[Elecraft] In Line Power Pole Fuses

Thu Jul 22 09:25:45 EDT 2021

Hi Ray,

Are you currently using a 25 amp?  If so, have you had any issues with 
that, and are you running P3/SVGA, etc?

25 amps seems quite close to the rated current draw of the K3.  I 
believe the K3 can draw 22 amps on full power, and as Jim said, other 
items all add up.

I also mentioned that the fuse is not there to protect the radio, but to 
stop other issues, and that I place the fuse as close to the PS as 
possible to protect the most part of my power wiring.

So for me 30 amps, seems OK.  If I get a PS short, a 30 amp fuse will 
blow almost as quickly as a 25 amp fuse, and that is what my main 
worries are, shorts caused by stupid mistakes on my part, or problems 
within the equipment connected to the radio.

As I mentioned, if the fuse is blowing, and it is a result of radio 
current overdraw, chances are the radio is already broken.

73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources

On 7/21/21 10:31 PM, Ray wrote:
> 30 Amp   --- A little too High for me !
> 
> I would use 25 Amp.
> 
> WA6VAB  Ray  K3
> 
> *From: *Dave <mailto:dave at nk7z.net>
> *Sent: *Wednesday, July 21, 2021 7:43 PM
> *To: *elecraft at mailman.qth.net <mailto:elecraft at mailman.qth.net>
> *Subject: *Re: [Elecraft] In Line Power Pole Fuses
> 
> Hi,
> 
> I am unsure what you are asking...  If you are asking about fuse values,
> 
> I select values a bit above the max peak current I expect.  For my K3 I
> 
> use a 30 amp fuse.
> 
> If you are asking about voltage drop, and want to know what the K3 sees,
> 
> there is a built in volt meter in the K3, (see the manual), which will
> 
> show you the voltage at the K3, after all your fusing, and wiring.
> 
> I always take my voltage readings at full output.  I try and stay within
> 
> the limits Elecraft sets for voltage.  If I am running low voltage on
> 
> transmit, I goose the power supply slightly, staying below the max
> 
> voltage rating Elecraft recommends when not transmitting at full power.
> 
> The fuse(s) is/are probably not going to protect my radio-- if something
> 
> happens, (i.e., current draw in excess of 30 amps), the radio is
> 
> probably already broken.
> 
> I use the fuse to reduce runaway thermal effects, (read that as fire),
> 
> on my power supply wiring in the event of a short to ground.  I place
> 
> the fuse(s) as close to the power supply as my wiring will allow.
> 
> 73, and thanks,
> 
> Dave (NK7Z)
> 
> https://www.nk7z.net
> 
> ARRL Volunteer Examiner
> 
> ARRL Technical Specialist, RFI
> 
> ARRL Asst. Director, NW Division, Technical Resources
> 
> On 7/21/21 7:18 PM, Peder Kittelson wrote:
> 
>  > I have fused my Elecraft radio equipment with inline power pole positive
> 
>  > and negative ATC car standard blade fuses.
> 
>  > I am now doing an audit of the fuses in my system to make sure they are
> 
>  > appropriate for the equipment they protect.  I realize there are internal
> 
>  > fuses in many cases, I prefer doubling my protection with inline external
> 
>  > fuses as well.
> 
>  >
> 
>  > I have not read or heard anyone discuss the appropriate amperage 
> ratings of
> 
>  > fuses for my equipment or equipment in general.  I would appreciate your
> 
>  > recommendations on fuse sizes for these, as well as general approaches.
> 
>  >
> 
>  > Equipment and Specifications from Elecraft Manuals:
> 
>  >
> 
>  > 1.  Elecraft K3s with 100 watt amp: Specs are 17-22 amps typical on
> 
>  > transmit, recommended 25 amp power supply.
> 
>  >
> 
>  > 2.  Elecraft KPA 500: Specs are PA Current 20 amp maximum.
> 
>  >
> 
>  > 3.  Elecraft KX3: Specs are 1-2 amp typical current in transmit.
> 
>  >
> 
>  > One other important question.  I have conquered much of the RFI in my 
> radio
> 
>  > room using power poles with extended thick Red and Black wiring wound
> 
>  > around toroids.  In this case the leads go from the Astron RS-35A to the
> 
>  > K3s.  I want to make sure there isn't too much drop in voltage over the
> 
>  > extended toroid wiring.  How can I best gauge what the K3s receives 
> in this
> 
>  > setup? The manual says it should receive 13.8 volts nominal, 11 volts
> 
>  > minimum and 15 volts maximum. I think I am beyond the provided and
> 
>  > recommended 5' power cable.  I have not had any problems (that I know 
> of).
> 
>  >
> 
>  > I do not have a desk full of electronic devices for evaluating this, 
> so is
> 
>  > there a simple way to be reasonably sure?
> 
>  >
> 
>  > 73 and thanks for your help,
> 
>  >
> 
>  > W7RPK, Peder
> 
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