[Elecraft] Elecraft Digest, Vol 146, Issue 28

[Howard Hoyt]

Hi all,

It is true that for fixed operation, weight and size would not be a 
factor.  For portable operation both are critical, and a true 3A 14V 42W 
linear supply is neither light nor small.  Even the 2A 12V (24W) linear 
supplies we have evaluated are over 32 ounces, are low duty-cycle, and 
very poorly regulated to boot, not to mention incapable of driving a KX3 
to full power.  Most amateur radio equipment such as the KX2, KX3, K3S 
etc are optimized to operate with 13.8V nominal to achieve low IMD at 
full power in the PA stage.  Under full load most 12V wall-wart supplies 
will deliver ~10-11V with a lot of ripple.  As many are commenting, 
switching supplies can contribute quite a bit of RFI, and many have VERY 
poor voltage regulation on load dump, as when you drop out of transmit 
to receive.  At least one report here on this list has blamed 
destruction of their rig on this type of supply flaw.

(commercial content) This situation was the driver for developing the 
Pro Audio Engineering Kx33 supply.  It is small, weighs ~12 ounces with 
AC cord, can deliver 14V at 4A continuous (56W) and is extremely 
low-RFI.  It is very popular for portable operation with the KX2 & KX3 
for these reasons.  Please check the website for more info if you are 
interested.

Cheers & 73,

Howard Hoyt - WA4PSC


On 6/20/2016 1:33 PM, elecraft-request at mailman.qth.net wrote:
> I
> have had my kx3 for three plus years and have been on many lists and most
> everyone wants a smps instead of a small 3 amp linear supply. Radio Shack
> and many others made these supply's and they are plentiful at Hamfests for
> 10-20 USD. It seems like a lot of folks operate from home and want a smps .
> Why, if the weight would not be a factor, do folks want to take a chance on
> a potentially noisy ps ?