Observation 2552848: KAITUO 1B (40912) - I need to make some sat band filters

Satellites & Observations Observations
1

Regarding Observation 2552848 …

I downloaded the audio and lowered the sample rate to beable to hear what was being said and I found that I am picking up repeaters again.

One repeater that made the blip in the middle of the observation was the following. Its about 17 miles away from me and still manages to over load my SDR input and alias into the observation.

Westmont NE 145.490 - WB9UGX WSTMTESDA 107.2 AP E L RACES 05/30/20

I also heard a second repeater in this observation.

I think I need to make some filters to block out the repeater output parts of the band to fix this issue.

Any other suggestions on what to do?

Also I marked the observation as good because the satellite is visable just barely in the middle of the observation.

2

Unfortunately making a filter sharp enough to knock down the level of that repeater, and not affect the rest of the sat portion of the 2m band is not easy. Doing it ‘properly’ will probably involve cavity filters, and even them I’m not sure how well it would work.

You may be able to get away with a coax stub notch filter ( http://www.arcticpeak.com/antennapages/quaterwavestub.htm ) , but I’d definitely want to check the frequency response before you use it, as even these are quite broad.

3

Unfortunately its not just one repeater so far I know of 3 that overload my SDR and one is even 38 miles away in another state.

I think I will have to do some more investigating to solve this.

4

Ahh yes, that makes it even more difficult.
One solution may be to switch to a SDR with a higher dynamic range on that band. Something like a Airspy HF Discovery, though this is a big step up in terms of cost.

5

I have a limeSDR but thats going to probably be even worse. (Plus I have to do active cooling with a fan for it.)

I wonder if band conditions have been different i use to only sometimes hear the N9IAA repeater (the 38 mile away one) and now its been a lot more. Or its just that more people are on the radio while being at home.

I might make two coax stub filters that target the center of the repeater output sub bands and see if that helps.