If you’re in the market for a decent L-band antenna with a built in LNA, one you can power via a simple 5v bias tee. Look no further than a GPS antenna.

These antennas are generally housed with their own LNA which is powered via a bias-tee. Generally all you need to do in order to make them useful for L-Band is to remove the 1575 mhz filter that is used to ensure only GPS frequencies make it though to the receiver. Once you’ve done this you have a nice cheap L-band antenna.

In my case I’m using an NMO mounted antenna so I can have a nice L-Band antenna on the car/mobile. While I’m using NMO here you can generally use this to modify any active GPS antenna.

NMO Mounted GPS Antenna Unmodified

You’ll first want to flip this over and remove both the rubber pad (if it has one) and the rubber inserts that cover the screws.

Once this is complete you’ll want to separate the top from the bottom, for an NMO type GPS antenna I suggest a small flat head screw driver, careful not to mar the screw fitting.

With screws removed light pressure under the teeth with a screwdriver should pop it out.

After you’ve removed the top and bottom you’ll need to remove the screws holding the top of the antenna to the base which contains a pigtail to the NMO connection. You will in this case also need to de-solder the shield so you can access the raw board itself.

You should now be able to pull off your shield and expose the 1575 MHz filter.

Back of GPS Antenna Opened to Expose Filter and LNA

Grab some pliers and a heat gun (or soldering iron) and work the filter off the board.

Filter is Usually Labeled 1757 (The GPS Frequency)

In my case I broke the filter and was unable to fully remove it, I simply bridged the pads with some wire and while it doesn’t look pretty it works great!

Broken and Burned Filter with a Wire Bridge over It.

Reassemble your antenna and you’re in business!

Antenna Soldered back into Place
Modified NMO Antenna Installed on The Car

Now you just apply bias-tee voltage and tune anywhere you want in the L-Band. I’ve successfully pulled inmarsat and iridium with this.