Series modulator options for the
FAT5 transmitter.
The high power modulator uses an
LM2876/3876/3886 IC which can cope with supply voltages up to
84V on-load. A downside is that the chip needs at least 24V to
overcome the internal low-voltage cut-out, making it unsuitable
for lower power transmitters.
The medium power modulator is adequate
for supply voltages up to the TDA2050 limits of 50V (less is
recommended for reliability). The TDA2050 has no low-voltage
cut-out and will work with low voltages such that a 10W carrier
transmitter can be built working off a modulator supply of
13.8V. Using the FAT5 PA module PCB, with all four FETs fitted,
50W carrier can be achieved with around 13.5 Volts on the FET
drains. After circuit losses this equates to a main supply rail
of about 33 Volts making the TDA2050 modulator the best choice
for most situations.
Download the series modulator full manual including FAT-MAX [here] |