Passive radar settings and performance

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Duppo
Posts: 19
Joined: Thu Apr 18, 2019 7:10 pm

Passive radar settings and performance

Post by Duppo » Sun Mar 08, 2020 12:34 am

Hi.

Has anyone had success with passive radar?
Which way time domain clutter cancellation is enabled? When I put tick to "Enable/Disable" It seems to be disabled and display is just full noise.

Also I'm getting 5-10 Hz updates while it's disabled but when I enable (removing the tick) it updates couple of time really slowly and updates seems to get slower and slower until it freezes after like 15 seconds.

I'm running Ubuntu 18.04 LTS on Lenovo P50 with i7-6820HQ. Not the newest cpu out there but I assume it would be powerful enough.

Thx :)

Duppo
Posts: 19
Joined: Thu Apr 18, 2019 7:10 pm

Re: Passive radar settings and performance

Post by Duppo » Sun Mar 08, 2020 10:08 am

Here is short video of my problem. (Mouse pointer seems to be a bit off where I click due some recording error)

https://streamable.com/38gva

rtlsdrblog
Site Admin
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Joined: Mon Nov 19, 2012 11:54 pm

Re: Passive radar settings and performance

Post by rtlsdrblog » Tue Mar 10, 2020 1:33 am

Time domain clutter cancellation should almost always be ticked (ticked = enabled).

The display will look like just noise if you have no antenna connected, or are not tuned to the frequency of an illuminator, or don't have your directional antennas correctly pointed.

I'm not sure why it's crashing when clutter cancellation is not checked though, will look into that. But regardless, leave it ticked and it should be stable.

Duppo
Posts: 19
Joined: Thu Apr 18, 2019 7:10 pm

Re: Passive radar settings and performance

Post by Duppo » Fri Mar 13, 2020 2:25 pm

rtlsdrblog wrote:
Tue Mar 10, 2020 1:33 am
Time domain clutter cancellation should almost always be ticked (ticked = enabled).

The display will look like just noise if you have no antenna connected, or are not tuned to the frequency of an illuminator, or don't have your directional antennas correctly pointed.

I'm not sure why it's crashing when clutter cancellation is not checked though, will look into that. But regardless, leave it ticked and it should be stable.
I didn't have antennas connected. I was just experiementing with settings.

Today I tried with directional log periodic 4g antennas. They were pointing approx 130 degrees from each other, one towards 658mhz TV transmitter and one towards clear sky.
Kept settings as they are, but I only get complete noise while clutter cancellation is ticked, unless I lower dynamic range to 1 or 2 from default 20.
I even tried unplugging survaillance antenna and connectinh terminator, which should mean its receiving no signal at all but still noise...

I tried unticking clutter cancellation and for couple of updates before complete halt I explained before graph looked like from videos. Alot of blue and some redspots in beginning.

As far as I know min gain to use is 15.7dB. With this gain even the survaillance antenna is able to receive TV signal, just way less than the antenna pointing at TV station. Maybe this is the problem? Should the reference signal be completely isolated from survaillance antenna?

rtlsdrblog
Site Admin
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Re: Passive radar settings and performance

Post by rtlsdrblog » Tue Mar 17, 2020 3:42 am

The display will look like noise if there are no objects being reflected. Was there any aircraft in the direction of the surveillance antenna?

If you uncheck clutter cancellation it will only pick up stationary clutter, and those reflections will overload the display, meaning that you can see nothing.

You need to isolate the surveillance antenna as much as possible, but it doesn't need to be 100% isolated. Also remember to have the coax lengths of both antennas identical.

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