Futaba 14MZ a dead radio?

[John MacDonald]

Just in passing, I received 8 identical notifications of answer to my last post! Someone with a heavy hand on the "Send" button?

[Robin Tapp]

No just they all got clogged up but they're back running properly again now.

[Slopetrashuk]

anyone seen this re the spektrum:
http://www.bmfaclassifieds.co.uk/detail.php?id=14361

[Tim Mackey]

Unfortunately NO FAILSAFE system can be perfect. For Instance, in my PCM receiver days, I had a favourite model bury itself despite having preset the surfaces to what I thought might be the best positions -and would have proved to be so in your scenario.
I set throttle to off (it was electric powered) ailerons level, and very slight up elevator.
However, the scene you describe will only work if the plane is upright,fairly fast and straight at the time. Mine was inverted, and 12' off the deck when PCM went into lockout. I now will not use PCM, and all my Spekky stuff is set to failsafe in the way suggested by the BMFA as a minmum requirement IE Throttle down.
This action seems to me to be the ONLY servo position which pretty much always has a good effect on a potential crash, whereas any preset control surface postions will never guarantee a good result because of the possibility of aeroplane attitude at the time. Just my opinion :)

[Tim Mackey]

Hi Andy :) I know you have expressed reservations about this aspect of the sets, and understandably so if you are flying very expensive and potentially dangerous models. However,If it is the one about "dont fit spekky receivers in carbon fibre fuselages" it was discussed at length on another forum, and the general consensus is that it is an unlikely story.

I have it in writing from Horizon hobbies that the receiver ( AR7000 anyway ) is perfectly ok inside carbon fuz. YES I know this is not a guarantee of performance, NOTHING gives you an absolute guarantee.
But the very vague post itself raises a few questions...
1) Was it a 6000 not a 7000 - AR6000 is NOT full range.
2) Were the aerials orientated correctly
3) Was the installation in general of a good standard, I mean we have all experienced some modellers ideas of a radio installation !
4) Have all other possible causes been thouroghly investigated - including dumb thumbs :)

Seems peculiar to post such a thing in the classified ads section - this says something to me to start with ! Also with such a lack of detail (EG not even the version of the Spekky used ) it is difficult to take seriously. I know it is not quite the same....but I have flown a mettallic painted model at a great distance ( the 2 pilots standing on the flight line with me both uttered suitable expletives about eyesight and the like ) and have had absolutely NO issues with reception, even as I turned the craft straight towards the tr aerial, and flew towards us for a few moments ( still at a huge distance ).

[bushwhackerbob]

Investing in new technology is usually expensive. At least these sets are relatively inexpensive.

Because there is a significant difference between the frequency differences ( 9 metre wavelength at 35mhz to approx 1.5 cm wavelength at 2.4ghz)there will be extreme difficulty in producing modules for existing tx's, both mechanical and electronic. Aerials and their mounts have a significant effect on performance at the centimeter wavelengths and this would create problems in producing/modifying existing equipment with simple / cheap upgrades.

It would be less expensive to buy a new purpose made set.

The only other solution is to wait until the technology is established and cheaper.

[YakMad]

Has anybody heard any new from the Nuremberg Fair as to what the "major" players are doing as regards 2.4ghz, I know Futaba have a 3 channel car set and have been using it on their industrial side of the business so the development costs for them cannot be that great or is it that they and JR have invested too heavily in their new high end 35 mhz radios.

[Tim Mackey]

Futaba have announced a 6 channel 2.4GHz set but it is poorly spec'd compared to the Spektrum,
for instance, only 6 model memory and 2 mixes.
I will try and find the link and insert here. Found it.....
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXPZT8&P=7
It is my GUESS that JR may be first off the mark with a well spec'd set, as after all, they are helping with the manufacture of the Spektrum:)
There was something on the macregor site recently about a new JR 2.4G system release
again, I will try and find link.

here ya go...check the bottom left of the page

http://www.macgregor.co.uk/newsletters/jan07.pdf

[Paul C]

I think a lot of the comments here are typical of the "must be bad because its different" mentality and the "I heard it was rubbish" gossip, normally attached to the above..

