1W 27MHz RF power amplifier

The BLT50 transistor looks like it can handle a little bit more power, so I rise the bias current from 75mA to 300 mA, for 7.4V lithium battery as power supply, it dissipate 2.2W in idle. It's a little bit out of normal working range stated on datasheet. But, who care.

Worry for the high RF power would burn up the spectrum analyzer, 2 pieces of -3db attenuate is inserted between power amplifier output and spectrum analyzer.  

In initial design, the output is directly connected to the collector of transistor, in such configuration the max output power can comes to +27dbm (0.5W) with 150mA bias current. In later design the collector loading inductor is replaced by a 1:1.3 step up transformer and bias current rise to 300mA, which give a max power of +30dbm (1W). +24dbm is shown on spectrum analyzer because of the action of -6db attenuator. There are quite high level of higher harmonics because the transistor is driven beyond it's linear region. Some output filtering is needed.

The second -3db attenuator. Brought from a used equipment online store.

Input drive required to be +7dbm to give full output power of +30dbm.