Futaba 2.4GHz with caution

[Former Member]

[This posting has been removed]

[Chris Dowsett]

Nothing RCM&E cannot solve!  It is a thread of images posted by fliers such as Richard Crapp who has retro-fitted 2.4GHz in his giant Fairey Swordfish (best biplane) and came 12th overall. Apparently there were 5 flight lines with two models always staged ready for next round. No mid airs and no runway conflicts on the ground.

[Roy Hill]

Thanks for that Chris, always thought it is the way forwards, still no probs with 2.4 at my club,it will be interesting to know the % of 2.4 used at Rougham show this weekend,I will try to find out and let you know, regards, Roy.

[Bravedan]

While seconding that the FASST Receivers are far too expensive, they are also awkward or impossible to use in many locations due to the side mount socket, and also are heavy.  Basically, not enough variants available.

 (Tried to fit one in an Alula???!!!.........or inside a Freeair Streetfighter???!!!

Why Futaba cannot do the right thing and issue alternative orientation cases/boards escapes me (and in this their 35MHz gear is just as bad).

I feel they are just LAZY!!!!!!!!!!!!!!!!!!!!!!!!! 

Same applies to model memories.......................awkwardly restrictive and poor value!!!! 

Few actually NEED loads of channels, so why concentrate on that being the only "range" difference???

And No, I don't own Spektrum....................I do own Futaba .

 

[Chris Dowsett]

Roy Hill wrote (see)

...it will be interesting to know the % of 2.4 used at Rougham show this weekend,I will try to find out and let you know, regards, Roy.

Any luck Ray?

Bravedan has made a number of points, for example the side mounted only connector configuration.

I tend to fit my RX's flat against a bulkhead with shock absorption in place so the connecting wires run straight down the fuselage.  Having said that I am actually using two different configurations, bulkhead and floor.

I do not have much news from my end at the moment, the wind is in the wrong direction, but I have managed to do a few more low power range checks and will register another cautionary note shortly.

[Bravedan]

For the record, I have a 6EX 2.4 and four 606 Rx's. Bought fairly early.

Not had any in use tech issues at all. Put into various 'craft, sometimes because I fly small stuff  inc lots of wings slammed against other things due size/space...........not the slightest connection issue at any time so far. Have recently been regularly flying higher and further than ever before in my 35 yr RC experience with total confidence in the reception. (after careful extended range tests)   I fly occasionally where glitches on 35MHz are commonplace...................NOTHING.

Ground Test on low power?..................all have resulted in me running out of room in a 120' garden, better than any of my 35MHz gear can manage. 

While I trudged to my LMS and had the All Zero's check done, they didn't have any official stickers to later prove I'd done so, they'd "run out", nor have they managed to get any out of Ripmax since............I have got fed up asking..........they wrote me a hand written "sick note"................heaven only knows if the officious officials at some locations will accept that or not.

I think the Black Ribbon idea is plain daft, and I absolutely refuse to attach ANYTHING to the aerial, I tie a ribbon or use a black strip of Vinyl which is more visible and less likely to blow around obstructing  the sticks attached TO THE HANDLE. 

Futaba need to get their very unprofessional act together, resolve the 6EX Zero's issue beyond lingering doubt and release end mounted servo connection Rx units a.s.a.p. AND do a smaller lighter unit with such connections, full range.

[Chris Dowsett]

One of the differences between 2.4GHz and 35MHz is the TX aerial.  

I do not like telescopic aerials because they cause glitches when the segments go intermittent.  Their length is a good feature because a ribbon at the top helps with wind direction.

The 2.4GHz aerial on my TM7 is obviously not designed to take a ribbon.  It rotates in 2 directions & is easily knocked out of position.   I always do the low power ground test in the worst position which gives me as low as 80ft range and as high as 180ft.  Having someone stand in front of the TX, clobbers the range.  However, like you Bravedan, and many others, I have had no problems in the air.

One advantage of lower power tests is you can see control surface movements so slow responses are obvious.

I have thought of leaving my 35MHz aerial in so I can fly a black ribbon from the top strictly for the wind and to be diplomatically correct.

Optimising the flight installation is important.  Here is one comment made by Richard Crapp on his return from Top Gun Florida - "My Swordfish has new 2.4 radio with the receiver in the pilots head, the twin aerials stick out of his ears! That is why he looks less than comfortable."

Both my 2.4GHz models are retro-fitted so there are limitations with installation.  On both the ground range is about 50% greater when tail on.  I am not too happy about that!

[Former Member]

[This posting has been removed]

[Chris Dowsett]

Just trying to lighten things up a bit Eric!   Whiskers seems a good, non-tech, term for a component of an aerial/antenna system, or even a pilot's ear.  The angle of whiskers might tell us about the type of aerial system. 

A pilot in an open cockpit seems an ideal place to avoid blocking.  Richard uses Spektrum who cater for more whiskers (diversity) than Futaba.  Here is Richard's comment -

"It(i.e. using the pilots head) was a necessity of retro fitting, the 9000 Rx in the front is probably fully shielded but the two satellite receiver’s are brilliant, and we are very pleased, especially convenient for international"

I do not remember if the Futaba 'book' describes the type of aerial system other by reference to diversity and 90deg.  I imagine each whisker is a half dipole.

