TRX4S Transceiver (Data Sheet)

430-440 MHz, 25W, 1200, 9600 up to 153 kBaud

Immediate download TRX4 users manual (1,6 MByte Acrobat .pdf)

Full description and pictures of TRX4S

Commercially available FM-radios are generally not suited for fast data transmission and receiption with amateur radio. Using these radios, you will find the following problems:
bulletTransmitter-keying is far too slow (normally 100 bis 150 ms).
bulletLower af corner frequency of the modulator is much too high (typ 100 Hz), caused by pll-feedback.
bulletUpper af-corner frequency is too low. This limits the speed of data transmission.
bulletIF-filters are too narrow, the group delay is not constant.
bulletIF-bandwidth limits the the data rate to 9600 baud FSK maximum.
bulletInterference to adjacent channels when keying the transmitter frequently.

A real data-transceiver should have the following properties:
bulletTransmitter keying faster thal 1 ms for duplex but also for simplex operation.
bulletModulator response 5 Hz to 10 kHz or up to 75 kHz for 153600 baud without phase distortion.
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 to adjacent channels by click or chirp.
bulletenough rf power for apropriate signal to noise ratio, low power mode for local qso
bullethigh intercept point receiver, capable to handle large in-band signals without distortion
bulletprogrammable to any rx and tx frequencies, including tx=rx

SYMEK has been specialist for development and production of high speed packet-radio modems and controller so far. But the transmission speed was limited because of there was no suited data-transceiver available. We decided to develop a special radio for high-speed data transmission. After finishing the development, we started production in end 1998. The first TRX4S are available since March 1999.

TRX4S, first developed for high-end amateur use, is now widely used in commercial applications and satellite ground stations. Samples had been proven good to be used on board of the ISS space ship in 2001 for amateur packet-radio on 435 and 145 MHz together with the TNC3.

At 9600 Baud, the transmission of a byte takes approx. 0,8 ms. In the time, a normal transceiver to switch from receiption to transmit mode (100ms), the TRX4S is able to transmit a complete data packet (100 byte). At 153 kBaud, the time for a 100 byte is only 5 ms, the delay has to be shorter than 0,2 ms for not to waist transmission time.

The TRX4S is suited for amateur radio on terrestric and satellite links, but the rugged commercial construction as well as the excellent large signal capabilities of the receiver makes it suited for commercial or digipeater use as well. Though developed especially for data transmission, the TRX4S is suited for fm fone radio operation or 1200 baud afsk packet as well.

There had been successfull attempts made to receive the new UOSAT UO-12 in 38kbaud mode FSK with a TRX4S. Within a single receiption period, there were 1.5 Mbytes downloaded from UO12 with nearly no failed packets. However, we recommend to use a highly sensitive preamplifier with the TRX4S for satellite operation. For decoding the fsk modulated packets, we recommend the TNC31S packet-radio controller, which is available with a wide variety of modems, including 9k6, 19k2, 38k4, 76k8 and 153k6.

Technical Data of TRX4S: (dBc = referenced to carrier. Frequencies at Fe=Fs=435,0 MHz)
bulletConstruction: The TRX4S is built-up on a single printed circuit board, which is mounted on a 100x160mm (5mm thick) aluminium panel together with power amplifier module. Together with a Nickel-Copper frame and a cover panel, the TRX4S is a compact bloc with approx. 30 mm height. On the rear panel, there are the connectors for antenna, 12V-power, modem and RS232, on the front you find leds, audio and squelch control and the receptacle for remote control. All connectors on front and rear are clearly inscribed. On top of the TRX4S case, a massive aluminium heatsink is mounted for cooling the transmitter.
bulletSize (complete box without cooler attached): B= 161 mm, T= 100 mm, H= 29 mm, weight 0,7 kg
Size (with cooler): B= 161 mm, T= 100 (plus controls and connectors), H= 80 mm, weight approx. 2 kg
bulletPower supply: 12 volt dc (11 to 16 V), RX: 250 mA; TX: max. 6 A (depends on programmed power)
bulletFrequency range: 10 MHz (range: 430 - 440 MHz), Channel spacing: 12,5 kHz, TRX2S: 144-146 MHz, other frequencies available on request.
bulletFrequency drift: <+/- 2 kHz, Temperature range: 0 to 50 C.

