Getting “stuff” from ham suppliers has been spotty the last 12 months. Things that you could simply order and have delivered a few days later are in short supply. I’m not talking about radios, but ordinary commodity items, like antenna tuners, coax and power supplies.
In February, I was still assembling my station and decided that my trusty twenty year old MFJ-4225MV wasn’t going to cut it when powering multiple radios. I’ve had really good luck with this power supply, so it was still going to be used, but I decided to order a new power supply from MFJ to supplement. I’ve been converting my shack to use Anderson Powerpoles, so I wanted a power supply which had the appropriate jacks. I order two MFJ-4230MVP’s.
And I waited. And I waited. After about two weeks, I inquired about my order. I was told they were out of stock, but were expected any day. So, I waited. And I waited. After another couple of weeks, I inquired again. This time I was told they were sitting in a cargo container of the Port of Los Angeles, but they were due to be unloaded within a few days. So, I waited. And I waited and I waited some more. By this time, it was approaching two months since I placed my order. I repeated my inquiry and was told there was no ETA at the time. I asked for a refund.
By now, I was in real need for additional power for my shack. I started searching for other places which carried anything that would my meet my requirements; at least 25A continuous, some sort of meter to tell me the voltage and amperage and, of course, Anderson Powerpoles. I searched in vain. There was simply nothing available from any manufacturer or distributor.
So I did what all resourceful hams do; I searched the internet for homebrew options. That’s when I came across all sorts of articles on bitcoin mining and how miners were making 12V, 60A+ power supplies from surplus, computer server, hot-swappable power supplies. And they were cheap too!
The typical computer server power supply puts out 12.3V at about 760Watts – continuous. That’s 62.5 Amps! And because the are used in equipment that is very sensitive to noise, their output is very clean. Buy one of these and with a little modification and a few external components, and you have a highly reliable, clean 12V power distribution system. Here is a picture of mine.
The silver block on the left is the power supply. It’s made by Hewlett Packard, so it is made to very high standard of quality. 120VAC is fed in through the bottom by a standard electrical connection. I added an 18″ extension which has an inline switch and a right angel adapter so the cable would exit the side and not the bottom. The output is fed through a powerpole cable into and Powerwerx Watt Meter. From there the power runs to a smart, 8 powerpole, individually fused power port distribution block.
The power supply does require a slight modification. You have to solder a 470ohm, 1/4 watt resistor between two of the pins on the external connector. It’s not hard, but it’s beyond the scope of this blog post. Search Youtube for this power supply and you’ll find dozens of diy videos on how to do this. If you’ve never soldered anything, ask your Elmer or some of your ham friends to lend a hand.
All of this is mounted on a nice plywood base from Hobby Lobby. I added the single drawer pull for easy carrying and the door pulls for protection and a place to wind the power cables.
How does it perform? Well, at 2021 field day it was in constant use for the entire length of time, powering an IC-7100 running FT8. Nominal, unloaded voltage was shown to be 12.3V. At a 50% duty cycle, we never had a problem and the voltage never dropped below 12.19V during transmit.
Many of you will immediately think “Most radios expect to see 13.8V nominal; 12.3V will result in lower output.” You’re are correct. 40 Watts on the transceiver shows as 36 – 37 watts on the SWR meter. That’s not too bad and is 12.3V is well within the requirements 11.7V minimum specified by Icom for the IC-7100.
But if you’re like me, you would like to make that 12.3V by 13.8V. That’s what the next article is about.
Component List
- Powerwerx Watt Meter-PP, DC Inline Power Analyzer, 45A Continuous, 12 Gauge with Anderson Powerpole Connectors
- Chunzehui F-1008 Horizontal 9 Port 40A Connector Power Splitter Distributor Source Strip
- HP 750W 739254-B21 742516-001 Common Slot Platinum Hot Plug Power Supply
- Pandora – Pull Bar Handle SOLID Stainless Steel For Drawer Kitchen Cabinet Hardware – 12 inch
- Rectangle Wood Blank Canvas – 10″ x 12 7/8″
- IEC C14 to C13 Power Adapter PDU Plug/Socket Up 90 Degree for LCD Wall Mount TV 2 Pack
- Toptekits PDU UPS Power Cord Cable 100-250V IEC-320-C14 to IEC-320-C13 Power Cord M-F with Switch 1ft/30cm