Intermediate RF amplifiers between low power devices & PA's
Posted: Tue Dec 28, 2021 6:24 pm
Hello
There appears to be an unsolved issue now getting enough power to drive a PA unit for UK repeater outputs which are 1308 to 1318 MHz range.
Unfortunately the internal printed circuit layout on the Mitsubishi RAH modules has been modified and they only work at the low frequency end of 23 cms.
That of course produced a nice neat 3 stage FET amplifier solution, but even there they needed modifying for 1316/18 to shorten some of the track loops on the board otherwise after 1300 MHz the output power dropped rapidly.
What is needed is a 10 watt CW peak amplifier that will produce 2-5 watts of clean digital to drive a power amplifier.
Ideally also it should be able to work with Portsdown or Lime SDR's etc where the output power is low (1-10mW).
There are a lot of internally matched cellular phone transistors but it has to be a broadband device or it won't work.
I use the NXP MMG2024HT1 mimic's 17dB gain and 3 of those in cascade from a DATV Express transmitter drive for example a 2.4GHz 8watt Wi-Fi amp which in turn drives the Spectrian amplifier for QO100.
I can use the same mimic's for 23cm but it needs the output transistor.
I spotted the M509070N transistors on eBay, but they look a bit too much power.
The MRF284S 30watts CW looks more the type of device, it is broadband, and is 26 volts but the PA probably needs 26 volts anyway.
As it has 9dB of gain we need a clean 600mWatts to drive it, as a pre-driver then we can use our mimics.
Has anyone done a board for this purpose? Is anyone prepared to make one?
Regards
Mike G8LES
There appears to be an unsolved issue now getting enough power to drive a PA unit for UK repeater outputs which are 1308 to 1318 MHz range.
Unfortunately the internal printed circuit layout on the Mitsubishi RAH modules has been modified and they only work at the low frequency end of 23 cms.
That of course produced a nice neat 3 stage FET amplifier solution, but even there they needed modifying for 1316/18 to shorten some of the track loops on the board otherwise after 1300 MHz the output power dropped rapidly.
What is needed is a 10 watt CW peak amplifier that will produce 2-5 watts of clean digital to drive a power amplifier.
Ideally also it should be able to work with Portsdown or Lime SDR's etc where the output power is low (1-10mW).
There are a lot of internally matched cellular phone transistors but it has to be a broadband device or it won't work.
I use the NXP MMG2024HT1 mimic's 17dB gain and 3 of those in cascade from a DATV Express transmitter drive for example a 2.4GHz 8watt Wi-Fi amp which in turn drives the Spectrian amplifier for QO100.
I can use the same mimic's for 23cm but it needs the output transistor.
I spotted the M509070N transistors on eBay, but they look a bit too much power.
The MRF284S 30watts CW looks more the type of device, it is broadband, and is 26 volts but the PA probably needs 26 volts anyway.
As it has 9dB of gain we need a clean 600mWatts to drive it, as a pre-driver then we can use our mimics.
Has anyone done a board for this purpose? Is anyone prepared to make one?
Regards
Mike G8LES
