DIYbanter - View Single Post - Using headset as cell phone radio antenna.

Terry Casey

In article ,
says...

On Sat, 28 Jul 2012 19:05:27 +0100, Terry Casey
wrote:

In article ,
says...

On Fri, 27 Jul 2012 10:12:54 -0400, micky
wrote:

For antenna purposes and those frequencies, are there any differences
from one headset to another?

Somewhat. There are headsets (4 wires) and earphones (3 wires).
Either will work. The problem is that some of the headsets come with
shielded wires, which will cause reception problems. I've only seen
one like this, and it has an easily identified thick cable.

Wrong! The shield is used as the antenna!

If that's true, then why does my shielded cable earphones fail to hear
much on FM?

I've no idea!

Is it any better with unshielded cable?

All I can tell you is that my earphones are definitely shielded - I had
to replace the connector as the cable fractured - and that it works fine
with my phone!

http://www.youtube.com/watch?v=Lm7V-JrDiwk
Notice that he's connecting the antenna wire to the center pin, not
the ground.

Well he does say in the accompanying text that his FM reception is bad!

Interesting the way his 3-pole plug turns into a 4-pole one!

I can't tell what this one is doing:
http://www.youtube.com/watch?v=D_JYNP410xU

Well, if he poked it any further into the jack he would have shorted the
audio output, so he obviously made contact with ground only (I'm
ignoring the mike connection, if there is one).

There is no way he could have made contact with the tip, like the
previous guy!

If I have time, I'll play with a connector and see which pin is the
antenna.

The shield should always be connected to ground, irrespective of whether
it's the barrel of the plug or one of the rings. Using a 3-pole plug
connects both together, anyway, so the shield will go to ground no
matter which way the jack is configured.

Note that it is not true ground, as far as the phone is concerned - it
is connected by an inductor which has negligible affect on audio
frequencies but a high impedance to the FM frequencies, thus allowing
the 'ground' connection to be used as the antenna.

--

Terry