Repeater FAQs

+ What is a repeater?

Genuinely speaking a repeater is a 'box' that has power connected to it. If a box has power connected to it then it is likely it means it has transistors/Fets (amplifying devices) inside that take power (AC/DC) and convert this power to amplify radio waves. When this is done (amplification), distortion is introduced. So this is where problems begin. A good analogy is with a stereo amplifier.....

Stereo Amplifier

As you know, as you increase the volume of your stereo the louder the sound gets. Which is genuinely fine until you turn it up to the point where you hear distortion. As humans, our ears don't like distortion. This is the same logic for phones as well. If the repeater has too high of an input signal or too much gain (volume turned up), it will distort the radio waves to your phone (and other phones in the area!) with common symptoms including, but not limited to, missing words, dropped calls, low data speeds etc.

There is another good analogy with a stereo amplifier you need to know about...

Have you ever been at a school play or school band, community hall, or even a big concert and you have heard a loud squeal coming through the speakers? Everyone in the audience cringes until someone pulls the microphone away from the speakers or a techo turns the gain down on the microphone. Sound familiar? This is what can happen with a repeater as well. In other words, if the repeater hears itself (input to output), it will oscillate and squeal too. You won't hear it as we can't hear radio waves but your phone sure will, and so will all your neighbours' phones - Hence why you can be prosecuted! And guess what, your phone and your neighbours' phones won't work until the repeater stops oscillating (turned off or gain turned down).

Okay so where were we? Right, so if you are not sure whether you are buying a repeater, check to see if it takes power (wires from it to a power source), and if it does it will have amplifiers in it.

We often get people ringing us saying they don't have a repeater but have this cradle they have bought from one of our competitors that takes power and amplifies the signal (but the supplier assures us it is not a repeater). Well unfortunately, they are wrong, this is an active amplifier (takes power) and is illegal. And it does cause Spark, Vodafone and 2Degress a lot of hassle.

So that should help you understand what a repeater is. If you are not sure, give us a call and we are more than happy to talk to you.

One last thing, beware of the companies out there who make a living from copying our products, without ensuring their products have the same level of integrity as ours. All our products are guaranteed and developed by leading New Zealand RF engineers. Our products, as well as the information and data on this website, is our original work.

Cellular repeaters (so active powered repeaters for cell phones/mobile phones) have to be licensed. By the way this includes any active amplifiers that are used in booster car kits. Despite some companies in NZ claiming car boosters to be legal, they are in fact illegal and cause many problems for Spark, Vodafone and 2Degrees. Furthermore, whilst we are talking about car booster kits, there is a company in NZ claiming to sell a Bury CPE1100 2.4W car kit on Spark. This is false advertising and is incorrect. The Bury kit does not offer any increase in power compared to any other Spark smartphone. The 2.4W is actually in reference to GSM which Spark don't use. So please be weary of other companies that either don't know what they are talking about or have false advertising.

While we are talking about false advertising. It is not true that the Cel-Fi unit is the only legal repeater in NZ. There are in fact two, and we are the only company that can sell two repeater types. We talk about this in other sections, but the two units are the Cel-Fi unit, and the Cellutronics fixed active repeater system for 2Degrees (does UMTS and GSM).

In NZ the owners of the cellular spectrum (2Degrees, Spark, and Vodafone) are the only people who can give approval and therefore license for a repeater. For some of their large corporate customers they will design and have repeaters installed for them professionally. However for the public you cannot install and operate a repeater unless it is a Cel-Fi unit purchased through an authorized reseler like ourselves, or a Cellutronics fixed install repeater on 2Degrees. They are the only possible options. Everything else is and will be illegal. Don't just take our word for it, here's what the government's Radio Spectrum Management arm has to say.

Another option is a passive repeater which doesn't require licensing and we have quality passive repeaters for all NZ operators.

So to sum up, all active repeaters (unless provided and installed personally by Spark, Vodafone or 2degrees), are illegal unless you have purchased:

  1. A Cel-fi unit from a handful of suppliers in NZ, including Cellutronics. (Your registration details are needed to obtain one of these)

  2. A Cellutronics fixed install repeater on 2Degrees (UMTS and GSM) and supplied by Cellutronics only. (Require registration by 2degrees via Cellutronics).

Everything else is illegal. This includes any old repeaters used on Vodafone, Telecom 025, AMPS, DAMPS, or active 3W booster kits. It also includes any repeater you buy on Trademe, or import from overseas.

+ I have a repeater, and I know it is not approved (its an illegal one). Will I get caught? And how much can I be fined?

