You may want to consider modifying your attachment so you do not place metal next to the tag where it can influence the antenna. The recommended set-up is to use a non-conductive pole (e.g. wood, PVC, fiberglass) and to attach the tag to something that simulates the animal body. The reason is that the antenna needs a counterpoise to radiate effectively. The two “popular” methods are a piece of hotdog or a small plastic flask/bottle filled with a sponge and saline solution. Both should be sized/filled to weigh about the same as the target animal. Then attach the tag to that with the antenna pointing in the expected direction, for example, horizontally to simulate a bird in flight.
Those are pretty cool screen shots! I have not been able to capture the signals with SDRsharp, they go by too fast for me. The only app that has worked for me is SDRangel, which has an “interesting” UI… But if SDRsharp works for you all the better!
I have been primarily working with RTL-SDRs, see the thread on RTL-SDR vs. FUNcube, but I may be able to help a little. On Sensorgnome V2 the file that controls some of the SDR detail settings is /etc/sensorgnome/acquisition.json, on SSv3 it lives at /data/sg_files/deployment.txt. In that file there are “plans” for rtl-sdr, funcubePro, and funcubeProPlus. Be sure to edit the plan that pertains to the SDR you’re using (e.g., "devType": "funcubeProPlus"). After editing, you need to restart the main process, on SSv3 that would be sudo systemctl restart sensorgnome and on SGv2 that would be sudo systemctl restart sg-control.
In terms of changing the devParams, I have only experience tweaking the ones for RTL-SDR. You mention the tuner_gain: that this setting is for RTL-SDR and not FCD. The FCD plan has gains for various stages and not being intimately familiar with FCDs I can’t comment on the default settings. The filter settings control the frequency band filters that the FCD can switch in/out and these are extremely unlikely to be wrong.
In terms of detection sensitivity: a Lotek tag emits bursts of 4 short (2.5ms) RF pulses with a spacing of up to ~100ms which encodes part of the tag ID, and these bursts are repeated every few seconds (7.1 in your case). Each pulse needs to rise at least 6dB above the surrounding noise (that’s the minsnr setting), where surrounding is ~20kHz in frequency and some ms in time (I don’t know the value). You will see the raw pulses in the Web UI (the SGv2 UI shows SNR, which I find very helpful in this context). In order to show a tag detection in the Web UI two things need to happen: you need to have uploaded the tag definition to the SS/SG and it needs to see at least two pulse bursts with the correct burst interval (it accepts 2x the interval as well).
When you compare distance results with other people remember that most probably use a 9-element Maple yagi, which has more gain (but also a much narrower beam). The height above ground does affect the range due to what’s called the fresnel zone (Fresnel zone - Wikipedia).
This is what comes to my mind at the moment… I hope others will chime in!
Welcome to the forum!