[amsat-bb] Re: Yaesu 847 power supply -linear vs. switching

tosca005@umn.edu tosca005 at umn.edu
Fri Feb 18 14:35:34 PST 2011

On Feb 18 2011, zach hillerson wrote:

 I purchased a Yaesu 847 for both satellite and HF work.  Since this is my 
1st base-style transceiver I am now in need of a power supply.  I was 
originally considering the Astron RS35M and am curious if linear or  
switching is the proper choice?  Is there a Amsat BB favorite between 
switching and linear? 
>Thanks for any help!


I've had my FT-847 for many years, and have used it both for satellites and 
VHF/UHF terrestrial work. (Very little HF, but some).

It has never "complained" about any properly working power supply it's been 
hooked to. These include an Astron 20 amp linear PS, an Astron 60 amp 
linear, an Astron 35 amp switcher, car battery plus vehicle alternator, and 
others when I've brought it out to Field day. Runs perfectly with any of 

In general, more power is better, because these amp suckers seem to 
multiply. My first PS, the 20 amp linear, worked fine with the FT-847, but 
when I added a linear amplifier for the 144-148 MHz band, the combined draw 
was too much. I've NEVER managed to draw more power than the 60 amp linear 
can provide, but it is an enormous pain (literally and figuratively) to 
pull it off its usual resting place in the shack and carry it up two 
flights of stairs to load into my SUV to haul out to Field Day. The 35 amp 
switcher has done a fine job for me, and the difference in weight is 
incredible, at least to a rickety old guy with worn out knees, like yours 

In fact, my FT-847 has NEVER refused to work for me, except for the time I 
set it up in a tent trailer for Field Day on a Friday afternoon, and a big 
wind storm came through overnight. When I arrived Saturday morning to 
complete final setup and get ready to operate, I found that the tent 
trailer was lying on its roof, with the FT-847's face planted in the ground 
and its back panel holding up one end of the tent trailer. At that point, 
the big knob on the front would not turn, but who could blame it? And best 
of all, the repairs cost $0.00! After Field Day was over, I brought it 
home, started a careful disassembly of the front panel, and discovered that 
the reason that the tuning knob wouldn't turn was because the steel 
sub-chassis onto which it was bolted had bent from the weight of the 
trailer on top of the radio. Some carefully-placed whacks with a big hammer 
fixed that. Put it back together and it's worked like a champ ever since. 
(I also used some toothpaste to polish up the scratches on the front face 
of the tuning knob, and you'd never know it had been treated so cruelly!)

In short, the 35 amp Astron (either linear or switching) will be plenty 
strong enough and reliable enough to power an FT-847 and a typical VHF/UHF 
amplifier, with power left over to run more small station equipment.

73 de W0JT

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