Alternative to using 2n4427 for 1 watt drivers

[Zozo]

Sorry I missed something you said about the emitter pins 1,4,5 & 8. Those are all common with each other and not grounded to deck.

Connectivity path for emitters in pink

Emitter Pins.png

[garada]

To obtain 1w a more modern alternative to the 2n4427 is the mitsubishi rd01, it has an smd format and it heats up very little, of course it is not a direct alternative, the price is also much lower than an original 2n4427

[Albert H]

I've been experimenting with the RD01, and have found that it's very efficient (little heat dissipated), physically small (very convenient), and has loads of gain!

I've just lashed together an exciter with a dual-gate FET Hartley VCO and an RD01. It's a two-transistor, at-frequency 1 Watt driver! With a surface-mounted PLL IC (I've still got a few SM MC145170s) and an SM PIC, it should be possible to make a matchbox-sized exciter!

It occurs to me that it might be worth identifying a cheap, Asian SM PLL IC and a suitable PIC or AVR to programme it (probably an 8-pin job for fixed frequency), and get a whole lot of tiny PCBs made in the Far East. Early research suggests that they should be around £5 each to get made, with all the components loaded!

It could be interesting to make a ½f doubler exciter (for stability in an RF-noisy environment), and I could use my very old diode-programmed 4-chip CMOS PLL circuit - but in Surface Mount - and get them made without the programming diodes, so the could be set to frequency as needed. This might be the way forward!