100W HF RF afterburner.

5W to 100W HF RF PA for the KX3.

Afterburner for Elecraft KX3 or Flex 1500 transceivers.

When the need for speed, er, power arises, I decided to adapt a commercial HF PA to suit my needs. The PA is pretty much complete and just needs a milliwatt or two to be able to produce about 100W RF output. All I had to do was provide some input Tx / Rx switching (relay), an RF attenuator pad (custom) for correct drive requirements, a band switch for manual selection of output filter (no micro required) and some visual (led) indicators.

Initial results.

It went pretty well and quite stable. No RF crazies with the lid off or on. There are several versions of these PAs found around the traps. Some PTH and some SMD versions as well as there being different band spreads. I was lucky to get a SMD variant, so it is a later unit (less dated) but one of the filter selection switching occuring in one of the ham bands. After studying the schematics, some changes will be happening soon to fix this. This will be used in the ham bands and the band selection switch will reflect this. So, with the filter modification table done, I hope to change the relevant parts soon and then re-test. More on this, when time permits.

Partial wiring done.

 Showing the inards partially  wired, including Tx/Rx changeover  relay.

Wiring almost done.

 The RF pad pcb in place and  clearly visible.

Trial fitment of cover.

 Fitting the cover and screw hole  alignment checks.

Initial front panel look.

 Getting an idea what the front  panel looks like.

DC input and RF output.

 The input DC lead and the RF  output socket.

RF and control input.

 RF input, band control and led  indicators.


VK5FQ website
12/02/14 Start build of new website.


Steph - VK5FQ
Adelaide, South Australia,