coup80

Hi could someone clear something up thats on my mind,think this is in wrong section though,i have 8 planes and 2 helis and over last few months i had been getting alot of interference with my futaba field force 9 35mhz,i was advised by club members to change to 2.4 so i bouht a spektrum dx7se transmitter as advised i would need most of the dx8 features,and bought several recievers to suit some ar500, ar6200, ar7000 after getting transmitter i noticed online that you cant use futaba charger on spektrum transmitter(hadnot charged yet so fine)bought a spektrum charger.

wot i want to know before i use is all my models rx batteries are 4.8v will these still be ok for the new 2.4 radio gear i have installed,as someone has told me it has to be 6volt for spektrum 2.4 gear.

as you can imagine after buying transmitter, charger and 10 recievers my wallets feeling lighter and iam hoping i dont have to buy 10 6volt rx batterys and a 6volt charger aswell.

thank you

coup80

i ment to write i bought a dx7se because i was advised i would not need most of the dx8 features.

Rafael23cc

My Feedback: (6)

It all depends on the servos installed on the aircraft, and the type of flying that you do. If they are "normal" servos (not digital), they are properly installed with no binding and no friction, and you fly lazily around the field, then you should be ok. If you have speed demon aircraft, or 3D crazy machines with 45 degrees of deflection and digital servos, then you might want to start upgrading the battery packs of those.

In either case, a good voltmeter with the ability to add a load to the battery should be a good addition to your toolbox. Test before each flight to be sure. If the voltage drops below 4.6-4.8 under a 1 amp load, it is time to re-charge. I'm not an expert in electronics. This is a self imposed rule that I developed over the years. Since changing to LiIon batteries, I still do the same check but now the cutoff is 7.0 volts.

I have this voltmeter in my box, and use the 1 amp load quite frequently.
[link]http://www.horizonhobby.com/Products/Default.aspx?ProdID=HAN171[/link]


Rafael

tim750r

If they all used to work fine on 4.8v before, they should still work fine. There is a lot of discussion about Spektrum receivers rebooting if the level drops below about 3.9v (I believe this is a pessimistic estimate and will still operate at lower voltage). If your 4.8v batteries, switches wiring and connectors are all in good condition, it will be fine.

However - for my own piece of mind I would want to try to track down the original cause of the interference. Glitching could easily have been caused by a deteriorating radio installation or ageing battery pack, and replacing the tx & rx with 2.4 may just mask the problem a little.

Rafael23cc

My Feedback: (6)

I agree with the above statement in the fact that if the radio signal is developing interference when before there was none, then yes, 2.4 is only masking the root problem.

I do not agree with the part of the statement where is suggested to still use 4.8v battery pack regardless of system load. And ignore a manufacturer recommendation of a specified voltage. I've seen these things completely quit working at the specified voltage. And that includes both brands, not only spektrum but futaba too.

Rafael

coup80

Thank you for all your replys you are all very helpfull
When i say i was getting alot of glitches they are not random glitches they are glitches that are happening when i fly near specific areas near my strip ie if i fly down close along side off hill next to flying club,or theres a part over far side where club members have been steering clear off for same reason,we at the club believe that the signal in these two areas is not as strong for the 35mhz users this being why they advised me to change to 2.4,since changing i purpousley fly in these areas and all has been perfect iam glad to report,very impressed with the spektrum gear and i feel much more direct with the controls,i have not tried it yet in helcopters so iam hoping they will be as good.

thanks for all your help

tim750r

Sorry Rafael, I have to disagree with you as you are perpetuating a myth.

The operating spec for an AR7000 for example is 3.5v - 9.6v. A 4 cell NiCad or NiMh pack working within its design capacity, with wiring, connectors and switches also within their rated capacity should not droop below about 4.4v until it is discharged. If it does, something is wrong with one of the components in the system. Its true that NiMH cells have higher internal resistance than NiCad - especially the high capacity AA sized cells, and are therefore less suitable for high loads (several high torque digital servos for instance) and is one of the reasons people have switched to sub-c cells or other different battery technologies.

If you experience sufficient voltage 'droop' to reboot a Spektrum receiver on a 4 cell pack, then you most likely have either:

Insufficient battery capacity for the load (too high internal cell resistance)
A dying cell in the pack
Poor wiring / corroded connectors
Poor switch contacts
Load is too great for the system.

The last item is commonly seen when BECs / Voltage regulators are underspecified for the load current that the servos are demanding.

Those little capacitors you can buy to plug into the receiver are designed to 'hold-up' the receiver supply voltage during a momentary droop and are really working around a defficiency somewhere else in the system

A 5 cell pack may merely mask the problem & is not the 'correct' solution. If the components are all good, you WILL get more speed, more torque, and the servos will draw more current. This will be advantageous to some, but some older servos will wear / burn out quicker. JR certainly never used to warrant their servos operated above 4.8v (nominal) unless specifically designed for higher voltage. Indeed, some gyro / tail servo combinations won't last any time at all on a 5 cell pack without regulation.

Going back to my original point, IF the system was problem free before on 4.8v, then it will still be fine with a Spektrum receiver on 4.8v. I have a number of models on 4 cell packs with DSM2 receivers and all are fine. As the OP states his problem was due to external interference, I would stand by saying he doesn't need to change all his battery packs unless he wants the increase in speed / torque and his servos / gyro are capable of operating at the higher voltage.

HTH

Tim

BarracudaHockey

My Feedback: (11)

If you'd like a little peace of mind and a little overhead at the expense of carrying a little extra weight, I'd follow the manufacturer recomendations and run a 5 cell pack. Other than the aforementioned weight and a few more dollars, there's really no downside.

Rafael23cc

My Feedback: (6)

No myth. But you answered the question yourself in the statement below.

When we flew in the FM band, there was no re-boot of the system and a voltage drop was seen as a glitch. There was no way of separating the voltage glitches from the interference glitches. Now a re-boot can cause your aircraft to crash. So you have two options: Either put a brick of 4.8 batteries (read: high capacity pack) or set-up a higher voltage battery with a regulator. The second option has been done for years on high performance helicopters using 5 or more digital servos, at least one gyro and one governor. Short of a giant scale airplane with more than 1 servo per surface, you can't draw more power from a radio system. And now the giant scale guys noticed the advantages and they are using the same set-up

Granted, if you are a weekend flyer, with a trainer or a small scale aircraft, you might not need all this power. I prefer peace of mind, instead of trying to figure out if I have enough capacity on my battery packs. As it stands right now, using LiIon 5200mAh 7.4 packs, I can fly almost a full weekend without worrying about battery charge. And I know that the regulator will keep the 4.8v accessories happy. I still check my batteries before every flight.

Rafael

krisma

Raf,

What kind of aircraft do you use this setup on? Just curious.

Rafael23cc

My Feedback: (6)

2 each 90 size helicopters, 2 each 50 size helicopters, and soon to be intalled with redundant receivers in a 40% Nemesis, a 40% BD-5J, and a 47% Velox.

The helicopters have 5 digital servos, 1 gyro, and 1 governor each. The 47% Velox will have approx 15 servos. The Nemesis will have approx 10 servos, and the BD-5J will have approx 9 servos.

Rafael