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Help setting up GPS antenna for JAERO and Inmarsat?

Posted: Wed Apr 13, 2016 1:12 pm
by Cy80rg
Hi all,

Having seen the article on here regarding using JAERO to decode signals from INMARSAT using a GPS antenna and RTL Dongle, I had a go at this last night.

Managed to hack the gps puck to remove the filter and bridge over.

Connected this to the dongle, setup the virtual cable, set up SDR#. JAERO got green lights on the Volume and Signal UI, but never got any data.

Reading a bit more on this, I believe this is because the gps wasnt being powered...

So, I get the general idea with this sort of thing (I'm successfully running piAware station with HamAMp etc) - just looking for a helpful forum or person where I can post images of what i'm doing, and they can then correct me etc?

I'm keen to learn this - but I'd like to do a "proof of concept" as cheaply as possible before I commit to any significant spend.

Any takers?

Re: Help setting up GPS antenna for JAERO and Inmarsat?

Posted: Wed Apr 13, 2016 11:41 pm
by rtlsdrblog
The GPS antenna will definitely require power via the coax cable. You need a bias tee circuit that can provide between 3-5V to power most of these GPS antennas. Our RTL-SDR blog units have a bias tee that can be enabled by bridging two pads. If you don't have our unit then you can either build an external bias tee, or hack it into the dongle like what is done here http://www.rtl-sdr.com/rtl-sdr-bias-tee-hack/

Re: Help setting up GPS antenna for JAERO and Inmarsat?

Posted: Sun Oct 09, 2016 10:28 pm
by Username
is there an usb powered bias T ?

Re: Help setting up GPS antenna for JAERO and Inmarsat?

Posted: Mon Oct 10, 2016 9:32 am
by rtlsdrblog
Username wrote:is there an usb powered bias T ?
Don't think so, not that i've seen yet.

Re: Help setting up GPS antenna for JAERO and Inmarsat?

Posted: Mon Oct 10, 2016 9:35 am
by Username
ok how can I power up an Bias T?

Re: Help setting up GPS antenna for JAERO and Inmarsat?

Posted: Tue Oct 11, 2016 12:17 am
by rtlsdrblog
The bias tee is the power source for the LNA. Our V2 & V3 dongles have a bias tee on them which is USB powered, but there are no bias tee only devices powered by USB as far as I know. You can easily build one, a bias tee is just an inductor and capacitor. Adam 9A4QV also sells bias tee PCB boards on his filters, but I believe they are designed to be powered via batteries or external power.

Re: Help setting up GPS antenna for JAERO and Inmarsat?

Posted: Tue Oct 11, 2016 9:35 am
by Username
i cand solder. :evil:
I am just a beginner in the (hardware) sdr word. SDR# thins and SIGINT stuff work.