[Martin McIntosh]

On the 2.4gHz theme, but diversing a little, I have just purchased a JR DSX9 set from a very well known retailer. The first thing they said was `this is very expensive for what  you get, you can do it much cheaper by buying a 9X11 and a module conversion`. Smell a rat? So did I. they are just trying to offload their old stock and flog you nearly obsolete gear at full price and not much saving. Beware!

Re pricing, these Rx`s probably cost under 50p to produce so we are being ripped off right left and centre.

[Tim Mackey]

Of course that applies to very many items Martin - not just 2,4Ghz receivers, and part of the cost is obviously for R+D and tooling etc etc....not purely materials / assembly.

I actually think most of  the Spekky receivers provide very good VFM.

[Nick Rigg]

Sorry if I'm repeating everyone else...but with all the promotional stuff being done by Spektrum/JR, Futaba are looking a little stingy

Time to start selling R606s at knock down prices - £25 would be about right or do what Spektrum did

[Chris Dowsett]

Ultimately it is the complete service that needs to be good 'Value For Money'  Timbo

Something I picked up on http://www.spektrumrc.com/Articles/Article.aspx?ArticleID=1731 .  It is an example of good service and a useful caution.   It explains some of my problems charging flight packs.

[Tim Mackey]

Chris Dowsett wrote (see)

Ultimately it is the complete service that needs to be good 'Value For Money' Timbo

Something I picked up on http://www.spektrumrc.com/Articles/Article.aspx?ArticleID=1731 . It is an example of good service and a useful caution. It explains some of my problems charging flight packs.

Exactly...which is why I said it - Spektrum have provided me with good products, prompt and informative responses to my queries from both HH in the USA and Ex Helger, here in the UK. They provide quick and honest information about any problems ( not that there have been any actual faults ) and the quick connect upgrade was done free of charge and promptly, even though it was not a fault....merely an upgrade to improve a product further. The link re: charging NiMh cells is actually just confirming / reminding people, about a procedure regarding charging hydride cells that many users have known about for some time, and I and others have diuscussed thge very issue several times here on the forum.

In my book thats GFM.

[Chris Dowsett]

Compared with the days when the UK designed and manufactured it's own radio gear current manufacturers are very remote.  The forums bring them closer but in a very hit and miss way.

Changing the chemistry of warrants a WARNING from each manufacturer.  Collectively we seem to approve of both Spektrum and Futaba but have both issued suitable warnings?

Any corresponding cautions for this thread?  Here is one suggestion.

#  Make sure the failsafe response is obvious.

Futaba RX's are designed to failsafe at 3.5volts (they assume NiMh rather than LiPo).  The R607 & R617 failsafe works on channel 3 output only .  That is normally throttle or flaps (but not crow braking).  

To get around the 4 servo wing problem I intended to plug telemetry into Ch 3 (which is otherwise unused) but it goes haywire before 3.5volts.   Might still work as audible failsafe response.

Personally I would approve of both Futuba RX's but not for crow braking.

The "unexpected throttle back, control to throttle back, control as required" failsafe procedure is a neat trick.

 Not sure about Spektrum. 

[Tim Mackey]

Right...just to elaborate a little further on NiMH cells. Like for Like size / weight comparisons, NiMH have much higher capacity than Nicd at least 20 - 30 % in most cases. ALL nickel based batteries should be trickle charged at about 1/10C for the first few cycles to "form" them properly, equalizing cells and compenastaing for possible inbalance due to differing self discharge rates and possible gravitation during storage. All nixx batteries actually charge better at fast charge rates ( 1C, - or above if cells are capable of 1C+) - typically achieving  90% efficiency compared to slow charging ( overnight or approx 1/10C) where around 70% is the norm with a full charge taking more like 14 - 15 hours minimum. "Burp" charging improves things even further, but most simple chargers do not deploy this method, relying instead on "delta peak detection" or NDV ( Negative Delta Voltage )  where the cell exhibits a very slight drop in voltage as it peaks. This is where the difference between hydride and cadmium cells can cause the problems mentioned by the Spektrum tech bulletin referred to earlier. The typical NDV for cadmium is around 30mv - and most chargers will spot this easily and correctly terminate the charge or switch to trickle mode. However - hydride cells exhibit a much lower NDV...typically around 15 mv or even lower, sometimes only 7 or 8 mv. This very tiny NDV is very hard for the charger to spot, meaning some ( many actually ! ) chargers just carry on pumping in charge, causing the cells to overheat and possibly be destroyed. NiMH cells are particularly vulnerable to excessive heat, leading to poor lifespan and componding the problem of NDV detection even further. Because they do not tolerate overcharging the charger MUST switch to a very low trickle rate of around .05C and chargers designed for Nicd will not be set that low with the recommended trickle charge for nickel-cadmium being anywhere between 0.05C right up to .1C - thats why you should NOT use a nicd charger for NiMH batteries. Now...back to the Spekky bulletin - to avoid the dangers of missing the NDV and overcharging your batteries, many chargers have their NDV detection circuitry set to very sensitive, and this can often cause the charger to "false detect" so stoping the charge too early. Result? a partially charged battery which you think is full.

