On 10/9/2017 9:00 AM, Rick WA6NHC wrote:
Overall, not a great plan.
Using an inverter, you will introduce RF noise, generate heat and poor
regulation,
I've used "good" ones (Samlex "pure sine wave" with FCC Part 15 Class B
certification) and they ARE NOISY. Using a lot of ferrite cores got
their smallest one (100W) quiet enough on 40-6M to run the logging
computer for a CW QSO party mobile operation.
If you use a power port (no longer called cigarette plugs), you will
again introduce noise for your radio because they seldom have decent
chassis bonding.
Chassis bonding is NOT a solution to noise in a vehicle. Noise does not
come in on the power wiring, it comes in on the ANTENNA. Indeed, there
is no good reason to bond a radio to the chassis of a vehicle.
They are also low amperage capable and you can exceed that (check the
owner manual or the fuse block), even if momentarily. Often they are
also part of the vehicle systems array, so you'll get noises and
generate issues to/from the vehicle electronics, some of which are
rather spendy to repair.
Many of the systems in a vehicle can generate noise, and some can be
quite sensitive to RF. One of the on-board computers in my Toyota
Sequoia (big SUV, same as their pickup) went into "limp home" mode when
I called CQ on 20M with 100W into a Ham Stick mounted to rear side rail
on the roof. Top speed became 15 mph. I learned this while driving I-80
through the Nevada desert between Salt Lake City and Reno. Not a great
place to break down. I got running again by pulling the positive lead
off the battery and reconnecting it, which rebooted the victim computer.
But this is an RF problem, NOT a power problem. When we run mobile, the
only chassis bond that matters is the bond of the coax braid to
conductive parts of the vehicle at the antenna. This provides the
antenna with a counterpoise -- that is, the vehicle becomes a very
necessary part of the antenna. This causes RF current to flow on those
conductive parts of the vehicle chassis and body -- IF those body parts
are connected together. And that's a BIG IF, because most body parts are
insulated from each other by PAINT!
In the long run, it's best (and least expense) to simply run the
(fused at both ends, both wires) power cable to a known, chassis
bonded source. Power is NOT a place to cheap out. If you're QRP,
it's simple, the wires aren't huge, check your IR^2 losses over the
run (make sure there is no voltage drop AT the radio).
I agree that I wouldn't power anything bigger than a talkie or receiver
from a lighter plug. FAR better to run a beefy copper pair directly to
the battery. NEVER, NEVER use the vehicle chassis as a return for DC.
Doing so causes the positive lead to form a large magnetic loop with the
chassis return, AND causing it to act as an antenna.
Hint: Make sure EVERYTHING, power at the source, power at the radio,
the radio itself AND the antenna are properly RF bonded (not DC) to
the vehicle and you'll have less issues
Again, the radio is NOT the sensitive element here, it's the ANTENNA,
which includes the chassis and other conductive parts. It IS important
that -12V be bonded at the battery, but it is NOT useful to bond the radio.
73, Jim K9YC
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