TRX4S High Speed Data Transceiver
430-440 MHz, 25W, bis 153 kBaud

This transceiver is out of production since 2005.

TRX2/4S is intended for use outside the Eupean Community (EU) only.
Shipment only to addresses outside of EU. Special applications (military, research) upon request.

User Manual: Download the complete users manual (1,6 MByte Acrobat .pdf)

Data Sheet: Details and all technical data

Questions and answers TRX4 / TRX2S data transceiver

Software and hints for TRX4S users

How to order - price list

TRX4.JPG (57812 Byte)     Front view (click to magnify)

TRX4S SYMEK High-Speed Data-Transceiver

We are proud to indroduce our new 430 MHz data transceiver TRX4S.

Here the most important qualities:
bulletvariable frequency, 10 programmable frequecies selectable with a switch.
bulletfrequencies, transmitter-power and receiver bandwidth (narrow/wide) can be
programmed and stored for every channel in eeprom via rs232 interface.
bullets-meter (signal strength indicator) can be read out via rs232 in dBm directly,
the reading is individually calibrated and stored in eeprom for every transceiver.
bulletvery fast receive-transmit and transmit-receive switching for any frequency and shift:
tx->rx: 10 Ás; rx->tx(wide): 50 Ás; rx->tx(narrow): 200 Ás.
bulletsmoothed transmitter keying in narrow mode (200 instead of 50 Ás) to reduce clicks
bulletfrequency range: 10 MHz (standard: 430 - 440 MHz)
bullettransmitter output power: 20 Watt (regulated and constant over frequency),
programmable in 4 steps (3, 6, 12, 20 W)
bulletaudio-frequency ressponse (transmitter) 10 Hz to 10 kHz linear without distortion
of amplitude or phase (for 9600 and 19200 baud G3RUH-FSK)
bulletaudio-frequency response of receiver: 10 Hz bis 10 kHz v÷llig linear,
no distortions (use of group-delay optimised if filters)
bulletgood rf sensitivity (0.15 to 0.2 ÁV for 12 dB SINAD), excellent large signal
qualities (symmetric diode mixers), dynamic range -120 dBm to -40 dBm.
bulletminimal spurious emissions (harmonic and nonharmonic products) under -60 dBc.
bulletminimal interference to adjacent channels, even while tx/rx switching.
bulletwide-modus (audio: 100Hz to 100 kHz bandwidth) for 76800 and 153600 Baud FSK .
bullet100% continuous transmitting (e.g. for digipeaters) with additional fan
bulletvery stable frequency (within 2 kHz over temperature).
bulletcooler temperature can be read-out vie rs232 in Celsius or Fahrenheit (calibrated).
bulletovertemperature protecttion of power amplifier (switches off at 65 C).
bulletsupply: 12 (13.5) Volt 0,3A (RX) 5A (TX)
bulletsmall size (ca. 100x160x29 mm) plus cooler
bulletoptional: reduced size and weight (500gr) for special applications

Standard FM radios are not suited for high speed data communication with amateur radio. 
Because of the typical architecture, the following problems are found:

bulletmuch too slow TX/RX delay time (typ. 50 bis 250 ms).
bulletlower corner frequency of modulator is too high (typ 200 Hz) caused by negative feedback in PLL
bulletupper corner frequency of modulator is too low and limits the data speed
bulletIF filter group delay is not flat over frequency (poor phase response). RX signals get distorted.
bulletIF bandwidth is too narrow. This limits the data rate to 9600 baud FSK maximum.
bulletinterference on adjacent channels with frequent T/R switching.

A real data transceiver has to meet the following requirements:

bulletTX/RS switching delay less than 1 ms for duplex AND simplex mode.
bulletModulator response 5 Hz to 10 kHz (9600 baud) or 75 kHz for 153600 baud without phase distortions.
bulletIF-filter bandwidth 30 kHz with flat group delay (for 19200 baud).
bulletIF-filter bandwidth 250 kHz with flat group delay (for 153600 baud).
bulletT/R switching without interference on adjacent channels (click / chirp).
bulletSufficient output power (>20 Watt) possible to reduce, continuous transmit allowed.
bulletReceiver with excellent large-signal capabilities and good sensitivity
bulletFrequency programmable in 12.5 kHz steps.

