Hi Roger.
Well, I work in EMC for my sin's, and two leading automotive test houses
are our customers.
Though they have many kW of power to play with for testing (that I among
others are responsible to keep going) that uses external antennas and a
semi-anechoic chamber for the whole vehicle test.
But... Though they also do tests with vehicle mounted antennas, they do
not use much more than a couple of hundred watts at most.
As to ...
"I don't think" there's any thing in the cars that will be directly
affected by a 50 MHz signal, but from sheer strength and rectification it
could do all sorts of things. OTOH I'm not at all familiar with what
cars you have "over there" but I understand the big cars are quite
popular.
(As for 60s cadi's. No computer controled systems to mess with, so not
an issue.)
Well, we have most the same cars (but with decent suspension and engines
that don't need an oilfield to run them, well, mostly...)
However, modern cars are riddled with computers, ranging from the
security system, to several dedicated to running the mehcanicals. Even
small "shopping trolly" cars are highly computerised, relying on the
electronics to be safe (ABS, Stability control etc) and economical (60MPG
easy) while also suprisingly lively (0 .. 60 times that a few years back,
were sports car performance!) Also to meet environmental regulations
(exhaust emissions, the catalysts fitted, need very stringent control of
the engine combustion parameters to work as needed.)
As a result of my "day job", I would not be happy at all to ride in a
modern vehicle with a HF, 6m, 2m or whatever radio in, and a PA that ran
over 250W out to a vehicle mounted antenna, of any type. There is just
too much that "could" be affected to ruin your day. At best just causing
a warning light to latch on (that could cost many ten's of $'s to reset
by a dealer) the indicators to flash at the wrong speed, a wiper to wipe
without your command, or at worst, the ABS system not working when you
most want it. Heck, there is even electronicaly controled power
steering these days. Would you want that to "go funny" on you at speed?
Seriously, you are playing not only with your life, but those of other
road users arround you.
For a static (parked up) car/van/truck etc, then run all the power you
want, if you can keep the engine running and the electrical system happy
to keep feeding you the DC power you need.
Remember, modern vehicles are not just a metal box with seats, 4 wheels
and an engine. They more resemble a computer network, powered by a local
engine-gen set, with miriads of controls and systems that all need to
work well together to stay safe.
I have seen what can happen, as a result of an EMC initiated ECU crash.
In that case, the (prototype) vehicle was still strapped down to the
rolling road, but it still made heck of a mess....
The 147MHz emissions issue is something else. Again, vehicles are
rigourousely tested for spurious emissions. If it's one particular
make/model of vehicle that is the culprit, and if your 2m band is
"protected", plus you can legally operate radio in your car while driving
(insurance issues, driving without due care and all that) then lodge a
complaint with the FCC or whoever.
Lastly, please remember, as a driver your "primary job" is to safely
drive the vehicle, observing road law etc. Anything else, is secondary,
and some insurance companies might not be happy, "IF" something bad were
to happen, while you were working 6m DX with over 500W out!...
Take care, apply common sense, please.
73
Dave B. (G0WBX/G8KBV)
Been doing mobile Ham stuff, for at least 30 years, QRP and QRO, FM, SSB
etc. Currently 50W on 2m and 70cms to a dual band stubby on top of a
Mazda 6 estate (at least three embedded computers, just for the engine!)
no problems. 100W+ to a "tank whip" on the side of a 200TDi Landrover,
no possible issues, as no ECU!
I was also the driver of (AFIK) the only successful EME mobile QSO so
far. Look up "G8MBI" for info. Absolutely no chance of any own vehicle
EMC issues (susceptability) in that case.
------- Original Message -------
Message: 2
Date: Sun, 20 Nov 2011 17:19:49 -0500
From: Roger <sub1@rogerhalstead.com>
Subject: Re: [Amps] RD100HHF1 work in 6m
To: amps@contesting.com
Message-ID: <4EC97D05.5030809@rogerhalstead.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
On 11/20/2011 4:32 PM, Dave wrote:
> More like EMC issues, affecting the engine ECU, or a critical sensor,
so
> it cut's the engine to be safe.
>
> Too much RF power for the car to safely handle. Do you realy "Need"
> 500W out mobile? The sort of near field that creates, will affect all
> sorts of things, not just your car either!
500 watts? I'd much prefer the legal limit. The mobile is one place
where
your signal can use the help from every watt it can get. OTOH here in the
states there are the required exposure limits that you'd either have to
calculate or measure to be legal and in city traffic you'd probably be
pretty limited to stay legal. Not that anyone would ever go over the
exposure limits.
I remember the guy who had the Cadillac with a complete S-line including
the 30S1 in it. I think it may have even made QST. (50's or 60's) I'm
sure
he's not the only one to run QRO mobile. When it comes to mobile I've
always been of the opinion that it's considered QRP if you key the mike
and the tires don't skid. > You should however try some good RF filters
on
the DC power cables, and > take great care over the RF grounding,
especialy the antenna, after all, > what amps of RF current you pump into
the antenna, a very similar ammount > also has to flow arround the
metalwork of the car, and that too will > create some "interesting"
field's in places. Today's unibody construction often works well for RF
... IF they did a proper job of welding. That's questionable though as
the
welds (even by computer controlled robot) can vary. Not as much as those
made by individual workers though. (I've worked on an assembly line
although it was many years ago) OTOH not too many years ago I purchased
a
new car and discovered the floor pan had never been welded in place (or
sealed). I discovered that after going through several water ponds on the
highway. I was on my way to work when I realized I had wet feet and the
water was about 4" deep "inside the car". Good thing I didn't have any
papers or rigs on the floor. > Chances are your car was only tested to 50
W of RF out to a car mounted > antenna above 30MHz. Depending on it's
age
and where it was built, and > for what country. In the distant past, on
many an occasion I've run 160 to 200W on 2-meter mobile. It really makes
a
difference when you are out on the fringes. Unfortunately we are legally
limited to only 50 watts out on 440 in this part of the world. Most of
today's VHF mobile antennas are only rated to 200 watts. Actually my base
station VHF verticals are only rated to 200 watts. On 6-meters you are
really antenna limited where a 1/4 wave whip is going to be slapping a
lot
of overhead *stuff*
"I don't think" there's any thing in the cars that will be directly
affected by a 50 MHz signal, but from sheer strength and rectification it
could do all sorts of things. OTOH I'm not at all familiar with what
cars
you have "over there" but I understand the big cars are quite popular.
I believe many of the newer cars are tested to 100W, but that's only 3db
difference and I'm not sure if the hybrids are tested at all. They do
not
recommend direct connection and high current draw from the tiny battery
used for the engine and it's pretty much impractical to use the "big
battery". The tiny alternators are pretty anemic for charging a hefty
battery to run a couple hundred watts let alone the 800 plus watts for
500
out.
BTW there are cars out there that have a very strong signal of 147.00.
Strong enough to over ride a 100 watt repeater a bit less than 2 miles
away when they are almost a city block away. As our repeater is 147.00
it
eliminated me purchasing one of those cars, but it gave me a good excuse
to purchase a Trans Am with the Corvette engine<:-)) My mileage may have
not been quite as good, but the car was a lot more fun until a SUV
shortened it up by several feet. I said I was going to keep that one
until the wheels fell off, but I didn't think they really would.<:-))
73
Roger (K8RI)
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|