Added an active GPS antenna to the RTL 4000 tuner/spectrum analyzer. Got a little active GPS antenna from ebay (item 150748428125) only 6 $, and made a little 'T' section to power it, while connected to the 4000 DVB-T tuner:
That is just a LM317 to create a voltage of 4.75 V here:
active 10p GPS -0-------||-------0- E4000 DVB-T stick connected to PC USB antenna | with xpsa spectrum analyzer software SMA ) LM317 ) _____________ | | | | +4.75
+9V top + 15V ----- |in adj out|----------------- | |_____________| | | === | [ ] 220 | | 1u | | | /// ------------| === iu | | | [ ] 6k8 [ ] 680 /// | [1] | /// /// [1] could not find a 560 Ohm SMDLM317 is a bit overkill, it is mounted on the back of the minuscule PCB. Could not find any 78L05.. Thing is powered from a very small wallwart.
There is considerable extra gain from this active GPS module, and the long cable allows to find a quiet place, far from GHz processor whisper.
So now I get a lot of very interesting GPS spectra, and I can record the IQ signal.
There does not seem to me an impedance mismatch (was my worry).