Introduction
Bill of materials can be found here:
https://github.com/satnogs/satnogs-anten...
CAD drawing (and designs) can be found here:
https://github.com/satnogs/satnogs-anten...
The Emerson calculation model can be found here:
http://oldsite.rac.ca/en/amateur-radio/o...
Enter 437Mhz as the frequency and 8 turns.
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We start by shaping up the wire.
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Print and stick to a surface the design of your antenna
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Cut a 8m piece of Galvanize Steel wire 2mm thick.
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Using a cylinder slightly smaller than the radius of the helix (in our case 130mm) start wrapping the steel wire around it. Repeat multiple times, till it starts to approximate the needed diameter.
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You should end up with a nice spring-like piece of steel wire.
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Next, we need to mark the PVC pipes
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Cut 3x140cm Φ16 PVC pipes.
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Using the design, mark the T-Holder positions on the pipes (3 each).
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Then we need to mark the wire notches on the pipes. Consult the design for exact dimensions. 165mm is the spacing between marks for each pipe.
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Finally, make the notches using a file (tool) on approx. 30 degrees inclination.
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For the antenna structure assembly you will need everything from previous steps plus the following 3D printed parts:
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9x T-connectors, 2x Y-connectors, 1x YO connector
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Put 6 of the T-connectors in place as shown, driven by the design.
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Make sure not to put the 3 outer ones (as you will need to put the reflector first in place).
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Using 6 small PVC pipes (see previous step) glue them in the 6 T-connectors as shown.
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Using the brass triangle as a guide mark the end of the wire
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Using sand paper, scrap off the galvanized coating of the wire. This will make soldering possible.
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Secure the brass triangle in place (see designs too) with tape. You can either choose to cut the wire or use it along the triangle. (depends on how you will solder, and how comfortable you are with it)
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Start removing the black tape that holds the wire on the pipes.
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Using a glue gun, secure the wires in place. You can add some tape on top of it for additional securing.
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Solder the triangle on the wire as shown, or cut the wire and solder the triangle end to end with n-type and wire.
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Your Helical antenna should now be ready!
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One Comment
I am building a groundstation to detect signals from cubesats or other signals in 420 - 450 MHz, but I do not see any signals.
I make a helical antenna with 10 dBi and I use a USRP to control the SDR. In the first part of detections, I need to see only the temporary signals on spectrum analyzer, due to the Cubesats pass for 10 minutes. But I can't see.
I tested the antenna, sending a carrier through the signal generator and it is OK. The USRP has a sensitivity of -110 dBm, using its amplifiers. Besides that I bought two LNAs with 20 and 24 dB of gain, ans it is not enough.
What I need to do more?
Regards and thank you for this great project!!
Fabricio Silva.