The 458MHz High Power Modules.

A guide to the SFX2, HMT2 and other 500mW TX power 458MHz products

LONG RANGE, HIGH PERFORMANCE, MULTI-CHANNEL RADIOS

In the UK, there is a specific allocation (detailed in Ofcom IR2030) on 458MHz for long range, high reliability wireless links (targeting industrial telemetry, tele-command and machine control tasks). These links are strictly narrowband only and are allowed to use up to 500mW TX power, yielding a practical range of well over 1km (with good aerials, mounted at elevation for best radio horizon, 5km can be exceeded).
Radiometrix provides a wide range of 458MHz band capable products, but uniquely matched to this band are the SFX2-458 high power fast switching transmitter and the HMT2-458 500mW transmitter.

In addition, there are 458MHz band variants in both the “high performance” and “LM series” product groups, providing a large family of common footprint and function modules, supporting reliable, long distance radio links with full multi-channel operation.

Key features  

Long range (this narrowband-radio-only allocation permits up to 500mW transmit power)
Multi-channel (parallel select, or up to 256 channels by serial command)
Excellent RF performance. Diode ring mixer for good large signal RX performance
Consistent footprint and pinout with other Radiometrix products
Interoperable with other Radiometrix 458MHz band modules
Re-programmable via RS232. Can be ordered on a wide range of frequencies
Range of well over 1km (2-5km typical with good quality antennas)
Conform to EN 300 220-3 (category one) and EN 301 489-3
Evaluation Boards available

Transceivers and transmitters

The core members of this family comprise of the SFX2 transceiver and the HMT2 transmitter. Both provide a full 500mW (+27dBm) transmit output power.


The SFX2 transceiver resembles the TR2M in all respects except a slightly taller (15mm) case, but employs a more advanced “up converting” transmit strip to both reduce the switching speed from 50mS to a lightning fast 5mS, and increase the transmitter output power to 500mW (+27dBm). In other respects the unit is similar, employing a low noise VCO/PLL locked to a TCXO reference, and providing the same full-featured user interface (with analogue and digital baseband ports, serial and parallel frequency programming and an optional noise squelch/mute).


The HMT2 transmitter is a very low profile (66x23x9mm) design, sharing a pinout with the SHX transceiver family. Internally, it uses similar PLL based circuitry to the LMT2 transmitter, with an added LDMOS power stage for full 500mW TX power.


Both modules are fully screened, with 2.54mm pitch pin header interfaces, intended for PCB mounting. A +5v regulated supply is required (at around 350mA), although a version of the SFX2 is offered with an internal LDO.

 

Receivers


While not explicitly included in this family, Radiometrix offers 458MHz band versions of nearly all of its narrowband UHF receiver designs, from the simple SIL NRX2B through to the LMR2 and RX2M units. All of these can be matched to a high power transceiver or transmitter.




APPLICATIONS

It’s all about range. These radios are intended for use-cases where more range (or raw link margin) is the driver, either to reach out to the radio horizon, or punch-through noisy local environments.

Their higher performance circuitry suits them to more demanding applications in “difficult” RF environments such as high end industrial control and monitoring, long range radio modem applications, remote actuator control, vehicle telematics and other high security, high integrity radio links.

Beyond the basic family

While this family already includes some highly effective modules, there are other modules in the Radiometrix product range that offer high power on this band.

The BHX2 is an older design (based on the TR2M circuitry with an added PA stage). This unit has been functionally replaced by the SFX2 (which has a far superior switching speed, lower price and smaller (59mm vs 85mm long) size). However, there may be applications where the BHX2 coaxial RF connector (SMA or MCX) is advantageous, or where the TR2M-type internal i1200 modem functionality is needed.

Where a highly robust, cased transmitter is needed, Radiometrix offers a 500mW 458MHz variant of the QPT(1) transmitter (usually offered as a 2 watt VHF unit).

Finally, there may be applications where even the HMT2 footprint is too large, but several smaller modules can be squeezed into the available volume. For these cases the AFT2 external 500mW PA module (33x23mm) might be suitable. This unit is designed to operate with any 100mW output transmitter (LMT2 or TX2M) or transceiver (TR2M).

Evaluation & Application Boards

To further simplify the implementation of user designs, a number of application/demo boards are offered, with necessary connectors and support and interface circuitry. These boards can be mounted uncased, or in some cased mounted in EAS series extrusion housings.
These boards include application board hosting the M48 modem chip and either an SFX2 transceiver or an HMT2 transmitter, plus a number of industrial control boards using the CTA88 chip, and variants of it.

If interoperability is needed with the internal i1200 modem mode offered by the TR2M and SMX2 families, then a simple external modem chip can be added to the design https://www.radiometrix.com/product/nbek-ic/

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