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pbrowne
20-06-2018, 06:50 PM
I am setting up a 2.4 metre parabola pointing straight up to observe the 21cm hydrogen line at 1420MHz with meridian drift scans.



I'm planning to place the dish on a steel pole embedded in the ground and protruding 2 metres from the ground surface.


There is a tree some metres away that has a few branches well overhead of the antenna. It's a Eucalyptus tree, so not heavy with green leaves.


Question: Should I be concerned about interference from a few overhanging branches (say about 15 metres above the dish)?



My understanding is that shorter lines in the cm range should be less affected by interference (e.g weather), but I'm not sure about trees.

billdan
21-06-2018, 08:46 PM
My UHF digital TV operates at 500-800Mhz and I have perfect signal/pictures with the antenna looking through the trees. The transmitter is 45Kms away.

So you should be OK, I think.

bojan
22-06-2018, 07:42 AM
You might be OK with couple of branches...

However, when I experimented with my 21cm receiver (http://www.iceinspace.com.au/forum/showthread.php?t=113407&highlight=radio+telescope), nearby hedge (http://www.iceinspace.com.au/forum/attachment_browse.php?a=161164) was very good thermal radiator, signal was significantly stronger than MW (http://www.iceinspace.com.au/forum/showpost.php?p=1142693&postcount=46) when I pointed antenna in hedge direction.