Title 42

35 MHz RC frequencies for model aircraft in the UK

We all know about getting interference while on adjacent channels

E.G. 61/62.....74/75.....82/83 and so on. This is the reason that some clubs

have a policy of only flying on odds or evens, in other words only fly using

channels 56-58-60-62 and so on or 55-57-59-61 etc

which in itself works very well. However there are other dangers out there

that not all modelers are aware of, and after seeing some first hand

frequency swamp incidents I wish to highlight some of the dangers here

Frequency chart 1

Channel		Frequency	Harmonic	Channel		Frequency	Harmonic	Channel		Frequency
Number		MHz	with	Number		MHz	with	Number		MHz
55	=	34.950		67	=	35.070		79	=	35.190
56	=	34.960		68	=	35.080		80	=	35.200
57	=	34.970		69	=	35.090		81	=	35.210
58	=	34.980		70	=	35.100		82	=	35.220
59	=	34.990		71	=	35.110		83	=	35.230
60	=	35.000		72	=	35.120		84	=	35.240
61	=	35.010		73	=	35.130		85	=	35.250
62	=	35.020		74	=	35.140		86	=	35.260
63	=	35.030		75	=	35.150		87	=	35.270
64	=	35.040		76	=	35.160		88	=	35.280
65	=	35.050		77	=	35.170		89	=	35.290
66	=	35.060		78	=	35.180		90	=	35.300

Dangers of harmonic interference.

Radio Controlled model aircraft "A's" radio frequencies can be swamped by transmitter "B"

if "B" is using frequencies 12 full channels either side of the one being used by "A"

and transmitters A & B are not close together. This is why it is very important for all transmitters

to be operated within a pilots box or area. If this fact is overlooked or ignored serious accidents

can be the outcome, as "B" may swamp "A" or vice versa. Harmonic frequencies are noted above

with two examples below.

As seen in chart above frequencies such as

55 67 79

64 76 88

And so on

can be effected by one another and are responsible for many of what

we would normally call glitches but in reality can be very dangerous.

See Scenario Below

Channel 61 and 73 are being used in this example.

They are harmonic and in some cases able to swamp one another as in the case below.

You can of course use dual conversion receivers which by and large reject the harmonic

interference, but for everyone's peace of mind you should stay close together where you

don't have to worry if the person next to you is on single or dual conversion, and it is

easy to talk to each other in the event of a problem.

Note on 35Mhz Radio Control Frequencies

Crystals are often only marked with their operating

frequency, e.g. 35.140. To calculate the channel

number just subtract 3440 from the first four digits.

In the example given above subtracting 3440 from

the `3514' of 35.140 gives channel 74.

2.4 MHz

In December 2006 OFCOM issued the necessary permissions and changes to Government legislation to allow the sale and use of approved equipment transmitting on the 2.4 MHz band at 100mw maximum radiating power. The 2.4 MHz band can be used to control any type of model, either airborne, ground or water based within the constraints of the law. Use of "after market" plug-in modules - which must be individually compliant and correctly CE marked - is permitted only where the manufacturer (or person who first places the module on the market in the EU), has taken the appropriate steps for ensuring compliance of the overall unit - ie transmitter plus module.

Users should be aware that they may be breaking the law when operating UK legal 2.4 MHz sets in certain countries within the EEC - for instance the maximum allowed radiated power at 2.4 MHz for model control in France is 1/10th of the UK level ie 10mW . Always seek advice before use overseas.

In the USA, the maximum allowed 2.4 MHz radiating power is 10 times that of the UK ie 1Watt and for that reason use of "grey" imported 2.4 MHz sets from the USA may well result in the operator of such equipment breaking the law whether or not a CE label has been attached to the transmitter or plug-in module.

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With effect from 21.5.1987, Statutory Instrument 776/87 confirmed the following bands for model control equipment:

(1) 26.96 MHz to 27.28 MHz. Maximum effective radiated power 100mW. General Use.

(2) 34.950 MHz to 35.300 MHz.Maximum effective radiated power 100mW. Model Aircraft Use Only

(3) 40.665 MHz to 40.995 MHz.Maximum effective radiated power 100mW. Surface Vehicle use Only.

(4) 458.5 MHz to 459.5 MHz.Maximum effective radiated power 100mW. General use and telemetry.

These are the ONLY frequencies allowed for model control in the UK

Certain frequencies in the 49MHz band are legally allowed for toy operation but the allowed power output is severely restricted.

Model Aircraft

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