RE: Quandary...
 

We call those - "mantlepiece" radios - I am still lookin-

RE: Quandary...
 

Hi LSp972,

I too have been "On the Fence" regarding 2.4 . I have 72mhz radios that date back to the late 80's that I still use. I tried a spectrum 6DX, 2.4 first generation and found it to be lacking. I have seen other members at our field experience mysterious failures of their 2.4 systems that no one could reasonably explain.

I would like to upgrade to a current system however, which one to get is a problem I have yet to figure out. I am leaning towards Futaba Fasst but, still not sold on the whole 2.4 idea. The thought of being secondary users on that frequency band verses primary on 72mhz makes me feel that we as a group are slowly being led out of radio control operations altogether. (Sorry but, I tend to be suspicous anymore, old age I guess )

It is too bad that the Frequency hopping technology cannot be developed for the 72 mhz band. Perhaps it would allow us to keep our primary user status of those frequencies and not be vunerable to interference from "2.4 Primary Industrial Users" who could care less about our hobby.

I guess we'll see what happens...

Carlos G

RE: Quandary...
 

You are not alone in misunderstanding the 2.4 radios .
The 72 stuf is NOT primary - it is shared and getting shot down is always apossibility.
2.4 is also shared BUT in a far different manner
The spread spectrum approach simply prevents others from aquiring your particular linkup.
The chance of the 2.4 band being taken over by some outside signal is very remote - others will say no but in real world -the chance is very remote.
Hopping - in 72 - not realistic-
I fly 2.4 -ONLY -and have done so since it hit the market - never a glitch
the unexplained crashes - 99% of the time user error in setup and or power setup - true -
again some will say no but realisitically that is what happens.
No matter which brand you choose - you have to do the antenna placement and power needs required - correctly
on 72 -as long as the antenna trailed - the signal got there and power could fall to very low levels - the servos just slowed -
The new stuff is simply FAR FAR more dependent on power levels. The system is based on using miniature computers- computers require specific voltage levels.
I have one non computerized car (84 MB td) and an all compuer car - Honda Odyssey - both great cars - but totally different basics. with far different capabilities
It is a learning curve - -I have been flying , including lots of competition since 1970- andsimply decided the 2.4 system was worth learning - Never looked back- you can do it too.

RE: Quandary...
 

Staying with 72 and you run the risk of being shot down by someone down the road door operating a little RC car.

Karol

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Okay; so what's to learn???

I have been looking for a primer on converting to 2.4, with no luck. I'm just finishing up a GP Stik .40 I bought last week; strictly as a radio "test bed". I'll get my new radio Tuesday, and hopefully it will have some pointers, etc. But absent that, I don't have the first clue as to what special needs- if any- the system has.

So... What do I need to know? Assume I am a very experienced R/C builder and pilot with many years of operating 72 mHz systems under my belt. Also assume I know zippo about 2.4.

.

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What new radio did you order?

RE: Quandary...
 

Not unusual -
Iwas in same situation when I started flying 2.4
One big advantage was that I had been flying electric power models and found out how many issues were possible using th e batteries /regulators ESC .
These can be a bit daunting - in that they appear to work perfectly on the bench but quit for " no apparant reason". The batteries which worked fine for you on 72 may be totally inadequate for 2.4 - believe this .

The other issue was receiver placement -
do NOT bury it in the model - the whiskers must have a clear view -no metal/liquids / carbon fiber etc., blocking reception paths.
Any brand - no exception- it is a 2.4 thing.
learn to do proper range checks - the antennas used demand that you check reception in all flight attitudes .
finally there are no magic 2.4 systems which have superior reception and range. This is all based on the type rx AND tx used
short range systems are killers used at long range - they willsimply quit
It's just like your desktop /laptop computer - they quit and until you can get a signal back they stay "quit".

RE: Quandary...
 

LSP972: What's to learn? Here are my suggestions
1. Batteries - use a minimum of 1600 mah in a 40 - 60 size sport plane. 4 cell Nicad or Nimh is ok, but 5 cell is better. You may want to go to LiFe/Lion/Lipo batteries later, but that's another learning curve.
2. Receiver - learn how to bind it to the TX before you install it in the plane. Read the manual about antenna placement and do so. Don't wrap the reciever in foam. These computer receivers generate heat and need to dump it.
3. TX - read the basics on programming. The basics (setting up channels, endpoints, reverse, and failsafe) will get you in the air. Read the part about range testing. The TX will have all sorts of other options, but they can wait.
4. Flight preparation. Be sure the fail-safe is working (with glow engine - engine off, TX and RX on, then turn off TX, check carb movement; with electric -similar except be sure the prop is clear (or not installed) since motor may go full throttle).
5. Range check - put the TX in range check mode, get to the proper distance, have someone pick up the plane and move it to different orientations. After using 2.4 for a while, my range check procedures are quite similar to my 72 mhz range checks.
6. Check servo movement, Go FLY!

Others may have more to add.

