[Elecraft] K2/100 Power Needs

[Ron D'Eau Claire]

K2 Group,
Would someone advise whether my Astron RS-20M power supply will handle a
K2/100 with some basic SSB/DSP accessories?
Thanks,
Stu, K2QDE

------------------------------------

Runs mine just fine with "room to spare" in the supply capacity. 

Since you brought up the question of power supply capacity, let me address
an issue about power supply ratings, especially the Astron power supplies,
that has created confusion among many users. 

The Astrons are rated for Intermittent Commercial Service (ICS) -- OT's will
know this as ICAS, Intermittent Commercial and Amateur Service but they
dropped us from their acronym. That causes some to say we should never
expect 20 amps from a "20-amp" supply. That's nonsense. 

You *will* overstress the Astron 20 if you set your K2/100 at 100 watts out,
put a brick on the key, and walk away for an extended period of time. That
is, you'll overstress the Astron unless the K2/100 emits smoke and quits
first. Neither is rated for full power continuous duty operation. Operating
100 watts CW or 100 watts PEP SSB stays comfortably within the ICS rating of
the Astron 20 supply. 

On many bands the K2/100 at full output stays comfortably within the 16 amp
continuous duty ration of the 20 Amp Astron (the overall efficiency of the
K2/100 varies with the bands, being best around 40 meters). When you derate
your K2/100's maximum power output for high-duty-cycle data modes to keep it
within specs, you are also reducing the current demand on the supply to keep
it within specs too. 

Shoot, I even run my K3 and a few bits of accessories from my Astron 20 with
no problems at all. My only concession is that on one or two higher
frequency bands, where the K3 current level is higher than others, I run the
power at 75 or 80 watts, max., to keep the Astron's self-protection
"crowbar" circuit from tripping. Of course the difference in transmitted
signal between 75 and 100 watts is meaningless anyway, so I don't mind. 

The Astrons are very well self-protected against shorts or very large
over-current loads with their "crowbar" circuits. If you've never
encountered it at work, should you exceed the crowbar trip point (IIRC, it's
about 25 amps for the Astron 20) you'll suddenly lose voltage to the rig.
The supply automatically shuts down to protect itself. Cycle the Astron
power switch to reset it and you'll have full voltage back as long as the
overload is no longer present. 

Ron AC7AC