M57727 Mitsubishi Linear Power Module 37W 144-148 MHz (NOT AVAILABLE - SEE NOTES FOR POSSIBLE REPLACEMENT)

M57727 Linear Power Module, 37w, 144-148 MHz, Mitsubishi

Frequency Range: 144-148 MHz
Max Bandwidth: 140-150 MHz
Power Output: 37W
Power Input: 300mW
Bias Class: AB
Case: H3B

No longer available, Discontinued

NOTES

Modification notes for replacing the M57727 with RA30H1317M1 in Icom IC 271E

I mounted it into an ICOM IC-271E.  I inserted a 6dB PI attenuator at the output of the driver stage, built with 1206 SMD resistors. I adjusted the tuning capacitor (that was already there) to 50mW.  The module was mounted in the same place with pins 1, 3, and 4 matching the pins 1, 4, and 5 of the M57727. Gate bias pin 2 has been connected to a resistive divider composed of a 1k pot to ground and a 560-ohm resistor taking voltage from the point where the former pin 3 of the M57727 would have been connected (+8V on TX). I found that maximum power could be obtained with 4.92V of bias. More will reduce output. I have been able to obtain 31W output past the radio TX/RX switch and low pass filter, this is in line with the specs of the radio and the module, so the substitution was 100% successful.

A side note: the new module is somewhat less efficient in comparison to what the datasheet shows. The radio has a power control mechanism based on output stage current sense and I needed to re-adjust it as now it needs more current to obtain the same power. In the BJT module, the first stage current came from another pin where it wasn't sensed, while in this one there is only one pin.