RF controller interference

[alistairsam]

Hi,

I'm converting my scope to use wireless motor control, position feedback etc, and wanted to know if there is any issue with using low power RF transmitters at astrocamps and whether they would cause interference with other scopes or equipment.
I came across some site that mentioned this.

i'll be using the 434MHz and 315MHz RF Link modules like the ones below.
power will be low as range required is only a few feet.
but just wanted to make sure i don't cause unintended interference.

these transmitters use ASK modulation

http://www.littlebirdelectronics.com/products/RF-Link-4800bps-Receiver-%252d-315MHz.html

http://www.littlebirdelectronics.com/products/RF-Link-4800bps-Receiver-%252d-434MHz.html

http://www.littlebirdelectronics.com/products/RF-Link-Transmitter-%252d-315MHz.html

http://www.littlebirdelectronics.com/products/RF-Link-Transmitter-%252d-434MHz.html

other option is a 933MHz module.

[wasyoungonce]

Have a look at the freq spectrum sharing chart here (http://www.acma.gov.au/webwr/radcomm/frequency_planning/spectrum_plan/arsp-wc.pdf).

As you can see at 315 ~ 434Mhz there are a few bands used, too many to mention but there is an Amateur band at 4.0005Mhz to 400.15Mhz.

Some garage door openers (http://en.wikipedia.org/wiki/Garage_door_opener) are on the 315Mhz as well as wireless burglar alarms...I think! Anyway these are coded transmissions.

Anyway at very low power it shouldn't be a problem to anyone else.

[alistairsam]

thanks for that. didnt think of the chart.

Did a search and noticed that RF interference affected radio astronomy.
I checked the frequencies used by radio astronomy. they're close but shouldn't be affected as they use filters to reject interference and harmonics.

anyways, I don't expect to see any radio astronomers at these camps.

322 - 328.65 MHz
FIXED MOBILE RADIO ASTRONOMY (°)

406.1 - 410 MHz
FIXED MOBILE except aeronautical mobile RADIO ASTRONOMY

[mswhin63]

These are generic Radio transmitters and generally do not have an affect on anything other than other radio receiver and transmitters of around the same frequencies (coded Tx and Rx functions is not affected only range is affect). All Radio Astro frequencies are protected by international law so any transmitter built on this frequencies is a no no.

Meteor detectors work on existing frequencies though but are much lower then the UHF modules.

The only problem that maybe experienced is AV transmitters and receivers.

There are also very small quality control needed on these frequencies because they are open to less standard regulation but are only available to low power devices.

[mswhin63]

Forgot to mention the freq from little bird 315MHz is not licensed for Australia, same with 933MHz. 434MHz is for Australia.

[Visionoz]

The 434MHz is reserved for Amateur band use and is therefore illegal unless you are licensed to do so within this band

Please see this link http://www.wia.org.au/members/bandplans/data/documents/Australian Band Plans 110127.pdf (http://www.wia.org.au/members/bandplans/data/documents/Australian%20Band%20Plans%20110127. pdf) (page 13 - 70cm Band, 420 - 450MHz)

HTH
Cheers
Bill

[mswhin63]

Sorry Bill bit correct - Take a look at this - http://www.acma.gov.au/WEB/STANDARD/pc=PC_2633

The document you have is only half the story as it is reserved for HAM band but is still considered a dual operational band, never use information from a single organisation only information from the licensing authority which in this case is ACMA.

This is a good chart - http://acma.gov.au/webwr/radcomm/frequency_planning/spectrum_plan/arsp-wc.pdf

[alistairsam]

wow. had no idea. how do you get licensed?
its a bit surprising cause these modules are very common and even jaycar sells them but no warnings.
guess this changes things. have to think of something else.

[Visionoz]

Yes Malcolm

I am not disputing ACMA's governing authority over the spectrum frequency usage

I am aware of what the ACMA document says - being an advanced license ham operator myself for the last 25 years or so - refer to page 13 of the document I referred to (the band 420-450MHz is allocated to Radiolocation/Fixed/Mobile as a PRIMARY band and therefore it is exclusive for amateur radio use; however I believe we share this with the military that originally are permitted to use it) and I can assure you that if you do NOT have that licence to operate within any ham frequency and DO so then it is a federal offence that you have committed and it is covered under the Federal Communications Act

There is a situation that one can use LIPDs - Low Interference Potential Device (which is what I believe that electronic kit is) that falls even within the amateur band because it is a class licence use device - and as long as it is an LIPD! See here at ACMA: http://www.acma.gov.au/WEB/STANDARD/pc=PC_1278

But if anyone that uses such a device with greater output power than it was originally class-licenced and as a consequence does cause interference to an operating ham frequency then probably the matter can be investigated by ACMA upon lodgement of a complaint process by hams

HTH
Cheers
Bill

[Visionoz]

Hi Alistairsam

These days they are practically giving away the ham licences!! :P With the demise of the requirement of Morse code a few years back, one can easily obtain qualification to be a certified ham operator; there being basically 3 types viz: Foundation, Standard and Advanced

The easiest to obtain would be the Foundation which requires only a few hours worth of attending a few tutorials and how-to and you can get that easily - see here: http://www.wia.org.au/licenses/foundation/about/
With the other higher licence types it means that you get more band privileges and you do have to pass an exam first

You can obtain more information if you go to WIA's home page @ www.wia.org.au (http://www.wiwa.org.au) and click on the "Get Your Amateur Radio Licence" menu option

HTH
Cheers
Bill

[alistairsam]

hi Bill,

how do I find out what the maximum allowed power is under the class license? could'nt find it under the LIPD section.
given that these transmitters are between 1mW and 5mW max, range of only a few feet, does it fit under the class license?

