Re: 5W PA on 472Khz?

Mont Pierce KM6WT

On Sat, Sep 25, 2021 at 10:38 AM, fintronicsusa wrote:
Am I assuming correctly that the 5w PA will not operate there as-is?
While the webpages for the 5W HF Amp don't mention it's specific frequency range, The Assembly Manual does...

Check the Assembly Manual, page 40 (click here).

5.5.8 Optimising for a particular band, or even Class-E operation
The recommended 10 trifilar turns on transformer T1 are suitable for the whole of HF but perhaps not
optimum at the extremes. It would be worth experimenting with fewer turns at the upper frequency
turns and perhaps more turns at MF/LF e.g. the 600m band.

For higher power operation the FT50-43 itself may saturate and so two (or more) could be stacked
together to reduce the load on each one.

Finally Class-E operation can offer extremely high efficiencies, over 90%, for continuous carrier
applications such as this. It’s an extensive topic, way outside the scope of this assembly manual.
Class-E will only be possible on a single band, unless you employ switching of the components.

6. Power Amplifier characteristics

These measurements were made using a QRP Labs Ultimate3S transmitter kit as driver, with a single
BS170 transistor running at 5V supply. The curves show the Power Amplifier kit with 12V and 13.8V
supply voltage. The output of the PA kit was connected to a QRP Labs Low Pass Filter Kit, whose
output was connected to a QRP Labs 50-ohm 20W Dummy Load kit. Measurements were made on
600m, 160m, 80m, 40m, 30m, 20m, 15m and 10m bands (frequencies 0.5, 2, 3.5, 7, 10, 14, 21 and
28MHz respectively).


Join to automatically receive all group messages.