2.4 Ghz Equipment Installation and Use

Jan 24, 2012   //   by Nigel   //   Tech Info  //  No Comments

2.4 Ghz Antennas: Installation and Use 

The “polar diagram” of the signal radiation pattern of a monopole transmitter aerial is a large donut shape around the aerial with little radiation from the top and bottom. It is a similar three-dimensional shape for both 35 Mhz and 2.4 Ghz types of transmitters.

2.4 Ghz transmitters require a very small aerial, due to the much shorter length of the transmitted radio wave. Pointing the transmitter aerial UP is better than pointing the aerial DOWN. Which is ALWAYS better than folding an aerial sideways across the top of the transmitter!! This only for easy packing and transportation or for flying directly above you, or below you ! I always set my aerial vertical in the same way as recommended by Multiplex. This is the optimum transmitting, and receiving position for any 2.4 Ghz equipment, located at 90 degrees to the transmitter aerial.

With Spektrum and JR. receivers, the second “earth” aerial is the counterpoise part of the antenna system, and is just as important !!

On Spektrum 5 channel AR500 and AR600 receivers, there is one quarter-wave aerial and a lengthened aerial, which is coaxially sleeved to extend it away from the receiver and oriented at 90 degrees to “see” a different part of the transmitted radio wave. This extended antenna is an end fed, half wave antenna, which both transmits to & receives from the transmitter via it’s own donut shaped propagation envelope.  The sleeved part should be gently bent so the one aerial is at 90 degrees to the other aerial. As stated in the manufacturers instruction manuals, NEVER, cut or lengthen these antenna wires.

It is also most important NOT to mount the “receiver” aerial wires close to carbon fibre or any metallic surfaces. You should also keep them away from servo wires as well.  I always use a small pad of foam rubber glued to the fuselage side with contact adhesive, with a pad of velcro glued onto that. The side of the receiver then has a mating patch of Velcro.

It’s either this, or fully supporting the receiver and aerials within foam blocks exactly as 35 Mhz receivers ‘should’ be mounted.  NEVER, mount the velcro patches directly onto the fuselage or helicopter chassis, as we have to insulate any receiver from as much vibration as possible.

With my own 2.4 Ghz receivers, I often cut small cubes of foam plastic and burn a hole through in the correct place with a small, red-hot nail. I then glue the cubes of foam to the fuselage side with contact adhesive, on each side of the “receiver”, so the short aerial wires are then supported within the foam plastic. As everything is then flexibly mounted, removing and refitting a receiver unit is quite easy. On some models I also cut short lengths of silicone fuel tubing to fit over the antenna wire.  Silicone does not attenuate radio signals and the silicone grips onto the moulded plastic stub on the receiver casing. This supports the antennas and keeps them straight.  

Now with metal and carbon structures, and especially large petrol engines with metal spinners, there can be a lot of reflective material for the 2.4 Ghz radio signals to get through, especially when your plane is flying straight towards you !!!

On my own ¼ scale Spinks Acromaster and Spitfire, I will be mounting an extra satellite receiver, offset within the wing structure on an extension cable. These longer extension cables are recommended for large models and supplied by Spektrum !!

IF, you use a carbon fibre propeller as well, this may attenuate your 2.4 Ghz signals. 

Please Remember that ALL 2.4 Ghz radio control equipment uses continuous two way data links……….it is not only when telemetary units are fitted………The receiver is transmitting data back to the transmitter all the time, because how else can the transmitter know when to shift frequency? or the next frequency to use with frequency hopping systems? 

Many modellers have both 35 Mhz and 2.4 Ghz radio control systems for their models. Never Forget to fully extend the telescopic aerial of your 35 Mhz tranmitter, before taking off !! You might get up to a hundred yards of air range with the aerial down………If you’re lucky?  Many pilots have done exactly this, and re-kitted their plane ?

Quite recently, I saw this almost happen again, but I was able to quickly extend the telescopic aerial of another member’s 35 Mhz transmitter, just in time to save his model……….and NO, I’m not saying who………..but he was an experienced pilot, and thankful for my actions. I do like using my  “Classic” 35 Mhz radio control gear. I suppose I am being sentimental, (some say tight-fisted !), But I’m also quite careful too……….

If any members would like to have their 35 Mhz equipment checked on a spectrum analyser, tested for FM deviation and relative transmitter output, as well as having their crystals checked for accuracy, please let me know……….We had a 35 Mhz and 2.4 Ghz equipment testing night at the Ten Tors Inn where many makes of radio control of equipment were tested. How  many perfectly good sets of “redundant” 35 Mhz radio gear are there? 

I also have a special receiver and computer program and that displays the transmitted radio spectrum of 2.4 Ghz transmitters and receivers.

Once you have verified that your transmitters are working properly, the best way to test your any receiver installation is by range testing in the usual way, and comparing the actual range achieved using different aerial orientations…………end on, and sideways to. You will quickly realise the best position for your transmitter aerial…….and it is NOT with the end, or the base of the antenna pointed towards your plane !!.

Please look at the following Video supported by Spektrum / Horizon Hobby about 2.4 Ghz radio gear installation . The two presenters seem a bit “goofy” but their facts are good and describe how radio signals radiate and receive via the antennas. Please forgive these “Young American” presenters.

”  http://www.youtube.com/watch?v=AOI1kWuT5FA&feature=player_embedded “ 


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