Personally, I switched to 2.4 three or four years ago. Haven't looked back.

Brian<br type="_moz" />

RE: Quandary...
 

Post #17.

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RE: Quandary...
 

Excellent...THIS is the sort of "nuts and bolts" information one needs.

What's the deal on the battery capacity? Does the 2.4 rx need more amperage, or whatever?

I have sufficient batteries (1690 mAH for the Stik, 2600 mAh for the 60" Katana, 3500 mAh for the 78" Extra), but these are all four cells. I have been contemplating going to five cells for the increased servo response; sounds like that benefits the entire system on 2.4?

.

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Can you expand on this?

I got the receiver placement warning.

.

RE: Quandary...
 

The batteries , need to be of BOTH a capacity (amps) and a C rating ( discharge capability) which will prevent a condition where high loads ( bad sizing of servos - sticky pushrods etc.), will never drag voltage down more than ONE volt when testing
this requires you have a voltmeter which can be placed between batt and rx.
Here is why: as batteries age and are depleted by use during a flight, , this voltage drop INCREASES
so it is not inconceivable that a freshly charged pack will drop one volt under test and half way thru the pack the same load will drop voltage up to 2 volts.
Batteries which ar more tolerant of this are genuine A123 and good Lipos
th downside is that voltage stays up right till a point then drops off rapidly
Bottom line: simply getting bigger NIMH may solve nothing - some of these cells are very low C rating
If this is confusing - go to NOBS battery or similar site and read up!!

RE: Quandary...
 

Weren't those days great? It was like having a private frequency in the 70s and 80s. But then some signals, legal or otherwise, started to come on the air. At a state-park flying site in the 'burbs, I had a near-shootdown, managed to get the airplane down, shut down the engine and turned off the transmitter and all the servos went full travel and stayed there. Never flew there on 50 again...

RE: Quandary...
 

I understand that; but this is a concern for ANY system, regardless of frequency or modulation. For instance, a lot of heli guys found out the hard way that if one's servo load dragged the system down to three volts, the Futaba 401 gyro would do a hard reset; with disastrous results. So I am no stranger to those concerns.

The "discharge rate of the cell" has me a bit confused, though. Batteries discharge at whatever rate they are being drained. I guess you are talking about making sure nothing in the model's system is dragging the servos, etc.

.

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Whatever causes the servos to draw an excessive amount of current (bound up control surface, extreme load on the control surface, current hungry servos, defective servos), the battery voltage, capacity, and C Rating (max current that the battery is capable of delivering) has to be adequate for the worst possible scenario.

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LSP972: This battery stuff is what I meant about another learning curve in my earlier post. With your GP Stik 40 and standard servos, any problems should be quite similar to any you would have in the past. A difference is that a really low voltage causes the 2.4 RX to totally quit working until the voltage comes back up and the computer reboots, if you have time. The 5 cell or lithium batteries have a little more safety factor than the 4 cells.<div></div><div>Once you leave the 40 - 60 size planes, things can be really different. Lots of TX channels just beg for more servos. New servos that are more powerful and faster, electric motors, electric retracts, gangs of big servos, etc. These need more amps. Even the larger nicads/nimhs won't deliver the amps unless you have several in parallel. This is where the lithium type batteries come into play. You may need heavy duty wire and connections, then you find out the RX cannot handle the amps all the servos can pull, so you add a power distribution point. On and on and on.</div><div></div><div>My take on the problem.</div><div></div><div>Brian</div>

RE: Quandary...
 

Heed the battery advice you are being given. A 2.4 receiver is literally a computer and will reboot if the voltage gets too low for even a fraction of a second. That's why the battery must be able to maintain a high enough voltage even during a instantaneous amperage surge.

Your 12Z radio will come with a 6014HS receiver. This receiver is capable of operating the first 6 channels in either a high speed frame rate or a normal frame rate. Only digital servos will work in the high speed mode, and high speed mode can damage or destroy an analog servo. If you are using an analog servo on any of the first 6 channels, be sure the receiver is set to normal speed mode.

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Yet another nugget I was unaware of. I have read through the manual twice, and did not pick up on that.

I hear what you guys are saying. I have no intention of going away from NiMH batteries; I have two Alpha 4 charging systems that work fine and with which I am comfortable.

So I will have to be very careful with the larger airplanes, battery-wise. Parallel packs are easy enough to set up.

You fellows are doing a great job of educating me on this "new-dangled" system. Please... Keep the tips/suggestions coming.

.

RE: Quandary...
 

Ohm's Law!

Suppose for an instant you can solder the positive end of a single 1.2V cell to its negative end. The wire has a finite resistance, Rw. The solder joints have a resistance to them, let's call it Rj. (Dick Hanson recently ran into the connection resistance in some testing he did. It's important to consider!)

If you make this connection and then measure the current I.

