New L-Band Filters from Adam Available

Adam (9A4QV) is well known in the RTL-SDR community for producing the LNA4ALL low noise amplifier as well as various RF filters that work well with the RTL-SDR. Adam is now selling some L-Band filters designed for improving reception with Inmarsat, Thuraya, Iridium, GPS satellites. It can be used for example when trying to received STD-C EGC or AERO data from Inmarsat satellites.

Adam writes that the filter will be most useful for those living in urban areas that are close to radio and TV towers. The filter is built on his standard filter PCB which also has the ability to add a simple bias tee circuit for powering externally positioned LNA’s such as his LNA4ALL which are necessary for good reception at L-band with an RTL-SDR.

He is currently selling it fully assembled for 20 euros, plus 5 euros for worldwide shipping.

Adam's L-Band Filter Characteristics.
Adam’s L-Band Filter Characteristics.


  1. Drone

    Only 10dB Ret. Loss (~2:1 VSWR) smack in the middle of the passband? Hmmm…. [I’d put this on Adam’s Blog but it’s a Blogspot nightmare with no simple way to post a comment.]

    • Adam

      The blog is opened for the comments but I can read here also. The RL from the first picture is simulation. I will measure the real S1,1 but should be very close to predictions. This kind of filters offering that figures, difficult to get all parameters by the book. (-3db, RL, IL, size of the filter etc.) This is why I post the measurements so the buyers know what they are buying and no negative surprises later on. I post the readings good or bad 🙂

    • Adam

      Blog updated with the S1,1 quick measurements with higher resolution where the markers can be read easily.
      Again very close to manufacturer S2p.

      • David

        “This is why I post the measurements so the buyers know what they are buying and no negative surprises later on.”
        Very good Adam, thank you.

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