7 channel receivers for Cockpit SX 35 MHz

[Grasshopper]

I use a Cokpit SX 35 MHz Tx. and after having had two disasters with Multiplex synth IPD receivers I have since used Corona 6 ch. receivers on all my models - and never had any problems.

Now however I need that 7th channel !

 

On PPM systems some manufacturers use positive shift - I think Multiplex, JR, Hitec and some negative shift - again I think Futaba - and this means that all ppm receivers will not work with any receiver. Oh - and I have tried Corona 8 channel receivers but although they appear to work correctly, for some reason the range is poor, probably because the receiver/decoder latches onto a false start point in the pule train?

 

Please can I have responses from people who have actually used non-Multiplex 7 channel receivers with a Cockpit SX. Which receiver did you use?

 

(yes I know - go to 2.4 GHz etc. but here in France the 'old' standard was 40/41 MHz and the 35 MHz band is totally clear so here I stay!)

 

Peter

 

Edited By Grasshopper on 28/07/2011 08:40:38

Edited By Grasshopper on 28/07/2011 08:41:38

[PatMc]

What about this Hitec HFD-08R0 ?

[Grasshopper]

Thanks Pat - and a good price it is.

 

One question - have you actually used this receiver with a Cockpit SX (7 channel Tx) - as it is an 8 channel receiver - and what sort of range did you get?

 

I have already tried several 8 channel Corona receivers and although they work at close range they jitter all over the place when I do a range test.

 

Peter

 

 

[Frank Skilbeck]

I've used the Corona RD82011 Dual conversion 8 channel Rxs from Giantcod (less that £8 each) in my gliders with great success, but then again my 7 channel IPDs have also been flawless as well. I use the Corona ones with a crystal as I have read that the synthesized ones can be jittery.

 

I've also used Futaba and Fleet Rx's with my SX with no problems, the only one which wasn't 100% was a Hitec park fly 35mhz Rx in an electric model.

[Grasshopper]

Frank,

 

how very odd! On my Luna glider I tried two new Corona 8 channel rx - a single and a double conversion, both with crystals and the range test was poor. That is aerial down I got loads of servo jitter at 80 metres. With two different 6 channel rx I was getting nearly 200 metres with no jitter - and this has been my yardstick on 8 or 10 models - with Corona receivers.

 

I think the best solution is to use the Frsky hack module and convert my SX to 2.4 GHz - as with a receiver I can get 7 channels for £25 or so for both units and then 7 channel receivers will cost less than £14.

 

Out of interest - have you used either Futaba R137F or R147F receivers as I have found a very cheap source ?

 

Peter

 

 

[Frank Skilbeck]

I must admit I've never done a range check at 80 meters, usually just the normal 30 paces. But I've not had any control issues at extereme range with my Mini Blade using using the Corona 8 channel Rx's or in my 1/4 scale HP 18 with some older Futaba Rx's 147's I think.

 

I have also done the FrSky hack module as well, plugging it into the trainer socket and that works well, but so far I've not used it in any larger gliders just a couple of electric planes as follows

 

8 channel Rx in 60" E Flite Beaver

7 Channel Rx in 1400mm electric aerobatic model

 

+ a 4 Channel park fly in my Alula

 

A few of the guys I fly gliders with have the FrSky modules in their Jr Tx's and are very happy with them.

 

[PatMc]

Peter, I use & have used a number of different makes of Rx with the Cockpit SX, ranging including MPX 7 synth, GWS, JR, several Micron home built, 2 Jeti Rex5s a Futaba 6M & a couple of more modern Futaba ones. All have been rock solid except the Jetis but I think that may be related to noisy servo/s (It's a problem I'm currently trying to solve) & range has never been an issue.

 

I don't have any Hitec Rxs but I know a few others who have & seem happy with them albeit none of these have MPX Txs.

Incidentally I usually use the "rubber duck" with my SX.

Also I've been warned that Corona can be a bit iffy at the low end of the 35 spectrum - from 60 down.