It is probably unlikely but you are carrying a big risk. If you get caught you can be fined over $100,000, and ordered to compensate the local operators (Spark, Vodafone and/or 2Degrees) for loss of revenue. And because these operators take thousands of calls each hour through each cell-site, this compensation could be more than the fine, if they can prove your repeater has been loosing them revenue over days, weeks, or years! The operators have the tools to do this as they can measure external interference at a site level, so it is just a matter of quantifying the level in dBm's, correlating this with cell shrinkage and then mathematically modelling and in tandem with GIS tools calculate loss of coverage. Once they know this it is just a simple matter of turning dBm's into Erlangs, and bingo from Erlangs you can formulate $$.

The risk of being caught depends on your set-up. It will depend on how 'fit' your repeater is. Specifications such as passband, noise figure, compliance to 3GPP standards (sideband emissions mainly), how hard you are driving it (P1dB compression and TOIP, third order intercept product) etc. It also depends on the number of users, (linearity degrades quickly as the number of users increases), isolation between your donour to coverage antennas. Other factors include MTBF (mean time between failure), AGC (automatic gain control), etc.

Cheap repeaters purchased off the internet and/or imported from overseas are built for a low price and more likely to cause interference and therefore increases your chances of getting caught.

The operators can track you down using directional antennas. (Much like what hunters use with pig dogs tagged with a transmitter. By using a directional antenna you can track the direction of the transmitter).

Once they find you. You will be asked to turn it off. In all the cases we have seen as soon as the unlicensed repeater is turned off the interference goes, and the neighbouring cell-sites return to normal. You can then be faced with instant fines, loss of revenue (as discussed above), and the costs associated with the operator sending out radio frequency engineers to find you.

This really is a combination of other questions and answers we have on repeaters. So our answer is similar. A lot of people don't realise that repeaters are illegal unless licensed and purchased as we have talked about this before. So that is why you often see them coming up on Trademe and new start up companies in NZ selling them. However what you don't see behind the scenes is these ads being removed and companies being shut down as legal intervention being made by all or any of Spark, Vodafone, 2Degrees, or the NZ MBIE RSM branch.

And the reason for all of this is the damage these unlicensed repeaters do to the NZ mobile networks. These units are often cheap, do create interference, likely for you to get caught, and be prosecuted. So for further answers about this please see these two questions below.

No. We don't carry any legal powers to fine and prosecute you. We are also not going to go to Spark, 2Degrees, Vodafone, and/or the RSM and 'dob' you in as we are not employed to do this. We are more interested in helping you with advice on how we can make your repeater legal or even just make it work better to improve its performance (both for you in terms of coverage and also for mitigating interference to the NZ operators). As we don't sell illegal units we cannot be fined, so we feel everyone wins if we offer our free advice to you. It also helps us by selling our products that are legal and fit for service.

Remember also we are NZ's leader in Cellular Repeaters. We are the only company in NZ to offer two active repeater solutions to the public. We also have passive repeater solutions which work great on all three operators Spark, Vodafone and 2degrees.

+ Why is a repeater illegal in NZ if it is not authorised? And what are the ways it can cause interferrence to other users?

As we have mentioned in earlier questions, repeaters are illegal if they are not licensed as they can degrade the mobile networks for other people. Simply put, they emit interference which causes any or all of dropped calls, poor speech quality, low data speeds, and loss of coverage. This can mean unhappy customers for Spark, Vodafone and/or 2Degrees, and more importantly loss of revenue to them!

Remember, the radio spectrum that mobile phones/devices use is called a 'licensed' band. It costs millions of dollars for the operators to use these bands, and they have invested millions and millions of dollars in base station equipment to make it work. Hence any means to cause operation of this network to degrade in performance is going to be costly.

If a repeater is licensed then there is two reasons why it has been licensed. Firstly, it means the equipment being used and placed in the network is fit for purpose. In that we mean it has been designed and tested to ensure that it will not degrade the network if installed correctly. Secondly by licensing it the repeaters physical address is generally noted and recorded so if the repeater does happen to go faulty it can be quickly found and turned off or repaired if necessary. For example our repeaters have been designed and extensively tested to ensure they meet performance.-

There are many ways a repeater can degrade an operators mobile phone network (create interference). Here is some of the most common methods.

Self Oscillation:

A repeater amplifies the signal coming from the Base Station (DL) and to the Base Station from the mobile (UL). Because it is an amplifier if the output signal is heard by the repeaters input it will oscillate and create interference. (A good analogy is what happens when you are in the audience of a town hall event and you hear the microphone squealing with the loud speakers. The is exactly the same phenomenon that occurs with a repeater except you can't hear it as it is occurring at frequencies beyond the human ear. But mobile phones can certainly hear it, and as in the case for your ear with audio oscillation it causes the cell phone to not work). Important parameters here for the repeater design is, gain, distance from the outdoor to indoor repeater, and whether or not the repeater has AGC (automatic gain control).

