Info page for Modifications of UHF FM RX TX Module

Each Module consist of RX/TX Board, Controller Board, and Power Amplifier Board.

Original working frequencies RX: 455MHz +/- 3MHz and TX: 465MHz +/- 3MHz, channel separation 25kHz or 12.5kHz.

These modules can be converted to work on HAM UHF amataeur band 430-440MHz.

The most interesting application is as RX/TX part of an UHF HAM repeater, as well as a part of Cross Band Repeater, Link, Packet Radio, etc.

There are two independent PLL frequency synthesizers MB1502 for RX/TX in the module, so FULL-DUPLEX MODE is supported.

Output power : +45dBm (32W @ 24V DC), max. 40W @ 24V DC, or up to 18W @ 12V DC for TYPE<2> modules. TYPE<1> modules can reach 50W.

Final stage of Power Amplifier is built with one of these transistors: Motorola TP5051 or Ericsson 20200 or ST Microelectronics SD1393.

The circuit type of the receiver is Double-Conversion Superheterodyne with 1'st IF=71.0MHz, 2'nd IF=455kHz and FM detector.

There are two types of RX/TX modules:

<1> With only one receiver.

<2> With two receivers tuned on the same frequency for Diversity.

TYPE<2> with Dual Receiver TYPE<1> with Single Receiver Size: 335mm x 260mm x 24mm Weight: 2.0Kg

Mechanical Drawing Block Diagram

RX/TX Board Pinouts Power Amplifier Board Pinouts

Click on the graphics for zoom or download all in a pdf file: UHF_FM_RX_TX_Module.rar

More information about some pins:

TXON: +5V to activate TX, 0V(GND) for standby (the same as usual PTT, but "logic1" to transmit).

PLV: Increasing the voltage to this input will increase the output power level (for example: PLV=1.9V TXout=5W, 2.7V->10W, 3.3V->15W, 3.7V->20W, 5.0V->30W, 6.2V->40W).

PF/PR: The output voltage is in direct ratio to the Forward/Reflected power (TX off -> PF=PR=0.03V, TXout=18W -> PF=3.6V).

TEMP: The output voltage is in direct ratio to the temperature (2.4V @ 30°C, 2.7V @ 36°C, 3.0V @ 42°C, 3.5V @ 50°C, 3.7V @ 55°C).

RSSIATT: 0V(GND) to activate RX 1'st IF attenuator, +5V to swich the attenuator off.

DC current of the PA is 2.8...3.3A at 12V(3.3A at 13.8V) and 4.2...4.4A at 26V (max.5A at max.28V). Note that the original fuse on +24V DC line is 4A !!!

Datasheets for some of the components:

RX/TX Board :

IC1 ; IC3A ; IC3B ; IC4 ; IC5 ; IC10 - DC Voltage Regulator LP2951

IC2 RX; IC11 TX - Serial Input PLL Frequency Synthesizer MB1502

DBM1A ; DBM1B - Surface Mount Mixer ESMD-C2HX2-1, datasheet for ESMD-C2HX2, the same mixer except Frequency Range

IC6A ; IC6B - Double-balanced mixer and oscillator SA602A

IC7A ; IC7B - High performance low power FM IF system SA604A

IC8A ; IC8B - CMOS Dual Operational Amplifier LMC662

IC9A ; IC9B - 14 Stage Binary Counter MM74HC4060

LNA1A ; LNA1B - made with NPN 7GHz wideband transistor BFG135

Power Amplifier Board :

IC1 - Low Power Quad Operational Amplifiers LM224

Class A preamplifier Transistor BFG135

PRE-Driver Transistor 20204 or TP5002S or SD1390

RF Driver Transistor 20203 or TP5051R or SD 1391

Final Amplifier transistor 20200 or TP5051 or SD1393

Original Controller Board is not interesting for any HAM applications, except few parts that can be used in the new controller board:

fuses, connectors, DC voltage regulators and two audio transformers.

! WARNING ! The white ceramic of transistors in PA board is Beryllium Oxide !

Please read this carefully before you take any action : > > > README.TXT < < <

NECESSARY MODIFICATIONS to cover UHF HAM band 430MHz ... 440MHz :

Two SMD RF capacitors (0805 or 1206 tolerance +/- 0.1pF) need to be added or changed on RX VCO and TX VCO.

Please pay attention to the tolerance and the quality of SMD capacitors, wich you will use.

Add 3th capacitor in parallel to Crx1/Crx2 -> 4.7pF or 5.6pF and also add 3th capacitor in parallel to Ctx1/Ctx2 -> 4.7pF or 5.6pF.

Other possibility is to change one of Crx1 or Crx2 and also change one of Ctx1 or Ctx2. For reference the original values are:

TYPE<2> Modules: Crx1=6.8pF ; Crx2=3.3pF ; Ctx1=2.7pF ; Ctx2=8.2pF

TYPE<1> Modules: twice and more than the values in TYPE<2> Modules (will be measured some day).

Also the helical filters need to be aligned :

RX/TX Board - HF1, HF2A, HF2B for best sensitivity on RX. (Voltmeter at "RSSIA or RSSIB" pin can help.)

PA Board - HF1 for maximum output TX power level. (Voltmeter at "PF" pin can help.)

For reliable operation of the module, a fan must be installed on the heat sink of the PA board. Any fan with capacity at least 30m3/h will do the job. The fan may be switched on during transmission only, for example by PTT. For better results the fan can be driven by TEMP signal.

PC Software for test purpose : FS1501v.zip . Thanks to OH8RO. With this software you can control MB1502 PLL via simple interface to PC LPT Port. Press F7 for the wiring diagram.

The next step to turn these modules in UHF HAM repeater is to build a repeater controller board. It can be fit in the place of the original Controller Unit board. Main functions of the controller will need to be: MB1502 drive, Xtal Refference Oscillator 10MHz(12.8MHz ... etc.), VCC Regulators for RX/TX boards, high VSWR / high TEMP protection, Fan control, Repeater Logic (audio,PTT,Squelch), CTCSS, CW ID, PC Programming interface (RS-232 or USB), External interface of PTT/SQL/Audio for link to PC and Echolink for example.

The "Diversity function" probably will not be implemented for type<2> Modules (with dual RX), but at least a simple logic for automatic selection of stronger RX signal (RXA or RXB) will help in some cases. For example we can use separate second RX antenna. This can be an yagi placed away from main TX/RX antenna system. In this case with the yagi pointed to known direction we can improve the reception from a given area.

The first working controllers for these modules have been made successfully in Norway. There are also many working repeaters made from these modules. If you are interested in a purchasing of working controller, or simply want to find other useful information, then feel free to visit http://www.radioteknikk.com/ .

HAM UHF Repeater built with one of these modules: UHF Repeater ver1

As soon as other simple repeater controller is realized, it will be published on http://sites.google.com/site/uhfrxtx/ .

For availability and pricing of these modules:

The page was created on: 09.may.2009 Last major changes: 25.august.2009