@zoltan wrote:
Ferrite Isolator Test
Likewise as Cecil did, I installed a Radio Shack snap on ferrite isolator on the cable between my SDR/hub and the CHIP, and observed higher SNRs at low Rssi receive signal levels.
An SNR of 6.23 dB (with an Rssi signal level of -113.93 dBm) is about 3 dB better than I usually get at that Rssi signal level. I could only wrap the cable twice, as the pigtail from my hub to the CHIP is too short. (The ferrite isolator is right above my USB stick in the picture). @zoltan @Abhishek please take note.
Interestingly enough, before I repacked my Alpha Lantern, I had all the components laid out and had the hub connected to the CHIP with a 4 ft USB extension cable with 2 wraps thru the ferrite isolator. (My LNA/SDR was 4 feet away from the CHIP with the ferrite isolator placed midway.) In that layout, my SNR performance was up another 3 dB peaking at around 12 dB with Rssi levels of -110 dBm
I know this is a more subjective test as signal levels bounce around, but I took observation over a 1 minute period in each case within a 10 minute time period.
The CHIP noise impact on the LNA/SDR appears to be proximity related, and can be mitigated successfully in the Lantern the way I did. No doubt those of you that have longer cable runs between your PATCH antenna and LNA/SDR should see even bigger improvements.
I'm wondering if I moved the LNA/SDR to the far left next to the battery in the Lantern case, if that would make a difference. I'll try that next time I open the Lantern by putting a shorter USB extension cable between the LNA/SDR and the hub. Ken
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