"Do you _need_ an AM radio in your car?"
No. But it was sure nice to have when we were heading north out of Weed
CA Route 97 on a dark December night not long ago. The sign said to
tune your radio to some AM frequency for traffic conditions. That saved
us a lot of time because the road was closed to all but four wheel
drive. So we turned around and returned to Interstate 5 and went
through Portland, normally a much longer drive. Cell phone coverage is
very poor along that route. So the AM radio was the only thing that
informed us.
Cell phone coverage is getting better and I am seeing more apps that
provide current road conditions. So I think that the "need" for AM
radio is decreasing. But I was sure glad we had it on that trip.
Later,
Cliff Crabtree
On 11/10/18 10:43 AM, Bill Dube via EV wrote:
There is no "ground" in a vehicle, only "chassis". (Unless the vehicle
is on charge and connected to the grid.) The drivetrain and the AM
radio share the chassis "ground", which is likely the root of the
problem.
The EMI comes from the controller PWM switching, goes into the
chassis, (and is radiated in general by the drive components,) and is
received by the AM radio.
The AM radio can be filtered, but that adds cost, is difficult,
reduces the sensitivity, and likely the sound fidelity of the AM
radio. The drive train can be designed to reduce the EMI in the
specific frequency region of AM, which adds significant cost, and is
_/very/_ difficult. You can locate the sensitive components of the AM
radio away from the drive train, which is a bit difficult and adds cost.
Is the cost worth the improvement of the AM radio reception? Most
folks don't care, and the added cost of clear sensitive AM reception
is not worth anything to them. Teslas answer is to "use streaming"
instead of the AM radio is probably the most sensible for most people.
This problem is similar to acoustic noise in airplanes. It is
quite costly to reduce the cabin noise in airplanes, and it adds
weight, which reduces efficiency and reduces performance. In small
airplanes, helicopters, and military airplanes, everyone wears
headphones (or ear plugs). In commercial airplanes, the airplane
itself is designed to reduce the cabin noise. However, it is very
expensive to solve noise the problem at the source end. Much cheaper
and lighter to solve the problem at the relieving end.
Do you _need_ an AM radio in your car? Probably not. You don't get
to your destination any quicker.
Bill D.
On 11/10/2018 1:03 PM, Peri Hartman via EV wrote:
Hmm, maybe cost savings of putting a grounded shield around the motor
and controller. For the AM radio, what could the cost be? $1.00?
Peri
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