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Noon question now noob question

Bill Cromwell
 

Ahem,

Fuses were not developed because of one mistake that one person made 125 years ago! Get and install the fuse as close to the power source as is practicable. The kits do not come with a fuse nor a fuse holder. They are not expensive. Just do it.

73,

Bill KU8H

Retired Firefighter

On 4/10/20 7:00 PM, Evan Hand wrote:
Different Hams have different views.  One of the RF Engineers on this board does not use fuses for anything other than keeping a fire from happening.
I would recommend a fuse more than 3 amps and less than the wire size can carry that you are using to power the rig. I use 3 amps, and it has saved me a couple of times that my fat fingers sauced a short that could have taken out some other components.  You diffidently want a fuse IF you are putting in the reverse voltage protection diode across the supply lines as the HF Signals assembly instructions suggest.
73
Evan
AC9TU
--
bark less - wag more

Ted
 

I will second Bill's assertion.  A fuse does not prevent the magic smoke from leaving your radio, though it's blowing "might" mitigate further damage if you're lucky.

A fuse keeps your house or car from suffering the same fate as whatever went wrong in your radio.  Period.  FWIW, I use a 4 amp in my field build and a 6 amp in the mobile [with 20 volts on the finals].

Ted
K3RTA

Don - KM4UDX
 

Ahem -- You can take Bill Cromwell's guidance to the bank. 

I used a 3amp fuse, and discarded the diode.  The way I figure it, every single power source in my house (and my zip code) has center pin positive (+) and the sleeve or shank or outside is negative (-).  So I have no fear of reversing the power. 

But I do have well founded fear of screwing things up, so the fuse is essential protection from fat fingering, lapse in judgement, intemperate decision making, lack of impulse control, or nature's choice of the moment to humiliate you (me).  If there is a wire or screwdriver or plug that can go where it shouldn't, then the cosmic forces of nature will ensure it goes there. It's like my daily dose of humiliation. 

So fuse up and get on the air.

By the way, when you get there, your uBITX is a perfect radio to send digital (sound card-based) modes. The native 10W will do wonders to get your around the world when conditions are good.

Don
km4udx

Arv Evans
 

The fuse is there to protect the power supply in case your radio develops a short!  8-)

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On Sat, Apr 11, 2020 at 3:03 PM Don - KM4UDX <dontAy155@...> wrote:
Ahem -- You can take Bill Cromwell's guidance to the bank. 

I used a 3amp fuse, and discarded the diode.  The way I figure it, every single power source in my house (and my zip code) has center pin positive (+) and the sleeve or shank or outside is negative (-).  So I have no fear of reversing the power. 

But I do have well founded fear of screwing things up, so the fuse is essential protection from fat fingering, lapse in judgement, intemperate decision making, lack of impulse control, or nature's choice of the moment to humiliate you (me).  If there is a wire or screwdriver or plug that can go where it shouldn't, then the cosmic forces of nature will ensure it goes there. It's like my daily dose of humiliation. 

So fuse up and get on the air.

By the way, when you get there, your uBITX is a perfect radio to send digital (sound card-based) modes. The native 10W will do wonders to get your around the world when conditions are good.

Don
km4udx

MadRadioModder
 

Attached.  Stop blowing stuff up…

 

 

 


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…_. _._

Bill Cromwell
 

Hi,

There are several reverse polarity schemes that can protect the radio from damage in a reverse polarity episode. That is an episode of connecting DC power source with the positive and negative switched. Those are worthwhile to protect the radio gear. Any of us could do that at any time. That is not what fuses are for.

Reverse polarity is not the only thing that causes excessive current flow (shorts). The reverse polarity scheme is not going to keep an overload from burning your house down - maybe with you in it. An appropriate fuse will. They are cheap and easy. Cheap too, Easy too. Inexpensive, too. Uncomplicated, too. Is that clear enough? Please install fuses so we won't have to read about your untimely status as a silent key. Go ahead and operate without reverse polarity protection if you desire. It IS your gear.

73,

Bill KU8H

--
bark less - wag more