[Grasshopper]

Thanks PatMc,

 

I think I will try the 8 channel Coronas again in another model to see what range I get. As I have said, with Corona 6 channel receivers, in 8 or 10 models, I have got almost 200 metres with the Tx aerial down so getting only 80 with an 8 channel Corona seems poor to me.

 

I also always use the rubber Mx. aerial and have never had any range problems.

 

On the Coronas and 'problems at low end of spectrum', I always fly channel 61 as I live in France and until recently, only channels 60 and 61 were allowed. I have never met another French modeller who used 35 MHz, always 40/41 MHz or now - same as in UK, 2.4 GHz. For this reason I have stayed 35 MHz. I have had no problems whatever with range, noise etc. except when I tried to use a couple of new Corona 8 channel receivers and found they gave 1/2 the range if the 6 channel ones. Probably still plenty but worrying all the same. My concern is heightened as I lost a Luna 2 metre glider on its maiden., over the sea, when a Multiplex IPD receiver locked in fail safe and it made a perfect landing on the sea, 1 km out!

 

Peter

 

 

[Peter Beeney]

Peter,

If I can join in here for a moment, I’ve used the R137F 7 channel with a MPX 4000 and a Royal Evo. I also use a rubber duck aerial on the 4000. I’ve never really put much faith on aerial down checks, they invariably seem to give mixed results, so I do a full range anyway, 600 - 700 metres distant, with the model on the ground. MPX xtal in the 137.

The 137 is immaculate, but it it doesn’t have a separate battery socket so for 7 channels you will have to splice in the battery feed. I’d solder it in, but a very short Y lead would also suffice. I’ve not seen the 147, maybe this is the same rx but with a battery socket?
I use MPX crystals in everything, they usually seem to work perfectly. Certainly in all single conversion stuff. One reason for this is because I’ve done a lot of training so I can use ‘my’ frequency and keep on flying. Also I don’t have to bother with keeping an eye on the beginners and wondering about constant frequency changes; although nowadays, as with every other flying site I imagine, the 35 band is getting very lonely.

I don’t think that I can remember finding a combination of different brand tx and rx that wouldn’t talk to each other but I’m sure there might well be such animals.
Also is possible your jittery short range Corona 8 channel is some sort of crystal problem? Although you are using a 7 channel tx and an 8 channel rx I’m sure this situation has arisen many times in the past with no ill effects. I’d be surprised if this is the cause. There is a facility on the 4000 for changing the transmission mode, 7 channel, or 9 channel etc., it’s an automatic adoption to servo count on the Evo, if it’s the same on the Cockpit, could this make a difference? What you really seem to want is another 8 channel rx of a different manufacturer and try that, you might then be able to find out if it’s a system fault or a brand name fault.

I have read somewhere with regard to Corona receivers that they shouldn’t be used below channel 60 and above channel 80. Whether this still applies I don’t know but I think I would assume it does. But as you are on chn 61 and are ok with the 6 channel lumps anyway I guess that’s not of any importance!

PB

[Romeo Whisky]

Check out the GWS 8-Channel Receiver. They're inexpensive and I've had loads of them. They're full range and totally reliable. Never had one fail. Available with either end pins or top pins to fit JR or Futaba plugs.

[Grasshopper]

Peter,

 

good feedback here!

I tried two new Corona 8 channel rx, a single and a double conversion, with (obviously) different crystals. Both gave about 1/2 the range I have always got from Corona 6 channel ones. All this on channel 61 by the way. As a retired hardware/software designer in embedded micro systems, I think it safe to say that the 8 channel single conversion rx will just be a software changed 6 channel one - so naturally my engineering background prompts me to not be happy with the 8 channel performance.

 

I am rapidly thinking (see earlier post) that the way to go is to convert my Cockpit SX to 2.4 GHZ using the Frsky hack module and then I can get 7 channels - at a cost of £25 or so for both units. Subsequent 7 channel receivers will cost less than £14. This is the one route I can see which removed all uncertainty and doubt - which again appeals to me (over?) logical brain!

