This Dualfeed is optimized for use in a offset dish to communicate via the first geostationary amateur radio transponder from Qatar (QO-100).
The Dualfeed consists of a holder for the Helix-Antenna and a LNB mounted behind it. The holder is simply mounted on the 40mm body of the standard LNB.
I have saved a suitable LNB, SMA socket and screws in a
shopping cart (many other LNBs should fit as well).
The reflector for the Helix-Antenna is made of 0.5mm aluminium sheet with the help of the Helix_marker. It is not recommended to use the sheet metal of a beer can, as it is very dangerous due to the sharp edges (but it's possible not to release blood :-)).
To form the enamelled copper wire of the helix simply wrap a 38mm tube with the appropriate pitch or use easyly the Helix_former.
As a weather protection cap (unfortunately not permanently uv-proof) I used a yoghurt cup from the discounter. Btw: I eat yoghurt regularly and therefore I have many weather protection caps as replacements. If the cup is to be painted, you could check the RF suitability in the microwave own.
Notice:
The helix must be adjusted to your offset dish (please download the enclosed Excel calculation). The Dualfeed may not match to your center feed parabolic antenna! The adjustment of the Helix-Antenna with an antenna analyzer is unfortunately unavoidable.
Tools that have been used additionally:
Stand drilling machine, VNA (N1201SA), soldering station, hot glue gun, tin snips, stepped drill, pliers, side cutter, files, hammer, nails, screwdriver, drills for 3mm and 6mm and a knive.
vy 73 es 55 de DH1ND
... and hope to hear you soon via QO-100!
DH1ND
