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Using headset as cell phone radio antenna.

On Ebay, I bought a cell phone with FM radio, that gets the radio from local stations, not from cell phone data, and after I bought it, I found the manual online, which says that the radio antenna is the wire to the earphones.

But the phone didn't come with the factory earphones.

Mostly I want to listen to 88.1 Mhz FM, and if possile 88.5, and

90.1frequencies.

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

Does the thickness of the copper wire matter?

Factory headphones may be impossible to get. without buying a second phone. Should I try to find out how long the wire is on factory earphones and get a headset with the same length?

Thanks.

Reply to
micky
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Yep. I have one like that. Motorola Droid X. The receiver sensitivity is horrible and it only works in strong signal areas.

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.

No. In theory, tiny wire may add some resistance or reduce the tuned bandwidth. In reality, the receive is so bad, you probably won't see any differences.

Baloney. Such headsets are all over eBay. It would be helpful if you would kindly disclose the maker and model of your phone.

No. While getting the length correct, the lack of a counterpoise (other half of the dipole) is probably more important. In ham radio, it's called a "tiger tail".

I played with it on my Droid X. It certainly improved reception, but it was still lousy. I'm thinking of an external RF amplifier, but suspect that will increase the sensitivity to the point where it will pickup computah noise from the processor (which is why the receiver is nearly comatose). Good luck.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558
Reply to
Jeff Liebermann

My friend had a Sony Ericson (model I forget, maybe w300i, several years old) that worked well on 88.1, but the phone broke in other ways, and her new phone is a Samsung something smart phone, and the sound goes in and out, sometimes good, sometimes not. . She gets consistently good reception on some commercial FM stations but 88.1 WYPR is public and she thinks the transmitter is weaker.

The station does come in well on my Sandisk Clip, a little MP3 player about 1.5" almost square, but I've mislaid that.

Good. I'll avoid that.

I meant get an actual Huawei headset, but I gather I don't need that.

Of course. It's a HUAWEI Fusion U8652, sold mostly by AT&T under their brand. It has stereo radio with RDS I haven't got the phone yet, it's still being shipped.

Maybe for us that would make the difference. Maybe we could each buy one of those rubberized cases for the back, and coil it around in there, relying on induction?

It should be 300,000,000 / 88,100,000 meters long? Or half that? About 4 feet? Or 1/4 of the first number, 2 feet? I"ve never heard of 1/8th wave, but maybe that works too? 1 foot?

Thanks.

Reply to
micky

No. Except for the shielded wires, every headset that I've tried works as an antenna. You can also make or buy an adapter that works:

3.5mm jack. However, I goofed. I can't count wires: 2 wires mono EP 3 wires stereo EP 4 wires some earphones with microphone and possibly PTT. 5 wires defacto stereo earphones, with microphone. If you buy a headset for your smartphone, it will be a 5 wire connector as shown in the first URL above. However, you can also just plug in a 3 wire stereo earphone, as you don't need a microphone. Make sure that they're somewhat high impedance (>40 ohms) as I don't think the phone has the power output to run a pair of 8 ohm earphones. All are high impedance so that the cabling requirements are minimal.

RDS isn't used very much in the USA. Very little RDS, RDS/RT+, or eRDS. At best, it will display the station call letters and the tune being played. Nifty stuff like weather and traffic reports are usually done using HD Radio PAD data channel.

No. You'll never get throug the shielding inside the case.

Sigh. FM broadcast is at 100MHz. One wavelength at 100MHz is about 10ft. Each side of the dipole is 1/4 wavelength long. Therefore, the antenna and counterpoise should be 2.5 ft long.

My Droid X FM radio application didn't have a signal strength meter, so judging improvements in antenna design was rather subjective.

Good luck.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558
Reply to
Jeff Liebermann

Any set of headphones should work fine.

I have a Nokia with FM and the correct headset but always use it with the earphones from my MP3 player (I don't use the phone hands free, so don't need the microphone).

The screen (US: shield) of the cable is used as the aerial/antenna but most (if not all) earphones use screened cable.

I don't think the length is going to be of any real consequence, though a quarter wave whip @ 90MHz is ~80cm (~31 inches) if you want to try and find a match!

--

Terry
Reply to
Terry Casey

Wrong! The shield is used as the antenna!

--

Terry
Reply to
Terry Casey

The earphones I use for FM are the same ones I use on my Sandisk Sansa MP3 player but they're Skull Candy, not the original Sandisk set

It is (300/90)/4 metres. 300/90 = 3.33m (full wave) Quarter wave is 3.33/4 = 83.33cm.

Antenna length is 95% of that - 79.16cm if you want to be accurate! Or 31.17 inches.

For 88MHz, the length is 1.8cm/0.7in longer.

FM aerials are usually cut for the centre of the band (98MHz). Corresponding lengths are 72.7cm/28.6in

However, this is all rather academic as these calculations are for a whip in free space - not in close proximity to a human body!

For what it's worth, my 'phones are 1.22m/4 feet long ...

--

Terry
Reply to
Terry Casey

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

Notice that he's connecting the antenna wire to the center pin, not the ground.

I can't tell what this one is doing:

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

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558
Reply to
Jeff Liebermann

(...)

Well, you're 1/2 right (and I'm half wrong). The antenna is NOT the shield but the shield is not the ground connection on the 3.5 mm connector.

I inserted a 4 pin 3.5mm plug into my Droid X, and setup the FM tuna to play through the speakers. Using a 2ft long clip lead as an antenna, I probed all 4 pins on the connector to see what it could hear. The sleeve (shield) connection did nothing and was the same as no antenna. I couldn't even hear a local strong station. The tip and the first ring picked up a few stations. However, the 2nd ring connection produced dozens of stations (along with their RDS data), so that must be the antenna wire.

It's the TRRS connector, with connections marked as: tip, ring 1, ring 2, and sleeve.

The typical wiring configuration is: tip Left Earphone ring 1 Right Earphone ring 2 Ground sleeve Microphone

If you plug a 3 pin TRS (tip-ring-sleeve) connector into a 4 pin TRRS jack, ring 2 and the sleeve are connected together, thus grounding the microphone connection.

The mic connection is also uses for controlling the music player:

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558
Reply to
Jeff Liebermann

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!

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!

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!

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
Reply to
Terry Casey

But if the 2nd ring is ground, the shield should be connected to it ...

... which connects the shield of a 3-pin plug to 'ground' - which also doubles as the antenna connection, as you have proved ...

--

Terry
Reply to
Terry Casey

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