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Not enough juice

Captain Kilowatt

Professional Amateur
Staff member
Apr 6, 2005
Nova Scotia,Canada
The fact that you are showing over 2 volts dropped at the power supply output proves that you are drawing far too much current. There is no way the input should drop enough to lose regulation like that. Get a BIGGER power supply and for God's sake get rid of the extension cord. That is the other half of your problem. Nobody makes an extension cord that is commonly available that long that can PROPERLY deliver the required current without a serious voltage drop.


Sr. Member
Jan 28, 2008
The Netherlands
Alwways calculate with headroom.
My ham station runs on a dedicated 230 volt 50 Hz line in the house with 16 amp breaker.
That is 3680 watts raw power from the net available for the ham station alone.
It runs a 30 amp supply for the Yaesu FT991A, again overcalculate amps for the radio (max the radio uses is 20 amp) the Heathkit SB-1000 runs 1000 watts out with new 3-500ZG tube after complete rebuild so i calculate 2000 watts in .....
Some other bits and bobs connected to that line so max use is 2000 + 500 for psu + 500 for other stuff = 3000 watts.
No sagging of any voltage here full output, nothing getting warm as well.

20% overcalculation does that.


Well-Known Member
Jan 29, 2006
IMHO, You need to run a subpanel off your main panel.

Hopefully, you are using a 50amp Astron for the radio since it can pull 45.6amps on SSB. A 50amp Astron needs 8.2A @ 120v full load. Your 150A Fatboy 14.5v PS goes up to 15.5v@150A = 2325w so figuring in inefficiencies, you will want at least 3000w available for it. So a 25A or 30A 120v breaker for the Fatboy and at least a 10A 120v for the Astron. Figure on 30A @ 120v per hot to be on the safe side. 100' @ 30A @120v = 6 gauge copper or 4 gauge Aluminum (3% v. drop). Code requires a 4 conductor feed, the ground can be smaller, so 100' of 4-4-4-6 Aluminum should do the trick. You'll have to buy a ground buss for the Subpanel because they don't come with one (go figure). Also put the 25/30A and 10A breakers side by side in the subpanel so they are on different hot feeds. Use a 30A DP breaker in the Main panel to feed.

NOTE: if the 8 pill is a class C, there is a good chance that 150A@14.5v isn't enough. If that is the case, you will need to put a High Output battery in line with the DC. A LTO battery @14.4v (6 x 2.4v cells in series) would give you the response that you need to handle SSB peaks. A 16v 500F super capacitor will also handle the SSB peaks.

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