I have personally run the Astron SS-18 for hours on end with a 20A test load. It barely gets warn and doesn't seem to care. This is the exact same power supply that TenTec sold with several of their 100W HF rigs. I usually over specify power supplies but in reality most people use HF radios on SSB or CW and the duty cycle is low.
There is a completely new trend in power supplies for amateur radio where you would have around a 5A switching supply and 15 to 30 Farads (yes, Farads) of capacitance at the output to handle voice and CW peaks. These power supplies are very small and lightweight for travel and seem to work just fine with 100W SSB radios even though they can only do about 5A continuous duty.
prcguy
QUOTE=kb2vxa;1015237]20A is cutting it a bit fine for the Mark, it does 100W of FM which means a 100% duty cycle and a baby supply can easily overheat and go poof. I recommend at least 30A continuous which should give you a minimum of headroom. Check the manual to be sure what it's actual power drain is, I don't recall offhand and double it if you want to be sure.
A word of caution, no old buzzard transmissions at full output regardless of the mode! Being so compact even with the fan running it tries to defy the laws of thermodynamics, gets pretty darn hot with that rather undersized heat sink. Be sure to use with adequate ventilation, if you touch the back and burn your fingers give it a rest.
Let's not get all technical with antennas and tuners, he's still wet behind the ears so give him a break. I'm pretty sure he'll start with one of those put it together and put it up 2M/70cM antennas and hopefully some RG-213 or LMR-400 coax, we'll find him on the repeaters soon enough. You don't feed a baby steak and potatoes, let him get some teeth first.[/QUOTE]