The all-important power supply is a lot like an antenna. Use anything and it will work! Well, that belief and statement have a good chance of starting you off on a wrong foot for both antennas and power supplies. These two elements typically are given no consideration, and the result is often poor performance of the radio.
A typical advert from a supplier who resells manufacturer overstock starts with 12VDC at 30 Amps open switcher all for $9.95 shipped. The price is certainly less than a Big Mac Meal at Mickey D's but should also give rise to an acid stomach. Too Good To Be True has a prophetic ring to it!
Power supplies commonly used with solid state equipment broadly fall into two categories: 1) Linear Supplies and 2) Switchers.
The Linear supplies are the old transformer rectifier kind and are often heavy. I have a Astron 35 Amp Linear supply you never want to drop on your toe. A Switcher uses that old back EMF principle to take the decay of a pulsed inductor field to create a series of high frequency pulses that are rectified into DC.
Switching frequencies may be as high as 50kHz and that is a problem. The issue of 50kHz frequency is much like sitting next to a spark gap transmitter. I had a homebrew SDR radio installed in a computer I refurbished and all along the spectrum was a blip every 50 kHz. One thing I didn't change was the computer switching power supply -- the culprit. I could also hear that computer switcher on my KWM-2.
The switchers, often open frame, are not shielded, and value engineering has minimized components that would mitigate the hash! A 360-Watt DC supply for $9.95.
For my QRP SDR radios I use a 5 Amp Linear supply from Pyramid available from Lauren Sanchez's boyfriend (Bezos). About $50.
Note about 5000 purchasers have given it a 5 Star rating. I bought mine a couple years ago and it was around $38. I use this and do not worry about noise.
But there are some switchers that pass the smell test and the 13.8 VDC @30 Amps Samlex Switcher is at the other end cost wise with a clean output. Inching toward $200. Small too!
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In another failure by me was to buy this 0-30VDC at 10-amp switcher that had features like LCD display, coarse and fine voltage/current adjust as well as current limit. I made a poor assumption since it was in a metal case and lot more than $9.95 that it would be clean. A scope on the output quickly proved that was a bad choice.
So, from my vantage point unless you head for a high end Samlex then a 5-to-10-amp Linear supply is a good choice for a bench supply costing about 1/2 the Samlex price.
An additional consideration is a linear variable supply where I homebrewed one of those that I use to test new circuits. Basically, I am trying to not smoke a device at power turn on. By inching forward in small voltage increments you can spot when a voltage limit is being reached before a total smoked part.
TYGNYB!
73's
Pete N6QW