TheRadioBoard

so one of the guys around says he's going to do some dx-ing with his car radio, and i have much respect for this guy, so i figure a walk in that direction couldn't hurt my radio listening pleasure-to be.

so, i start by collecting a few old car radios, some still on the way, but at least i know i need an antenna to make them work, so that's why i'm asking here.

first, these radios are of two types: modern, digital (eg 2003 honda civic am/fm stereo, nib 6.00!) and vintage (eg gm, yr unkn, am-only, but probably transistorized), and possibly even an old tube/vibrator type. dunno yet bout this one. my main requirement in searching for the ideal toy is that it be 'mechanized', meaning shaft-tuned, not buttons for seek or scan.

so, questions are 1) is there something special about a stock car radio ant i need to know? are they just a metal mast with a wire to plug them in, or is there some matching stuff built into the ant base?

2) what if i just plug my long wire ant into it? should it work as-is?

3) since i'll be running this radio from a lawn chair with jumper cables to a 12v car battery, do i need to do anything to replace the effects of the 'missing' car body?

i'm just hoping to catch some decent dxes on the am band between skeeter slaps out in the back yard. anyone have some experience with car radios like this?
thanks, jw

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onct, when i was younger, i knew everything. now, i'm old and jeswondering.

Best DXing car radio I ever had was in my first car, a 1953 Pontiac Chieftain! There's usually no matching network in the antenna itself. The antenna, being very short relative to wavelengths, is high impedance, and matching is done internally. Because of the poor antenna, car radios usually have lots of gain, and adding a long antenna could overload the front end. The AM band was much less crowded in 1953, and in 1966-67 when I had the car. I could copy WKBW 1520 in Buffalo from Charleston, SC, almost every night, as there were no low-power stations on the clear channels then. You should be able to adapt a tuned loop antenna, and maybe connect it directly to the radio. You'll probably do better with the older sets. As time passed, AM was less important and the quality of AM in car radios plummeted. The AM-FM one in my 2001 Mercury is a poor excuse for a radio!

The big advantage of car radios was their sensitivity and shielding against electrical noise. Selectivity was good enough for the time but, as noted, the band was less crowded and decent fidelity meant wider IF bandwidth, which isn't so much of an asset now.

An excellent portable radio for AM DXing is the Tecsun PL-380. Used with a Terk or homemade loop it does very well, having excellent selectivity. I've logged almost 30 countries on the AM band down here in Florida. And it runs on internal batteries, which last quite a while. If you get serious, you might consider one.

73,

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http://kr1s.kearman.com/
http://qrp.kearman.com/

Hi Jeswonderin



Most of them are/were just a metal mast. They had a coax cable from the car body/antenna mount to the radio.
The only "matching stuff" usually is /was just a Hi input Impedance RF amp.

It probably would work just fine on an older car radio that doesnt have a sensitive J-fet as the rf amp.


Not for the battery, the radio almost surely has a ground/negative power connection or wire.

For the antenna, YES YOU DO. Well actually you might get by without it but the car body was actually the "ground plane" of the antenna. The coax shield connected the radio case to the car body in most cases.

While you are gathering some car radios to try(auto junk yard?) grab some of the coax ant cables as well, or just make your own ground(RF not power) to the case of the radio.



Some car radios work GREAT on AM. They had to be better because inside of a metal car is just about the worst environment you can have for AM.

73
kb0lxy - Eric

Here is some more.

http://pe2bz.philpem.me.uk/Comm/-%20Con ... anning.htm

http://www.bobsamerica.com/buickant.html

73

The 50 and 60 vintage car antennas used very low loss coax, low capacitance , the center wire was like a 30 gauge wire and if you broke it it was a real bear to repair .
A car radio and antenna never seams to work like they did in the car . After AM_FM car radios came out the AM sections where inferior to earler units
With a car radio out of the car the antenna input needs some protection a ne-2 lamp and a pair of back to back 1n418 diodes across the input work well . Then you can use a 15 to 20 foot long wire on them . Ground the chassis to earth and use a low noise 13.8 volt power supply

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Mark

Hey All,

FWIW, I have a 1980's (?) Ford AM only slug tuned radio fit in a wooden cabinet and run on D cells. It works GREAT with a 3 ft police scanner radio antenna ( this antenna has a right angle Motorola male , so it fits right into the radios female jack).

I haven't tried it with any misc length wire antennas or external "gnd",but maybe a 20 t 40 ft wire lightly coupled might not overload such a rig.Trial and error I guess.

K

I have an 80's Chrysler car radio with memory presets that I have at my bedside.
I power it with a wall wart and voltage dropping resistor. I have an auto antenna that I
plug into it and I have a ground wire that removes hum.
The hum is low level but it does go away with the ground attached.
I have used it for 6 or 7 years. I recently got an internet radio and that's all I use anymore.
Beware, internet radios can be hazardous to AM dxing!
Mikek