Posts by Martin - G8JNJ

    Hi All,


    Here are some details of my helical feed, which is mounted just above the LNB on a 09m offset dish.


    I'm not sure why the images are blocked on the forum but you can use the link symbol to view them.


    [Blocked Image: http://www.g8jnj.net/LHCP%20Feed.png]



    The Helix was copied from G6LVB's AO40 S-band design "Modify An Anchor Sky TV Dish for AO-40 S-Band"


    I think it would be better to use a larger diameter outer tube than the helix acting as a radome.


    The helix reflector plate has probably made a bit smaller, but it did not seem to degrade the RX S / N by any appreciable amount, so I did not bother chopping it down. I used PCB because I had it to hand, but aluminum, brass or whatever would be OK.


    The underside of the 1/4 wave impedance matching line has the self-adhesive Mylar foil on it, so that it doesn't short against the body of the N connector when it is bent close to the reflector in order to achieve the best Return Loss.


    [Blocked Image: http://www.g8jnj.net/LCP%20side.png]


    The foam at the back is just to keep the LNB short term drift under control When the sun goes behind a cloud.


    More details on my website https://www.g8jnj.net/qo-100


    Regards,


    Martin - G8JNJ