My RV has a 3 KW inverter; I've not noted noises from it on any band but
it was NOT cheap and it has it's own battery supply (not the house
battery) and the radio has it's own battery supply. There is no
physical contact, only proximity.
We're not in disagreement here but we're approaching it from different
angles (you have the formal training, we both have some experiences).
My rule: Bond EVERYTHING to the chassis, including chassis elements to
each other (paint is a pretty good insulator). While that does have a
*small* effect on noise (the every wire IS an antenna consideration);
mostly bonding is to keep the RF (more correctly RFI) out of systems
where it doesn't belong , including induction and radiation along the
power cabling; to radiate from the antenna (while power sources are also
another good place to provide some twist in the cable). More bonding
means more energy to the (intended) antenna and higher efficiencies.
When running >QRP the radio bonding can greatly reduce the effects in
the radio from RFI. Simply bonding the 200W RF deck in my truck to the
chassis removed >90% of the RFI (except 40 meters sometimes turns off
the cruise control). The control cable and the mic cable each have
ferrites in place; they weren't enough. So we will disagree on your
last point; my experience in that install provides that. It's all within
7' of the antenna, hard to keep that any cleaner with that level of
exposure.
The good news is that the newer vehicles have less cabling since wiring
is replaced with fiber optics. The bad news is that there is more
'stuff' in a newer vehicle to generate and be sensitive to RFI. I'd
score that as a wash.
73,
Rick nhc
On 10/9/2017 10:06 AM, Jim Brown wrote:
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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