External magnetic antenna for Car reception?

[JH_Radio]

Hi there.
I have a radio built into a custem box with a line out jack for the car. The current antenna in the box is an amplified antenna. Let's just say it sucks. The only way i can see getting any sort of decent reception is to get an external antenna. Are there any magnetic antenna's for the car that is like the traditional rod antenna? then i could run that into the car and hook a coax cable to the radio in question. Then i can record airchecks while on the road. if i wanna move the radio and antenna to another car, i could do that too.
Other then that, the only other way i can see is putting a fixed antenna on the car (which would require drilling holes in a new car), and leaving the radio in a fixed location.

 

[spunker88]

In a car you are going to want an external antenna. All of the metal in a car's body can degrade the amount of signal that makes it to the interior. Amplified antennas are a bad idea for short antenna runs, like in a car, since they don't provide any benefit and can often add noise.

Does the car not have a factory radio and antenna? You could just splice into the audio output from it and run that to a recording device, or hook your radio into the factory antenna.

 

[rbrucecarter5]

By magnetic antenna, you probably mean box loop for AM. There are two main problems, maybe three:

(1) Box loops are direction, with deep nulls. Murphy's law - the station you want will be in a null when you are on a long, straight road.
(2) Box loops need to be re-tuned for each station. Fiddling with the radio and antenna is a distraction that leads to unsafe driving. If you are really good at watching the road and have the loop tuned by varactor and the control is on the steering column, maybe it wouldn't be too bad. But a real annoyance to "tune twice"
(3) Box loops are so sensitive - 40 to 60 dB gain - that any source of noise like ignition is going to be a problem.

Best scenario for car radio - drill that hole and put in a 60 inch whip antenna. It makes AM come alive, and even helps FM. I know people that put bottom loaded whips on their car for even more electrical length, and have AM reception from hundreds of miles. That is assuming that today's car radios can even support a whip antenna with the proper connector on the back of the radio. If not, they you are stuck with aftermarket and a lot of kludging to make it integrate with the car's audio and steering column systems.

 

[JH_Radio]

i'm blind so wont be driving the car.
the radio is not a factory radio. it is mounted in a box with paragraphic EQ. it sits in the back of the car just behind the console so i can control it from the passengers seat in the back.I have one output running from the EQ so i can plug my headphones into the EQ. the other output is comeing directly off the radio which can be plugged into any line-in source such as a laptop or boombox with audio input.. This way i can listen to the EQ output, yet stil record airchecks from a flat output.
I've figgured out what you mean about horible reception from the amplified antenna.
See what the guy did was mount the EQ in the box, then put the radio above that with the amplified antenna below the radios faceplate. I know about reception and that external is always the best way to go, but I trusted his judgement with regards to the amplified antenna working wel for reception. I dont know a lot about car audio.
My intire point of this is to be able to record airchecks on trips. My guy was thinkin along the lines of portibillity. The radio has a lighter jack that you plug into any car with an on/off switch. My purpis of having a magnetic antenna was so that you could just put the magnit on the car, with the rod atached to it.
Though the radio has a CD player, line in jack, and USb port, that doesn't much matter to me. While i could see myself possibly useing the CD player or line in jack, i'm most interested in the radio and recording airchecks. If i had to pick between having a fixed location with an external antenna (which it sounds like the way i'm gonna have to go), and a portibal option with the amplified one, i'll go for the fixed. I mean you gotta understand, this box was custem built, wood, with rug carpiting and everything. Considering how much money it cost to get it done and the fact i dont think i can take it back, i'd really like to make this work somehow. I'll mostly be recording off FM, though if i can get an antenna that can do both AM and FM like a factory radio, that would be a plus. As i read the replies to my question, i realize i didn't explain what it is i had and wanted to do very well. Sorry for the confusion and hope this helps.

 

[K6JHU]

In the halcyon days of CB they made both window mount and gutter mount for car CB antenna temporay mounting. They still make magnetic mounts for the trunk or roof. Run is 50 ohm coax with a PL259 connector. The screw in antennas were tuned for 27 MHz. I would recommend going to the swap meet, finding an old mag mount, re-terminate the PL259 to whatever the antenna connector is on the radio, stick the mag mount on the roof of the car and see what happens. Worse case is that you are out a connector and whatever the antenna cost you at the swap meet.

 

[rbrucecarter5]

As i read the replies to my question, i realize i didn't explain what it is i had and wanted to do very well. Sorry for the confusion and hope this helps.

When you said "magnetic antenna" - I was assuming an antenna that intercepts lines of magnetic flux, which implies loop antennas for AM - as opposed to antennas for FM.

The magnetic mount CB antennas are pretty much a thing of the past, but you might be able to snag one at a garage sale or Goodwill, They are electrically correct for 27 MHz, so may be a poor choice for either AM or FM. Still, you could get somebody to gut the mount, and put in a straight whip. At some point, it would get so long that the wind from a moving car would push it over, but probably not at decent length.

The thing is - only car radios are really optimized for that sort of antenna. Get one and use a cigarette lighter for power, magnetic mount antenna for antenna, and somehow kludge the speakers to drive headphones, and it should work. Without a bolted ground to the car, I am concerned you would have some interference from the alternator.

Something I discovered when I was riding with my parents - reception is decent in the upper corners of the back windshield. For some reason. Many a trip I had sore arms from holding a portable up in that corner for hours on end.

 

[Darth_vader]

"In the halcyon days of CB they made both window mount and gutter mount for car CB antenna temporary mounting."

They still do. I came across a bunch of the window-mount type aerials at the "local" TA truck stop just a couple weeks ago!

[size=8pt](I assume you mean the ones that you clip on to the top of the window glass, like those little "window-shade" things you sometimes see.)

 

[Steve Green NEPA]

Perhaps not a definitive solution, John H, but at any rate :

I'd posted a question here before -- and got a nice & correct answer --about some noise reduction. The car radio always worked better at night.
Duh : Switch on the headlights in the day, I was directed.
Even just the dims work for me. As a side-benefit, I've gotten into the habit of checking the taillights of any car I'm a passenger in or driving every time it gets shut off.

I actually had been driving home once with a rented HQ-180 to which I hooked up the car aerial (stock '70 Olds). I got squatto on it. On all of the bands. Once home, the radio was terrific.

You'd figure with all the NON-metal in cars nowadays, reception would be better. But the 'station' car here the past few years has been a 1992 Topaz. It has so much metal in it that I could probably junk it and get back more than I paid for it.

But the headlights do the trick nicely. In the meantime, there HAS to be, at least, some sort of a magnetic/stickum mount around, into which an aerial cut to specs would work.

 

[K6JHU]

Modified my old CB mag mount to a 2m/440. Going the wrong direction in frequency I know, but it is just an example of easy it is.

All I did was unscrew the mag mount portion. That left me a screw thread up in the air. Found a nut that fit. Then I bent a piece of coat hanger around the screw thread and tightned the nut. Biggest issue after that was trimming the antenna with my meter. Not required for AM.

But any piece of wire outside the car body is an improvement. Looking at some external car antennas, it sure looks like cutting to 31" (for FM) is what most of car manufacturers have done except for those who wrap a short loop of wire up the length.