[amsat-bb] Re: Simple 2.4Ghz helix plans?
ko6th_greg at hotmail.com
Sat Oct 31 00:15:46 PDT 2009
I followed instructions from Howard Long, G6LVB, posted here a few
years ago. (If the archives go back far enough, it was in November of
2001). I don't have it electronically, but the instructions went
something like this:
Get a long piece of thick bare copper wire (#10 is what I think I used), and
put a small mark on it every 5 3/4 inches (146mm). Sharpie marker works well. Wrap it around a
cardboard tube that's about 1 3/4 inches in diameter. The tube from a roll of paper towels works fine; the dimension is not critical. Space the turns about 1 1/4 inches (32mm) apart.
Now, here's the magic part: once you get the helix about right, sight down one edge, and you'll see those 146mm marks you made in the first step. Twist and stretch the coils so that they all line up, AND at the same time, keep the turns spaced (center to center) 32mm apart. Take your time. The diameter of the turns will take care of itself.
For the first 1/4 turn (the matching section), decrease the pitch so that it gently slopes away from the reflector, which needs to be something around 4 or so inches in diameter. The rest of the mechanical stuff you can pretty much make up yourself. There are a lot of examples if you browse around the web a bit.
Helix antennas are pretty forgiving in construction, and really cheap to make.
p.s. If you already have a Wi-Fi antenna, it should work too. Conversely, I've found that a Helix easily outperforms those "Pringles can" Wi-Fi antennas that were popular a few years ago, in a Wi-Fi application.
> Date: Sat, 31 Oct 2009 00:03:02 -0400
> From: mat_62 at netcommander.com
> To: amsat-bb at amsat.org
> Subject: [amsat-bb] Simple 2.4Ghz helix plans?
> I threw this out there on the eham satellite forum looking for answers
> but I'll try here too.
> I'm looking for some fairly simple plans for this antenna. Everything I
> find either seems to be intended for WiFi or if it is ham related is
> full of mathematical formulas to figure length, diameter, spacing etc.
> Math was never my strong suit so I'd prefer to find something with the
> actual already computed dimensions clearly stated. Preferably in English
> rather than metric measurements. I found an article in the May/June 2008
> AMSAT Journal that looked promising but there are no hard numbers, just
> the formulas and I don't have a calculator capable of some of the
> computations, much less being able to work them out in my head. Been a
> long time since I was in school!.. hi hi... I have a downconverter I'm
> not sure even works and I don't want to spend a huge amount of time and
> trouble to be able to test it.
> Tnx and 73,
> Michael, W4HIJ
> Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
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