Side Band Noise

Do you remember being at a concert, or a party and wishing the stereo was turned down as the volume was turned up so much the amplifier was producing noise (distortion) and hurting your ears? Again this happens with a repeater. If the repeater is overdriven, or has poor linearity due to cheap transistors/FETs, it will produce distortion. This distortion in the frequency domain causes other users interference and effectively causes loss of coverage, dropped calls etc. It could be other users nearby, it could be other users on different operator networks, or even users 10's kilometres away.

High Uplink Noise:

As a repeater amplifiers the uplink, if the repeater is close to a base station, a mobile even on minimum output power, under the repeater could be overdriving the base station. The network has closed loop power control and will tell the mobile to power down. But if the mobile is powered down to its minimum level and the signal is coming in too high because of the repeater, the problem will be the base station will be overdriven. This is very bad and causes lots of damage to the cellular network. (Analogy to the human ear is someone has a speaker turned up right next to your ear and you are trying to still hear someone talk to you from the other side of the room.

Incorrect Passband.

What catches a lot of people out in NZ, is Vodafone and 2degrees use the GSM band. Whilst they use different frequencies they both operate in the 890-960MHZ band. Or more exactly 890-915MHZ Uplink, and 935-960MHZ downlink. Many a times someone has illegally installed a GSM band repeater for Vodafone and for then 2degrees to come along and then find the Vodafone repeater is now being overdriven by the new 2degrees base station. This is very bad and causes all three operators a lot of headaches. The interference is so bad it wipes out all of Spark, Vodafone and 2degrees in the area. This is another reason why repeaters needs to be licensed to make sure they have the correct passbands.

Poor quality components

Let's say you have a copy cat repeated and it meets all the specifications. That's a start but as with all products it must also have a track record of reliable performance. For example, gain and self oscillation increases with lower temperatures. How does your repeater perform in winter at -5 degrees? Will it go unstable and oscillate? Or what about the antennas you connect to the repeater? If they gather moisture and present a low VSWR to the repeater will the repeater oscillate with time? Therefore it is also the antennas that connect to the repeater that are also important. Even simple affects such as poor quality electrolytic capacitors used on DC feeds to amplifiers can be known to cause oscillation. Or even dry soldering joints. MTBF (mean time between failure) is just as important as RF specifications.

+ Is Cellutronics a leader in mobile repeaters in NZ?

Yes. We are the only company that is legally able to offer two active repeater solutions to New Zealander's. In fact we were the first company to provide a legal repeater solution in NZ available to the public. We have also been selling repeater components to some of NZ's leading operators for over 10 years.

We have engineers on hand to provide technical advice. We also have technicians in the field that can design, install and commission repeaters if required.

We also have a lot of test equipment to ensure our products meet standards. Including network and spectrum analysers, GSM/UMTS/LTE demodulation analysers, drive test equipment, intermodulation test equipment, spectrum mask analysers, power and noise figure meters etc..

+ You sell passive repeaters too? Is this a good choice for me?

Passive repeaters are an excellent choice too. We have a good entire section on this here. Briefly, the Cellutronics passive repeater has the following advantages:

Less than half the cost of an active repeater. Requires no licensing. Available for Spark, Vodafone, 2degrees and all at the same time. Does all cellular technologies, GSM, UMTS, LTE, 2G, 3G, 3.5G, 4G, etc. Patented indoor passive radiator technology. And by using this with the Cellutronics XDECT phone system, you can make and receive phone calls anywhere around your home or office. Furthermore, with Smartphones you can activate "hotspots" so this allows you to stream data coverage wirelessly around your home or office while using the Cellutronics Indoor radiator.

Please be warned by copy cat companies that follow us and try to duplicate our products. Our passive repeater system is unique. We have spent considerable R&D on making our passive repeater perform exceptionally like it does. We are not going to tell you how and why it performs so well here. All we can say is it is due to our technical RF cellular expertise and RF test equipment.

+ Do you offer free advice on coverage solutions such as repeaters? And do you guys really know your stuff about repeaters?

Yes please feel free to contact us. It is likely that if you call you will talk directly with one of our RF Engineers straight away. We also have several highly skilled contract RF Engineers that have designed over 100 micro and macro repeaters in NZ and overseas.

We work closely with all three NZ mobile operators and MED NZ.-

As far as our knowledge goes, we know about all the cellular standards, effective radiated power, coverage, interference, RF health issues, non-linearity, path loss etc. the list goes on and on. Our knowledge together with our software and hardware tools including radio prediction tools, drive test equipment and lab test equipment helps us provide the best solutions to you.