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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: Lap top Computers
01/10/2020 09:23:15

My current laptop came from PC Specialist  **LINK**

and I'm very happy with it. However, I hesitated to suggest them to Erf because, although they do off-the-shelf systems, their systems tend to be tailor made. Erf has made it clear that he's not up to speed on current terminology and buzzwords, and I thought PCS might be confusing for him.

I still think that one of the two options pointed to by Robin and myself earlier at Curry's would be the best option for him - both well specced and not outrageously priced - provided he can fight off the sales staff! wink

Cheaper options are available (as are MUCH more expensive ones!), but I'm not sure they would meet all of his requirements.




Edited By Peter Christy on 01/10/2020 09:23:48

Thread: Synthesised transmitters and mobile phones
01/10/2020 09:13:50

And the prices have gone through the roof! (I, too, have lots of JR gear 2.4 & 35, still all working well!)



30/09/2020 19:30:12

Tomtom: I hear what you are saying, and really don't want to get into a "BrandX Vs BrandY", so I'll confine myself to saying that I've never had a problem programming OpenTx. My comments were based on watching a flying buddy struggling to set up crow braking, but he does tend to over-complicate things! wink

Coming back to the original topic, mobile 'phone interference has been repeatedly demonstrated on some well known brands of equipment. Not all systems suffer from it, but some do - hence the BMFA bulletin on the subject.

The problem is that its not even just a brand issue, as some models within a brand range appear susceptible whilst others do not.

Mobile 'phones do put out very powerful, pulsed signals on occasions, and will break through into anything that is not well shielded. I'm sure we've all heard that rat-a-tat-tat noise on a stereo or computer speakers at some time.

That bulletin is still as valid today as it was back in the days of 35 MHz. I had hoped that 2.4 GHz equipment would, by its nature, be better screened, but it would appear that not all of them are!

Be careful out there!



Thread: Lap top Computers
30/09/2020 14:54:30

Erf: If you look at the laptops that Robin and I linked to, you'll see that both come with DVD drives built in.

Maths co-processors are a thing of the past - all modern PCs will be able to handle calculations easily, some even offload really complex stuff to the graphics processor!

One problem you *may* find is that Windows is not as backward compatible as it once was. If you are running very old packages, you may struggle getting them to run under Win 10.

Most of the laptops referred to previously referred to will be able to cope with modern CAD packages without problem, and should be more than capable of running laser cutters and 3D printers.

The biggest problem will be deciding between a wealth of choices!



Thread: Synthesised transmitters and mobile phones
30/09/2020 10:17:09

And as I said: "Such measures inevitably increase production costs"!

Very nice, if you can afford one, but the receivers are also very expensive and the transmitters appear even more complex to program than OpenTx! (One of my flying buddies has one!)

Well out of my price range, I'm afraid!



30/09/2020 08:34:25
Posted by Steve J on 30/09/2020 06:54:24:

Personally, I would rather fly with a transmitter that is compliant with modern EMC standards.

The problem with modern EMC standards is that they are mostly designed to stop the transmitter interfering with other users.

In this case, it is a transmitter being susceptible to interference from other users.

Enclosing the electronics in some kind of Faraday cage (ie: a metal box) not only protects a transmitter from external interference, but also reduces stray radiation from it. Not all of the output from a transmitter goes up the aerial!

Many "plastic" transmitters do include some kind of screening - either a coating sprayed on the inside of the box, or enclosing critical components inside internal metal compartments - but such measures inevitably increase production costs. And none of us wants to spend more than we have to!

The best solution remains a metal cased transmitter. Sadly, these are now a thing of the past!



Thread: Lap top Computers
29/09/2020 21:52:26

Erf: Most laptops come with camera and mic as standard these days - certainly the HP one I mentioned does. I didn't check the Dell, but I'd be very surprised if it wasn't so equipped.



29/09/2020 16:17:45

I have found that Currys/PCWorld are OK, PROVIDED you know exactly what you want! Their prices are good, their advice and know-how lamentable!

If you need advice, go to a specialist supplier, but expect to pay a premium.

Lots of good advice above, especially regarding screens! Like many, my eyesight is not what it once was, but I did buy a smaller laptop for reasons of portability. I also do a lot of video editing - not always on the laptop, but if I'm travelling..., and the one I specified had better colour rendition than the normal ones. Useful for colour balancing...

Smaller screens *can* be OK, but you need at least 1080 vertical resolution. Best advice is 15" as a compromise between portability and screen, 17" if portability is of lesser importance. Also, look for an easily replaceable battery! Internal batteries can be difficult to replace, and if you look after your laptop it will probably outlast several batteries!

Since you are posting here, you obviously have access to some kind of computer. Does that have an optical drive? Software is usually fairly easy to swap between optical and memory sticks, but operating systems can be finicky! I run Linux, and have never had a problem with loading software from memory sticks, not even the OS.

