Akademisk Radioklubb

LA1K / LA1ARK / LA1UKA

Satellite dish measurements pt. 3: Fixing a broken RF Hamdesign five band ring dish feed

After we had found out that the problem with our parabolic dish was that the feed probably was broken, we finally had an undeniably good enough excuse to open it and take a look inside. LA3WUA itched to pry open the can and discover the hidden wonders inside, and got to wield the heat gun.

Turns out the error in the feed was not very subtle or difficult to find. The antenna is not supposed to be heart shaped and misaligned, and it is not supposed to be bathed in a sea of moisture.

LA3WUA therefore went on to fix it.

Correctly aligned 23 cm antenna:

The next step was to avoid accumulation of condensation again by inserting a gore-tex plug into the feed, allowing moisture to go out of the feed box without any water entering.

We could then seal the box again …

… and re-insert the feed into the dish.

We could then lean back and enjoy the view of the evening’s good work.

… until we discovered that the LNA also had stopped working, and we had to take everything down again.

LNA box.

LB6RH and LA3WUA took out the LNA, took a good look at it, tested it, found no error, reinserted it, and somehow made it work again. We will probably have to follow this up later.

The full reception chain of the dish at 23 cm is apparently working again, and we could finally receive our first satellite with the dish (Inmarsat 3F2). Phew :-). We look forward to get on with the 1-10 GHz project.

3 Comments

  1. Excellent work and very entertaining read! Are those four 50ohm terminators installed at the dish feed? What is their function?

  2. Nice to see the rise of the new generation of Adjustment Aces at LA1K.

    Keep up the good work!

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