Size (TRX4S, no cooler): B= 160 mm, T= 100 mm, H= 29 mm, mass 0,7 kg
Dimensions (TRX4S with cooler): B= 170 mm, T= 125 mm, H= 80 mm, mass 2 kg
Power supply 12 V DC (11 to 16 V)
Power consumption: Receiver: 250 mA; Transmitter (max. power) 6 A
Frequency coverage: 10 MHz (Standard: 430 - 440 MHz) or 4 MHz (144-148 MHz)
Channel spacing: 12,5 kHz
Frequency range: 420 to 450 MHz (factory adjustable), 100 to 520 MHz on special request
Frequency constance: +/- 2 kHz  or 5 ppm
Temperature (operation): 0 to 50 C (all specifications within limits)
T/R Delay: wide: RX-TX: 50 us, TX-RX: 150 us; narrow: RX-TX: 2 ms, TX-RX: 5 ms

Display-LEDs: Power, Transmit, Receive, DCD, Narrow/Wide
Internal power supply: 5 V, 5V TX, 5V RX, 5V VCO, +10V, +/- 10V (RS232), transmitter (Driver): regulated 4 to 9 V, power amplifier: 11 to 16V unregulated. Fuse: 6,3A
Frequency programming: via RS232 serial interface, 9600-N-8. 16 channels can be stored.
Frequency memory: For each of the 16 channels you can store: TX-frequency, RX-frequency, bandwidth mode (wide/narrow) and transmit power (3/6/12/25 Watt). All settings are stored in a  EEPROM memory. The channel used last is also stored and after power off, the same channel is selected as before power interruption.
Channel select: by two push-buttons 'up' and 'down'. The current channel number is displayed on a 7-segment display. However, all settings and channel selection can be done via RS232 as well.
Remote control: All functiones of TRX4S can be controlled via RS232 interface (RJ45-connector on the ear panel of TRX4S) or via the pseudo-RS232 interface on the front panel.
The following commands are available:
bulletset current channel number (0 to F)
bulletread current channel number (answer: 0 to F)
bulletprogram channel 0 to 15 (TX-frequency, RX-frequency, bandwidth/mode, transmitter-power)
bulletread setting of a channel (Answer: TX-frequency, RX-frequency, bandwidth/mode, transmitter-power)
bulletread s-meter abfragen. (Answer: signal strength in -dBm (range approx. -30 to -130 dBm).
bulletread amplifier temperature (Answer: 0 to 99 (C)) or
read output power (answer: 0 bis 45 (dBm))
bulletread software version (answer: version-number stored in CPU-ROM)
bulletEEPROM-poke: programming and reading EEPROM-memory (for service, fully documented)

General data:
bulletDisplay leds: Power, Transmit, Receive, DCD/RSSI, Narrow/Wide
bulletInternal power-supply: 5 V, 5V TX, 5V RX, 5V VCO, +/- 5V (audio amplifier), driver: regulated 4 to 9 V, power-amplifier: 11 to 16V (not regulated). Fuse 6,3A
bulletFrequency programming: with serial interface (rs232), 9600-N-8. There are 10 channels available to program rx-qrg, tx-qrg, tx-pwr, wide/narrow. The frequencies are stored in a eeprom. A clone-function for copying all data to a slave TRX is available.
bulletFrequency control: with up-down buttons on the board. (10 channels) or via rs232.
bulletFrequency readout: all stored settings can be read-out via rs232 with a pc.
bulletS-meter-reading: via rs232, the signal strength can be read out in dB(mV) directly. According to the narrow/wide setting, the rssi signal of the narrow or wide if amplifier is used. The s-meter can be calibrated via rs232 individually for every transceiver.
bulletTemperature-readout: the temperature of the power amplifier can be read out via rs232 in °Celsius. Optional: readout of transmitter output power 0...45 dBm. (can be calibrated individually)
bulletOvertemperature-protect: a temperature sensor switches off the transmitter when overheated.
bulletDisplay: 7-segment led-display on-board. Can be switched off to save power.
bulletModulation connector: Mini-DIN-receptacle, 6-pin (data in, data out, ptt, dec/rssi, +10v, gnd)
bulletPower supply connector: 2-pin AMP-connector.
bulletComputer (rs232)-connector: RJ45 connector (as TNC31), txd, txd, gnd. RS232 with MAX232.
bulletRemote Control: 10 pin connector with 5V-pseudo-rs232-interface to remote control unit,
bullet3-wire interface for channel-display, up and down button, 5v-supply.
bulletAntenna: BNC-connector. Antenna-Switch: 3 power pin-diodes.
bulletUseable Packet-rate: max. 50 packets (256 bytes ea) or 100 packets (100 bytes ea) per second.
bulletParts (approx.) 33 IC, 10 transistors, 25 diodes, 6 ceramic/crystal filter, 35 coils, 11 helix-coils, 240 capacitors, 165 resistors, 2 balance mixers, 1 microcontroller, 4 quartz crystals.
bulletMechanic: Multilayer-printed circuit board, gold-plated, 160 x 100 mm with smd components on both sides, mounted on aluminium panel.