I think a couple of comments may help clarity (apologies for the long post and please no flames for the tech details, i've tried to keep it simple).

The original 2.4ghz sets were limited by European law to an output power of 10mw (10 thousandths of a watt), about the same as the transmitter in your car alarm key ring ! This was to conform with CE directives and with other devices using this band.

These original sets were marketed as Park flier only as they obviously lacked range.

Recently OFCOM (the UK governing body for Radio licensing) agreed to bring us (the UK) in line with newer thinking on 2.4ghz devices and allowed 100mw, 10x the power and about the same as your 35mhz Futaba/JR/Multiplex set your using today.

Therefore only the Newer sets have full power transmitters.. (DX7 for one)

As to the size of the antenna(s), this is totally dependant on the frequency of operation and requires some maths to resolve (I'll spare the details here) but a full length antenna (TX or RX) on 35mhz would be 8.57 meters long, 2.4ghz would be 12.5 Centimeters long, much shorter but not any less efficient. yes, 12.5cms at 2.4ghz in radio terms is the Same as 8.5m at 35mhz.

Normally, wire antennas are cut at the 1/4 or 1/8 length for convenience while still offering a tuned length for best transmission or reception (this is why you should never cut your RX antenna wire !)

A 1/8 length for 35mhz is 1.07 meters long which is about the length of the wires on most 35mhz receivers. The 1/8 length for a 2.4ghz antenna is 1.5cms, this is to get the same receive power to the receiver.

On the Spektrum units I've seen the wires look about 3cm long so they must be working on 1/4 length so already much better for the receiver.
The next method to collect a better radio signal to the receiver is to add a counterpoise. This is another antenna pointing in the opposite direction to the original and normally grounded, in radio/electronic terms this is a dipole. Again, without going in to the math, this gives a much better signal again.

On the transmitters, the DX's have helical antennas which are the full length wound in a special coil, again just as good as your pull out metal job but without the dirty joints !.

So purely mathematically, in radio terms, the Spektrum system is more efficient and this extra gain will more than counteract the fact that in a straight battle, 2.4gh will never travel quite as far a 35mhz.... except Spektrum went one better and added a whole extra receiver !

If you want me to write on packet networking (binding I think they call it here)and why in theory its better I'll gladly have a go.. ether that or tell me to bugger off :o)

[Tim Mackey]

The binding referred to here is the name given by Spektrum to the process of uniquely matching the individual receivers with their transmitters. Each receiver hasits own unique "code" embedded within, and the binding process ensures that the reciever will only accept signals from the transmitter it has been "bound" to.
Furthermore...."modelmatch" ( another spekky term ) ensures that only when the correct model is selected from the tr's 20 model memory store will the receiver concerned respond. Select the wrong model, and the receiver in the model that is sitting on the floor in front of you will COMPLETELY ignore the transmission.
Yet another unique safety feature not found on 35 MHZ - top end sets included !!
I agree with you about the negative brigade, and also would add a further reason for the doom merchant brigade.
1) They are snobs. Try telling the people who have either been life-long users of the high end german stuff taht there is a radio system that is actually better in SOME areas than theirs - then get out of the room fast. Ditto to the poor souls who just spent 700 quid+ on an "old" new 35 meg set.

[Bladerunner]

Not at all Paul, you seem quite confident with the subject...let us have the run down on packet networking.

[Bob Howard]

I have a nagging doubt about the 2.4GHz system.

On start-up, the Tx looks for 2 clear channels to use. Provided that all other
transmitters are within range, there is no problem. However, we all know that
ground-to-ground range is significantly less than ground-to-air range - or is this not
the case with 2.4GHz?

Suppose that a flying site was within ground-to-air range of another user (don’t forget
this could be a model car user in a nearby park). When either Tx is switched on, the
two transmitters may be beyond ground to ground range, and thus be unable to interact
with each other. There is a 40 to 1 chance that either of the two channels selected
could already be in use at the other location. When the model is airborne, the greater
ground-to-air range could well bring it within range of the other user. Obviously the
second channel will provide full control, but the additional safety of 2 independent
channels is gone.

I realise that, with 80 channels to choose from, the probability of this happening is
fairly small, but nevertheless the risk is there. Or does somebody know better?

