CMDA Antenna - still useful?

**wrinklearthur** · 6th July 2011, 02:35 PM

Hi Lotz-A-Landies

The inductive coupling is more along the lines of a 1:1 transformer, but uses the signal that is fed to and from the aerial.

I made my own coupling attaching it to the top of a off the shelf mobile phone clamp and it works like a treat, feeding through some low loss RG58 type coax to a 6dB gutter mount whip.

I agree that a constant strong magnetic field could cause problems with some screens.

Inductive coupling to the aerial will not be harmful as the power is only slight and the signal frequency is in the Ultra High Frequency band, all parts of the handset are designed around those parameters anyhow .

Cheers Arthur

Originally Posted by Lotz-A-Landies

Don't know how true it is, but have heard that the inductive couplings (which use magnets to make the connection) damage the phone's LCD screen, shortening the life of the phone.

I got so frustrated upgrading my phone car kits and the lack of modern phones with the antenna connections, that I now buy second hand phones of the same model off eBay to fit my current car kit.

In fact I recently bought 2 new kits off eBay UK for $30 each when the original one cost me around $300 fitted.

**Graeme** · 6th July 2011, 03:36 PM

I tested my 6.5 db CDMA antenna with my then new Nokia 6120 via an inductive coupling in a marginal area (my property) but it made no difference to the number of signal strength bars. The Nokia got so much better reception than the new CDMA phone it replaced (replaced because of very poor reception) that it didn't need an antenna in my area so haven't bothered with an external antenna. I could do with an antenna in my tractor because of the sheltered areas behind hills so might do some more testing.

**wrinklearthur** · 6th July 2011, 04:12 PM

Hi Graeme

When I was playing around with the inductive coupler that I made, I needed to move the phone or the coupler orientation about to find the best effect, can be touchy finding that sweet spot!

Park the vehicle in a spot where there is half the signal shown on the phones strength bars, inside a shed is as good as anywhere, use the half way point as a refence.

Keep in touch as to how you get on.

Cheers Arthur

Originally Posted by Graeme

I tested my 6.5 db CDMA antenna with my then new Nokia 6120 via an inductive coupling in a marginal area (my property) but it made no difference to the number of signal strength bars. The Nokia got so much better reception than the new CDMA phone it replaced (replaced because of very poor reception) that it didn't need an antenna in my area so haven't bothered with an external antenna. I could do with an antenna in my tractor because of the sheltered areas behind hills so might do some more testing.

**Graeme** · 6th July 2011, 04:54 PM

Thanks Arthur. I'll have to see if I can find the coupler or another one as its not with the antenna I used on the tractor and I gave the car antenna away after the test.

Edit: I now remember that I gave the coupler away with the car antenna!

**Brad110** · 6th July 2011, 08:16 PM

Same freq, I am still using an old cdma one mainly for data on car and boat.

**Reads90** · 3rd September 2011, 04:52 PM

I was in Dick Smiths this afternoon and they had the CDMA aerials in the kits with all the bits for $5 each, you know the 1.5 m fiberglass ones. So I bought 3 one for each truck

But I have found these for connecting the iPhone to them

ANTENNA PATCH LEAD CRADLE HTC IPHONE LG NOKIA SONY ZTE

Cant get the link on the iPad but just search the above in eBay and you will see the cradle

Ali

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