Ohm's Law tells us that V=I/R, and we have just said that R is composed of at least two items, Rw and Rj. By that we would assume that 1.2V = I/(Rw + Rj). But upon actual measurement, it turns out there is a huge discrepancy. The current isn't as high as we expect, and the battery voltage that we're measuring is not 1.2V any more but actually much, much less. And the battery got hot too, not just the wire!

There is another term we missed: Ri the internal resistance of the battery.

The hint is that the battery voltage decreased when we did this. It is entirely due to Ri.

This Ri is different for every different type of cell (basic chemistry) as well as for individual cells of the same type (manufacturing differences, impurities, etc.).

In practice this means that for high-Ri cells, the voltage delivered to the system (rx, sx, etc) can be much lower than we expect it to be. The lower the resistance of the components, the higher the current draw will try to be, and it will be limited by the resistance of the cells. If the servos demand too much current, the volts available to the receiver chip can drop below the micro's minimum voltage, and a brown-out is the result.

Another factor is that high current discharges can damage certain chemistries, shortening their useful life.

The concept of "discharge rate of cell" brings these factors together. High discharge rate cells will have a lower internal resistance to provide the nominal voltage at higher currents.

In short, use appropriate battery technology. In the old days our servos were slow and didn't draw much current, and we could get away with AA cells. As planes grew in size and digital servos became commonplace, wise manufacturers provided higher-voltage packs (5 instead of 4 cells) and larger cells (in general, the NiMH/NiCd cells have lower resistance in the short/fat format (SubC) vs the long/skinny format (AA)).

I hope this helps. MERRY CHRISTmas!

Andy

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Be VERY careful with NiMH batteries. Those chemistries are notorious for high internal resistance, which is what Andy was referring to in his post. Therefore when a high amperage load is applied, even instantaneously, the voltage drops severely. Choosing a NiMH with a high total capacity does not guarantee the battery can maintain it's working voltage under a load. With 72 mhz, that last sentence was a trivia question. With 2.4 it is imperative that you fully understand this.

RE: Quandary...
 

PS -if you do not have a load meter which shows voltage/amps relatioships - you won't really know how well your batteries really work. the old setups which added 50 ma loads are frankly worthless .

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Hmmmm... now, I'm beginning to wonder if I should even mess with this. Its turning out to be more effort and expense than I want to invest.

I'm already highly annoyed that a charger which you plug into the TX is an "accessory" on this 12Z; it came with a stand-alone charger requiring that the battery be removed from the transmitter each time. Several problems with that, IMO; aside from the fact that I've seen, numerous times, complaints that this particularly battery has a rather short endurance... the 9Z had this issue as well, but was easily fixed. It would seem the only solution on the 12Z is to buy another, extra, battery. Plus, the manual is strictly oriented to 72mHz operation; there is a 20-page supplement entitled "T12Z Software Update" that doesn't say jack about handling the receiver. IOW, nothing about mounting it, etc. And there certainly is NO information regarding receiver battery concerns that you guys have enumerated here.

I believe what you are saying. This "2.4 supplement" (if that is what its supposed to be) is typical Futaba. Plenty of information, but presented in a manner that assumes the user knows more than he actually does. Seeing as how I'm basically 'flying blind' -i.e., starting from scratch, with NO knowledge of the idiosyncrasies of 2.4- it isn't of much use to me.

So perhaps, before I use it, I should return this radio while I still can... IF I still can.

No doubt I could learn all of this... but between the effort required to do so, and the additional expense of proper batteries/charging systems/etc.; nah, more trouble than its worth.

I appreciate you guys trying to help.

.

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If you decide to send the 12Z back then you will be making a mistake. You definitely should keep it.

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I doubt they would take it back anyway. My wife must have gotten one of the last ones; it now shows as Discontinued.

One wonders if Tony will continue to support it as long as he has 9Zs...

I'm told that most of our club members flying 2.4 are using NiMH or NiCad receiver batteries, with no issues. That puts me back on the fence.

I'm going to call Futaba Support tomorrow, with a list of questions. How that conversation goes will determine which way I "jump".

.

RE: Quandary...
 

LSP972

If you are a hardcore 3D heli pilot, then you can take advantage of the high speed channels from the R6014HS receiver. More than speed, it delivers more holding power. Otherwise, don’t waste your time as you will not feel a different when using it in airplanes.

You mentioned something about the 401 gyros and 3.0v. With Futaba receivers (2.4 and 72MHz), when the voltage drops bellow 3.7 volts, the throttle channel (3)ONLY will go to failsafe to warn you that there is an issue with the power system. For a Futaba 2.4 receiver, 2.7 volts is the lowest the rx can go.

I fly helis as well, and I still have two Raptors running 5 cells Sanyo NICAD packs with no issues at all, but they will be replaced this year with A123 packs.

Your 12Z radio is an awesome radio. It has a lot of programming options. That radio is now discontinued, but Futaba has mentioned that it will continue to service the radio for 4 or 5 years from now.

Go here http://futabarc.com/faq/faq-12z.html if you need help with the radio or post your questions here and we will help you with your system.

Hope that helps,
Doug.