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Radioshark to Car Antenna

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  • Radioshark to Car Antenna

    I got the radioshark hoping to achieve AM and FM integration with Roadrunner (see this plug-in. Well it works, but as everyone has determined, the radioshark's reception is horrible. I found this antenna hack and I want to use this process to wire the radioshark to my car's antenna. Inside the radioshark is a single-wire FM antenna and an AM antenna coil. My question is this: does a car typically share the same antenna for AM and FM or is the external antenna for FM only (with AM using an internal coil of some sort)?

    Also, how should I wire the antenna? The car's antenna connector is basically a coax cable, which means it has 2 conductors: an outer negative shield wire and an inner positive signal wire. Since the radioshark antenna only has one FM conductor - the antenna wire itself - how do I connect the two? My initial idea is to solder the radioshark's antenna wire to the car's antenna-coax cable's center. Or maybe the other way around (this woudl do nothing for AM, but I'm assuming that all radios use an internal coil-type AM antenna).

    Basically I don't know anything about this and any help woudl be appreciated!

  • #2
    I realize that my background is in 2.4GHz, but even in the 100MHz range I would not expect it to be acceptable behavior to use 2.5mm jacks and standard wire to carry signals, or to attach anything to the end of a preexisting antenna. I would try to find some sort of cheap adapter or something with a socket you can cut off that will accept your car's antenna connector. Preferably something with a few inches of cable still attached since I'm not sure what impedence coax cable to recommend you use. Remove the stock antenna and attach the center lead of the new socket in it's place. Run a wire from the nearest ground location to the shielding of the cable.


    • #3
      Great - thanks very much! I assume that I should just leave the AM coil alone then?


      • #4
        I wouldn't know. Sorry. Radio isn't my thing.


        • #5
          how far did you get with this? I've tried a few things and I was uncessful. Any ideas?


          • #6
            I haven't gotten very far. I haven't really tested much though because I haven't yet moved my CarPC into the car. What have you tried godraj and what has not worked?


            • #7
              Originally posted by theminor
              What have you tried godraj and what has not worked?

              Perhaps I can be of some assistance.


              • #8
                So far what I did was take the radioshark apart and put it into a smaller case. Then I used the FM copper wire that the radioshark comes with to solder onto the tip of a motorola plug. Then I took another wire and used that to go from the shielding of the motorola plug to a ground location to the car. After all this my reception didn't change at all. I get a few stations really clear, but other stations that I would get on a HU I nolonger get on the radioshark. Also I've noticed that when I'm driving i hear lots of static, if I'm stationary it gets a little better. The pic is of the radioshark in the new housing. Any suggestions? And in advance I appreciate any help you guys can offer.
                Attached Files


                • #9
                  So does the tip of the moterella now connect to your car's antenna? That is, does your car antenna now run into the moterolla plug you made? I plan to do exactly the same thing, only I'll use a coax female plug soldered to the radioshark and then I'll run coax cable to the car antenna jack, center connected to the antenna and shielding connected to ground. Is this your setup?


                  • #10
                    Yes, that's basically my setup, and it didn't affect the reception at all. I was looking over the link that you posted, and it seems that this person decided to use 2 wires, both which are soldered to the board. 1 wire looks like it's going onto the FM side, and the wire is going onto 1 of the AM connections. How do you think that will affect the reception?

                    Also, why will you use coax cable and coax female adapter? The motorola plug is what the car antenna jack plugs into.
                    Attached Files


                    • #11
                      Very interesting - I never noticed but I think you are right. And actually it looks to me like the wires aren't going to the antenna wire at all. To get a closer look, I just pried my radioshark apart and looked at it. What do you think? I think his 2 wires are going to the outside terminals on the PCB that are not connected to anything. On my radioshark, there are 5 terminals there (these are labled "JP10" on the PCB) in this order:

                      Blank, AM, AM, FM, Blank

                      I think he's soldered to the two blank spots, but I'm not certain. I tested these with my multimeter but I can't determine where they go. Neither blank is connected to the PCB's ground. The two AM connections get resistance to ground, 1 with a little more resistance than the other (which makes sense since these are just wires going through the AM coil). But it appears from teh picture that he's got the outer blank connections connected to his jack.

                      I also tried following the wire visually in his picture (the one you posted above) and I say he's got the center of the connector attached to the wore that connects on the left side and the outside of his jack connected to the one on the right (the one next to "FM"), but that is really a guess since it is hard to tell by the picture.

                      I don't know how to do it, but I'd say we'll have to experiment with the FM connector and the two outer connectors, connecting the jack in different combinations hoping something will work. Please post if you come up with anything!

                      As far as using coax, I noticed that the antenna wire in my car was basically coax, so I was going to try to match it, although it probably doesn't matter. Maybe it isn't coax at all, but it feels like it!


                      • #12
                        Here is a close up of the connectors I'm talking about (orientation is the same as the pic godraj posted in post# 10 above)

                        Click image for larger version

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                        • #13
                          Well, what I think he did was feed the wire through the two holes, and probably soldered it on the underside of the board to the FM and 1 of the AM points (probably the one farthest from the FM point). Because the the 2 holes wont' really do anything.

                          I also looked at radioshack's website, they sell the motorola to bnc adapter, which is the metal thing that I used in my setup. But I also noticed that radioshack sells a female BNC to male RCA phono plug. Which perhaps would provide a better connection to the motorola plug then just soldering wires like I did. This will probably be what I try this weekend. But I've run into some issues with my music setup.

                          What kid of sound card are you using? I'm using the griffin firewave to work on my mac, and the sound quality is pretty horrible. I realized today why that is the case. Apparently AudioMidi (Apple sound software) turns off the ability to use 4 channels on my sound card if I'm running application that uses only 2 channels. What that basically means is, if I'm running itunes, then I can either use the front 2 speakers or the rear 2; if I'm running DVDplayer, then I can use all 4. And this is def. bad news, b/c if I'm unable to use all 4 speakers for music, then I may have to go back to using a HU (which do not want to do nor have space for).

                          Are you running everything on a mac or windows?


                          • #14
                            I'm running windows and I'm uning my motherboard's on-board sound. Why don't you just get a splitter and just turn your computer on 2 speaker mode, which, on output, gets split into 4 channels to be amplified to your 4 speakers. You won't get true 4-channel DVD playback, but you'll get stereo DVD oumped into all 4 channels. I'm surprised you can't do this through software though...


                            • #15
                              Ya. that's a good point. Is that how HU's work? Are all HU's 2 channel output that just get split to front and rear? Kind of sad that we all have a COMPUTER in the car but we can't achieve true sound. Let me know how the radioshark works out. I'm going to start on it this weekend using the extra bnc to rca plug.