Posts by PA3FYM

  • Stopft LNB den RX zu?

    do1ctl Have to ask, I got them in a SMD strip from a friend of mine (they are very small !)


    BPF can be easily made with two wires (acting as stripline) with two trimmers and low tap for in and out.

  • Stopft LNB den RX zu?

    Daempfung waere ein(e?) gutes Idee. Sehe hier. Ich brauche hier 30 dB Daempfung zusammen mit ein 739 MHz SAW filter.


    (Verzeihung fuer mein Deutsch, es ist nicht meine Muttersprache und die Grammatik is furchtbar (fuer mich ; -)

  • POTY and return loss plot

    While doing some shopping this afternoon I philosophized a little why these dips do not appear on some equipment (see BATC link in posting above).


    Could it be that 'scalar equipment' is not able to visualize the dips, while 'vectored equipment' is?


    In other words, while the 'balloon' circles around Z = 1 (normalized) in the Smith Chart, scalar equipment cannot derive the sign of 'j', while a real VNA can?

  • POTY and return loss plot

    PA1EW Concerning the (theoretical) double dips, I read a thread somewhere on the BATC forum that some equipment are not able to resolve this double dip.

    The trick then is to tune/tweak the response so that a shallow (broad) dip of ca. 20 dB occurs at 2400 MHz. If you've sharper dips then the two resonances coincide and and affect the axial ratio (read, it'll produce CP elsewhere).

    Your response looks fine to me, so I am curious how it'll perform compared to your previous feeds.

  • Anregung: DL-Anruf- bzw. Stand-By-QRG

    Frank , I suggested .690 (or whatever) as 'calling frequency' (or 'center of activity')

    some time ago, but it remained relatively silent on this forum then. . .


    If it's .700 , it's fine with me, as long it's a known frequency : )


    Edit: PS. I am not referring to a DL frequency, but a general frequency.

  • minimum RX station

    5 mW in a 90cm wide offset dish still gives FT8 decodes which are 'way too loud' ; -)


    Concerning Ublox modules (NEO-6M, 7M) <-- have been several discussions on this forum here (and loads of discussions elsewhere) --> forget it ... doesn't work. If you don't believe, try it (and burn your time ; -)


    What works like charm is a cheap Ublox module, OCXO and a TIC (but that may be another thread . . . )

  • Anyone using the transverter solution from Rene, PE1CMO?

    G4NRT ... you say the cliff is 50 ft high (ca. 17m). Suppose you need 27 degrees elevation, then when you place the dish ca. 34m in front of the cliff (on the ground, higher would be handier, read: then the 34m distance decreases) you should be able to see the satellite (perhaps with some losses). I don't have any clue how your possibilities are in front of your house, but perhaps this may be a way of thinking?

  • POTY and return loss plot

    What is very important is that the distance between the plates is 3.0mm (measure it e.g. with a 3.0mm drill) and that the screws to mount the flange are not protruding. Personally I also remove some teflon from the flange. Success!


    PA1EW Regarding your question concerning the 'double dip' of a helix: "No". A helix can be considered as a 'traveling wave' antenna.

    The patch can be considered as two antennas: one somewhat too short (high frequency, therefore capacitive), the second somewhat too long (low frequency, therefore inductive). We learned LEICIE, and the trick now is to have each antenna lag or lead by 45° , so that the total becomes 45 -(-45) = 90° ( or -45 -(+45) = -90° ) and therefore producing a cork screw, aka circular polarization (CP).

  • POTY and return loss plot

    Tweaking is possible by pressing sides/corners of the patch towards the reflector (so decreasing the distance somewhat) when the max RL frequency is too high, or pulling the sides/corners of the patch from the reflector (so increasing the distance between patch and reflector somewhat) when the resonant frequency is too low.