another wot4 crash caused by radio failure :(

[Erfolg]

Does it matter if it is a Spektrum branded supply?

If the buddy lead works when initially used/tested? After all, it is just a cable and plugs. If it works when testing, why should it not some time after, as long as it remains undamaged.

[Phil Green]

Posted by graham dewis on 11/08/2013 18:16:02:

Posted by andyh on 11/08/2013 17:06:48:

stupid questions:

1. is the full (~140mm) length of the Rx antenna "live", or just the uncovered end (~30mm) portion?

For 1. Just the end portion is live

Graham

This is a very common misconception. The 30mm-ish whisker bit is NOT the only functional part of the aerial - any quarter-wave aerial needs a counterpoise to work against in order to radiate or receive efficiently.
There are two common types of aerial on typical 2.4g receivers - the 'whisker only' type and those with a longer feeder with an exposed 1/4 wave at the end.

In 'whisker-only' receivers the aerial wire is roughly a 1/4 wave element mirroring against against the ground plane which is the bottom layer of the receiver board. For best performance, both the aerial element and ground plane should be 'RF' visible, eg as happens in a foamy. Some receivers are so small that the groundplane isnt big enough to make a full 1/4 wave counterpoise, but its all a compromise after all.

The 'exposed 1/4 wave at the end of a length of coax' type aerials again consist of a 1/4 wave element, but the coax shield is also the counterpoise and a quarter-wave of the shielded part of the coax should be RF visible as well as the last 30mm 'whisker'. This is far from ideal as the coax is badly mismatched and the signal distribution will be unpredictable at best. Again its a huge compromise.

One answer is the a third type of aerial, which most of us are currently using in transmitter aerials, thats a coaxially-fed dipole which is also used by Hitec who misleadingly call it a 'BODA' or Boosted Omni-directional Antenna. The only part of that acronym thats completely true is the 'A', its an antenna.
These aerials are a genuine dipole with two opposed 30mm elements. One is the coax inner (the whisker) and the other is a brass tube through which the feeder is routed, making it a centre-fed, coaxially-routed dipole. The tube is only connected to the shield at the feed point, so its a true 1/4 wave counterpoise.

This is a very good impedance match and hence a huge improvement in VSWR and the effectiveness of the overall radiation pattern in transmission, and improved transfer in a receiver.

Ultimately, if a dipole isnt fed through a balanced line (which ours arent) or via coax without a balun at the feed point, then the feeder shield becomes part of the aerial, radiating in the case of a transmitter and sensing in the case of a receiver.

So contrary to popular opinion, for optimum results the whisker is not the only part of the aerial that should be exposed or at least visible to RF.

Cheers

Phil (G4PHL)

Edited By Phil Green on 11/08/2013 22:52:57

[andyh]

Posted by Phil Green on 11/08/2013 22:48:15:

The 'exposed 1/4 wave at the end of a length of coax' type aerials again consist of a 1/4 wave element, but the coax shield is also the counterpoise and a quarter-wave of the shielded part of the coax should be RF visible as well as the last 30mm 'whisker'. This is far from ideal as the coax is badly mismatched and the signal distribution will be unpredictable at best. Again its a huge compromise.

thanks Phil, very interesting, although some of the RF stuff is a bit over my head!

are there any pratical consideration for this? should the full length of the aerial be run as straight as possible, or is it only the orientation of the whisker that really matters?

Edited By andyh on 11/08/2013 23:06:45

[Peter Beeney]

I’ve not met that particular lead, Andy, but I’d be surprised if it were the genuine article. Without going into a lot of detail, for now anyway, at least, we’ve found that there is an issue with using the DX5 and a non genuine lead, which is at best intermittent working, and worst case, no comms link at all.

So could it be that by some very strange quirk of coincidence you have two bugs in your system? Very much of a long shot, perhaps, but stranger things have happened. You may well be able to enquire at some stage if that lead has been used with a DX5 before. Although it may well work with the 5, of course, I’m afraid I’ve no idea.

