Observation 7966723: NOAA 18 (28654)

Regarding Observation 7966723

Hi, I scheduled my ground station to observe NOAA-18 and got this result.
what may be the problem for this type of waterfall with good response?

I’d start with verifying cables and connectors.
Also describe the entire RX path from antenna to SDR.

I have V-dipole antenna of 135MHz - 139MHz tested with NANO VNA. It is connected to RTLSDR V3 (RTL2832U) and then to Raspberry Pi 4 Model B

I did not use LNA

schedule a bunch more obs then. if you set up the gain properly it should work, granted the cable and connectors are all ok. if you have very strong broadcast FM nearby you might need the FM notch filter to tame that down.

okey sure…
thank you @SA2KNG

Lets try to stay with as few threads as possible so it’s easier to follow this.
Regarding this thread I’d say check the gain, either overloaded or some interference would be my guess.

Knowing nothing more of your complete setup nor what experience level you are, here goes.

There’s a few threads on the setting gain topic, as well as a bit down in the Omnidirectional_Station_How_To.
Using too low or too high gain leads to reduced signal to noise ratio and in the too high scenario leads to a lot of other odd artifacts as well.

RX chain, basically it boils down to keeping RFI from the antenna (and antenna away from the sources), good placement, grounding and RF chokes on the coax. The antenna needs to be designed properly, when browsing the net and stumbling on pictures like this

I’d say the “optional” part with the balun is not true, at least use some chokes or the simple coax coil close to the feedpoint.

1 Like

Thank you @SA2KNG

I will check every connections and try to set the suitable gain…

This is recent waterfall I get from the Observation SatNOGS Network - Observation 7978437
and got no any image

Is this because of interferences due to not notching the commercial FM bands?

I’m not sure what that signal is, but it’s certainly strong and messing with the reception. gain still 44.5 which is max ?