GPRS PCMCIA card - antenna matching Q

[Peter]

Hi All,

I am using a Sierra 750 GPRS card

http://www.sierrawireless.com/ProductsOrdering/AC750_GSM.asp

but I am connecting an external antenna to it via about 1ft of 50 ohm
coax cable.

The external antenna is in an ix104 tablet computer and if you like a
lot of reading the details are here

http://www.peter2000.co.uk/ix104/index.html

I have no data on the ix104 external GPRS antenna characteristics but
it is certainly a lot smaller than the little rod one that comes with
the 750 card.

To connect to the 750, I cut off the rod of the antenna which comes
with it and solder the coax direct to the RF connector which forms the
base of the antenna.

Unfortunately there are several components (capacitors and inductors)
on a tiny PCB at the base of the antenna. I can't avoid damaging these
when removing the plastic moulding.

The finished thing does work! The sensitivity appears comparable to
e.g. a Nokia mobile phone, so I am content with it. However I am
concerned about the VSWR resulting from an impedance mismatch - can it
damage something?

I know about hardware/software but my RF knowledge is minimal.


Peter.
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[James Meyer]

On Thu, 17 Mar 2005 10:58:33 +0000, z180@nospam24.com (Peter) wroth:

The finished thing does work! The sensitivity appears comparable to
e.g. a Nokia mobile phone, so I am content with it. However I am
concerned about the VSWR resulting from an impedance mismatch - can it
damage something?


Peter.

If it works, don't sweat the small stuff. There isn't enough power
available in a typical cellphone output stage to damage anything even with 100%
of its output reflected back.

Jim