power supply


hello i am preparing for the arrival of my ubitx  and whilst i have a 35 amp power supply for my shack i think it would be best to have a lower rated supply for the bitx. i have a few ex laptop supplies, should i modify one of these  . if  use the bitx away from the shack i plan to use 11.1 v lipo batteries, but i  need something slightly less powerful  for shack. use any ideas would be great    dave c  gw0nvf.

Doug W

why not just use your shack power supply with a fuse?

Evan Hand


I would look into a buck boost supply that can supply 3 amps.  This would work with both power supply options.  The potential disadvantage is the possible HF interference from the switching nature of the device(s).  I had read here that some included an LC filter after the supply to overcome this disadvantage.

The buck boost would allow a constant 12 vdc to the rig.  Though the finals are not that fussy (could run the 19.5 vdc direct from the laptop supply) the main board is.  It really should stay around 12 volts unless you start adding heat dissipation to the Raduino regulator.  I found that higher than 12.5 volts the regulator got very hot.  I am supplying 13.5 volts, I added a heat sink to the regulator, AND dropped the voltage to the main board  through 2 1n4001 diodes.  The diodes are not in the circuit to the finals.  

If you run higher voltage to the finals, you will need to beef up the heat dissipation.  Most have just added a fan to run when transmitting to conserve power.  Not needed if you feed the rig with 12 vdc as designed.  You could wire the circuit to run the fans when on the laptop supply and not when running from battery to conserve power.

There are quite a few buck boost supplies on the web.  A lot of bear bones with adjustable voltage are available for under $2 each in small quantities (2-8).  The devices with built in displays run more.

The above are my recommendations, and may be in error.  I would verify and test.


Ian Reeve

The ubitx  or bits does not need more than 2 amps but crucially no more than 12v for the supply voltage.The supply you have can be used as long as it can be reduced to 12 v or slightly less, 13.8 volts is too much.I use a 12 v battery or a 19 or 20 volt computer laptop supply which tend to be well regulated and noise free.A suitable voltage regulator than be bought easily to reduce down to 12v.If you can find a 12v laptop supply you have a neat reliable solution.

From: <> on behalf of Doug W <dougwilner@...>
Sent: Monday, August 19, 2019 2:28:17 PM
To: <>
Subject: Re: [BITX20] power supply
why not just use your shack power supply with a fuse?


Yes a low amperage fuse for now. There are many linear power supplies well under 10 amps on the planet, likely you can find one at what you in the UK refer to as a rally.

I have a little mfj switching supply, and I imagine some have homebrewed one similar.

Enjoy your build.