Peter

 

 

[PatMc]

Peter, I don't think the number of channels available on the Rx is ever an issue.Most of my Rxs are 7 but at least one - GWS - is an 8 & I use them all with 7 channel Txs.

In the past I have used them with a 4 channel Futaba Conquest Tx. Using this I accidentally found that channel 6 & 7 of any 7 ch Rx responded to ch1 & 2 of the Tx.

i.e. They acted like a Y lead to these.

On a couple of gliders I actually used this feature to give me coupled aileron/rudder.

[Grasshopper]

Pat,

all understood and clearly described, thanks for the input.

The fact remains that I make notes of everything I do on a flying spreadsheet:- every flight, range test, transmitter program change. Anorak stuff I know but I had to do this in my work so it is ingrained. Also useful to be able to look back.

 

When I look at the range test notes of this 2m Luna glider, I got 60 metres with both of two 8 channel receivers on channel 61. Tx aerial down, batteries all fully charged. In the same glider with 2 different Corona 6 channel receivers on channel 61, I got 200 metres, again Tx aerial down, batteries charged.

 

So - - 60 metres, say 90 paces - is this what folk accept as 'good range' ? Maybe I am looking for too much but then again how to explain the 3x range of the 6 channel receivers?

 

 

[Ben B]

I use a futaba tx not a cockpit but I use the 6Ch Single conversion Corona receivers all the time and have not had a single range problem despite flying almost out of sight. So something strange is going on... But then I don't test with the aerial down as I don't see it as an accurate test- some tx's may have more attenuation when you do this than others. I just leave my plane with someone and go for a super long walk then wiggle the sticks and get the person with the plane to see if it moved. If I get out of sight performance at ground level I'll get better performance when it's in the air. Or that's my thinking anyway.

[Grasshopper]

Ben,

 

yes, I have never had a glitch with the Corona 6 channel ones either !

 

The problem arose when I tried to use 8 channel ones and found the range poorer. Maybe still OK, but just poorer and that set alarm bells ringing. Scan the posts and you will see what I mean.

 

Peter

[Peter Beeney]

Peter ,

Thanks for your reply, I think it’s quite possible your 6 channel rx’s are exceptional and the 8 channel is about the normal standard! I saw a new SkySport tx many years ago with a aerial down range of only 15 paces and yet the aerial up range was perfect.
Oddly enough, with respect to dual conversion receivers, the only rx that I’ve viewed with some apprehension is the Futaba 138 Dual Conversion; and I gather there were some some issues with this one, which caused a few tangles.

With regard to 2.4 GHz, you might also like to look at some Assan kit. A friend studied all the respected hack modules quite a while back and he thought the best of the bunch was the Assan.
He’s used it with great success for some time, in a FF9, and has had no suspect moments at all, a 100% success.
He bought me a tx module and 6 channel rx, for the Evo, which I’ve tried but not yet got around to doing permanently. I need to have the tx upgraded first. It worked instantly, and certainly seems to be very good quality. I think the cost is very competitive with the rest, too.

I don’t know if the hack module will fit in a Cockpit tx, it’s a snug fit in the Evo, but I’m sure the information is out there somewhere. You can email someone in the company direct, I did and got a reply by return.

Incidentally, you mentioned fully charged batteries when range checking. I played about with this once upon a time and I don’t think range is very voltage dependent. I found a 35 rx would work down to 2.8V, still with good range, but stopped entirely at 2.7V. Whereas my Spektrum 2.4 AR500 rx will work down to 2.7V. Below that the rx is still trying to work, i.e. it hasn’t shut down but the servos have called it a day anyway. Which, to say the least, is somewhat different from the conventional view; but that’s a whole different story.

Pat, - I’m guessing here, but is it possible the Futaba four channel tx uses a minimum of a 6 or 7 channel encoder? With the end channels tied to the first stick outputs. Gives you an ‘hidden asset‘ of a two channels working in tandem but I don’t think they would want advertise it. You can’t do any mixing or variable control throws etc. so as you say, a Y lead would do the same trick.

