IRF510 more Volts = more W? #ubitx

Rob Snow

I'm following this with lots of interest.  I still don't have my uBITX and probably won't until March or so.  My personal goal is for ~10W out 28MHz, preferably with some headroom if I wanted to push it or just for a margin of error.  To that end I've ordered extra IRF510s and some RD16HHF1's as I have poor magic smoke herding skills and even poorer PA skills!


Nick VK4PP

Maybe the bias needs re-adjusting for 24v operation?
I really dont know much about the technical operations of these things, I am still learing...
I am tempted to replace the Electro caps with 35v versions and try maybe 30v in the PA... I have spare IRF510s... lol.


Very odd, but I am now seeing the same thing on my BitX40v3. On the test bench I was seeing what looked to be an output that increased by the square of the PA voltage ratio, but since packaking, shorter leads, some common grounds, I actually see the same or even less output at 24v than at 12v (or 13.8). I must have some wiring issue, but I did directly jumper the 24v to the PA and saw no difference, so ??


Nick VK4PP

I did this last night with the uBITX, went from 13.8 to 24v. and only saw an increase of +-2w.

80m 24v=12w 13.8v=10w
40m 24v=7w 13.8v=9w
20m 24v=3w 13.8v=4.5w
10m 24v=1w 13.8v=2w

Also cause weird display glitched during TX....

Doug W

If you access the list from instead of an email client you will have access to the search function.  Searching for irf510 24v will yield enough reading to keep you busy for a while.  Best of luck with your experimenting.  Should your quest result in releasing the magic smoke, fear not, a search for irf510 replacement will get you back to good.

Jim McKay

I could not find the answer on the forum but I apologize now if it has already been answered. Noting the need for an improved heatsink/s. Has anyone done any experiments with increasing the PA voltage  (brown wire) up 24V to see if the output significantly increases. I did this with a BITX40 for a significant increase in W.