The Dell suggested by Robin C above is a good spec, Intel I5 processor, SSD for the OS and a big "spinning rust" disk as well for bulk storage. They also do an AMD version version for the same money that is *slightly* higher specced Bigger SSD and twice as much RAM!: **LINK**

Its Hewlett-Packard, so a well known brand. Be warned though: If you go to Currys, decide what you want, and don't be swayed by the sales-person (see Keith's comments above!) wink.

Also, watch out for them trying to sell you unnecessary extended warranties! You are already well protected by the manufacturers warranty and your consumer rights. Most electronic gear will either break down very early in its life or very, very late, and any extended warranty will not protect you against either!

Best of luck!

P.S. Both the Dell and HP have a DVD drive built in! (According to the specs!)




Edited By Peter Christy on 29/09/2020 16:22:17

Thread: Synthesised transmitters and mobile phones
29/09/2020 11:05:43

Strangely enough the only case of this that I've actually witnessed also involved a Multiplex Tx, though I can't remember which type.

It was many years ago, and the model that crashed was a turbine helicopter (ouch!), being flown by a very capable and experienced pilot. I seem to recall that it was a Multiplex Tx controlling a JR receiver in the model, a strange combination, but it had previously been reliable.

A post mortem test revealed that a mobile phone in close proximity to the pilot caused the link between pilot and model to fail when the 'phone rang. Indeed, I think this was one of a couple of similar incidents that prompted the BMFA bulletin. The time period seems about right.

Tests with other transmitters didn't show the same problem (can't remember which transmitters were tested, but would almost certainly have included JR as they were very popular with heli pilots at the time).

The conclusion we came to was that plastic cased transmitters were vulnerable unless they included some kind of screening inside. Not all do!

Personally, I've never liked plastic transmitters, purely from an engineering point of view. In days of yore, transmitters were made of folded sheet metal, which not only provided good protection against outside interference, but also made a much better "earth" contact with the pilot, improving the poor radiation pattern from telescopic aerials.

However, as is so often the case (Boeing 737-MAX?) economics took priority over engineering and we are where we are!



Thread: Best interference free 2.4 tx under ?350?
26/09/2020 21:59:12

Funny thing is that not only is 35MHz almost deserted these days, but so is 27MHz!

Thinks: Must dig out my Minimac receiver....!




Thread: Ofcom trace interference to a lightbulb
25/09/2020 19:39:29

Many decades ago, I worked at the Holme Moss TV transmitter, just outside Huddersfield. This was a 405-line VHF transmitter (Geoff will know what I'm talking about!). I was told that it was the original Alexander Palace transmitter, famous for bending the German navigation beams during the war, while it was still at AP.

It looked like something out of H.G.Wells! Lots of brass, ebony and ivory, a "dynamotor" (3-phase electric motor turning a generator) to produce the current for the filaments in the valves, and a 3-phase mercury vapour rectifier, nicknamed "The Mekon" (again, older readers will get the reference!).

The actual circuitry was pretty basic, but the scale of it was enormous! Old hands used to measure the SWR by sliding their hands along the co-ax feeders (looked like sewage pipes!) feeling for "hot spots". Quite often, a day or two later, their hands would be peeling from RF burns!

I was on duty in the control room one day when the transmitter suddenly shut down! I hit the big red "Alarm" button to summon everyone to the front and started powering up the standby transmitter. Unbeknownst to me, someone was in the modulator section of the standby transmitter (a room the size of a small garden shed!) and was quite surprised when relays started pulling in all around him! Luckily it was all heavily interlocked, so he was in no danger, but it sure made him jump!

In the control room, circuit diagrams were pulled from their pigeon holes - a bit like legislation in the Houses of Parliament - and the various parchment scrolls studied.

"I reckon its R34", pronounced one of the senior engineers, "Have we got one in stores?". Receiving an answer in the affirmative, said engineer vanished into the transmitter hall, and into the bowels of the transmitter itself. Much banging and cursing later, he reappeared with a 3 ft long charred carbon rod. This had been "R34"!

"Told you so!", was all he said!



24/09/2020 12:03:03

On a similar note: **LINK**




Thread: The Gov't, CAA, BMFA & UAV legislation thread
23/09/2020 14:05:13
Posted by MattyB on 23/09/2020 13:24:47:
"Drones flying within Arrow Drone Zones need no specialist equipment, such as new sensors, to utilise the Zone.”

Erm! So how does this work for us? Telepathy, perhaps? And since when has "drone" been a legal definition?



Thread: Future balsa supplies in UK
22/09/2020 16:14:10

Thanks for that, Robin! Yes, you could be right! It was a long time ago!

But as I say, not the first time this has happened, and I doubt it will be the last. I do recall being horrified by the quality of the very expensive balsa being sold after the last round of shortages...!



22/09/2020 07:56:27

This isn't the first time this has happened! Those of us of "a certain age" will probably remember the last balsa shortage - back in the 70s IIRC!

Back then, it was blamed on a new generation of massive oil tankers which required balsa for "insulation" of the tanks. I've no idea if that was fact or fiction!

I do know that it was followed by a sharp rise in the cost (and drop in the quality!) of balsa!

