2.4 radio issues and recommendations

[Al Kramer]

I am posting a good message that Fred Champagne took the time to write. He makes several accurate observations and suggestions to help make our flying safer and more reliable. Thanks Fred!

I have noticed that there are some issues with the 2.4 systems. The main problems are not with the product but in how it is used. With the smaller receivers with no satellites, it is very important to not place the antenna in an area where the signal may be blocked by carbon fiber or some other material that can block signal. After installing all of the equipment you need to range test at the manufacturers recommended distance but at all angles. have someone turn the aircraft in all directions including top and bottom to verify no signal loss during range test.

Receivers with multiple satellite antennas should have the satellites mount in a way that all antennas are pointed in different orientations to one another in different parts of the aircraft. The same range test rules apply. CARBON FIBER WILL STOP THE SIGNAL.

The next main issue is low voltage brown outs. It is strongly recommended to use 6.0 volt ( 5 cell nimh or nicd ) or larger. Though a 4.8 volt pack shows 6.0 volts at full charge, once under heavy load it will draw below the low voltage cutoff of receiver and cause a brown out or temporary loss of control. If the battery is not fully charged at the time of this brown out, the receiver may continue to brown out until the plane hits the ground. You can run 6.6 volt Life batteries directly to most servos; except some futaba and older hitec, without any fear of damage. Check your servo specs. If they rate for 6.0 volts operation, you are fine on a 6.6 volt pack. However, you do need to make sure you do not have any servo binding issues or you will fry your servo (especially throttle,choke and flap servos). Always power up a new built airplane with the servo arms off to prevent end point binding.Your receiver will easily handle the voltage of 6.6 volts (or more in most receiver cases).

There have been some bad 6000 series Spektrum receivers but you can catch these during your range test.

An ESC that has a BEC will regulate your power so should not have brown out issues unless your batteries are bad.

Don't assume because you crashed that your equipment has failed. this is rarely the case. Proper battery use and maintenance will prevent most issues.

Fred Champagne

[Al Kramer]

There is one other item that is mentioned in most manuals that are included with radio gear and that is to orientate your TX antenna so that it is not pointing at your aircraft. Your plane will see the lowest signal strength in this position.
This is true for both 72 and 2.4

[champ874]

Thanks Al, Yes that is true about the antenna on the transmitter. Here is a bit more info from some questions I have been asked.

It has been asked if a 2.4 GHz radio system can have interference from a higher watt 2.4 GHz source. 2.4 GHz can most defiantly be interrupted by another High watt 2.4 source but generally it has to be pretty close to the receiver or transmitter. If someone was transmitting a signal from a video downlink running on 2.4GHz you may get blocked. For this to happen though they would have to be very close to you. Most video and FPV stuff is transmitting on 5.8 GHz nowadays though so should not really concern us.

Another question is will a full fuel tank block signal. A receiver surrounded by a liquid may block some signal and reduce range but I would be surprised if just the fuel tank would. With the plane pointed directly at you, the signal may be blocked by the engine. but you would have to be flying directly at yourself at radio level to notice this.

Helicopters are a good example of how good the modern 2.4 GHz radios are. Helicopters are made up almost entirely of carbon fiber and various moving metal objects. They have large High current Batteries,speed controls and motors. Despite all this, you rarely hear of radio interference. Airplanes are a much more hospitable place for a receiver to live.

The 2.4GHZ receivers lock out when they lose signal but within a very short time they start looking for the signal again. this means lockouts are for a very short duration. The cause of the lockout will usually be gone once the plane changes attitude and you are linked up again. So if you have a lockout that lasts long enough to causes a crash(more than a couple of seconds), it is most likely a battery issue or loss of bind which is very rare.

Receiver switches can also fail so make sure you use a good quality switch (not a toggle switch) and two batteries with two separate switches for redundancy if your plane is big enough to carry the load. You can plug the second battery into any unused servo port on the receiver. Bear in mind though that if one battery fails, you will not know because the other continues to carry the load. you can tell if both were working properly as when you charge them they will take close to the same amount of charge to recharge them. Also use two batteries of the same type and capacity ie. two 6.6 volt life batteries of 2100 Mah each. This gives 6.6 volts at a total of 4200 Mah of capacity.

Aerodynamics is a funny thing. When a wing stalls in either high or low speed, it can feel very much like your radio has failed. Everything happens very fast and it is hard to remember exactly what happened. When a radio loses signal it will default to the servo positions that the radio was at when you bound it last. so if you have a Brown out the plane will either fly straight ahead or go into a gentle turn or dive. It will not generally go crazy. The throttle will usually go to idle if that is where it was when you last bound. This is why it is important to rebind after you have done and servo replacement or significant trim adjustments. As well, make sure you have the throttle set to the position you would like it to be at in the event of a signal loss before you rebind.

For those of us that are old enough to remember and were in the hobby years ago, we ran FM receivers. previous to that we had about 8 AM frequencies and they were denoted by colours rather than numbers ( i had one radio on orange and white, and one radio on purple and white). When FM came along we had more than 20 available frequencies. If you flew FM you had to cover 3 frequencies with your pin on the frequency board. one above and one below. if you flew AM you had to cover 5 frequencies. two above and two below. Even with poorly tuned receivers and frequency cross overs we did not have a lot of radio interference. Again, batteries were our a Achilles heel. We used alkaline dry cells in a plastic holder and who knew when they would die or pop out of the holder.

As I have said before, do not be so quick to blame the equipment. It was most likely pilot error that caused the crash. Pilot error can be poor battery maintenance, improper user installation of equipment, poor preflight checks and testing; or as in my case, the thumbs Went the wrong way or I slowed down too much. I have a room full of tails ( the only part big enough to save) to prove it.