FAQs

Q: What is the difference between MPT1411 and MPT 1329 standards?

MPT 1411 This band is allocated on a shared basis to the Utilities for Scanning Telemetry.  The band is designated for duplex operation which allows the equipment to simultaneously transmit and receive.  In order to achieve this there are two blocks of channels allocated which are separated by 5.5 MHz. These are as follows :

                            Base Transmitter (Scanner) - 457.5000 MHz to 458.5000 MHz

                            Remote Transmitter (Outstation) - 463.0000 MHz to 464.0000 MHz

Each section is divided up into 12.5kHz channels but rather strangely into two groups overlaid onto each other as Group A and Group B.

The popular group is Group A and this is offset by 6.25kHz from the band edges (i.e. the first channel is 457.50625 MHz paired with 463.0625 MHz). The channels are all given a number within each group. The licences for MPT1411 are issued on a strict basis by the licensing authorities for a defined link between two points with carefully characterised antenna gain and path profiles. The license specifies the power level that will be radiated for the path in question and this could be up to 10 Watts carrier power from the equipment itself and a further antenna gain of 12dB or more.

Equipment for use on the MPT1411 frequency band has to meet a technical specification that is much tighter than that demanded by normal low power equipment designed for MPT1329 or ETS 300 220. This is quite essential when the products in use have to operate in duplex mode.

Items such as signal handling, blocking, spurious responses are vigorously checked which are not demanded as part of ETS 300 220. This adds to complexity and of course the price of such hardware.

It does mean that the equipment is better specified and therefore more capable of surviving in harsh RF environments. It will also be more expensive. Wood & Douglas Ltd make a range of MPT1411 hardware under the product range ScanLink.

MPT1329 now changed to (ETS 300 220)

Equipment for MPT1329 is designed for low power applications with a maximum radiated power output of 500mW. This means that the antenna gain must be taken into account when considering the allowable transmitted signal for a given application. Equipment for MPT1329 must operate in the following band:

                                                  458.5000 MHz to 458.9500 MHz

The band is divided up into voluntary 12.5 kHz and 25 kHz steps. There are three spot frequencies set aside specifically for alarm applications, otherwise the band can be used by anyone on any one of the channels without a licence and providing they do not use the band edge frequencies. The alarm channels are 458.825, 458.8375 and 458.900 MHz.

The technical specification for MPT1329 hardware is very similar on transmit to MPT1411 but quite different on receive where only the amount of interference the unit generates is checked. This is measured from the case and also from the aerial connector. The transmitter units have to be formerly submitted for test at a test centre but the receivers are self certified by the manufacturer.

Such a relaxed technical requirement leads to a vastly different standard and range of hardware being available on the market which is free to be used by any individual on any channel without recourse to anyone or any notice being given.

It also gives rise to a wide range of prices for the hardware. The manufacturer is now defining the technical standard that his product meets and not the MPT specification. A low cost product manufactured to meet MPT1329 can be as simple as a super-regenerative unit with all the attendant problems of stability and spurious outputs. A technically more astute manufacturer will be aware that such a minimal specification product will not perform dynamically very well in the crowded radio spectrum likely to be found in service. Their products will however have a premium on their purchase price. This gives a commercial disadvantage at the point of sale but an investment in service for the more knowledgeable purchasing body.

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