Further result? Well you dont need a further example do you

So.... if using NiMH ( and most of us do these days thanks to the green brigade ) ensure you use a good properly designed charger and preferably use a loaded EVM meter / indicator regularly to check the charge state of your packs. Simply sticking a DVM across the pack when its not actually connected to anything is pretty much a waste of time due to the flat discharge curves of nixx cells. 

[Roy Hill]

well said timbo, it,s happened to me,nice article cheers ,roy

[Bladerunner]

Many chargers have a capacity counter (typically mAh) which is a useful indicater of successful charge, as it allows one to compare to the rated capacity of the battery pack.

[Chris Dowsett]

Thanks for clarifying the effect of the change in NiMH chemistry on the -dv/dt  characteristic  Timbo (see)

...back to the Spekky bulletin - to avoid the dangers of missing the NDV and overcharging your batteries, many chargers have their NDV detection circuitry set to very sensitive, and this can often cause the charger to "false detect" so stoping the charge too early. Result? a partially charged battery which you think is full.

I  was previously unaware of this and it does describe the symptoms of the new cells I bought for the telemetry ground station.  I appear to be getting repeat  "false detects" which previously I have put down to a poor mains supply.

 Last Tuesday was too good a day to miss so a took the Harmony up in the hills for some failsafe practice with, or without, telemetry.  BMFA/CAA guidance says that if you have failsafe it must be enabled (meaningless with no throttle or flaps).  The telemetry was connected to the 'failsafed otherwised unused' channel 3 so it reports battery volts.

I had already ground tested the Harmony and Sword(all carbon with digital servos) with good 2.4GHz results  only.  Low battery conditions were a problem but not with the Futuba RX.  I will come back to that in a later post.

 One of the issues once committed to aviation is there is no clue about battery state.   Just past experience.  For test purposes I had already decreased flight duration from 40 mins to 10 mins.  Now the Harmony is up in the hills set the timer to 15mins and to see how far I could push the test envelope. 

Climb out lift all the way.  Figure of 8's  to test 360deg on the horizontal.  Loops to test 360deg in the vertical.  Progressively flying further and higher away.  A few chandels to celebrate (almost the limit with the Harmony).  Play with the Griffons.  High fast  flight to the downwind side and then back out again. When  the 15min bleep occurs (simulating a failsafe) get out of the sky pdq and onto spot. 

All perfect flights.  In future I will be increasing the flight time progressively checking consummed capacity as I go. Standard procedure.  The telemetry can wait until I can resolve battery problems.

[Alan Shipley]

Hi guys, quite new to forum so hope I'm asking in the correct place. I think Timbo would be able to answer my questions.

I have an old Futaba FP-8JN which I think has shorted out from me messing. Is it possible to get it repaired or do you think I should bin it? If I bin it would the receiver which is FP R8J & one of  FP R6H work with a Challenger FP-T6NL ? I have the Challenger TX but not the RX.

I am also looking at the Futaba 2.4 cus thats the way I will go in the future. Read all the info above and found it very helpful.

[Tim Mackey]

Hi Alan. Must confess I am not familiar with the set, - but thought this was  a US spec set - on 27 or 72Mhz ?

Anyway...it is getting pretty long in the tooth now with switched functions rather than software menus, and frankly, I doubt it would be cost effective to get it sorted, much better to put the money toward a nice new sexy 2.4Ghz set!

[Alan Shipley]

Hi Timbo, that old 8 channel set was the bees knees when it came out, doing things like they do now. It was a module system for 35MHz or 27MHz. It was sold here by Ripmax.& think it was top of range.

Yes I think its time to go software now. I take your point about being cost effective, thanks for your help.

Alan  

[David Ashby - Moderator]

Give Ripmax a call Alan on 0208 282 7500 - they can probably quote over the phone but as Tim says probably best to upgrade.

[Chris Dowsett]

Hi Alan,

If you go for a 2.4GHz system go for Futaba, or Spektrum (& JR).  Make sure it has the features you need (as your accustomed to on your old FP8JN TX).  Incidentally this TX has an RF module so you may be able to replace it with one for 2.4GHz unit.  The advantage of a module is that it keeps  your options open (Futaba or Spektrum).

[Alan Shipley]

Thanks David, will give them a call as I hate throwing things away.

Timbo's report on batteries was brill. I bought batteries some time ago from a model shop and I thought I was buying nicad cus nothing was said. I never felt they held a charge for two long so I was carefull how long I flew. After reading Timbo's report I took the plastic cover off battery pack and found the batteries to be Ni-MH , these had been charged by the norm charger that comes with the radio gear.

When you buy a new radio set, say a Futaba 2.4 do you know if they charge the Ni-MH battery that are most used with the charger that is supplied?