However, even if he is, it may be too late for the new incumbent to stop the process - or even be aware of it.

Again, the one thing on our side is that the implementation date is around the time we are all battening down the hatches for winter. I - and I suspect many others - will be quite happy to forego my winter flying and refuse to pay this unwarranted tax. Perhaps by next spring, sanity will start to prevail...



14/05/2019 17:30:21

In other words, this is a purely political decision that has nothing to do with the reality of the situation!

Failing Grayling strikes again!

I wonder if, in addition to the Baroness, a letter to the Public Accounts Committee, asking them to investigate the waste of money being proposed might also be productive?



Thread: IT help required please
14/05/2019 17:26:19

If the computers are running windows, we need to know which versions are on both. If its a large SD card (many are these days) it might be formatted with exFAT, which may not be recognised on an older version of windows without exFAT being specifically downloaded.



Thread: Warning X8R RX - do not use with CDI on IC powered 'planes
11/05/2019 21:06:35

Ron: PM sent.

It may be enough that the two batteries were in proximity for interference to "jump the gap". I used to make CDI units for cars back in the 70s - putting 400V through the coil instead of 12! Believe me, they never failed to start! surprise

The pulse energy drawn from the battery was awesome, and suppressing the interference to a car radio was not easy! I'm thinking that having the two batteries close to each other could be inducing spikes in the Rx voltage supply, leading to the lock-up.

Having said that, my only gasser is a scale Bell 47 helicopter, with the batteries next to each other under the cockpit floor. That uses a Spektrum DSM-2 receiver. I have lots of problems with that heli, but mostly related to the vibration from the engine, rather than anything to do with the radio!



11/05/2019 17:27:33

First of all, thanks Ron, for your very thorough tests and demonstrations. I'm surprised that the shielding didn't work, but that - coupled with something else I saw - makes me suspect that the interference is breaking through via the power lines.

I noticed that in one of your demos, the receiver locked out while you were holding the spark plug over the battery, not the receiver. In your SBach, was the receiver battery close to the CDI or its battery, by any chance?

I don't know if you have the facilities to carry out this test, but it might be illuminating. You may recall that Spektrum, at one point, provided capacitors mounted on a servo plug, to help mitigate against the "brown-out" problem they faced on some receivers. I wonder if one of those would make a difference on the X8R?

A large electrolytic, like Spektrum used, is probably the wrong thing for RF suppression, but it might be worth a try in the first instance. I would have thought a smaller value - around 1nF - would work best for high frequency interference, but since this problem is proving devilishly difficult to cure, it might be worth trying the big electrolytic first. Also probably simpler, because you might know someone who has one! wink

The capacitor connects the positive and negative supply rails, and should provide a short circuit to high frequencies, whilst blocking DC. This *should* stop interference breaking through via the power supply.

Electrolytics are very good at suppressing low frequency AC, but are quite inductive and become less effective as the frequency rises. For high frequencies, a small value ceramic plate capacitor is probably better.

I can probably supply one of each, mounted in plugs ready to use, if you want to PM me your address.




10/05/2019 19:43:05

Ron, the trick is to connect the litho shield to the receiver -ve line.

A badly shielded spark plug - as in your case with the extra spark gap - produces an enormous EMP. You don't notice it so much these days, with TVs all digital, but back in the analogue days, a badly suppressed motor-bike could cause interference over a 100 yds away.

That's not to say that there isn't a problem here, just an illustration of the scale of the problem. I have to admit that its something that would never have occurred to me!

Many years ago,a club-mate (now well known in the large model fraternity) was having problems with a very well known and normally very reliable Japanese radio. The model would lock out at random and crash, yet when the wreckage was retrieved and plugged back in, everything worked faultlessly!

The service agents were unable to find a problem, so I got roped in to look at it. At the time, I had a very old, all valve EMI oscilloscope. I was prodding around the receiver, looking for anything odd, and when I changed ranges on the 'scope, the receiver locked up! The decoder chip got too hot to touch! Switching off and on again restored normal operation. Change range on the 'scope, and it all locked up again!

I came to the conclusion that the (proprietary) decoder chip had a faulty voltage regulator in it, which was latching up in the presence of the sparks generated internally in my 'scope when I changed ranges! Just like your X8R. I suspect one of the servos was noisy and providing the necessary glitch on the power rails to trigger the fault.

I sent it back to the official service agents, as they wouldn't sell me a decoder chip. They did replace it, and after that it behaved faultlessly, but it came back accompanied by a very snotty letter about letting "unauthorised personnel" tinker with "their" gear! And this was in the days of 27 MHz AM radios!

Seems some things never change! wink

At least FrSky do seem to respond to customer input!




Edited By Peter Christy on 10/05/2019 19:43:28

10/05/2019 18:44:32

OK, Ron, thanks for that. That eliminates the power supply from the problem.

My best guess is that the EMP from the spark is breaking straight into the microprocessor, as I theorised at first. I would guess that the "watchdog" is a piece of software in the processor, rather than an external kicker, so once the processor locks, so does the watchdog.

