A network analyzer will allow you to measure all the S parameters.
These will show you how much from the incident power is reflected and
how much is transmitted. You can't adapt by hand a PCB antenna if you
didn't simulate it first just a little. The 1.5mm thick PCB epsilon is
between 5.0 and 5.5 (ordinary pcb). This may help if you have a ground
plane (hope not) to compute the antenna capacitance or the parasitic
capacitance.

As a homebrew solution try a grip-dip-meter. But you didn't say if the
antenna is just for receiving or for transmision too. At 3dB input
power with -1.5dB loss on antenna ( a very good situation) you'll not
be able to transmit something.

cheers,
Vasile

On 9/7/05, Shawn Yates <SYates@caretech.com> wrote:
> 
> I have a PCB with a loop trace (correct term?) antenna.  That is, its a
> track that's right around 1/2 wavelength long.  I want to put a variable
> cap on that and then be able to tune each pcb for optimum resonance at
> my radios freq.  What equipment would I need for that?  A signal
> injector?  A network analyzer?   The freq is 916Mhz fixed incase that
> helps.  The output power of the radio is about between 3 and -3 db, very
> low power.  If anyone can suggest equipment, including make and model it
> would give me a starting point to do some shopping.  or if you can tell
> me some of the specs to look for that would be great.
> 
> Any input is welcome and appreciated.
> 
> Shawn
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