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Tuesday, 3 December 2013

Who's Lindenblad I wonder?

Well,

Since the launch of the new cubesat Funcube-1:

http://funcube.org.uk/

I've been watching the path of the satellite while I've been in the shack (tracking it with logger32) and downloaded telemetry data on a number of the birds passes using the funcube dashboard (available on the link above).

I've only been using a vertical "white stick" that I have on the side of the house, and the antenna is far from optimum for listening to Low Earth Orbiting Satellites (LEOs).

So, I did some research and found this:

http://n3ujj.com/manuals/Lindenblad-2meters.pdf

This is an easy to construct Lindenblad antenna - designed specifically for LEOs reception. Now, "easy to construct" for me was not so easy. Anyhow, I ordered the metal I needed and some other bits and bobs and today I have been to see my friend Paul who has a metal workshop. He has helped me cut, bodge, bend, hit and rivet stuff. I've brought all the bits home and assembled something that looks like this:


So what we basically have is four dipoles all slightly non-resonant such that they present a 200 ohm impedance so when they are connected together we end up with a 50 ohm antenna.


The feeder arrangement is rather odd; the pdf linked above suggests soldering the four cables into the N-Type socket but that looked as near to impossible as makes no odds so me - I'm trying this bodged arrangement first!


I'm just off to get the "corporate" antenna analyser that covers 144MHz - then we will see if I have created an antenna or a clothes line of some sort.

Cat's been no use whatsoever today:


Interesting, egh?

2 comments:

  1. Hi
    I have just finished building one of these to the dimensions shown on the .pdf available on line. I cant get the low SWR claimed though, with it being 1.5:1 at the desired 145.900 mHz. 144.300 mHz is a bit better at 1.2:1, and impedance around 49.1R. I did manage to get all 4 centre connectors into the N Type and solder the braid round the 4 outer braids without melting anything!
    Did you get yours to work okay?

    ReplyDelete
  2. Hi
    I have just finished building one of these to the dimensions shown on the .pdf available on line. I cant get the low SWR claimed though, with it being 1.5:1 at the desired 145.900 mHz. 144.300 mHz is a bit better at 1.2:1, and impedance around 49.1R. I did manage to get all 4 centre connectors into the N Type and solder the braid round the 4 outer braids without melting anything!
    Did you get yours to work okay?

    ReplyDelete