I’m going to describe the construction of a double turnstile antenna suitable for receiving the satellites in 435MHz band.
The original design is developed by Ivo I6IBE:
I found many pictures on the web which uses different materials and techniques.
Here below I describe my personal interpretation, which uses very common materials like PVC boxes and tubes, and threated bars.
The Bill of Material is:
- N.2 threaded metal bars, 4mm x 100mm
- N.1 10cm x 10cm square PVC Gewiss box
- N.1 85mm circular PVC Gewiss box
- N.1 joint from 20mm PVC tube to box
- N.1 PVC tube 20mm diameter
- RG58 and RG59 coax cables (see lengths in the first picture)
- N.4 ring contacts , 4mm diameter
- N.1 “N” flange connector
- 4mm wahser and nuts
- Cable ties
- Insulating tape
- Silicon sealant
First of all, I started from a 10cmx10cm PVC box. I made a central hole for placing the 20mm box-tube junction and one hole for every side of the box.
Then I cut 4 pieces of 16,3cm threated metal bars and installed with two nuts and washers:
At this point, I cut a piece of 1meter of PVC 20mm diameter tube and I made 4 holes for the reflectors, at 13,8cm from the radiators:
Now it’s time to cut the pieces of coax cables. We should refer to I6IBE lengths (see picture at top of the article).
Then I separated the shield and the central pole, then I soldered ring contacts at the ends:
I soldered together the balun coax pieces:
Then I installed the ring contacts inside the top box, to the radiators elements. I made two holes on the bottom of the box to let the cables exit from the box:
Then the most difficult part is to solder together the coax coming from the radiators and the coax of the balun:
At this point, we should put adhesive tape on the solder joints. Also some sealant or glue could be used to prevent water enter in the joints. Now we can build the box which will enclose the N connector. We can use a flange connector and make a hole on the cover of a circular 85mm PVC box.
At the end, we can put all the pieces together:
We can hold the circular pic box on the main tube using cable ties.
The final installation will look like this:
I checked the ROS and it’s perfect on 435MHz band. If some adjustment is needed, we can cut the radiator elements (it’s better to cut the elements a little bet longer than the design dimensions).
I tested the antenna with RTL-SDR dongle and I perfectly received Bugsat-1 satellite:
Happy receiving to everyone!
73′ de IZ7BOJ Alfredo