Transmitter:
bulletRF output power: 4 adjustable steps (3W, 6 W, 12W, 20W) to be selected  and programmed for each channel.
bulletOutput power regulation: constant over total frequency range within 0,1 dB.
bulletContinuous operation: 70% Transmit ratio (full power) at 40 C ambient temperature. 100% with additional fan.
bulletTX-ON-delay: Delay from 'PTT=low' until 90% transmit power: < 50 ms (0,05 ms) (wide), or 100 ms (0,1 ms) (narrow mode).
bulletTX-OFF-delay: 'PTT=high' until tx-carrier is below -130 dBm (< 0,1mV): < 10 ms
bulletA new developed switchable oscillator circuit 'TXD-Null' is used.
bulletTransient signals: (transmitter ptt is keyed with 10 Hz: (50 ms TX, 50 ms RX), > 50dB (adjacent channel), >60 dB (500 kHz distance), >70 dB (2 MHz distance) referred to full carrier and channel bandwidth (wide).
bulletModulation bandwidth (narrow): 3 Hz to 15 kHz (-3 dB) (19200 Baud G3RUH)
bulletModulation bandwidth (wide): 30 Hz to 80 kHz (-3 dB) (153600 Baud G3RUH)
bulletModulation input (narrow): 0,5 V ss at 47 kW for 5 kHz deviation (adjustable)
bulletModulation input (wide): 0,5 V ss at 47 kW for 50 kHz deviation (adjustable)
bulletTransmit carrier supression: (PTT = high) infinite
bulletHarmonic signals: below -70 dBc, nonharmonic signals: below -70 dB (carrier)
bulletTransmitter keying (PTT): 5 V, <1mA to ground.
bulletTrimmer: rf-limit, mod (wide/narrow), compensation (wide/narrow), reference oscillator, pll-center, driver match, tranmit power 1-4, temperature limit.

Receiver:
bulletSensitivity: typ. 0,2 uV (50 Ohm) for 12 dB SINAD (narrow), typical -118/-109 dBm (narrow/wide) for 12 dB S/N.
bulletIF-bandwidth (narrow): ± 15 kHz (-3dB), 2 filters 10,7 MHz, 2 filters 455 kHz. (wide): ± 125 kHz (-3dB), 1 saw-filter 71 MHz, 2 filters 10,7 MHz. Other IF-bandwidth available upon request (e.g. ± 70 kHz (-3dB) for 76 kbaud)
bulletSelection (narrow): ± 35 kHz: >90dB; stopband : >110 dB (wide): ± 300 kHz: >60dB; stopband : >110 dB. All filters with constant group-delay!
bulletMirror frequency supression: 506 MHz and 364 MHz: >70 dB
bulletReceiver architecture: dual conversion (wide) or triple conversion (narrow).
bulletMixer: dobly balanced diode mixers.
bulletGroup delay (narrow): constant approx. 100 ms from 10 Hz to 10 kHz,  Group delay (wide): constant approx. 10 ms from 100 Hz to 75 kHz
bulletRX-ON-delay: time between 'PTT=high' until normal receiption: < 10 ms
bulletRX-muting: the data output is muted while transmitting.
bulletData-output (narrow): 0,5 V ss (Ri=220W) when receiving a fm-signal with 5 kHz deviation. Data-output (wide): 0,5 V ss (Ri=220W) when receiving a fm-signal with 50 kHz deviation.
bulletAudio output (speaker): 0,5 Watt at 8 W (Volume adjustable), 3,5 mm connector.
bulletSquelch (speaker): adjustable squelch, built-in speaker.
bulletSignal strenth indicator: can be accessed via rs232 and computer. Reading in dB (mV).
bulletHF-DCD: open-collector output, pulled low when a signal (level adjustable) is present.
bulletTrimmer: reference oscillator, pll center frequency.

