Tuesday, September 14, 2010
Flying 2.4GHz Radio Control Systems: Latest Report -- Allen Fraser
In the July- August 2010 SAMAA Newsletter we informed SAMAA members that all 2.4 GHz radio control equipment operating in South Africa must comply with technical specifications determined by the Independent Communications Authority of South Africa's (ICASA) and that type approval was necessary for all 2.4GHz radio control systems imported into the country.
After more discussion with ICASA we are pleased to confirm that all 2.4GHz radio control equipment with a maximum output of 100 milliwatt and 20-dBm gain (radiated power), is legal to fly in South Africa. The SAMAA insurance claims will therefore be valid on all sets conforming to the 100 milliwatt specification.
Equipment exceeding the ICASA specification, like some imports from America with an output of 200 milliwatt, do not comply with specification and are considered to be illegal by ICASA, and as such can be confiscated by ICASA and the user prosecuted. It may also impact on the SAMAA insurance in case of an accident claim.
Please note, this is an ICASA ruling and we respectfully request all SAMAA members to adhere to this ruling. The United States of America is the only country that we are aware of that have adopted the 200 milliwatt limit and not all their equipment is at 200 milliwatt that is why we stress some imports.
Of importance to our members, is that during a recent meeting between ICASA and the South African Revenue Services it was decided that, individuals may import five of an item at one time or one of an item five times per year without needing to obtain or produce type approval for 2.4 GHz radio control equipment used exclusively for models provided they conform with ICASA's 100 milliwatt and 20-dBm gain specification.
Anyone importing more than five of a item at one time or during the year must apply for type approval at a cost of R4,000 per set. Type approval stickers are available from ICASA to distributors who have type approval certificates. Note, the ICASA issues over a thousand type approvals per month for an assortment of electronic communication appliances and they have informed SAMAA that it is impossible for ICASA to inform the SAMAA which importer were granted type approval for 2.4GHz radio control equipment used exclusively for models. Dealers and importers will therefore, in future have to inform the SAMAA of their type approval for publication in the newsletter & to enable advertising of type approved radio sets.
Whilst not conclusive, independent tests conducted have shown that equipment with dissimilar outputs of 10 to 200 milliwatt, operate harmoniously together. The set with the lower output will not experience interference, but will have a reduced range in comparison to the greater powered sets.
To ensure compliance with ICASA's specifications, SAMAA recommends that members obtain 2.4 GHz radio control equipment from recognized dealers in South Africa, that stock ICASA approved sets with type approval stickers attached to them. This will be a 100% guarantee that the equipment conforms to ICASA specifications and is legal. Members that have purchased sets from registered dealers without type approval stickers need to apply for their ICASA stickers from the original dealer. Please notice that members purchasing sets without ICASA type approval assume responsibility for ensuring that their equipment conforms to the required ICASA specifications.
Also note that the SAMAA recommendation of a maximum of six aircraft flown in circuit simultaneously is not for technical reasons; it is simply a safety recommendation for Clubs and is equally applicable to any other approved radio frequency.
Please don't hesitate to send me an email at fraserrc@global.co.za should you need more information.
Allen Fraser
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3 comments:
I have been observing the 2.4GHz radio debacle with interest and amusement. I hoped that SAMAA would keep its nose well clear of this hornets nest aspect of ICASA rules and regulations and would always place the interests of their members first, even if it meant ignoring certain irrelevant, unpractical, and in its present form, unimplementable regulations that has no benefit for members or their safety. After reading Allen Fraser’s report I don’t think this is going to be the case.
First let’s make a correction. The term:
“100 milliwatt and 20-dBm gain (radiated power)”
Has no meaning. I expect that it should have read:
“20dBm (100 milliwatt) effective radiated Power”
ICASA rates transmitter output in terms of dBm this means that it is compared to a transmitter with an output of one milliwatt (1/1000 of a watt) and the difference is expressed in dB. In essence an power output of 20 dBm is 100 X one milliwatt thus 100 milliwatt. The decibel is typically used to indicate the gain of an antenna but in this case I don’t know why the “gain” was added. “Effective radiated power” or ERP is a term used to indicate the power of a transmitter after the gain (effectiveness) of its antenna has been taken into account. For example : if an transmitter has a output of 20 dBm and connected to a ¼ wave antenna that has 0 dB gain the effective radiated power would be 20dBm(20dBm + 0dB =20dBm) or 100 milliwatt. If a transmitter has an antenna with a 3dB gain its power input to the antenna must be reduced to 17dBm (50 milliwatt) in order to maintain a ERP of 20 dBm (17 dBm + 3dB = 20 dBm)
If you could double the power of your model plane’s engine the effect would be dramatic but not so when it comes to radio transmitters and thus it is referred to as a gain of only 3dB. In fact in practice if you extended the distance between your transmitter and your plane from 10 to 20 meters the signal level measured at your plane would decrease 4 times (-6 dB). If you then extend the distance to 80 meters it would be 64 times weaker (-18 dB) than it was at 10 meters but as we all know it would still operate perfectly so double or half the power has little effect in practice. But in this case it could mean the difference of being a criminal or not, suffering significant financial loss or not.
Measuring the power output of transmitters operating above 1000 MHz (1GHz) accurately is very difficult but measuring the ERP of any handheld transmitter accurately is imposable. At best it would be a calculated guess, not something that would stand up in court. Very few type approved 2.4 GHz transmitters will have an output of exactly 100 milliwatt and because the manufacturer would rather err in favour of their customer most would have an output of more than 100 milliwatt. But ERP is not only determent by power output but also by antenna efficiency. A ¼-wavelength antenna is considered to have 0-db gain, for 2.4 GHz this would be an antenna that’s about 3 cm long. All type approved 2.4 GHz transmitters have antennas longer than this and are 3\4 or 5\4 wavelength long with a calculated gain of more than 3dB and thus a calculated ERP of more than 200 milliwatt! (23 dBm)
In all honesty if I were flying with a”legal” 100 milliwatt 2.4 GHz transmitter and were joined by a pilot using a 10 milliwatt and another using a 200 milliwatt: I would be more worried by the 10 milliwatt TX because it is the most likely to go out of control and pose a danger to the me and my equipment.
Piet le Roux
I suppose in terms of practical operation Allen's note applies to equipment from a reputable manufacturer with a nominal output of 100 milliwatts.
There is no ruling that each transmitter must have a ICASA sticker on it. As long as the importer has his approval certificate available on request, it is deemed legal.
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