Bias-T Not working

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Bias-T Not working

Post by ryan422 » Mon Sep 16, 2019 12:44 am

I have been using my RSP1a for a while and everything seems to work well although I have not been able to power my LNA with the bias tee. In SDRuno and the SawBird+ GOES connected and bias tee enabled nothing happens. I also tried a SawBird NOAA and a diffrent SawBird GOES, none of these LNA's lit up the LED indicating they were being powered. Is this software? Hardware? Any suggestions?
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Re: Bias-T Not working

Post by g1hbe » Mon Sep 16, 2019 8:19 am

Hi Ryan.
Do you happen to know how much current your devices draw? If it's more than 100mA, this will cause your RSP's safety cut-out to operate, and the 5v will turn off and stay off until a power-cycle.
Have you any way (such as a volt meter) of checking there is 5v on the centre pin of the antenna port without any device connected? Careful you don't short it, it's very fiddly.
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Re: Bias-T Not working

Post by RSP2user » Wed Sep 18, 2019 1:52 am

Ryan and Andy, the current draw for the SawBird+ GOES is 180 mA according to the NooElec web site: ... s-302.html

Ryan, the maximum current available from the Bias-T on of the RSP1A is only 100mA as stated by Andy. So the power output from your RSP1A is shutting down when you connect the SawBird+ GOES to the RSP1A Bias-T. Note though that the NooElec SawBird GOES (the nonplus version) uses only 30mA to 40mA and can be driven by the Bias-T on the RSP1A. You need the lower current version of SawBird GOES, if you intend to power it from the RSP1A Bias-T. The 30mA to 40mA version is available here: ... s-305.html

Also, make sure that you have the correct end of the SawBird GOES LNA attached to the RSP1A. The end to attach to the RSP1A has the power LED on it. If you still can't get it to work, be sure the connection cable is good and make sure you have the Bias-T power selected on the PC software that you are using with the RSP1A.

if you are planning to build a GOES weather satellite image receiving system, there is a post here with a wealth of information that may be of help to you: viewtopic.php?f=5&t=3262
Last edited by RSP2user on Wed Sep 18, 2019 2:48 am, edited 3 times in total.

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