AM Radio in the Car

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digitalanalog

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I am looking to improve the AM Radio reception in my car. Bigger antenna?, Amp? any ideas?
My channels are always fading in and out, it's a stock 2007 Chevy Cobalt with stock radio and stock antenna.
Thanks
Jim
 
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prcguy

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I haven't played with a car AM radio since the early 80s but back then you could usually improve reception using the antenna matching trimmer capacitor that was in most radios back then. If they still exist its a small hole on the rear or side of the radio with a recessed adjustment screw or you went through the cassette or 8 track door with a long insulated tuning stick (oh gawd I'm showing my age). You simply tune the radio to the middle of the band or your favorite station and tune for best reception. The adjustment is only for AM and will not affect FM.

These adjustments were put in for the radio to be optimized in whatever car its installed in. Whenever I installed a new car stereo I had to do this on each and every one. The problem is an AM car antenna is so small in wavelengths its extremely high impedance and very touchy on how its terminated. The coax to an AM/FM car antenna is much higher than 50 ohms and every car antenna and coax run is different, so it needs a way to compensate. I've not touched a car radio in years and things might be done differently, but its worth checking out.

I've not had any success in lengthening an AM car antenna, even after peaking the adjustment on the radio. If you make the antenna a few ft longer its still insignificant with respect to wavelength. However, in most cases I've seen a noticeable improvement by peaking the trimmer on stock car radios and it can be a big improvement. I remember cars with the antenna wire in the windshield never worked as good as an external rod antenna.

The only problem with the trimmer trick is getting to the back or side of the radio in a modern car. You might call your car dealer and speak to a tech to see if they know of the adjustment and if so it could save you some time finding it. Its also possible it doesn't exist any more or the service techs are oblivious to it.
prcguy
 
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digitalanalog

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Yeah getting to the back of the radio is probably not going to happen, it is (as you can image) buried with plastic covers and moldings. I will take a look but not promising.

I was wondering if i could get to the back of the radio if i could take a length of wire and make a long wire and run it along the inside of the roof. My listening is 5700 - 6400AM but again everything is smothered in plastic, I guess a handheld/portable shortwave radio.

Thanks for the info, I appreciate it.
DigitalAnalog
 

prcguy

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An AM broadcast antenna inside a car would be shielded and would not work very well. In my experience adding wire to an existing antenna outside the vehicle doesn't do much unless you peak the antenna trimmer common in older radios, then you might make use of the larger antenna. If you add wire and don't peak the antenna trimmer in the radio, whatever wire you added will probably detune the system and loose any benefit from the wire.

I think the best thing you can do is find out if your radio has an AM antenna peaking trimmer, then you have many more options from peaking your existing antenna to installing a larger one and peaking that for better performance.
prcguy


Yeah getting to the back of the radio is probably not going to happen, it is (as you can image) buried with plastic covers and moldings. I will take a look but not promising.

I was wondering if i could get to the back of the radio if i could take a length of wire and make a long wire and run it along the inside of the roof. My listening is 5700 - 6400AM but again everything is smothered in plastic, I guess a handheld/portable shortwave radio.

Thanks for the info, I appreciate it.
DigitalAnalog
 

prcguy

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Here is another possibility if your handy with soldering and building stuff. Look up the AMRAD VLF/HF active antenna project featured in QST magazine many years ago. This is a top notch bullet proof high level active whip antenna.

The AMRAD is usually made inside a short length of PVC pipe with a 3ft whip. I'm thinking if you made one of those and fitted it to an NMO mount, or hogged out the innards of a base loaded NMO antenna and put the AMRAD guts inside, you would have one bad a$$ AM broadcast and SW mobile antenna.

I buit an AMRAD antenna many years ago and I can pick up the low power LAX airport information radio at 530KHz 25mi from the airport. These antennas work really well.
prcguy
 

MTS2000des

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Replacing the stock radio with a high quality aftermarket unit with a good front end is also a thought. In my previous work truck, a 2011 Ford F-150, the OEM Ford radio had a pathetically weak FM front end, despite the fact that the truck was equipped with a proper full length rod antenna.

I bought this Kenwood HD-262U CD/radio with an HD Radio tuner for less than $100 including the needed wiring adapters and dash trim piece and instructions. Not only was this a huge upgrade feature wise (full Smartphone/USB support/MP3 CD playback, etc) but a superb analog AM-FM tuner with amazing sensitivity. Could hear weak analog FM signals the Ford radio couldn't even detect, and it also decoded free OTA FM HD streams (and did a pretty good job of it).

I've since turned in the F-150 and now have a 2016 Explorer with Sync. The Explorer has a "fin" style antenna but uses an antenna pre-amp. Does okay on FM but very marginal on AM.

Automakers are not concentrating on AM/FM reception, they are concentrating on on board WiFi/4G, and other online entertainment people want nowadays. Your 2007 should not be difficult to get a cheap aftermarket radio with better performance. Just a thought.
 
