Tests were done today and the results are in… the DROK adjustable voltage regulator is a clear winner in my sBitx V3 radio. This is a simple multi-choice voltage regulator circuit that can be used on a whole host of applications. That row of SMD resistors across the top is for fixed voltage applications and then there is a small potentiometer in the upper corner for the variable voltage applications. I just dialed the potentiometer down to 5VDC and called it good… Let’s take a look at what I found today when I compared the results of the old voltage regulator to the new DROK regulator on the oscilloscope.
When you buy these little power supply circuits, they come attached to each other and you simple pop one off to get it out to use it. So I broke one off the set and soldered a set of header pins into it and then connected it to my homebrew variable bench power supply, then also to my HP 8840A/AF bench multi-meter and my Siglent Technologies SDS1202X Oscilloscope. This allowed me to vary the voltage applied to the input and to measure the output voltage as well as see what the quality of the output voltage looked like. Now, to be fair, I didn’t load either the original unit or the new one, this is simply static voltage output being viewed for cleanliness.
The below photo shows how it looks on the workbench when you have a power supply, a scope and a multi-meter all connected at once to a tiny little circuit board…haha.
I first connected the old one to see what it looked like on the scope and to be honest, it didnt look too bad at 13.8VDC. It has some noise on it, but it was not too bad. But then I thought, “You know, my truck power port is more like 12.4VDC so lets lower the input voltage and see what the waveform and output voltages look like. This is where things got real interesting. I found that the noise was akin to a sort of high frequency ringing and the scope could not get a clean trigger on it. So instead I turned on the persistence mode and then set it to a 1 second decay rate so it would build up on the screen and this gave me the visual that I could share that is relatable.
All of the input (13.8 to 12VDC) voltage adjustments that I did only changed the output a few milli-volts, it was so little change that I didn’t even bother recording it. I adjusted the output till I was at 5.0872 volts, this is only a 1.7% variation from 5 volts so I figured I would be good to go here. The original was off by more and it worked too, so there is also that.
The first photo of the oscilloscope screen is from the new DROK voltage regulator showing the output from the new board. The variation is less than 80mV as you can see the cursors are not right down on the waveform, so I figured it was close enough for what I was doing. Might have been 75mV if I had gotten really close… Adding the persistence to the waveform allowed it to fill the screen and gave me a bar I could more easily measure.
Below is the original voltage regulator with the supply voltage at 13.8VDC. I was intrigued by the fact that a higher supply voltage made the device work better. So my Astron RS-35M power supply was making it work better in the shack where I was trying to recreate the problem from when it was in the truck…lol. You can see how the wave form has grown with all the signals below the main area of concentrated garbage. With a 1 second decay rate the old wave forms would fade out after 1 second so it would not simply fill the screen with a yellow bar. I really like these new oscilloscope features. These are all in the megahertz frequency range too…
Below is what the old regulator looked like with the voltage reduced to 12VDC. Look at all that RF hash! What a terrible DC waveform… It has completely filled in the 1 second decay rate with trash. This measures about 137mV so if you do the simple math of 75mV and 137Mv you come up with about 50% reduction in RF hash on the 5VDC bus. That is a solid 3dB of noise that I removed or in ham speak a full S unit…(At least that is how I understand it). That is a pretty significant amount in my book and I for one am glad the email group found these devices and shared it with the rest of us.
I call this a win. If you have an sBitx V2 or V3, this is a worthy upgrade and it really is quite simple to install. You have to solder in some header pins (you can recover the ones in the old voltage regulator if you don’t have new ones like I had today) and simply plug it into the header on the main board and your done. Remove a few screws, unplug a few connectors, solder in four pins, unplug the old and plug in the new, reconnect the plugs (they are all different so you can’t put them back wrong) and put back the 6 or so screws and your done. Literally 20 minutes start to finish. I wished I had done it sooner knowing what I know now, I have had my DROK boards for a couple of weeks at this point…so sad… You can get them from Amazon for real reasonable money too. here is the link to Amazon if you want to get some for yourself.