DC Power Supply

The power supplies, switching or linear?

By Pascal VA2PV

Written in French in 2003 for Radioamateur.ca

rs35mfp-1023

Recently I had a problem with my old PSU (power supply) 13.8 Volts. So I had to replace it quickly in order to be operational. Since I was on vacation and it was -25C outside, the problem was more urgent as I had nothing to do. So I took the road to the nearest ham radio retailer to buy a new one.

I was always told that “switching power supply” could cause RFI (interference) problems to our receivers. Following this information, I opted for a traditional power supply (linear) 35 amps. The weight of the equipment was 27 pounds! Arriving at the QTH I unpacked the monster and I made the necessary connections to reactivate my station. It was an excessively noisy power supply, especially when I asked him for 100 W. My 1kW linear amplifier was practically less noisy? Dissatisfied, I returned to the dealer with the “power supply” in order to replace it with a new one and hope it would be less noisy. Once there, the second power unit was as loud as the first.  When I say loud I’m talking about vibration.

Since my audio matters to me I absolutely do not want any ambient noise in the “shack”. I’m also concerned about the fact that my PSU must be designed for my radio. Unfortunately, the manufacturer of my device no longer manufactures linear power supplies, it produces only “switching” models. I then asked the question, how a type of power supply “switching” could affect my RF signal?

It seems that it takes a high-precision spectrum analyzer to see a faint trace. Knowing an operator (VE2MTK) which operated with this type of PSU, I decided to give the “switching”PSU a try, so I pick up a Yaesu 23 amps continuous. In addition, it was $ 100.00 less than the linear model and its weight is only 3.5 pounds.

After operating for nearly 10 hours with this power supply, I was very satisfied, no interference in my radio set, extremely quiet and it stays cool!

After some Internet research here are the differences between the two types of power supplies:

Conclusion

This was my 2002 review, but today the switching PSU are all over the place and the work very good for ham’s as long as it of good quality.   In 2016, I have to Astron linear PSU in the shack, a 20 amps and a 35 amps, I modified both with rubber bushing so they do not vibrate.  I’m very happy with it.

73 de Pascal VA2PV

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Author: Pascal VA2PV