(A "watchdog" is a piece of circuitry that resets everything if it fails to detect activity for a set period.)

The interference rejection of the *receiver* (as opposed to the control circuitry) looks as if it holds up quite well. Its the controlling logic which appears to be the problem.

If I'm right - and this is all speculation - then it is difficult to see what can be done to improve things, short of a re-design, which is what they appear to have done.

It might be worth trying with some thin metal sheet wrapped around the receiver (not the aerials) and connected to the receiver ground. I would expect that to show a marked improvement. If it does, all that would be necessary would be to replace the case with something conductive and grounded. It doesn't need to be a metal case - a plastic one with a conductive paint would probably do, as long as the "shield" was grounded to the receiver.



Thread: Paid-for flying lessons
08/05/2019 18:56:23

I'm with Peter on this! A lot of models sold nowadays as trainers would have been considered hot, aerobatic jobs back in the 60s!

What we need is someone to put something like the Veron Robot or Mini-Super back in to production. Excellent trainers and a handy size!



Thread: Warning X8R RX - do not use with CDI on IC powered 'planes
08/05/2019 12:49:48

Ron: Should have added - use a decent 4-cell pack, and plug it straight in to the receiver, not via a switch.

I'm trying to eliminate as many variables as possible!



08/05/2019 10:41:05

Hi Ron,

I've now had chance to review your tests, and thanks for a very thorough and effective demonstration of the problem!

Could I ask you to try one more thing? Can you repeat the test on the most susceptible receiver (the X8R that crashed, from your videos), but using a standard 4-cell NiMh pack as a supply, instead of the LiPo / regulator setup?

Again, I'm trying to establish just how the interference is breaking through - whether it is pick up in the power supply rails or directly into the processor. This test may (or may not!) give a different result.




06/05/2019 19:20:04

Hi Ron,

I won't have time to view all the videos tonight - or even maybe tomorrow - but I will have a good look at what you have done.

All my X8s and 6s are currently buried deep in fuselages, and not very accessible, but I'll see if I can get one out over the next day or two. I don't have a CDI lying around (again, mine is in a model!), but I do have a piezo gas lighter that might do the trick.

Thanks for your excellent work on this, and also for publicising it. I was considering removing the DSM-2 Rx from my scale heli (Rxcel ignition) and replacing it with a FrSky, but I think I'll wait pending further investigations.

After all, if it ain't broke, don't fix it! wink



Thread: CAA registration consulation
06/05/2019 17:59:40

I have a feeling that this meeting will just be the first round. The BMFA will know how keen everyone is to be updated, but I wouldn't expect too much from the initial get-together.

But even if it goes very quiet for a while, that may not be bad news, as it will indicate talks are in progress. I'll be much more worried if it all falls at the first hurdle.

In the meantime, its up to us - all of us - to keep the pressure on.



Thread: Warning X8R RX - do not use with CDI on IC powered 'planes
06/05/2019 16:53:11

Now we're getting somewhere, thanks to Ron! It looks as if its a shielding problem, and that should be easy to sort out.

I would suggest trying wrapping some cooking foil around the receiver (making sure the aerials are outside the foil, of course!) or maybe sandwiching the receiver between a couple of sheets of thin carbon fibre. I suspect both will prove effective.

Then do a careful range check to ensure that this has not been affected. It shouldn't affect the range, but it pays to be cautious!

If this fix provides the desired results, we can forward the info to FrSky.

I always said receivers should be in metal cases.......! wink



06/05/2019 12:03:31

This is good info, Ron. When you have finished your tests, tell us exactly what it is you did, and the conditions under which the failure occurred.

One other thing that might be worth trying: although conventional wisdom is that it is best to keep the ignition system and radio gear completely isolated from each other, does the fault still occur if you connect the ground (negative) leads of the two systems together?

Ignition interference is funny stuff - like earth loops in audio equipment - and sometimes doing the opposite to what common sense tells you can fix a problem.

Worth checking.



06/05/2019 11:28:32

I've been using FrSky gear for 7 or 8 years now, without issue. I started out using D8 and a "hack" module in a "cuddle-box" transmitter. It proved 100% reliable, so I splashed out on a Taranis and started buying "X" series receivers. Recently I bought an X10S.

So far, everything has behaved impeccably on both glow and electric models. The range is excellent. I had one receiver that was DOA, and it was changed immediately and without quibble by T9.

My experience so far has been that it is every bit as reliable as the JR systems that preceded it, but at a fraction of the cost.

That is not to say that I'm doubting that there may be an issue under specific circumstances, as outlined by Ron. But as I pointed out earlier, unless you can reliably replicate the issue on the ground, it is very difficult to produce a fix.

FrSky have previously shown themselves very responsive to customer input - much more so than many established manufacturers. This is why I believe it is important to get to the bottom of this, and why I've been asking Ron to carry out some bench tests to try and establish exactly what it is that triggers the fault condition.

In my experience, there is no issue with either glow or electric operation.



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