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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