All this now fading fast into oblivion now; and 2.4 getting ever increasingly smaller. And lighter, too! MPX give you the gen. on how to modify their six channel 2.4 rx down to 1.3 grams, although they then nonchalantly inform you it nullifies the guarantee, but I saw a 4 channel, make unknown, on a stand at a show at 0.75 gram! At this rate we will soon be assembling models under a microscope! And flying them in a empty goldfish bowl!

PB

[Grasshopper]

Yes Peter,

 

it's clear we are thinking along the same lines here, and I suspect we may have similar engineering backgrounds? I intend to range test the 8 channel receivers again and see if in fact I was aiming for the moon. I note that Futaba and co say 25-30 metres is good with tx aerial down so as you say, I was perhaps misleading myself.

 

I will look at the Assan kit - although I have a very experienced friend who has gone down the Frsky route and says it went like a dream. In practice these modules are similar in function/design and the fitting thereof is simplistic to anyone who can handle a soldering iron and has a little electronics knowledge. M-m-m --- perhaps not too many folk then?

 

Peter

 

[PatMc]

Peter,

I've been using a FrSky in a FF8 Tx for some power (electric) models & am pleased to say the results so far have been good. I've now bought a telemetry hack that I will be putting into my SX when I have some spare time but I intend to make it switchable between 35 & 2.4 as I have so many 35 Rxs it would be a waste. AFAICS the hardest bit of the conversion is siting the bind/range test button.

 

Pat.

[Frank Skilbeck]

Pat

 

I made mine into a box which plugs into the trainer port and velcros to the back of the Tx, but I have seen a conversion where it's fitted inside the case with a switch to allow switching between 35 and 2.4. If i find the link I'll post it.

[PatMc]

Frank, I don't like the idea of using the trainer/charger port as it means plugging & unplugging every time the battery is charged. The only advantage I can see would be that the bind/range test button etc are conveniently placed. That's why I'm going for the "hack" conversion.

I already have this link showing a conversion to Corona which would be the same for FrSky but thanks for your consideration.

Incidentally I have a Spektrum DX6 set including a single AR6000 Rx that I got for indoor flying. Unfortunately it doesn't work with DSM2 & the only Rx available for it is about £30+ . The cheapo Orange Rxs can't be used so I converted the Tx to FrSky. If anyone is interested I can open a new thread & post some photos of the conversion.

 

Pat.

[Frank Skilbeck]

Pat

 

Thanks for that, that is similar to what I'd seen and I may do in the future, but probably with a 2 way hack module.

 

I agree with you on the plugging and unplugging, but as this is how MPX's own plug in module works I guess it should be OK.

[Peter Beeney]

Peter,

One rule of thumb that has been quoted is that the air range can be 10 times the ground range. So my aerial up ground range of 500 metres is then a 5000 metre radius. I’ve always found my eye sight to be the limiting factor.

I was never into computers and such, just a spanner man sparring about with power and backup systems. I did have a roving commission though, for many years, with a finger in many pies. What is they say about that - Jack of all trades…. ?
I’ve been retired for a long time now, when I left the first pagers were only just coming in!

Just as a point of interest, the Assan radio is slightly different, at least to the Spektrum, the only other one I know anything about installing. There is no bind button, the bind plug shorts the signal pins on the receiver channels 1 and 3, and to bind the system you then operate channel 2, this being the throttle on the Evo. Also no soldering, just 3 wires with a small square socket which plug onto their respective pins. Plus a coax cable to the 2.4 aerial. Which in turn means you could convert back to 35 in a twinkling if you wanted to. In the instructions, it says it can take up to 2 minutes to bind but in my case it was instantaneous. There is also a pilot pre-set ‘failsafe’ position for all the servos. There is no limited power/range check facility, but when we did a full range with my colleague’s Futaba/Assan at 700 metres, model on the ground, arranged in different orientations and also at the same time trying the tx aerial in different configurations it was a 100% result. The aerial on the 6 channel lightweight rx is a piece of wire three quarters of an inch long which just sticks straight out. The next time we do this test with a 2.4 radio I shall find a few tx’s, say 3, switch them on and put them close to the model. If there is a 100% working result at this point I shall consider the system to be fairly bullet proof.

