[Elecraft] K3 Power Supply Question

[Harry Yingst]

I run an Astron 50 amp linear supply and a 4' cord between it and the K2
I see .6 of a volt drop on keydown at 100 watts






      From: James Bennett <w6jhb at me.com>
 To: Elecraft Reflector Reflector <elecraft at mailman.qth.net> 
 Sent: Thursday, March 9, 2017 8:09 PM
 Subject: [Elecraft] K3 Power Supply Question
   
Hi All -

I’ve been powering my station for anywhere from 7 - 9 years (can’t recall exactly how long!) with an MFJ4245MV switching power supply. I use it in conjunction with a 72 watt GE solar panel, 110 Ah AGM battery, ProStar charge controller, N8XJK Boost Regulator, and a KI0BK Low Loss PowerGate. All cables have been fitted with multiple mix 31 ferrite dounts with multiple wraps - I’ve got pretty much NO RF hash on any of the HF bands on the K3 or my KX3. All the above power equipment feeds into a Rig Runner 4008. Anderson PowerPole connectors connect to as short as possible #12 cable to several devices: K3, P3, KX3, PX3, KXPA100, and a home brew W6PQL 2 meter all mode amp.

Haven’t had any issues with the above configuration. Until today, when I happened to punch the K3 DISP button, changing it from reading my VFO B frequency to the other various bits of information. One of them was the rig voltage. Sitting there on 17 meters in CW mode receive it was showing a nice 13.8V. Cool. I hit the key and - wait a minute…… it dropped way down to 12.4v. Huh - not so cool. My first thought was that the Boost Regulator was not doing it’s job. But I decided to start trouble shooring at ground zero - the MFJ 4245. I disconnected it from the Power Gate and ran it directly to the K3. Key up = 13.8V. Key down = 12.0V. Yikes! I think (IMHO) calling this poor regulation (15%) would be a gross understatement. 

Am I wrong for expecting a desk power supply to do better than this? I had purchased this 4245 years ago because the price was right AND that it can run on 117 or 220 volts. At one time I had been contemplating a move to the Philippines and a 220v supply would be needed. By the way, nothing else running here in the shack other than a computer which was in sleep mode anyway, so line voltage sag likely is not the issue.

So, if this this a common problem with the MFJ stuff, what other 25+ amp supplies are folks using with their K3’s that have better regulation than 15%?

Jim / W6JHB







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