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basics | Replacing a headphone cord antenna with with an external one: how to do it?


There are 4 messages in this thread.

You are currently looking at messages 0 to 4.

Replacing a headphone cord antenna with with an external one: how to do it? - Tron - 2006-09-16 20:49:00

I have a portable radio that uses the headphone cord as the antenna. The
radio's reception is very sensitive to movement of the headphone cord. I
want to build a plug-in device so that a telescopic antenna will replace
the antenna function of the headphone cord. The headphone will connect
to the radio through this external device. Not being an RF person I'm
not sure what kind of circuit would work (well). Can someone suggest a
circuit design (with component values) for the purpose? Thanks.



Re: Replacing a headphone cord antenna with with an external one: how to do it? - Homer J Simpson - 2006-09-16 21:02:00

"Tron" <_...@_.invalid> wrote in message news:nY0Pg.2130$Se.778@trndny03...
> I have a portable radio that uses the headphone cord as the antenna. The
> radio's reception is very sensitive to movement of the headphone cord. I
> want to build a plug-in device so that a telescopic antenna will replace
> the antenna function of the headphone cord. The headphone will connect
> to the radio through this external device. Not being an RF person I'm
> not sure what kind of circuit would work (well). Can someone suggest a
> circuit design (with component values) for the purpose? Thanks.


You need a choke and a capacitor, the choke to run the headphone from and 
the capacitor to connect to the antenna.

Re: Replacing a headphone cord antenna with with an external one: how to do it? - CheapscateDave - 2006-09-19 19:48:00

Tron wrote:
> I have a portable radio that uses the headphone cord as the antenna. The
> radio's reception is very sensitive to movement of the headphone cord. I
> want to build a plug-in device so that a telescopic antenna will replace
> the antenna function of the headphone cord. The headphone will connect
> to the radio through this external device. Not being an RF person I'm
> not sure what kind of circuit would work (well). Can someone suggest a
> circuit design (with component values) for the purpose? Thanks.

I would connect the antenna to the common connector on the headphone
plug. The only difference in the headphone circuit is the actual
resistance of the phone coils (8 ot 30 ohms).  The headphones will
still be part of the antenna system.

Dave

Re: Replacing a headphone cord antenna with with an external one: how to do it? - jasen - 2006-09-21 02:27:00

On 2006-09-17, Tron <_...@_.invalid> wrote:

> I have a portable radio that uses the headphone cord as the antenna. The
> radio's reception is very sensitive to movement of the headphone cord. I
> want to build a plug-in device so that a telescopic antenna will replace
> the antenna function of the headphone cord. The headphone will connect
> to the radio through this external device. Not being an RF person I'm
> not sure what kind of circuit would work (well).

connect the antenna to the common (back conductor of the plug)
wind the headphone cable through a ferrite core a dozen timnes or so.

you may get a better result connecting the antenna to battery negative
instead.

Bye.
   Jasen