[Visionoz]

Methinks that here is where you can get the info: http://www.comlaw.gov.au/Details/F2009C00545

HTH
Cheers
Bill

[alistairsam]

Thanks. will look into that. have always wanted to get into amateur radio, but kept away due to the cost of the transceivers, I am well versed with electronics though, just need a cost effective circuit.
I did attend the Marine Radio officers course and passed the stage2 morse code exam at 20wpm.

but to get back to these modules, i'm guessing there is some sort of a generic license and not necessarily a ham license, as these are essentially like garage door transmitters or car keyless entry transmitters.

will keep looking. thanks.

[alistairsam]

ok according to that, my transmitter comes under number 17 in schedule 1 where the upper limit is 25mW.

so I'm guessing these should be ok as i won't be exceeding 5mW.

[Visionoz]

You might like to call ACMA and check to see if your MRO Stage2 does give you a waiver to get some type of ham licence - I know that most electrical/electronic engineers with a Bsc degree get straight into the Advanced Licenced without having to sit the full exam except the "Regulations" portion only

Yep you're right, with the very low EIRP from these devices it is already a class-licenced product anyway (on the proviso that it operates on the allowed freq) and you do not need to worry about using it freely

HTH
Cheers
Bill

[Visionoz]

FWIW Alistairsam, there is a distinction between a "ham licence" vs "class licence" - ie with the "ham licence" it is the person that is licensed and not the equipment - hence if I wanted to build say a transmitter from glass bottles and wire-hangers and as long as I keep to what my licence allow me to operate under I can do so without getting into trouble - whereas in the case of the "class licence" it is the device/equipment/gear that is licensed and therefore anyone can operate it under that particular device's allowed class licence

HTH
Cheers
Bill

[mswhin63]

I think the thread is off topic as the device originally mentioned is a LIPD.

I am also a commercial Radio technician and have a lot of experience with the complete spectrum with the exception of HAM.
I never had time for HAM operations but do understand the technical condition and well experience even with the current products I have at my disposal.

I am just saying the original article in this post you mentioned the devices are illegal, this is not the case. They are legal as they are also available and approved for use in Australia.

They do not require special licences to use them.

[alistairsam]

Malcolm,
yes, i guess the thread is a little off topic but still relevant. thanks for everyones input.
i was looking for interference to scopes but did learnt quite a bit.

given that these devices are freely and legally available from australian suppliers, is it acma that prohibits those two frequencies from being used in australia?

only downside is that the max power allocated for these two frequencies is in micro watts.

[mswhin63]

ACMA allow these products in an open spectrum for low power device. They still need to conform to Australian Standards but they have a difference compliance acceptance. This makes it easy to allow them in Australia hence the reason they they are cheap.

I have used these products on many occasion, commonly used to transmit serial data. Still need and interface board to get them working may be able to find something which combines both so there is little set-up required.

One of my suppliers was this company, noticed they now sell direct - http://www.lprs.co.uk/

I have used them many times

[mswhin63]

At this stage don't use 315MHz. When i used to make radio gear this freq was not allowed in OZ but was available in US. This may have changed recently.

[Visionoz]

My first post regarding the 434MHz being amateur et al might have given you the impression that I made a sweeping statement about useage of LIPDs - I am sure I did not mentioned that the LIPDs were illegal in Alistairsam's case; especially in subsequent posts what I said was that it is illegal to transmit in the amateur bands IF you are not licensed to do so and I also clarified that it being an LIPD device that it was anyway alright to do so without any need for a licence since the device is already class-licensed.

The other matters might be OT but it was only in response to the OP that I elucidated the matters that he queried about

Cheers
Bill

[mswhin63]

Anyway the only issue with these is the range which can be extended based on the antenna. One change I noticed is the EIRP is 25mW although in my days it was only 10mW. The range though with the right antenna can be as much as 1 km. I have tested this arrangement and still have the TX and RX here non modem version.

Spurious radiation is tested based on the appropriate standard. The AS compliance is related to the appropriate CE or EU standard and does not require re-testing. Not like telephones and general consumer equipment.

The LPRS equipment meets the standard very well, heavily shielded but the most problems that are experienced is other LIPD's around (garage door controllers) which use the same frequency and may reduce performance of the radio side. This at the moment is a rare occurance until the spectrum is flooded.