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:d...@nk7z.net>
*Sent: *Wednesday, July 21, 2021 7:43 PM
*To: *elecraft@mailman.qth.net <mailto:elecraft@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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