I thought the same about the 5e and the DX6i switches, they look identical, but I’ve never known anyone to have any problems with this transmitter. Maybe the switch is different internally, though, which would be entirely logical.

But at the end of the day, it may well be that your misfortune is something completely different. Let’s hope you soon manage to crack it.

I’d also agree with you, Erfolg, but as I’ve said in previous threads on this problem, a mono plug is merely a mono plug… …except when it’s a Spektrum mono plug…

Simply a little mechanical bone of contention here; most contacts are well fitting, good and secure, but some only make by good fortune and a following wind…   and this is one of these.

PB

Edited By Peter Beeney on 11/08/2013 23:07:57

[Glyn R]

Its amazing how much damage is caused by technical failures and how little by pilot error

[andyh]

Posted by Glyn R on 11/08/2013 23:13:16:

Its amazing how much damage is caused by technical failures and how little by pilot error

I'd be less annoyed if it was pilot error - at least it would be my own fault then!

[Tom Wright 2]

Posted by Peter Beeney on 11/08/2013 19:42:25:

Andy, Assuming you mean a DX5e tx then it’s just possible the problem is with that. We had some Spektrum issues quite a while back which resulted in at least a couple of the lads going Futaba. One gentleman persisted with his Spektrum 5e though, but in his garage. The troubles had generally been a loss of signal but sometimes it would restore before the model actually crashed. By giving it a good trial he soon found the fault was in the tx switch, it appears it is a multi way device and it can switch off the rf output section without switching off the l.e.ds. He was able to demonstrate this at will by squeezing and/or griping the front of the transmitter; he took it all to pieces and, as an ex. motor engineer, (long retired), said he thought the switch could be politely described as ‘of dubious quality’. He banished the gremlins, though, by soldering a wire strap across the switch and turning it on and off by removing one cell. Now he often uses it to fly one of his ParkZone models, it’s never missed a beat since! Which, of course, completely proves the point.

PB

We had three DX5e in our flying group,all three were found to have faulty switches after several models had been destroyed . I posted our findings on this forum but no one seemed to take much notice . E mails to Horizon were answered with the same silence . We sorted out the switches and have not had a problem since. Although horizon generally have a good reputation for service I for one would not buy again.

Tom.

[andyh]

Posted by Tom Wright 2 on 12/08/2013 02:02:15:

We had three DX5e in our flying group,all three were found to have faulty switches after several models had been destroyed . I posted our findings on this forum but no one seemed to take much notice . E mails to Horizon were answered with the same silence . We sorted out the switches and have not had a problem since. Although horizon generally have a good reputation for service I for one would not buy again.

Tom.

thanks Tom. I just had a quick google & this seems to be a common problem - lots of discussion on various forums & youtube videos illustrating it. I haven't managed to replicate it on mine, but I don't think I'll be using it any longer! I have a DX7s on order, so I think I'll use that with a cheapo park flyer until I build up some confidence

I'm still interested in peoples' thoughts on aerials, satellite Rx's, etc. though, it can't hurt to give the Rx side of things the best possible chance of working!

regards

Andy

[graham dewis]

Posted by andyh on 11/08/2013 22:57:33:

Posted by Phil Green on 11/08/2013 22:48:15:

The 'exposed 1/4 wave at the end of a length of coax' type aerials again consist of a 1/4 wave element, but the coax shield is also the counterpoise and a quarter-wave of the shielded part of the coax should be RF visible as well as the last 30mm 'whisker'. This is far from ideal as the coax is badly mismatched and the signal distribution will be unpredictable at best. Again its a huge compromise.

thanks Phil, very interesting, although some of the RF stuff is a bit over my head!

are there any pratical consideration for this? should the full length of the aerial be run as straight as possible, or is it only the orientation of the whisker that really matters?

