Re: [amsat-bb] AO-40 reception on 78 Turn Helix

["Edward R. Cole" <al7eb@xxxxxxxxxxxxx>]

>From Pieter Ibelings: 
>> I just finished building a 78 turn helix for mode S. I had already tested
>> the helix antennas at the short end of the range. Now it is time to test it
>> at the other extreme. This antenna is almost 8 feet long. It is wound like
>> all my other helixes on a transparent plastic form and using copper tape of
>> .250 thickness. I have tuned it and it gave me about 1.2 SWR. I plan on
>> testing it on tonights pass.
>
>WOW!
>You have great patience!
>
>I will be curious about how you finally end up mounting it to prevent 
>sag. It would seem that any misalignment on the order of a inch or two 
>may affect the performance. Please post the details of your support 
>bracket. Also, is the tape really .250 thick? Maybe it is foil that is 
>.250 wide? I'm a little confused there... Or are we talking mm ?
>
>My son, KD4YJB, Vince,  is ready to build one of these!

And we will be interested in how it performs.  Most engineering literature
states a practical limit to the length Helical beams at 7 wavelengths.
That is 13cm x 7 = 91cm [~3 feet] at 2400 MHz.

Be nice if you could compare it to a known antenna like a dish.

Ed


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