Car audio Siginal amp?

[myp71]

I would like to build a car radio antenna signal amplifier. Does anyone have a circuit diagram that I could use?
I think it would require 12 volts to power it, right?
I'm looking for something that I can tee-in between the antenna lead cable and the back of the radio where the antenna plugs in.<p>Do you guys think that would the best way to get a better siginal? I bought a new radio and it seems much better than my other radio but still not the greatest.The siginal seems to fade when I'm near a tall building. Does That sounds like a bad siginal issue?<p>I have a good GND on the antenna so it's not that.<p>^ This is for Fm siginal^<p>Also on my old radio and new current radio doesn't get an am station.why would this be??<p>
Thanks<p>Ryan

[richfloe]

Ryan,
I used to see FM preamps being sold many years ago, exactly what you are looking for but havent seen any lately, probably because any newer radio already has a good front-end to the receiver. You might check J.C. Whitney or some place that has been around for a while that might still have some on the shelf.<p>As for the AM station, the typical antenna on a car these days (about 30 inches) is just right for the FM broadcast band but is horribly short for picking up AM signals. On the older car radios there was usually a little hole on the front where you could adjust the antenna matching circuit in the radio for AM to make it as good as possible but with the standard antenna you are at a real disadvantage.<p>As for the FM signal dropping out behind a building, that would be expected. It blocks your signal and also if there are other buildings around, you get reflections off them but the phase of the signals reaching the antenna are shifted which will interfere with reception. You might notice that if you come to a stop and the signal drops out, all you have to do it roll forward a foot or two and it clears it right up, a clear sign of the multipath problem.<p>How does your reception compare to that of another car parked next to you? If there is a significant difference, you might have a problem with the antenna or cable.<p>Rich

[myp71]

Sorry this is a late reply I've been busy lately.<p>Anyway I don't know about the sound quality of the other radio because the Truck has Xm radio and it never goes off.I don't have a fm antenna on the truck so i really don't know about that. <p>
I went ahead and bought a new antenna for my car with in-line amp.I haven't had a chance to try it yet.I hope it works for $ 25.00.<p>
Thanks for your help<p>Ryan

[Bob Scott]

Ryan,<p>Buying that a new antenna was a good idea. If the radio does not pick up AM and you have trouble with FM, then it means the antenna wire is broken, proabably at the base of the antenna. Notice that if you plug an antenna extension cable into a car radio and DO NOT connect it to an antenna you will experience identical symptoms.<p>I used to be part owner and service manager of a car stereo shop with installation bays.<p>With a properly working antenna you probably don't need any type of signal boosting circuit. To minimise AM noise, make sure the antenna base is properly contacting sheet metal when you're finished installing it.<p>Bob <p>[ July 28, 2004: Message edited by: Bob Scott ]</p>

[myp71]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>then it means the antenna wire is broken, proabably at the base of the antenna. <hr></blockquote><p>That's one thing I didn't want to check is the antenna wire.It can't be broke at the base because these are all brand new antennas I have had on this car.But you still could be right Since this is a Ex police car who knows what the did to the antenna wire so I will have to go through the whole car and find that break in the wire. <p>Ryan

[myp71]

OK I got it to work much better. I Put a 12 guage Ground wire to the antenna base( overkill I know) and hooked up the center wire inside the antenna cable.Only problem is that I do not get one station.But, if I disconnect the center wire inside the antenna cable It comes in clear but then the other stations fade out.Any reason for this?<p>Thanks<p>Ryan

[myp71]

OK I got it to work much better. I Put a 12 guage Ground wire to the antenna base( overkill I know) and hooked up the center wire inside the antenna cable.Only problem is that I do not get one station.But, if I disconnect the center wire inside the antenna cable It comes in clear but then the other stations fade out.Any reason for this?<p>Oh!!!With the center wire connected I get Am <p>
Thanks<p>Ryan

[dyarker]

The center wire is the receive RF signal. The coax braid and/or base of the antenna should be grounded. An ungrounded 12ga wire connected to center conductor makes a good, but ugly, antenna.<p>If there is a poor ground connection else where you might have accidentally made the body a 1 channel antenna.<p>Cheers,

[myp71]

I took The 12 guage Wire and body grounded it to the Antenna metal Base because I didn't think the metal prongs where making a good ground.( not touching the body)<p> 4 out of 5 channels come in clear on my presets. If I where to disconnect the Antenna all channels would come in just not the best sounding.<p> What happends to this one station when I use the antenna?
why does one station just disappear ? <p>
Thanks again <p>Ryan

[myp71]

EDIT: That one station 98.5 fm that goes away when I use the antenna....it has a bad interference bad enough so you can't hear the music.But when I unplug the antenna the interference goes away.

[myp71]

I'm about to give up on this radio antenna!! I have no idea what to do next.I guess I should check the antenna wire.If I need a new wire, cable T.V antenna wire will not work because of different resistance correct?? <p>It just seems like I get one good station.One is really bad(noise) and the other station has a little noise on it.I just don't get it.<p> <p>
Thanks Ry@n

[myp71]

Ok last one and I will give up on this. I disconnected power from the antenna amp and now all of the stations come in clear.....For now<p>Still