In the last seven years (since I retired!) I've built a few models from plans, mostly 5-footers and designs from the 60s. I was staggered by the cost of the wood alone! Were it not for the satisfaction factor of flying something I've built myself, I would stick to ARTFs, which are much cheaper than building your own!

If only most of them weren't so fragile and UGLY....!!!



Thread: How do you clean your glow engined models after flying?
18/09/2020 09:47:58

Muc-off - followed by mechanics paper towels.

Muc-off is also good for cleaning trannies without affecting the plastic!



Thread: To stabilise or not to stabilise - the gyro question
12/09/2020 09:01:59
Posted by TonyS on 12/09/2020 08:18:42:
Isnt that a bit like a Ford Pop driver poo-pooing a paddle shift gearbox and saying that anything other than double de-clutching isn’t really proper driving but is cheating?

Well, a paddle shift gearbox may well be perfect in a Formula One car (less than one turn on the steering, lock to lock), but is absolutely abysmal on a road car. Its simply a gadget for wannabe racing drivers.

I was racing with sequential gearboxes decades ago, and if anyone had suggested a shift mechanism like paddle shifts, he would have been laughed off the track!

We used something akin to a column-shift, moving it one way to change up and the other to change down. It was always at your finger-tips, regardless of the position of the steering wheel. Paddle shifts are just ergonomic insanity in a road car.

The occasions when I've had to drive a car with them, I've just left it in full "auto" mode. Absolute nightmare devices!

And don't get me started on electric handbrakes!

Bah! Humbug!



Thread: Researching the ancient Ripmax Futaba M6
09/09/2020 12:06:20

The digital vs analogue argument is not completely clear cut. Many early proportional sets were genuinely analogue, and operated in a variety of ways. One common method was to transmit two audio tones alternately. The frequencies of the audio tones provided two channels, the mark/space ratio between them a third channel, and the rate at which they alternated a fourth.

Other systems used a sequence of four different audio "tones".

At the receiver, the signals were decoded into a varying voltage that was fed to the servos as a control signal, eg: 1V = left, 3V = right.

Analogue systems provided very good interference protection, but suffered terribly from drift, poor resolution and slow response. It was also difficult to re-use circuitry for different channels, and almost impossible to implement more than four proportional channels.

The first digital system (designed by Don Mathes and Doug Spreng) was an attempt to overcome these issues. It was digital in the sense that the signal was either "on" or "off", but sort of analogue in the sense that it was a pulse width that represented the control signal. However, even in the servo, there were no varying voltages, the drive to the motor being either "on" or "off" (0 or 1, so in a sense "digital".

Some early digital systems did convert the "digital" signal to a true analogue one, as at the time, the digital servo amp devised by Doug Spreng was a spin-off from military technology, and some manufacturers were worried about being prosecuted by the government! This didn't last long, though, and after short time everyone adopted the Spreng design. It was so successful that it is still in use today!

The original Mathes/Spreng Digicon did transmit the full control pulse of 1-2 mS per channel. However, back in the days of AM rather than FM, this caused problems in the design of the Automatic Gain Control - AGC being an essential part of an AM receiver. It was Frank Hoover of F&M (a major American manufacturer at the time) who is credited with suggesting that rather than transmit the whole pulse, it would be better to transmit a short "marker" pulse to indicate the beginning and end of the actual control pulse.

With the introduction of digital integrated circuits a few years later, this had the added benefit of making a "digital" decoder extremely simple in the receiver.

So you see, the digital vs analogue argument is not clear cut! Early "digital" systems were neither truly analogue nor truly digital. However, the fact that we still use the same system to this day to drive our servos, added to the fact that the control signal is either "on" or "off" (0 or 1) leads me to believe that it is more digital than analogue!




Thread: To stabilise or not to stabilise - the gyro question
09/09/2020 11:34:46

I learned to fly helicopters before gyros were invented. Never really gave me any problems. I've never really understood why they would be needed on a fixed wing model, other than in exceptional circumstances!

To me, the enjoyment comes from the challenge of flying smoothly and realistically - whatever the conditions. However, I am getting older, and my eyesight and reactions are not what they once were, so I now - reluctantly - fit tail rotor gyros on my helis.

And yes, I have two flybar-less models that I fly quite happily without any electronic stabilisation of the main rotors!

None of my fixed wing models have gyros, save one. That is a tiny UMX Pitts Special. I am told (by someone who managed to figure out how to disable the gyros!) that it is unflyable without them. With them it flies very well, to the point of being BORING!

To me, gyros are a training aid - a bit like the stabiliser wheels on kiddies bikes - and something that should be dispensed with at the earliest opportunity!

For heaven's sake, learn to fly the aircraft - not a computer flying it for you!




Thread: Farm vehicle interference on 2.4?
07/09/2020 22:20:12

I refer you to what I said earlier: This smacks of radar or microwave link interference. Such interference is not on 2.4 GHz, and won't show up on a 2.4 GHz scanner. It works by directly interfering with the processor in the receiver, which also prevents the failsafe from operating.

I would suggest contacting Ofcom, copying in the BMFA. If I am right (and I think I am) finding the source of the interference will not be achieved with the kind of equipment most people can afford!



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