Hans G0UPL has just announced that the PA used in the upcoming QSX kit will be offered as a stand-alone kit for those who might want to use it with an existing QRP rig.
In his own words:
This PA board is so GOOD that it will be made available also as a standalone 10W HF Linear PA kit. It is ready for production and should be the first of the QSX modules ready for sale.
The requirement for expensive Mitsubishi RD16HHF1 etc transistors in a decent amp is an absolute misconception. In reality they are very very expensive and not necessary in HF applications such as this.
This amplifier is proud to use two inexpensive IRF510 transistors. A great deal of attention has been paid to a symmetric and compact layout for best performance.
More details soon but briefly:
- Two IRF510 in push-pull, two BS170 in push-pull as the driver.
- Gain 26-28dB, better than 2dB gain flatness from 2-30MHz. Still only 4dB down even at 6m, and respectable even to 4m.
- Can easily achieve 10W across 160-10m using 12V supply
- 80m band tested harmonic levels 2nd -38dBc, 3rd -31dBc. Thats BEFORE a low pass filter is added - addition of the LPF will result in a very clean output.
- Very large heatsink for the 10W power rating. Ran continuous 100% duty cycle at 10W output for 1 hour without failure or degradation
- Tested to 20V supply voltage; tested open load; tested shorted; tested with 20W 100% duty cycle for 10 minutes... all with no failure or degradation
- Quite easily delivers a lot more than 10W too...
Above results are for the PA module alone, not integrated within the QSX. I think it is very unlikely that that you would be able to replace the PA module in the QSX with anthing that could deliver as good performance, even assuming you are willing to spend a lot more money.
Anyone who thinks IRF510s aren't good for the job, will need to reconsider their view after this.
Using Hans' 26dB gain and 10-watt out figures, the required drive for full output would be 25mW.