Edited By andyh on 11/08/2013 23:06:45

Very good Phill, I went for the easy answer and you are correct, does that make it that the last 60mm should be straight at the required orientation .

Graham (ex G8JCK)

[Stevo]

Interesting!

A couple of years back :-

Here's a different angle... Spektrum DX7 and ar6000 receiver in a WOT4, with an old Jen 53 engine. Straight and level flight, twitched like hell and went into a dive under full power.

Recovered airframe after two week in the wilderness and when the farmer cut the grass.

Loads of Aircrash Investigation. All covered in Profilm, Grey on the fuselage and Blue Chrome on the wings. Assembled Rx, 4 servos and battery... went to local park to experiment.

Powered it all up, stirred the sticks and all servos moved. Reduced power on Tx, (i.e. range check mode) and all still fine at 20 paces. Covered receiver with an offcut of blue chrome profilm. You can see where this is going.. All servos stopped and we repeated this every time.

I emailed a few guys in the know... emailed BMFA - to which I never receved a reply. Managed to post on various forums at the time regards the danger... Told LMS and by enlarge no one seemed to bother!

[FlyinBrian]

I would not use any covering that was mettalic in nature with any 2.4 receivers du to signal reflection and blanking possibilities

[andyh]

apologies for bumping my own thread, but I'm still interested to hears an views on aerials/satellites/etc.

the DX5e problem does sound like the smoking gun, although I'm still not sure it explains the issue when the 6e was buddy-boxed to a 6i, & I'd still like to get an idea of best practises on the Rx side

many thanks

Andy

[Peter Beeney]

For what it’s worth, we’ve done a few experiments with various types, deliberately trying to provoke some sort of loss of signal. We’ve not managed to do it yet. So for this reason alone, I’m not entirely convinced that aerial orientation and satellite receivers are quite as strictly necessary as convention seems to insist. For instance, my colleague researched the Assan brand some time ago, this seemed to have as good reports as any, so he duly purchased a kit. There is a six channel rx and a Hack tx module to drive it, this in in a FF9. The receiver has an aerial which is a piece of straight wire three quarters of an inch long. This receiver set the benchmark for the others, we could not get it to fail under any circumstances.

However, we’ve not tried the test with any metallic covering. A very interesting post by Stevo, so this is something we will now have to have a go at, hopefully it will fail so we will be able to attempt to effect a cure. I’ve read other reports about carbon etc. too. For another reason I did try to construct a “Faraday cage’ around the receiver from wire mesh, to try and reduce the signal strength power to the receiver, but that was a failure too, I never did get it stop working. I’ve just this minute put a rx, servo and power supply in a large copper flower pot, with a piece of metal for a lid, but that still works ok at about 30 metres at full tx power. But it was a fast one-off, I shall take it to the patch and do our long range test with a bit of assistance. There is also a bit of scope for trying different materials, the rx aerial placed inside a piece of carbon-fibre tube, perhaps.

It’s very difficult to say exactly how much difference any of this makes, if we cannot reach a point where it fails; and from what seems to be the ongoing total reliability of the radios at the field it would seem to suggest there are few problems. I can’t help feeling that if there is a problem it’s rather more tied up to that specific radio set, and it’s not a generic fault with 2.4 GHz in general.

Just a general line of thought…

PB

[Steve_Wright]

I have had a few failures with my DX7 & orange Rx's. After some playing it seemed when the Rx ariel was pointing at my Tx I lost about 1/2 the range. was a single 7cm (ish) ariel on the rx in a twinstar pointing tail>nose. Going to the same setup but a speky Rx didn't see the same problem

[andyh]

my shiny new DX7s turned up today - looks rather nice

I'm coming to the conclusion that Orange Rx's are a false economy for all but the cheapest models, so I think I'm going to go Spekky. any recommendations? 6 channels will do me for now, so I'm looking at the AR600 & AR6210 at the moment, unless anyone has any better suggestions

thanks

Andy