Real S-meter, transmit power display / temperature display: these values can be read-out via  RS232. The s-meter reading is calibrated in dBm (Range approx. -30 to -130 dBm = 10mV to 0,05 uV). The RSSI-output of the wide or narrow demodulator is measured and converted to dBm with a lookup-table stored in EEPROM. So, the values are exact within 1-2 dB accuracy. Every transceiver is calibrated individually. The same algorithm is used for reading temperature (in degree Celsius) or output power (in dBm). Measuring of transmitter output power is normally disabled as this value can be measured only while externally enabling the PTT.

Overtemperature protect: There is a hardware-set protection, which disables the PTT at temperatures above 65C.

RX-RF-amplifier: 3 wide-band resonant circuit filters, 2 helix filters, RF preamplifier with good sensitivity and high 3rd intercept point (ERA-3, f=2dB), 3 helix filters, second RF input amplifier (ERA-3), dioden-balanced mixer. Sensitivity typ. 0,2 uV (50 Ohm) (narrow) for 12dB SINAD.

IF-amplifier: Wide mode: Dual conversion circuit. 1. IF: 71 MHz with 250 kHz SAW-Filter, 2. IF: 10,7 MHz with two ceramic 250 kHz-filters. Narrow mode: Triple conversion, 1. IF: 71 MHz 250 kHz SAW-Filter, 2. IF: 10,7 MHz with one ceramic 250 kHz-filter and a monolithic 30 kHz crystal filter. 3. IF: 455 kHz with two ceramic 30 kHz filters. All filters used are group-delay optimised. Selectivity (narrow): ± 35 kHz: >90dB; stop band : >110 dB; wide: ± 300 kHz: >60dB; stop band : >110 dB. Mirror supression: 506 MHz and 364 MHz: >70 dB.

Audio-Amplifier: 0,5 Watt for monitor speaker. Volume and squelch can be adjustet with two potentiometers on the front panel. External 3,5 mm earphone connector, switches internal speaker off. The speaker is active even in transmit mode. This makes it possible to monitor the own transmit signal while in simplex mode.

Data-Output (Receiver): separate low-pass amplifiers for wide- and narrow-receiver mode, automatic selection of wide/narrow output signals to pin 4 of the output connector. Frequency response: 10Hz to 30kHz (narrow) and 50 Hz to 200 kHz (wide). 0,5 Volt output level (low impedance). Connector: 6-pin  mini-DIN-connector (standard as usual with all other 9600 baud transceivers available). Data output is muted while transmission.

Signal detection (RSSI-DCD): two (separate for narrow and wide) potentiometers can be used for setting the trigger level for input-signal derived DCD display. The DCD-signal is displayed with a LED and is available on pin 5 of the data output connector.

Data-Input (transmitter): separate low-pass amplifier for wide- and narrow transmit mode. Automatic selection depending on the mode. Corner frequencies: 5Hz to 22kHz (narrow) and 15 Hz to 80 kHz (wide). 0,5 Volt input voltage at 10 kOhm (can be adjusted separately for wide and narrow).

Modulator (transmitter): Two-point modulation: A crystal oscillator cannot (because of the high Q of the quartz resonator) be modulated wide-band. A PLL however cannot ne modulated with low frequencies because this would be compensated by the negative feedback of the PLL-loop. So, the TRX4S uses both ways to modulate the carrier in parallel: The reference (quartz) oscillator is modulated with the low frequencies and the PLL is used for the higher portions of the spectrum. There are two separate filter-amplifiers, which generate a lowpass and a highpass signal for the two modulators. Band-width  (narrow): 3 Hz to 15 kHz (-3 dB) (can be used fur up to 19200 baud G3RUH), band-width (wide): 30 Hz to 80 kHz (up to 153600 Baud G3RUH). Modulation input : 0.5 V at 10 kOhm for 5 kHz deviation (narrow) or 0.5 V for 50 kHz deviation (wide)

Reference oscillator: A high-quality 12,8 MHz quartz crystal with typ. 5 ppm (= 2,5 kHz at 430 MHz) accuracy is used. Optional, a TCXO with 2,5 ppm (-20 to +70C) can be used. (typisch less than 1 kHz frequency drift). The oscillator is used for transmitter, receiver and as clock for the microcontroller. The 12.8 MHz signal is accessible at the remote-control connector for adjustment of for clock-supply of external microcontrollers. 

