Sergey, EX8MLE, has designed a 25 W PA for 50 MHz that matches the drive power from the RFzero. The PA makes it extremely easy to build a beacon for 50 MHz either as a stand alone beacon or to take part in the Synchronized Beacon Project. The PA also features an on-board low pass filter and bi-directional coupler.
The PA, fully assembled and ready-to-use, is available for only 86 USD plus shipping directly from Sergey. All you need to add is a suitable heat sink. Please contact him directly using the email address from QRZ.com.
If you are not already familiar with Sergey’s PA designs you may take a look at the 4 metres Website. Sergey is a really skilled PA designer from low power to kilowatt. This PA is using the AFT05MS004N and the RD70HVF1. Thus the output FET is very rugged for 25 W continuous operation.
Why not use the RA30H0608M power module from Mitsubishi? Well, the the second harmonic on 100 MHz is only -5 dBc. This means that 6 W of RF, and even more on DC, is wasted continuously. Even if you add a good low pass filter the second harmonic power is reflected back into the power module meaning it is subject to a permanent minimum SWR of 3. This is neither good nor efficient from an electrical bill point of view.
|Parameter||12,6 V||13,2 V||Notes|
|Frequency range||50 - 54 MHz||50 - 54 MHz|
|Output power||>44 dBm/25 W||>47 dBm/50 W|
|Input power||-6 dBm||0 dBm||On-board input attenuator pad. Resistors' wattage limit the drive power|
|Gain, max||50 dB||47 dB|
|Harmonic suppression||>70 dBc||>70 dBc|
|Current||5,0 A||6,5 A|
Spectrum performance. Picture courtesy Sergey, EX8MLE.
Frequency response. Picture courtesy Sergey, EX8MLE.
The PA schematic. Picture courtesy Sergey, EX8MLE.