5300 100W Amp - How it Works
Posted: Tue Mar 02, 2010 2:47 pm
Interesting...
The 100W radio starts off as basically a 50W radio, MRF247 (75W rated) final.
The 50W goes out of the main chassis to the amp chassis.
The 50W goes through a 2-way 3dB hybrid power splitter/combiner, now you have 2 x 25W outputs
25W from each side of the power splitter goes to 2 x 6dB gain 100W transistors SD1477....so now you have 2 x 100W outputs.
the 2 x 100W outputs are combined with another 3dB hybrid to make a 100W output.
The 100W goes BACK into the main chassis for T/R switching....then back out the same as in a 50W unit.
So we're making 250W of RF just to get 100W. What a waste. No wonder the 100W ones take a gajillion amps!
Looks like it would be pretty easy to 'downconvert' a 100W to a 50W, too.
So anyone have a clue why it was designed this way?
Coupla thoughts:
-50W radio was already designed...easy to do the splitter/combiner "thing" from the existing 50W output rather than redesigning it ?
-Soft fail...one final dies, you still have ~50W ?
The 100W radio starts off as basically a 50W radio, MRF247 (75W rated) final.
The 50W goes out of the main chassis to the amp chassis.
The 50W goes through a 2-way 3dB hybrid power splitter/combiner, now you have 2 x 25W outputs
25W from each side of the power splitter goes to 2 x 6dB gain 100W transistors SD1477....so now you have 2 x 100W outputs.
the 2 x 100W outputs are combined with another 3dB hybrid to make a 100W output.
The 100W goes BACK into the main chassis for T/R switching....then back out the same as in a 50W unit.
So we're making 250W of RF just to get 100W. What a waste. No wonder the 100W ones take a gajillion amps!
Looks like it would be pretty easy to 'downconvert' a 100W to a 50W, too.
So anyone have a clue why it was designed this way?
Coupla thoughts:
-50W radio was already designed...easy to do the splitter/combiner "thing" from the existing 50W output rather than redesigning it ?
-Soft fail...one final dies, you still have ~50W ?