Dual Feed For Uplink / Downlink

  • Hi All,

    Well all of these are wonderfully made. I've never been good mechanically, but yesterday I added a 2.4GHz "feed" to my LNB downlink. Highly complex and expensive (not!), and note the "super expensive" adhesive as you can see from the picture.

    Originally I only had the dipole (6UKP from one of the FPV drone guys, but cut to 2400MHz for me). Reflector (<2mm diameter copper wire from the junk box) added ~4db S/N for me through the transponder, position of both reflector and dipole element a compromise to prevent impact to the downlink signal.

    Probably going to add extra yagi's at 90, 180, 270 from the existing one, but for multiple uplink capability rather than phasing them together



  • DH2VA :Dish is 1.1M

    Power is a bit debatable. P.A is one of those 8 Watt "Wifi boosters", fed by a four watt version (my 100mW USRP hasn't got enough puff to push the 8W one into transmit mode [needs 400mW] , and I am *not* doing SMA soldering), but there is some debate as to whether the 8W versions are 8W or 4W as they have a 4W part.

    After that, there is a 5m run of Aircell 7 at present, so ~1.8db loss (I have plans to cut that run to <1m), so currently power to the dipole is probably either ~5.28W, or ~2.64W.

    For a Carrier, I am hearing myself 6-7dB above my filter noise floor (6kHz wide, -3k/+3k complex bandpass) with the dipole. With the reflector, that improved to 10-11dB above the filter noise floor)

    In the same filter, the LB peaks at about 16dB above the filter.



  • And here is my final version after several optimization. Helix in front of the LNB feed gave me to much losses (arround 5-6dB). With mounted solution above the LNB no degradation measured in downlink and the uplink signal was increased a little bit by downtilt the Helix towards the center of the dish. The return loss of the helix was optimized and tuned with a mechanical C (piece of aluminium) nearby to the feedpoint of the helix. Finetuning by moving the aluminium piece. Max. return-loss gave me - 26dB.

    The remaining open point is to make that water/winter resistant.