Re: BitX40 voltage booster implementation

Vic WA4THR
 

Did some testing today. Running the booster at 14v input and setting the output to 23v I could detect no discernible noise change either on a dummy load or on an antenna. Transmit audio was recorded on a nearby receiver and no added hash or other artifact was noted either. Idle current with no load is perhaps 10ma, so leaving it on all the time the rig is powered is probably no issue. I was reading power into a 450w metered dummy load, so accuracy was not great, but the power level seemed to be up to around 15w (not PEP) on steady AHHH into the mic, as opposed to close to 5 with the standard configuration. Makes sense, (23/14.4)e2 times 6w says I should see 15w in this setup. So this looks like a go, giving nearly an S-unit improvement for little effort.

As an aside, i can tell almost no warming of the PA transistor heat sink during these tests, something I was concerned about. I've been struggling to find a suitable replacement heat sink, keeping with my target of minimizing purchases and using mostly junk-box parts. I do have a potential heat sink that I can use, but it was designed for a different transistor case style so the surface I would use with this TO-220 case is somewhat rough, like a cast finish, and I'm not sure that is a good idea. With the results I've seen is a bigger heat sink really needed? What power level was this one designed for? I only intend to use SSB on this particular rig, too.

=Vic=

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