433 MHz Radio Control Transmitters

[VK2YK]

Hi all,

I've been asked a question from someone about getting a licence as he want's to use a 433Mhz transmitter (o/p - 500mW) with his remote controlled plane. Link below is the Txer in question;

http://www.hobbyking.com/hobbyking/stor ... _uhf_.html

My concern after reading the specs is that it uses a FHSS (Frequency Hopping, Spread Spectrum) which link hops to a new frequency every 22ms. Also it uses GFSK (Gaussian Frequency Shift Keying) modulation.

I wonder if anybody out there has been approached or questioned about this before?

I see that if people did get a licence for this purpose alone and start using these transmitters would it be even be legal to be used under any of the Amateur licence levels and LCD's?

I look foward to people's comments on this.

[VK2GOM]

Why doesn't he just use a 2.4GHz transmitter module? They are the standard for airborne models these days. No license required.

Or is he FPV'ing and wanting a longer range Tx setup? If so, many are using patch antennas for 2.4GHz with good results - up to 6km LOS with off the shelf transmitter modules. Further than anyone would usually want to fly anyway.

73 - Rob VK2GOM / GW0MOH

[VK2YK]

Thanks Rob,

I think he is looking at a greater range from what he has mentioned to me as I think he does the FPV thing.

I will mention the patch antenna for 2.4Ghz as an option, but I think he thinks the UHF txer will have less issues with the distance side.

[VK4TIM]

I'm asking the same questions as Rob.
Why would he want to use something that's not readily off the shelf like the 2.4 GHz units.
I would not have thought that using 433 MHz to control something such as a model aircraft, was an intelligent choice, as there's too many things out there to cause interference to the airbourne receiver. Loss of control command could lead to the aircraft crashing.

I hope he'd never fly it anywhere near an urban area, or GRN radio site. What would his insurance say when the aircraft crashes into people/property because the airbourne receiver suffered interference?. Sounds like it could turn into lawsuit magnet.

Also, the other side of the coin, whether it would comply withthe Amateur LCD is another issue, one that would be best answered by those with more legal knowledge than myself.
I've heard that in Europe that "unlicensed" controllers operate in the 433/434 band legally at 0.5W, not so here..That's why many Eurpoean vehicle manufacturers now use 868 MHz for vehicle remote keyless entry. We already have enough trouble with 433/434 LIPD gear in the everyday domestic and industrial environments.

Looks to me like this is another potentially troublesome device that if it's not controlled (eg prohibited) in Australia, will cause seious problems. The same website mentioned also has similar devices advertised at up to 1 Watt.

[VK6ZFG]

In Australia, LIPD devices operating on 433MHz are limited to 25mW EIRP so the device in question would not comply as it exceeds the power level.

A licence for the system to operate at a higher power level is highly unlikely to be issued by the ACMA as this is not apparatus licencing spectrum.

Amateur licence - stretching the Amateur LCD somewhat I suspect. Its use is not related to Amateur radio activities.

[VK4GHZ]

My seven year old HiTec R/C radio system (still in use today, but for a ground-based remote pan/tilt camera head) uses 36 MHz.
The good ol days!

From a manufacturers point of view, a common world-wide band like 2.4 GHz is a God send.
Minimises inventory, product variations, and the inherent support costs.

A 2.4 GHz control system obviously rules out 2.4 GHz FPV.

I think he is looking at a greater range from what he has mentioned to me as I think he does the FPV thing.

That's certainly a valid reason.

You haven't mentioned what FPV band will be utilised, but most of the FPV gear in use is on 5.7-5.8 GHz.

Unless he plans to run a high powered 5.8 GHz (keeping some context in mind), then it's highly likely he will loose the PFV link, before the craft reaches 2.4 GHz control range limit, let alone 433 MHz control limits.
Reputable sellers usually have a disclaimer that a "ham" license may be required for any 5.8 GHz transmitter over 25mW.
They're often ignorant that this 25mW limit relates to EIRP.


If there is no Flight Controller (and hence no GPS receiver) involved, then perhaps a 1.2/1.3 GHz FPV system may suit?
Having just purchased from ReadyMadeRC last week, I can thoroughly recommend them.
Ordered Monday, on my door 3 days later via FedEx.
They have FPV gear for all the common bands.
http://www.readymaderc.com/store/index. ... Path=11_30



ps
I was at a Brisbane multirotor meet at Pine Rivers Park on the Saturday of the recent Winter Field Day.
There were a number of stations around greater Brisbane supposedly active on 5760 MHz that afternoon.
5760.000 MHz is a common FPV frequency selectable on the Nexwave-based modules!
(notably Fatshark and ImmersionRC, which happen to be the most popular units in use)
No one bitched about QRM to their FPV at the meet resembling speech patterns, and I'm sure the hams active that day were oblivious to the fact that three or four 5.8 GHz video transmitters were running at any one time right underneath their noses that day!

YouTube video of the day: https://www.youtube.com/watch?v=hyiWeWsQ9lE
All those nerdy FPV goggles!

[VK4GHZ]

I've been asked a question from someone about getting a licence as he want's to use...

It goes without saying, with an Advanced ham license, a video transmitter operating within the 23cm, 13cm, or 6cm ham bands would be considered as ATV.
Suddenly any 25mW EIRP limits go away!

Identifying your FPV transmissions becomes another issue, however.
As simple as writing your callsign (in texta?) on the craft - in clear view of the FPV camera - should satisfy this requirement.

Either that, or electronically insert your callsign.
There are kits available for ATV operators that do exactly this.
So the issue of FPV video TX identification isn't a real barrier at all.

[VK2GOM]

I wouldn't advise anyone to invest too heavily in FPV gear at the moment... look what just happened in the USA!

Users and companies supplying the stuff are all up in arms.

I've got my Fat Sharks here (and a 600mW 5.8GHz video Tx) and various quadcopters, but have to say the FPV thing made me feel a bit queasy. I still prefer just flying line of sight.

73 -Rob VK2GOM / GW0MOH

[VK2XSO]

Yes, I'd say go even better than 2.4GHz and use 5.8GHz FPV.
This is an example of a guy who flys 5.8GHz near me.
https://www.youtube.com/watch?v=XiP0gHh ... XS1d3YoAfQ

Bit of a shame there's that big hill on the left else my 5.8GHz ATV gear would be on constant lookout for his adventures.

[VK2YK]

All,

Thanks for all of the reply's. From what Igor put in his response, I've had a little bit more of a read of the Amateur Radio LCD and it states the following in Para 6;

Use of an amateur station
The licensee:
(a) must use an amateur station solely for the purpose of:
(i) self training in radiocommunications; or
(ii) intercommunications; or
(iii) technical investigations into radiocommunications; or
(iv) transmitting news and information services related to the
operation of amateur stations, as a means of facilitating
intercommunication; and
(b) must not use an amateur station for financial gain; and
(c) must not transmit:
(i) a message that is, or includes, an advertisement; or
(ii) any form of entertainment.

In Australia, LIPD devices operating on 433MHz are limited to 25mW EIRP so the device in question would not comply as it exceeds the power level.

Amateur licence - stretching the Amateur LCD somewhat I suspect. Its use is not related to Amateur radio activities.

I think that because the transmitter will be used for sending flight command information, the use doesn't really come under the use of an amateur station.

It speaks about communication in the main part of Para 6, I feel that it is really stretching it to even use this transmitter under an amateur licence because it is only being used for one way communication to the radio controlled plane.

Thanks again all.

[VK5HP]

The biggest issue would be not transmitting his call sign on the uhf LRS system, all amateur transmission must identify every 10 mins etc.. no way of doing that with those systems.