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A simple amplified GPS antenna

I was in need of an external antenna for my Trimble GPS Disciplined frequency standard. This design is based on the N7KKQ design from the October 2002 issue of QST. The Trimble needs >25dB of gain to lock to the GPS data, so I added a single stage MMIC amp. This was mounted as close as possible to the antenna (actually on the microstrip down lead) and can be seen in the photograph below.

Base of GPS antenna showing MMIC amp. Click for bigger & clearer

The MSA-0886 MMIC is the tiny black blob with four legs. The 22 Ohm resistor provides bias to the MMIC and the 11pF capacitor is blocking the DC supplied from the Trimble (it only supplies 5V, which is too low for this MMIC device). The bright yellow inductor is there to prevent our precious amplified signal from vanishing into the power supply.

Overview of whole GPS antenna prior to boxing up.

This version of the amp and antenna does not provide enough gain to reliably lock the Trimble unit. Lock is very sporadic. This could be fixed by adding another stage of amplification or moving to a higher gain MMIC device. For now this is good enough to work as an extra antenna for another of my GPS receivers.