It seems to me as though these cheaper conversion systems are perhaps all very much alike; but they certainly seem to be able to stand in their corner when it comes to comparing price and performance with the brand names.

Although the warning about remembering to pull the aerial out when going back to 35 from 2.4 must be very much part of modelling folk lore now, a little rule that quickly sprang up, we had one very able gentleman that found with the best will in the world that when he ‘picked and mixed’ it was easy to forget! After he’d totalled his second model because he forgotten to extend the aerial he decided enough was enough and he’d just use 2.4. Makes me think I will do likewise.
Oddly, I’ve experienced the inverted version of this, when flying on the 2.4 trainer box I’ve glanced down at the tx and for a split second I’ve thought I’ve forgotten to pull the aerial out! The expression ‘my blood ran cold’ springs to mind. I’ve done it a couple of times, and it only lasts a micro second but it sure does startle me!

Having said all that, there might now be another obscure but distinct advantage in using the ‘duckky' aerial. You don’t have to think about pulling that out and I’m sure that Pat will agree that this could take some pressure off when swapping between the two. In fact, it might help to make it idiot proof, so in which case that might lessen the chances of me getting it wrong down to around 50%!

As my father once said to me, “Son, you were only ever right once, and that was right in somebody’s road……”.

Some things never change.

Good Luck with the range testing.

PB

[Peter Beeney]

Just to update my last post, on the 30/7/2011, and if it’s not too far off topic, we’ve had a little bash at the receiver check that I mentioned. The one with the three ‘interfering’ 2.4 transmitters.

We used my Spektrum 5e ‘buddy box’ and an AR500 rx with two servos and a 6V battery plugged in; this just laying on a metal framed folding chair; the short aerial straight out and the long aerial curled up. I didn’t want to make it too easy! We then placed three other 2.4 tx’s at the base of the chair, which were switched on. Everything worked ok, so I put the tx in the car, still switched on, and drove to a point 600 metres away, as accurately measured by a land registry man on his large-scale map, and tried again. At some point on the journey the red led on the rx extinguished, indicating a loss of signal; it returned as I removed the tx from the car. This exercise is line of sight. The servos still travelled to and fro ok in response to all stick movements, and no glitching, I was holding the tx normally throughout. I tried the tx in several different aerial orientations, including the aerial pointing straight at the rx, with the same 100% working. We also tried it with everything at idle for periods of 20 - 30 seconds at the time, one servo gave a very occasional twitch, which apparently was only just perceptible. Fairly understandable under the circumstances! There was also one man flying on 2.4 approximately 40 metres away from the test piece. As far as we could tell, the servos did not fail to respond to my signals once.

I reckon this is a bit of a result, although I’m not quite sure what of, exactly! But if nothing else, it does seem to prove that relative signal strength is not a problem. The ratio is 0.5 metre to 600 metres, that’s a fair old ‘power-ful’ ratio. I might try and do the arithmetic to get difference in decibels.

One of the tx’s was my mate’s Futaba with the Assan module, we might well try this next with a Assan rx, it only takes a few minutes to do. Also we can experiment with non line of sight, we can put a hill in between; and to get a another perspective, if we can get find enough 35 meg kit now we should perhaps see how this performs in the same test.

As a compliment to this, I was swanning around in a reputable European r/c website recently and I noticed that they consider that up to 200 2.4 GHz transmitters can be used simultaneously without any interaction. Now that would really be what you could call a Balbo! Team Panic often flew with 20 models up together, how about 200?
Maybe this might well now lead to some ‘How many models in the air at once?’ type of competitions though, who knows?

Or perhaps ‘how many mid-airs can we have in five minutes’ might be more appropriate……

PB

[Tim Mackey]

Seems a very good result to me Peter.