How to extending aerial antenna for mobile phone FM tuner while using a 3.5mm to cassette adapter?

Michelle O November 28, 2013
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We have bought a 2nd hand car of Japanese origin, and the stereo unit works through a touch-screen that also controls volume, balance, air-conditioning and just about everything. It has no 3.5mm jack input.

Rather than hack around, I figured I could use a cassette adapter to 3.5mm jack plug for my old iPod Classic. Works a treat. Unfortunately, the FM radio bandwidth in Japan is restricted, so we can only get a couple of a stations here. In our other Japanese imported vehicle, we got round this by sticking a new stereo in.

I have managed to get FM radio by using an old Nokia n900 in place of the iPod, which works, except the reception is poor. I can also use a Samsung Galaxy S3 if need be (would prefer to use the n900, as I use it for nothing else these days). The cable from the cassette adapter is less than a meter, and by the time the FM device is mounted in the holder, there’s probably only a vertical run of under 1/2 a meter.

My understanding is that for decent FM reception, the length needs to be at least a meter (which if inside the windscreen would be horizontal – ideally it should be outside, but that is impractical). I have seen lots of answers that cover extending an aerial on a smartphone by replacing the headphone wire with a telescopic aerial, but that only works for using the internal speaker.

Is there some way of extending the antenna in such a way that you can still use the jack socket to feed the car stereo?

I will get a 3.5mm male to 3.5mm female extension lead for now, but it doesn’t seem very elegant at all, and if I could get this working without it, I could eventually look into utilizing the car’s own built-in aerial antenna at some point.

  1. Mish
    December 1, 2013 at 8:19 am

    Thanks, I have now found that the problem is not with the jack-connection doubling as an antennae, it is that when the phone is connected to the cigar-lighter USB charger, it sets up interference. Have tried in two vehicles, with three different devices' FM players (Nokia n900, IPod Nano, & Samsung Galaxy S3) in two different vehicles, and all works fine using the jack-connector to the stereo units, until connecting to power via USB.

  2. Mish
    November 30, 2013 at 3:16 pm

    You are confused because you did not read the question. I said quite clearly it is a cassette adapter. So, most of your reply is irrelevant. The wire from the jack (that plugs into the mobile phone with FM receiver built in ro it) acts as the antennae as well as feeding the sound into the cassette adapter.

    • Oron J
      November 30, 2013 at 10:05 pm

      You are right, I didn't pay close enough attention, sorry. In mitigation though, there's an awful lot of extraneous information in your question, such as the story about the iPod.
      As far as I know, there's no way to "split" the antenna from the phones line. A better solution may be to get a separate "proper" radio (one which has its own antenna).

  3. Oron J
    November 30, 2013 at 3:07 pm

    I am confused. Are you using 1) a cassette adapter which fits into the car's cassette player, or 2) an FM transmitter, which you receive through the car's radio unit? If it's the former, then the length of the cable is not particularly important, and you can get an extension if you like. If it's the latter, then the aerial is built into the transmitter itself (not into the 3.5mm lead) and again, the length of the cable is not hugely important, but of course you could keep it short by moving the transmitter closer to the iPod.