[Elecraft] In Line Power Pole Fuses

[Bill Frantz]

I'm in general agreement with Bob, but there are some details.

(1) You don't want to melt you power supply wires. If you trust 
the power supply device to properly current limit, then you 
don't need a fuse. If you are using something like my old 
solar/deep cycle battery supply, you definitely need a fuse.

(2) The important thing about voltage drop is getting enough 
voltage to the final amp in the radio to avoid producing all 
kinds of distortion in the output signal. This distortion 
results in a bad signal that causes interference with neighbors 
on the band. If you are running 14.5 volts receive load, you can 
afford a bigger voltage drop than if you are running off of 
batteries at 12 volts receive load.

In this latter case, you probably can't afford any voltage drop 
at all and should throttle back to a maximum of 50 watts or so 
to clean up your signal.

Our real-life experience was one Field Day with our QRP digital 
K3 station. The deep cycle lead/acid battery was getting tired. 
The people in the CW tent were complaining of interference from 
the digital station. A fresh battery fixed the problem.

73 Bill AE6JV

On 7/22/21 at 6:27 AM, rmcgraw at benlomand.net (Bob McGraw) wrote:

>With that power supply, which has both good over voltage 
>protection and current limiting, adding fuses in the DC line 
>will add resistance to the line.  Even being a small amount, 
>it will affect voltage regulation from no load to rated load at 
>the radio.    For this reason I do not recommend adding 
>fuses to the DC power cables.
>
>I agree that all 100 watt transceivers should have their DC 
>power leads connected direct to the power supply terminals and 
>not through any DC distribution device.    As a rule, 
>receive load to 100 watt CW/key closed transmit load, the 
>voltage drop at the radio should be less than 0.5 volts.
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Bill Frantz        | Art is how we decorate space,
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