Posts by DJ7GP

    Hi Rasto,

    yes of course I will provide you with the measurement results as soon as we have carried out the outdoor-measurements.

    Of course you need the construction data of my duo band feed for the simulation. I would like to send them to you by email. My email address is: call (at)

    73! Peter, DJ7GP

    Hi Rasto,

    usually we (Peter, DG5ACX and me) do the antenna measurements outdoors with the arrangement shown in the picture. To measure the circular polarization, the antenna rotor is tilted by 90 degrees, so that the antenna to be examined can be rotated by 360 degrees about its own axis.

    In the present case, however, this was not possible due to the rainy weather. We therefore carried out the measurements in our club room on a wooden table. Arrangement of objects 0.75 m above the table. Distance of the objects 1.30 m. The comparison with old outdoor measurements showed a good agreement. Since the rotor was not available, we rotated the log per transmission antenna by hand in steps of 45 degrees.

    The connection of the measuring points by straight lines is certainly not professional. The scale in the diagram shows the values in dB.

    73! Peter, DJ7GP

    Hi Achim,

    Your statement: “The QO-100 S-band RX antenna is good in terms of circularity but not perfect.” then calmed me down. I think that my efforts to improve the circular polarization of my duo-band feed (with round patch disks) according to the "cut and try" principle were probably not in vain (see the attached pictures).

    73! Peter, DJ7GP

    Hallo Mic,

    a few minutes ago I sent the following mail to an OM who asked the same question:

    Your thoughts are correct!

    The radiator and the reflector disc have a mechanical and thus also an electrical connection. At 2.4 GHz, of course, it looks different. Just think of a loop dipole, where you also measure a short circuit at the (symmetrical) feed-in point. ...And it gets even worse! If the loop dipole is directly attached to the boom at its point of symmetry (which is indeed permissible), there is also a conductive connection to the boom. ... and still the structure works. That is the "exciting" thing about HF technology!

    I wish you much success and lots of fun with your activities over QO-100!

    73! Peter, DJ7GP

    PS .: If you have any questions, do not hesitate to contact me!