Posts by DL5RDI


    just a very trivial remark to save costs in becoming QRV via P4A.

    RF-specialists: please stop reading here. ;-)

    To save money for expencive 50 Ohm I use cheap 75Ohm Sat-coax not only for receive, but also for the connection of my 2m or 70cm TX with my upconverter. You just have to take a lenth of multiples of 1/2 lambda (keep in minde the shortening factor of your cable - if you don't know then just make try and error). And you should use very good shielded coax (like for reception also; e.g. 130dB four layer shield).

    Thus you have no transformation and 50 Ohm in and out. The signal loss is not significant.

    I have 20m to my antennas and an SWR of 1:1 with costs of less then 4 Euro (even RG58 is much more expensive).

    73 de Johannes

    P.s. some may think : Even my grandmother knew it

    My answer: But she didn't publish it :-)

    Hello Iain,

    it's a bit off topic - but do you really have to care about a few adapters or the cable length ? The LNB converts the 10GHz Signal to the IF and has here a very high signal level. In "normal" conditions (e.g up to 20m coax and a few adapters) the total signal (even the noise) drops, but in these conditions you do not really have a change in S/N. Or am I wrong ?

    If someone knows better then I appreciate every comment - please with explanation. (I'm a physician and not a HF-engeneer :-) ).

    73 de Johannes

    Hello Rene,

    you are right with the LNB even in the cassegrain antenna counterclockwise... I disregarded that you also turn the LNB 180° (looking towards the dish in "normal" configuration, but turned 180° around its vertical axis and then pointing towards the "sky" in cassegrin antenna.)

    Thus the polarisation is of course "mirrored" by every reflector, but the LNB orienttation is in both cases counter clockwise because of the additional "mirroring" of the LNB.

    73 de Johannes, DL5RDI


    Nice duoband-solution. The RX seems to work very well.

    Did you test the Helix feed (of course NOT in direction to 26E ;-)) ) - is there interference of the TX-signal on 2,4 GHZ with the reception of the LNB ? What about the loss in gain because of the helix-feed is "to close" to the dish and not really in the focus ?

    Any information and data would be appreciated.

    73 de Johannes, DL5RDI

    P.s. thanks to Heiner for posting the Youtube-Video !!


    is it really the same angle ?

    Each reflector acts as a mirror. When you take porarisation: in a "normal" dish you have a LHCP feed and get (because auf the mirror-effect) RHCP polarisation.

    The skew angle is "part" of the polarisation. If you are standing behind a normal dish with view to the satellite, the LNB has to be turned counter clock wise for all east positioned satellites. But in yor case you have an additional mirror and thus I believe your LNB has to be turned clockwise (seen from the same postion as described above).

    in my QTH (JN58xx) it is a bit more then 13 degree for 26 E. But you can also take the empiric way and tune to a TV transponder on BADR4 (e.g. 11996 SR 27500) - it's the strongest one) and see the change in quality of the signal.

    (For all TV-Sat DXers - Astra is not a "normal" satellite in this way, because SES "tilted" the satellites a bit to have a skwe angle of near to zero in DL - the main viewers).

    73 de Johannes, DL5RDI

    @ PE1CHL and ON4BHM

    in south east Germany (JN58xx) I can receive all BSS BADR4 transponders with my 85cm offset dish (strongest one is 11996 H (e.g. Deutsche Welle), but not the mena beam. On 11.270 I can see just a slight higher "noise" in the spectrum of about 35 MHz width - maybe that is the rest of the signal of the transponder from ES Hail 2 TV-Test pattern ???

    Hello ON4BHM (I do not kano your name - sorry),

    this a link to the BADR4 trasponders in 26 E postion.

    If you see transponders with other data then in the list above, they are probaly from Es Hail 2.

    With your 1,8m dish you should not receive ASTRA 2 or other sat-postitions, when pointing to the ES Hail 2 postion in the moment (26.28°).

    Pse tell me if there are any "new" transponders active.

    73 de Johannes


    I just joined the forum. Just replaced my (unmodified) OCTAGON LNB with the DB6NT LNB and it is a difference like day and night concerning the frequency stability listening to the beacons. After 30 min no relevant drift, thus 100% suitable for "normal" users. The Qctagon LNB was always drifting a little bit even after 24h on power supply and no significant change in temperature.

    I used the Octagon LBN to adjust my 85cm offset dish to BADR 4 postion (near the final Es Hail Sat postion 26°). Unfortunately the TV transponders of BADR 4 which are not "covered" by same QRG-transponders of Astra 2 can not be received (with my receiver) with the Kuhne LNB (these transponders start just below 12 GHz). (I reveive a few strong "lower frequency" transponders from ASTRA 2 even pointing on 26° E but that's due to my "small" dish)

    The beacons in the moment seem to TX in H and V polarisation simultaniously (is this right ?) , thus I could not realy adust the skew angle right now (took -13 degree like for BADR4). But when the Amateur transponder beacons with H or V polarisation are online. the fine tweaking can begin.

    73 de Johannes DL5RDI / AC2TR