Talk:C-band Receiver Station

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TODO

  • Thermal box for LNC (alu case, see Electrokit → Apparatlådor → Metall)
  • Mount feed and LNC on dish
  • Band pass filter for WBX (tbc)
  • External clock for USRP (tbc)

Wireless link between LNC and control room

The LNC is very good at stable; however, everything is relative and at 5.8 GHz even very small temperature variations can cause several kHz of drift. Keep in mind that 1% of 5.8 GHz is 58 MHz!

We have been considering two potential solutions for this:

  1. Put LNC in a box with active cooling and heating.
  2. Put the LNC in a

A quick and dirty solution that might provide some improvement is to:

  1. Put the LNC in an insulated box (passive)
  2. Measure the temperature inside the box. Assuming that we can map the LNC frequency drift vs. temperature, we can use the temperature to estimate the drift.

This would also need some sort of wireless link from the antenna to the control room:


Logbook

2010.01.28

I found about about UNITEC-1 via Southgate ARC. Interesting but there seemed to be long time until launch (20 May maybe).

2010.01.30

Discussed the UNITEC-1 tracking with Scott OZ2ABA. We are considering and we will look for LNCs.

2010.02.01

Kuhne has several LNCs for the 5.8 GHz band that cover the whole band from 5.6 to 5.9 GHz:

The first option is probably better due to lower cable losses – we have about 40 meters cable from the antenna feed to the control room.

2010.03.07

Email from Mineo Wakita JE9PEL on AMSAT BB noting that the PLANET-C and UNITEC-1 launch date is now set for 17 May 2010 21:44:14 UTC. Time to get C-band gear ready!

2010.03.09

Official kick-off. At the AMSAT OZ meeting today we agreed to proceed with the project and to inquire about the KU LNC 5659 C PRO down-converter. The LNC will be the property of AMSAT OZ. Using the 400-700 MHz version of the LNC we can use the existing cable going between the tower and the control room. First we try without any buffer amp between the LNC and receiver.

Sent inquiry to Kuhne.

2010.03.11

Ordered KU LNC 5659 C PRO down-converter.

2010.03.12

Made the first blog post about the project.

2010.03.15

Received the LNC. Visual inspection OK, see video on YouTube or Ustream. Added photos to Picasa album.

2010.03.16

  • Made blog post about LNC.
  • Brief chat with OZ2ABA about tracking accuracy we can achieve:
    • Hydraulic drive has optical encoders with resolution 0.05°. Az encoder connected, El encoder is not connected.
    • Temp stability of LNC: Measure temp profile in lab and equip LNC box with a thermometer
    • USRP: Use 10MHz Rb reference as input to 64MHz signal generator.

2010.03.17

2010.03.21

  • Created a prototype CW receiver for the OZ7IGY tests on Tuesday by reverse engineering the flowgraph of the SDR transceiver
  • Blog post with video demo of the receiver.

2010.03.23

2010.03.31

  • Found out how to implement SSB in the simple receiver. See blog post.

2010.04.05

  • Implemented SSB in the simple receiver (V0.4).
  • Decided to separate the band pass filter from he frequency xlating filter as described in the blog post.

2010.04.08

  • Found suitable values for Fast, Medium and Slow AGC. Not quite perfect but usable. See blog post.

2010.04.09

  • Experiment with binaural CW reception, see blog post.
  • Investigated using complex LO instead of freq xlating filter hoping to save some CPU by removing low pass filter. Got the opposite result, see blog post.
  • Finished version 0.6 of the receiver where a USRP frequency entry widget has been added.

2010.04.10

2010.04.13

  • Successful on the air test of receiver and LNC using OZ7IGY beacon signal. 5-10 dB SNR but the direction was almost 90 deg off, meaning that we were receiving a reflection. See blog post (TBD).

2010.04.16

  • Very preliminary link budget indicates that we should be good to 20 million km. Not bad.

2010.04.30

2010.05.04

2010.05.08

2010.05.11

  • OZ2ABA mounted new cables on the antenna.
  • Created functional diagram of WBX receiver.

2010.05.12

2010.05.15

  • UNITEC-1 Operation Center website announced.
  • Software for trajectory estimation is available: Windows binary or Excel sheet.