With the TRX4S, we have developed a data transceiver without compromises, which allows transmission and reception of signals with up to 153 kBit/s data rate without limitations.

The time needed to transmit a single byte with 9600 baud needs approx. 0,8 ms. A normal transceiver has a delay (from PTT to transmit) of typically 100 ms. With the TRX4S, this time is enough to transmit a complete data packet (100 byte). Using higher data rates (153 Kbaud), the packet-length is  5 ms only, hence the TX-delay should be less than 0,5 ms.

TRX4S / TRX2S are suited for amateur radio, but the rugged design and the excellent large-signal quality makes the transceivers suited for continuous operation (digipeater use), commercial or space applications as well.  

Thouhh designed primarly for data communication, the TRX4S max be used for FM (audio) applications as well. The bandwidth makes the TRX4S also suited for high quality audio-applications hi-fidelity or special audio measurement). 


The printed circuit board and the power module is mounted on a thick 5mm aluminium base (100 x 160 mm). Around the base there is a 30 mm precision frame and a second aluminium cover with the speaker and display makes the TRX a brick-like very compact and small size transceiver. The base with the power module is cooled by a big cooler good for 50% transmit to receive ratio. 

TRX4BRD.JPG (127327 Byte)    circuit board of TRX4S, click to magnify.

Requirements for high speed data transceivers:
bulletany frequencies programmable, 16 frequencies stored, automatic resume at power-on
bulletprogrammable frequencies, bandwidth (narrow, wide) power for each channel
bullets-meter calibrated in dBm and read-out via RS232.
bulletreceive to transmit delay less than 500 microseconds delay, even in simplex mode
bullettransmit to receive delay less than 100 microseconds for any frequency and shift
bulletslow keying of rf power in narrow mode to avoid adjacent channel interference (clicks).
bulletfrequency range 430 - 440 MHz or 144-148 MHz
bullettransmit power 20 Watt (regulated, constant over frequency), programmable in steps (3, 6, 12, 20 W)
bulletAF-frequency response (TX) 10 to 10 kHz linear (no phase or amplitude distortion) for 9600 and 19200 baud FSK
bulletAF-frequency response (RX) 10 Hz to 10 kHz linear, group-delay optimised IF-filter
bulletgood sensitivity, high 3rs interception point (large signal quality)
bulletharmonics and spurious signals (RX and TX) attenuated below 60 dB
bulletminimised adjacent channel interference when keying the transmitter
bulletwide band mode (100Hz to 100 kHz AF-bandwidth) for 76800 and 153600 baud FSK 
bulletcontinuous transmission (100%) e.g. for use as digipeater
bulletgood frequency stability over temperature
bulletdisplay of power-amplifier temperature via RS232
bulletovertemperature-protect for foolproof operation in any environment
bulletsupply 12 Volt 0,3A (RX) 6A (TX)
bulletsmall size (ca. 100x160x29 mm) plus cooler

TRX4rueck.jpg (23478 Byte)    rear view (click to magnify)

trx4persp.jpg (21929 Byte)    TRX4S with antenna, power, data and RS232 cables (click to magnify)

This is how the eye diagram at the data output of TRX4S looks like.

eye153.jpg (226352 Byte)    Setup: FSK modem at 153kBaud, TRX4S as transmitter, TRX4S as receiver. (2us/div)

TRX4S is available for 2m band 144-146 MHz (TRX2S).
Other custom frequencies (100 to 560 MHz) upon request.

TRX4RX.JPG (25908 Byte)    circuit diagram (receiver, IF-amplifier, PLL) (click to magnify)

TRX4TX.JPG (31244 Byte)    circuit diagram (transmitter, amplifier, antenna switch) (click to magnify)

1 year full warranty, free update service

Any more questions? Call us or write an e-mail!