PLL-Synthesizer (transmitter and receiver): Changeing the frequency of PLL-synthesisers takes (caused by the loop filter) long (typ. 20 ms to 200 ms). This is no disadvantage with normal FM radios. But for high-speed data radios, this delay cannot be accepted. Further, PLL-oscillators generate heavy interference on adjacent channel frequencies when locking. So, we designed two fully independent PLL oscillators for transmitter and receiver, which must not be changed in frequency when switching from transmit to receive mode or vice versa. The oscillators are programmed only at power-on and when frequency setting is changed. So, the lock-in delay is relatively long to ensure a clean signal with minimum phase noise. The VCO-coil is a piece of  semi-rigid cable with minimum susceptibility to mechanical or accoustical influences. The VCO is made with a modern IC with integrated buffers. Supply voltage of VCO comes from a regulator with extremely low noise (0.5 Hz lowpass filter). The PLL consists of a dual-modulus prescaler and a Motorola-PLL-synthesizer with serial programming by a microcontroller.

Transmitter design: The transmit signal is generated by mixing of the modulated VCO-frequency (339-349 MHz) with a special designed "TXD-null" 90.45 MHz oszillator. In receive mode, the 90 MHz-oscillator is totally switched off. The oscillator uses the 60.3 MHz signal of a quartz used for the 71 Mhz to 10.7 conversion of the receiver.

Disabling the transmitter when receiving: When reveiving, there mus exist absolutely no signal on the transmit (=receive) frequency. Hence, the VCO cannot oscillate in the transmit frequency directly. There is a mixer needed to add VCO frequency and any other local oscillator to generate the transmit signal. When receiving, this local oscillator has to be totally switched off. Otherwise, the combination of the existing frequencies would generate weak signals directly on the receive frequency. While receiving, ther must be no oscillators active, if any possible combinations of their frequencies fall on the receive frequency. A good quartz-oscillator cannot switched on or off in less than 10 ms and cannot be used for that. TRX4S uses a frequency divider as local oscillator. When the divider is disabled, it generates absolutely no signal (even no spurious) on the output frequency. When enabling the divider, the oscillator is ´immediately ON without any delay. 

Transmitter-keying: When in receive mode, the TX drivers and the local 90 MHz oscillator of the transmitter are switched off. Swithcing on the transmitter is by principle possible without any delay. (typically time from PTT to 90% transmit power = 1 microsecond). Because this would cause excessive 'clicks' over a wide band, the supply voltage of the transmitter is slowly increased after PTT to reduce the speed of keying. In wide mode  (high speed), the time constant of the transmitter is approx. <50 microseconds to avoid adjacent channel interference. With narrow mode, delay is increased to 200 microseconds additionaly. Only 50 microseconds after releasing PTT, the receiver is able to receive valid data with full sensitivity.

Power amplifier: Modul-amplifier (max. 35 Watt). Power-regulation by sensing the output power and controlling driver power to achieve constant output over the band. 4 programmable power levels: 3 W, 6 W, 12 W, 20 W. Accuracy of output power: +/- 0,2 dB. Continuous transmit operation with full 20 Watt power is possible, if an additional fan is added.

Transmitter harmonic and spurious signals: below -70 dB(carrier)

Transient spurious signals:  (PTT keyed with 100 Hz, 5 ms TX, 5ms RX): <- 40dB (adjacent channel), <-50 dB (500 kHz distance), <-60 dB (2 MHz distance) referred to carrier and channel bandwidth (wide).

Microphone use: Connection of a microphone is not supported. However, there is a 10 V (max. 5 mA) output at the data connector to supply external microphones with amplifiers.

Power supply cable: 2-pin AMP-Connector and 2 m cable.

Computer (RS232)-connector: RJ45 connector (as TNC31), TXD, RXD, GND. 2m cable with 9 pin Sub-D (female) is included.

Connector for remote control unit: receptacle for 10 pin connector (2.5 mm spacing): GND, +5V, 12,8 MHz, Buttons UP and DOWN, data, clock, enable (for 7-segment display), pPseudo-RS232-interface (TTL /TXD, /RXD) to remote control unit.

Antenna connector: BNC.

Antenna switch: 3 power-PIN-diodes.

Usable packet rate: max. approx. 30 Packets (256 bytes each) or 50 Packets (100 bytes each) per second. (TNC with TX-delay less than 10 ms required)

Components: 27 IC, 24 transistors, 18 diodes, 6 ceramic/xtal filters, 30 inductors, 11 helix-resonators, 241 capacitors, 185 resistors, 2 balanced mixers, 1 microcontroller, 4 quartzes, 12 trimmer resistors, 2 potentiometers, 5 LEDs, 1 7-segment-display, 1 power-amplifier module. 4-layer printed multilayer circuit board (surface gold-plated) size 160 x 100 mm, loaded on both sides with md-components, mounted on a 5mm aluminium plate.

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