What happened to Car Radio Antennas?

kW-1MW

There was one 500KW AM station, WLW. It was on 700KHz and it operated under an experimental license, and it was shut down in 1939. I saw the site 30 y ears later, along with the Bethany Ohio VOA site.

Modern AM broadcast transmitters are a lot more efficient. All solid state, and no separate modulator which operates like a digital audio amplifier. I t is built of plug in RF trays that can be hot swapped without shutting dow n the transmitter. The built in computer monitors the operation of each tra y, and lets the staff know that a tray has failed, or can email the enginee r if he is off site. Harris Broadcast introduced the first generation in th e late '80s. Harris used to have white papers on their website. You might f ind them on the 'Wayback Machine' if you want more details.

-- A host is a host from coast to snipped-for-privacy@nrk.com & no one will talk to a host that's close.......................... Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433

^^^^^

The transistor had not been invented when WLW's transmitter was built. It was decades later before high power FET's appeared.

--
A host is a host from coast to coast.................wb8foz@nrk.com 
& no one will talk to a host that's close.......................... 
Unless the host (that isn't close).........................pob 1433 
is busy, hung or dead....................................20915-1433

I assume you are pulling his leg. Think of the power levels involved in the drive motor electronics.

(You might research what FCC regulations cover electric car RFI. You can be sure Musk did...)

--
A host is a host from coast to coast.................wb8foz@nrk.com 
& no one will talk to a host that's close.......................... 
Unless the host (that isn't close).........................pob 1433 
is busy, hung or dead....................................20915-1433

I would not at all be surprised when FCC regulations covering RFI specify maximum levels that are still way too high to allow reception of AM radio in the car itself.

No, not pulling a leg, just guessing.

Many devices will interfere with AM radios. The FCC has a limit on how much is allowed. The car may just produce enough to affect the onboard AM radio, but not ones 50 feet away.

People buying the electric cars probably do not listen to the AM stations anyway,but FM and the Sirus radio.

Think it through: A vehicle is a rolling Faraday cage. Even the glass will be from about 0.2% to 0.8% iron, providing some shielding (and why many aut omobiles have passive cell-phone 'repeaters' for lack of a better word - an tenna designed to take cell rF to outside the vehicle - both our Ford C-Max & our Subaru Forester are so-equipped). This suggests that a well-designe d & shielded AM front-end and an external antenna should do the trick nicel y. Yeah-but.

That would make that AM front-end no longer a trivial 'extra chip' in an al ready trivial device. And put at least one more step in the glass manufactu ring process. Not gonna happen. Note that it is not just the Tesla that has dropped AM - several other all-electric vehicles have done the same. Funny thing, however. The C-Max with a (depending on conditions) 15-35 all-elect ric range does fine in AM.

Peter Wieck Melrose Park, PA

That is what I mean. To know the difference between RFI regulations and reasonable AM reception, just ask any radio amateur (as the previous poster probably is). The common levels of interference these days, likely emitted by fully compliant devices, overwhelm all but the strongest signals on frequencies below a couple of MHz.

I am aproching 50 years an a radio amateur. It is not just a couple of MHz but even higher. Riding around with a transceiver around 52 MHz and some of the fuel pumps and even the stop lights create some noise problems. Even some of the lights in homes will cause radio problems.

The FCC allows a certain amount of unwanted radiation by almost any electrical device . I have not kept up with things like that in a long time. When the personal computers came out there were some programs written where you could sit a radio near the computer and use the computer to make music with. The FCC came out with two sets of rulings. One for home devices which were stricter than the computers used for industries.

The FCC regulates emitters/emissions by category. The fun part is which one does a car fall under?

--
A host is a host from coast to coast.................wb8foz@nrk.com 
& no one will talk to a host that's close.......................... 
Unless the host (that isn't close).........................pob 1433 
is busy, hung or dead....................................20915-1433

I rented a new, '20 or '21 Uhaul (GMC Sierra) pickup truck for a day. The AM radio is actually incredible; sounds better than it does in any of my 20+ year old cars. I was very impressed, it seemed that it filtered out lots of static. Distant stations had minimal static interference, just the audio went in and out slowly as the station got weaker.

Ralph Mowery wrote: ==================

** AM radio has a huge advantage at long distance from the Tx.

But seeing as Teslas cannot do long trips into the countryside.....

...... Phil

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There are some traffic lights around here that you can hear change colors f rom almost a mile away. The noise is coupled into the power lines feeding a substation, and it is re radiated from them. Basically a carrier current n oise source from a poorly filtered SMPS. The high failure rate of the LED l amps in the traffic lights has more being switched back to lower efficiency , extra long life incandescent bulbs. Just about every LED light you see ha s one or more clusters of dead LEDs, in spite of some people's claim that t hey do not fail..

I thought that was the reason, so I tried it with a Walkman-type AM radio inside the car, and the reception was actually very good. I couldn't hear any significant interference, even with the motor operating - admittedly just gentle driving. Perhaps with a station on a more unlucky frequency it wouldn't work so well, or at least not quite well enough for the fussiest of customers.

Since AM radio is used for emergency info in Australia, if the car doesn't have AM radio built in then it might make sense to keep a cheap pocket AM radio in the car for the possiblilty that there is no cellular or DAB reception (both of which provide the same stations in normal times, but which might not work during a real emergency).

Maybe down-under. Around here, one is seldom more than 15 miles from a charger. At our summer house (north-central part of Pennsyltucky) there are three within 7 miles. This, by the way, is Ford F150 country.

Note also that a Tesla carries an on-board charger as well, meaning that it may be plugged in to any standard 120V or 240V receptacle (Slow & Medium Charge), or to a 240V, 100A heavy duty pin-and-sleeve receptacle for a very fast charge.

Be careful with your 'cannot'. Absolute statements are typically absolutely wrong.

Peter Wieck Melrose Park, PA

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** Regular AM portable radios barely work inside steel body cars. Why the f*ck to ALL car radios have* external* antennas ?? ** Bollocks.

.... Phil

We even have a brand of traffic light systems that emit a carrier (some clock crystal) with a harmonic that interferes with the local

70cm repeater on 430.125 MHz. When you stop at certain traffic lights, you get a whining noise on a receiver tuned to the repeater because it isn't exactly the same frequency. But the range is only some 25-50m.

Come on, you used to put much more effort into your insults!

I didn't expect it to work, I expected to hear interference and not much signal. Admittedly the transmitter was only a few tens of km away, but that is the situation that I was interested in.

Depends where you are. I know the Supercharger network is not widespread i n your area, but it's very widespread in Europe and available nearly everyw here in the states. A Tesla will run for over 4 hours on a charge at highw ay speeds, and there is never a charger more than 15 minutes away anywhere in the Northeast U.S.