My Icom radios come with the power cord fused for both negative and
positive. From what you say, I should remove the negative fuse if I
install
the radios in a vehicle. Now when the radios are at the fixed station the
same power cord is used (both lines fused), I understand that the negative
line fuse should also be removed.
The standard from UK is well worded:
"4.6.4. Negative Feed Connection
In the case of negative earth return vehicles, the negative power line
should not be fused. It should be connected to the vehicle body as close as
practical to the point at which the battery-to-body connection is made. Do
not connect the negative power line directly to the battery.
For heavy commercial vehicles (>7.5Tonne GVW) only, and those vehicles with
tilting cabs where the cab may be isolated from the chassis by rubber
mountings, a ground point is provided by the vehicle manufacturer within the
cab to provide battery to cab grounding. Generally this is located within
the main fuse box. It is recommended that this point be used for
installations in this instance. With certain equipment it may be necessary
to connect the negative supply line to a local earth point. In this case an
existing vehicle earth point must be used."
I just went through terrible problems with an aftermarket EFI system that
insisted on a battery negative connection. It never worked properly until I
used the vehicle chassis as the negative.
I regret now, after years of experience with problems, ever following the US
and Japanese standard of using a battery negative pole or terminal, and not
the vehicle chassis. I still, because the warnings to use the battery
negative were so strong in an expensive EFI system, I followed it (knowing
better) and had a ground loop noise problem right away.
I've damaged radios and accessory equipment several times over the years,
and the ground loop also makes common mode noise and audio hum and noise
problems worse. I used to buy into the common advice, because I never really
thought about it. No negative fuse holder for me, and no negative battery
post connections for me. My three wire plug shack power supplies have all
been modified now, and no longer have a ground loop from mains or station
ground to the negative power lead.
The UK standards have it correct.
73 Tom
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