Hello,
just finished my first helix.
It is a self supporting 3 turns helix via a l/4 trafo for matching impedance..
Not 100% at the frequency but I think it is an good start. What do you think about the plots?
73 de DG5LM, Matt
My first attempt...2.4GHz self supporting helix 3turns via l/4 trafo
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Return loss (or matching) is only one side of the coin. 3 turn helix feeds are known to have not very good circularity. The only way to measure this is on a test range with two antennas (TX-RX, one preferable being a linear antenna) used and one being rotated along its boresight axis. Good circularity would result in no change of received signal level while rotating.
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May I ask what gauge SWG or diameter mm/inch is optimal for a helix?
I can only get 2mm from usual supplies on the Internet.
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I take succesfull 2,15 mm , it is 4mm² wire for electrical installation.
73 Wilhelm
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Helix Antennas are broadband by design, so an thick wire is not really needed. To be mechanically stable, it is better to use a plastic holder to support the wire. This example of my helix is built using 1mm Wire, supported by printed PETG holders and is very broadband as you can see. Impedance matching is done by a metal vane wich can be easily bent to get perfect match. Five windings give you good circular polarisation and high gain. Combined with the LNB in the middle of the Reflector, LNB loss is very low (about 0.5 to 1 dB)
because of very low shadowing the LNB by the thin wire. -
Hello Helmut,
can you give the dimension of the matching vane?
Thanks!
73 Wilhelm
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Hi Wilhelm,
currently the Helix is mounted outside on the dish, so a cannot measure it, but f i remember it correct, the vane was about 10x12mm, made of a part of the same material like the shielding boxes from Schubert. Distance was about 2mm from the wire,
but you must try size and distance, because it controls directly the matching. Also the used material changes vane size and distance.
I screwed it to the reflector and bent it until i got perfect match. This is easy if you have a vector network analyser. I used the cheap one shown, but my big HP give similar results.
Interesting was, that my helix shows much less loss on RX LNB as a POTY and i got good readable signals with this TX Helix with only about 200mW over QO100 using my 1m Dish. This is why i prefer Helix antennas.... -
Hi Helmut,
many thanks for Information. Will try at next time alternative to Lambda/4 strip.
73 wilhelm
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Helix Antennas are broadband by design, so an thick wire is not really needed. To be mechanically stable, it is better to use a plastic holder to support the wire. This example of my helix is built using 1mm Wire, supported by printed PETG holders and is very broadband as you can see. Impedance matching is done by a metal vane wich can be easily bent to get perfect match. Five windings give you good circular polarisation and high gain. Combined with the LNB in the middle of the Reflector, LNB loss is very low (about 0.5 to 1 dB)
because of very low shadowing the LNB by the thin wire.Nice realization.