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Automobile radios have changed (for the worst), today's radios are not designed the same as your Grandfather's Oldsmobile. Those were real radios with several stages of amplification in both the RF and IF sections plus a decent audio section to boot. Back then AM was king, FM was a late comer around late 70's or thereabouts. Gotta love those glow in the dark radios!
 

digitalanalog

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Thanks for all the good info, I appreciate it. @ prcguy, That looks like a great project for my SW radio at home, don't think I want to add it to my car though :), anyway I think my best option is to just remove and replace the factory radio as MTS mentioned above but as also mentioned by rfradio I think I will just find an older moder (late 70's with antenna trimmer) radio on eBay and put it in the car and hope it plays better with the factory antenna. Since it's a double din factory radio section I might as well just put a scanner in the second din space to fill the dash.
Thanks agian for the input.
Jim
 

lmrtek

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For AM reception you need a MUCH longer antenna

Since a 1/4 wave whip would be at least 150 ft long at 1600,kHz, you need an old school car antenna from back when cars were cars and antennas were antennas!

Go to a junk yard and get an old telescoping car antenna from the
60s since they were about 5 feet long

Or Evan better, look for one with a loading coil on it
 

ridgescan

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I own a 2001 Toyota Tacoma and a 2016 Lexus RX350. I could jump into either of these and DX in MW just as well as I can on one of my comms receivers here in the shack on a roof loop up 50'. These are amazing signal grabbers for what they have to work with. The Tacoma has a 3' whip with the loosely wound coil going up it under coating. The Lexus has that "fin" but that is for the GPS/FM/Lexus Assist etc., but I learned actually uses a portion of the rear defrost grid for the AM antenna! I sure wish I knew all they employ before that measly antenna to achieve signals at these low frequencies.
I am guessing some carmakers don't put the greatest effort into AM radio and some still do. Maybe Toyota and Lexus do because of heavy AM use overseas and Chevy see no call?
 

hill

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My 2003 Impala's radio does alright on AM and it's antenna is in the back window. When I got the car thought the AM would suffer without an regular whip, but going forward seems to do alright.

With over 261K miles on the car I am getting ready to purchase an replacement vehicle and will see how the new one works on AM and feel it will be worse. Having had good luck in this car it will most likely be a GM product. I go to work in the early morning hours and mostly listen to WSM in Nashville from Baltimore, Maryland, since not much on the radio at 3-4 hour and no one on the local ham radio repeaters at this hour
 
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I've noticed, there is a clear difference in how some of the more modern antenna designs are shaping up. AM is not band things are designed for anymore. A good example, I directly compared my 2013 Sierra to a 2017 Tahoe PPV (which has the antenna in one of the rear windows) and it was a night and day difference on both bands. Back when I had my old F150, I ran a Firestik diplexer and had some interesting results with it. Been thinking about relocating one to use with a Larsen NMO27 mounted on my fender. As it is, AM reception on my pickup is decent as I can listen to KLBJ (590) in a good chunk of the state during daytime operations. As far north I've gotten is the HWY 114 corridor around Lubbock which is nearly 400 miles from the transmitter and it's completely usable as long as it's a non-stormy day or your not in LCL.


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KC4RAF

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Ah, remember the old AM radios of the by-gone era cars. Lot of time all you had to do was pull the 2 knobs off, use a 1/2 (?) socket and out came the radio, (generally) where you could take a diddle stick and fine tune the antenna!
But with his stock 2007 Chevy, that just ain't gonna happen. Even trying to get to the back of the radio to connect an active antenna would be a challenge. Unless you could get at the antenna itself.
 
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Ah, remember the old AM radios of the by-gone era cars. Lot of time all you had to do was pull the 2 knobs off, use a 1/2 (?) socket and out came the radio, (generally) where you could take a diddle stick and fine tune the antenna!
But with his stock 2007 Chevy, that just ain't gonna happen. Even trying to get to the back of the radio to connect an active antenna would be a challenge. Unless you could get at the antenna itself.
If it's like other GM vehicles of the era, it's actually stupid simple. Pop the dash panel, move the gearshift into drive so you can pull the panel off, and there are two 8mm bolts that actually secure the radio. Unscrew those and the radio comes right out.

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SCPD

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My ford radio blows away any Kenwood or aftermarket car stereo out there on AM!
I notice a big difference when I changed the radio,even on FM.It works ok,but not anywheres as good as the ford on AM.
 

Your_account

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in my dads car i tried to play with the longwave ?! think from idk 500khz to 1600khz?! there come only scweaking noise and wired thinks. total useless!
 

KC4RAF

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K1NNG jogged my memory and I recall back in about '62 or '63, I had an old 1949 Buick straight 8 that was junk yard bound. But I pulled the radio out because it was really great in reception.
Put that radio in the bedroom with a car battery and pulled in station far away. My store bought Admiral radio could not hold a leg to the performance of that ol' Buick radio. It was AM only back then.
 
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