32.7°W Orion 4 [USA-139] (incl.)

**s-band** · June 10, 2020 at 8:37 PM Official Post

An old sigint satellite and on Ku band, as opposed to Ka on the later ones, Mentor4/Orion6/USA202 and Mentor6/Orion8/USA237 (see Ka band E/A data section). I wonder if it is still working correctly as the spectrum looks quite strange. It is only 2.5dB over noise. There are carriers at 12500MHz and 13300MHz in the peaks of the noise.

Vertically polarised. Blue trace on a wide band 1.5dB NF LNA, red trace on a 11.3GHz LO, Ku, LNB. 1.2m dish. The wide band system loses sensitivity below 12.5GHz.

**s-band** · June 9, 2025 at 3:52 PM New

Only 5 years since I last looked for this. I moved the thread to ext Ku as that's where most of the power is concentrated. It still looks like the lower transmission is distorted but it's an old satellite. The TLE gave a location a few degrees from true but the data was about a month old.

The plots from 5 years ago were done using circular polarisation for the wide scan. Today's are with a linear polarised feed with skew control.

I'm not certain but it looks like there is a different transmission on on each polarisation the higher wide signal

1.2m dish, 1.2dB LNA. Wide sweep normalised to system noise level.

Horizontal

Vertical

32.7°W Orion 4 [USA-139] (incl.)

qwer July 12, 2023 at 5:44 PM

s-band June 9, 2025 at 3:37 PM

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