[Elecraft] HPS-1a Gamma Hybrid,Communications Power Supply

[Paul Christensen]

> It works at 100W SSB with 10-20dB compression.
> For CW at 20WPM you need to go down to 70W or so.

I've been testing the Gamma supply with my K3 on CW.   It works very well at 
95W down to about 15 WPM.  I rarely send below 20WPM and at that speed, the 
rig's full 100W can be expected.  Even with this limitation, it's a 
remarkable device, given its size.

I'm a bit leery of the over-voltage protection circuits built into these 
small supplies.  I added a Vishay 1.5KE15A 15-volt transient suppressor, 
reverse-based across the DC output (Mouser P/N 625-1.5KE15A).  The diode is 
in parallel with the DC output terminals but a series fuse is inserted just 
ahead of the diode.  This is essentially a zener crowbar device that upon 
reaching 15 VDC will conduct and blow the DC fuse before any damage is done 
to the rig (or one hopes!)

My only nit with the supply is that the AC line cord is hard-wired into the 
unit.  An IEC receptacle would have been a nice addition. But in all 
fairness to the designer, there's almost zero room inside the enclosure for 
the receptacle.  One alternative is to cut the line cord ~ 6-inches from the 
cabinet and add an IEC pig-tail.  This offers the benefit of being able to 
use an IEC RFI/EMI filter as part of a disconnecting pig-tail assembly.

Paul, W9AC
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