[Tim Mackey]

I dont think the receiver would respond to the "other" transmitter as it has not been "bound" to it.

[Robin Tapp]

Due to the short wavelength, line of sight is much less of an issue, at 2.4ghz. It's the same frequency used by computer wireless kit and that works through walls :>.

The point may be that if you were to be standing by your model and a long way away another model was being used out of range. Then if you fly your model out in the direction of the model and it suddenly becomes in range of that other tx. What's the chances? I'd say truly minimal. I also don't know exactly how it works and if it transmits an id as it binds with the model if it does then this would be a 0 chance as it would only bind with one tx at a time. However I suspect it's not as smart as wireless computer technology unsurprisingly as it's somewhat larger range would make it tougher.

Anyway I should go and read up on the tech to find out how it actually works.

[Bob Howard]

Granted the receiver would not bind with the wrong Tx, but would the second signal not scramble the signal from the bound Tx?

Is there any technical gen available that we can read to gen upo on all of this?

[Tim Mackey]

try horizon hobbies / Spektrum...quite a few video interviews with the designers etc.

[Steve Barrow]

I have been using my DX7 with a new Swallow 90 over the last two weeks, which has performed faultlessly.
However during the initial installation there was the odd occasion when there was apparently no radio link between the transmitter and the model even though eveything looked okay at the receiving end ( both receiver led's glowing steady).The link was restored by turning the receiver off and back on.
It would seem once the link is established there is no problem. Any idea's ???.
Very pleased with the set, but wish it was more like my FF9.

[Tim Mackey]

not heard of this one..try an email to horizon hobbies US.

[stan pratt]

I am lead to believe that the DX7 has a range of 5 miles! and I am also lead to believe that the transmitter output is 100mwatts, if these two items are correct, what range will the DX6 cover with an output of 10mwatts? An awful lot of people have expressed the pro & cons of the DX7 but no one seems to know anything about the DX6? Can anyone enlighten me?

[Malcolm Milburn]

my dx7 arrived monday charged up system removed my futaba reciever fit the ar7000 . done the binding bit set up the control throws etc. then waited for the weekend saterday morning arrived abit foggy all clear by 11am. down to the airfield i went.by the way all fitted to my pride of the fleet fliton 330 frestyle. out of the car it came.everthing fitted range check done.after some debate with other flyers. time for the test sart up taxi take off flying time 15mins.no problems no glitches no nosence just felt so safe.3 flights sat 3 flights sun big smiley wots the fuss lads. by the way when i came to rebind the system for low throttle the futaba switch harness is no good it only has 2 wires you need a three wire harness

[Essjay]

Malcolm, I believe Timbo has already covered this. If he doesn't mind I'll go over it again. It is not necessary to use the switch harness when binding.
If you remove the battery connection on the receiver and place it in a spare channel, then place the bind plug where the battery was, you can then carry out the binding as normal, and when you've finished, just replace everything. In actual fact this is the way it's done with the DX6 as well.

[Malcolm Milburn]

i must have missed that one .cheers steve. it would have save a trip back home for the dx switch harness

[RAMON MITCHELL]

I AM NOW USING A DX 7 SEEMS TO BE VERY GOOD
RE THE GHARGING SOCKET IF YOU SHOULD SHORT THE INPUT LEADS IT WIIL CAUSE THE INTERNAL 3amp FUSE TO FAIL (how did i find this out) FUSE TYPE 3AMP QUICK BLOW.
TO use 2 elevator servos YOU must INH the AUX2 @ THE model select screen.Iwas told you have to use a Y lead

[trevor hoskins]

Funny how us britts focus on the negatives with anything new!
I have been flying rc for 40 years I purchased a dx7 in december and have six
models flying on 2.4ghz spectrum radio,including 1/4 scale jobs with flaps and retracts ALL perform with NO PROBLEMS.
Over the years i have seen more models crash through interferance/faulty gear and taking off with the wrong model programed in on 35mhz including shoot downs than i care to remember.
As for the concern with carbon props two of our local club members fly helis with carbon blades on spectrum radios with no problems
My local club, weston model flying club have several members flying on 2.4ghz and all as myself find the advantages just to many to ignore.

[Chris Dickens]

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