Well I tried searching around my area with a frequency counter set for up to 3 ghz it has it’s own adjustable antenna. Most things detected were in the 500mhz range, nothing in L-band. Put it near the electric utility smart meter no real response. Not sure if the sensitivity is good enough for finding this RFI.
Is there a bandpass filter that can be inserted in the feed line or do you think this type of interference is being picked up at the LNA itself? It’s pretty bad during the day, will have to see if I can reaquire the GOES signal at night as before.
I can only guess it is possibly a secondary harmonic in the 800mhz band pushing it to 1691mhz. It doesnt attentuate very much until I tune down to around 1647mhz.
That interference looks like it’s actually in band, directly over the GOES signal. If it was out of band it would probably be desensitizing the LNA or RTL-SDR enough to make the actual signal invisible.
Another way might be to use the RTL-SDR dongle with a laptop and a small portable antenna (indeally directional like a log periodic yagi) to try and find the RFI source.
Well years ago I used to have a loop yagi for L-band but no longer own it. You have given me another idea in that perhaps I should relocate the dish and give GOES West a try. I think this repeater cable may reach that far and maybe that location will get me away from this noise source. I have a tree blocking GOES W at this position so that’s why I have been trying GOES E.
Well I checked everything this morning while it was dark and the noise spikes are still present. Next I rotated the dish in AZ in the general direction of GOES 18 (218deg) and the noise pattern still present. Next I aimed it directly at my house which is two story and noise pattern still present and I had to lower the FFT to get the spectrum back in range since it had risen, here is a screen capture of that.
I guess it is a reasonable assumption that this RFI is local since pointing does not matter. Haven’t tried moving the dish assembly to a different part of the yard since I only have 60 feet of active USB repeater to work with.
In that regard is it possible the USB repeater cable is the culprit…? Might have to install Satdump on a laptop and go inside a nearby shed to avoid glare and see what happens. I also unplugged the RTL SDR from the end of the USB repeater cable and measured 5.06vdc, plugged the SDR in and voltage dropped to 4.68vdc with .150A current.
What do you think of this as a RFI source: USB 3.0 (SuperSpeed):
SuperSpeed (5.0 Gbit/s): Significantly faster than previous versions, using a 5 Gbit/s signaling rate.
Noise and Interference:USB 3.0 data transmission can create noise that reaches the 2.4 - 2.5 GHz frequency range, potentially causing interference with 2.4 GHz wireless devices.
Finally Working!! —AFter trying all kinds of stuff without listing here I ended up relocating the dish 30 feet south and a bit east. Only need to do a little more tweaking position and skew and I think I am finally in business.
I think I know now what the root cause of the RFI was, up above on a mast and also on the chimney are two Davis Wireless weather station devices that transmit their data to the main unit inside the house to a dedicated computer. Don’t remember what frequency they work on at the moment but because of their promimity and moving away is most likely they were the prime candidate for this trouble.
I’m skeptical that it was the weather stations, those typically transmit a short pulse only every minute or so. Unless the weather stations happen to have very noisy internal electronics for some reason.
I’ve seen similar wideband noise spikes before from some IP based cameras though, especially the Wyze brand.
I have two sensor suites localed in two different locations, they transmit every 2.5-3 seconds and may overlap depending on the timing between them on 902-928 mhz. They do frequency hopping spread spectrum. Made by Davis Instruments.
I went through the breaker panel and turned off verything in the house except for the computer area, in there I just unplugged the router and cable modem. Made no difference until I relocated the dish away from the weather sensor suite above it.
