[Elecraft] Taking the K2 in theauto ...

[Gregg Lengling]

I think I've posted to this group before about power wiring in vehicles.
I spent over 20 years in the 2-way radio business and have installed
thousands of mobile radios.

#1 Don't use cigarette lighter plugs on anything that takes more than 3
amps current.  If you do make sure you use a good quality plug.  Some of
the cheap ones have only 1 ground finger and a very small positive pole
area.  As power is drawn the connection heats up and the voltage drop
continues to get higher, thus resulting in lower voltage, more current
draw and more heat until you eventually melt the cigarette lighter plug.

#2 When direct wiring to the vehicle fuse the positive lead at the
battery.  This will protect the wiring if a short occurs anywhere in the
engine compartment or when transitioning the firewall.  Yes some of the
radios are supplied with a full negative lead cable enabling you to
connect straight to the battery (with fuse) and as mentioned this fuse
if very important to protect the equipment should the vehicle battery
ground fail...HOWEVER...I would never wire directly to the battery.
This is a sure way to induce alternator noise and ground loops to the
radio system.  Here's why-----

A vehicle battery is grounded to the engine.  The engine is grounded to
the frame.  The frame is grounded to the body of the vehicle.

Now in this case when powering the negative from the battery you have 3
different ground potentials.  The power to the battery.  The radio to
the body.  The antenna to the frame or body.  This sets up voltage
differences in the ground system due to the different ground potentials.

Ground the radio with a short ground lead to the body as close to the
physical ground of the radio.  This will limit the amount of noise
pickup and differences in ground.  I have found many hams that wired
directly to the battery with the ground and ended up with tons of
alternator noise, which they then tried to clean up with a choke.  While
the choke removed some of the noise, it also added resistance to the
power lead and lowered the available voltage to the radio.  By properly
grounding the radio after my suggestion they found they could remove the
choke and have a cleaner power feed.

Just remember Kirchoff's law!!!!


Gregg R. Lengling, W9DHI, Retired
Administrator http://www.milwaukeehdtv.org
K2/100 S#3075
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