Posts by YU7RSX

    Recently I had the same issue with one quartz oscillator at 20MHz.

    I left it powered for a few days at room temperature and monitored frequency.

    It wobbled on it's own. No pattern I could determine. At the end cheep XTAL was problem. Replaced with another and frequency was stable.

    Thanks all for clarifying. I expected such situation, just needed some confirmation.

    I remember the first day perfectly listening to SSB QSO with DRO LBN only. That was above my expectations.

    Yesterday I have received beacons and some SSB signal with LNB only, but signals were very weak.

    However this is still promising. I expect adding any small suitable antenna or reflector with 10-20 dB gain should be sufficient for nice portable or even mobile work.

    P. S. I have 1,2m dish, but it is not interesting. It is like working local repeater with roof mounted antenna ;)

    I0LYL we had the NB transponder adjusted twice in this period to optimize the dynamic range (and not waste satellite power into noise). The transponder gain was decreased by 4 dB on Feb 28th and another 6dB on March 13th. So in total this should amount for 10dB less transponder noise, which is close to what you see.


    But as you still see the transponder noise, your system is still fine. Note that the beacon levels have been increased as well.

    How does this adjustment would affect stations with small receiving antennas and small TX power? I am thinking about portable stations, for example horn for RX and helix for TX. I know initial specification for ground station that rely on dish antennas, but we had numerous successful tests with not so directional antennas and less gain.

    SSB on NB transpoder is ok solution, but it has some drawbacks.

    Not all stations can achieve prefect frequency alignment, so it might be hard to operate DATV and adjust talk back frequency. Ad to this multiple operators on same frequency with short conversations. It is not going to work.

    Also NB transoponder uses vertical polarisation and WB horizontal.

    Another thing is simplicity. For example I put my HT near cable from LNB and can hear beacon and all SSB stations. If they were on FM it would be perfectly receivable. Also it is much more easy to transmit in FM than in SSB. Maybe some hams are not interested in SSB work.

    There are more reasons...

    Talk back is add-on to DATV and should make QSO easier, not make challenge itself. Grab a HT instead of telephone talk.

    That's my personal view of talk back channel.

    Could weak NBFM channel cause some disturbance to DVB carriers?

    Thank you for reply, Remco. I mean only the WB-Transponder for a narrow Talk-Back-Chanel, never using the NB-Transponder for FM.

    Follow Situation: One Station transmit DATV and 10 are only looking (Not all have the Power for a DATV-Signal). They have no easy way to communicate with the transmit Station. In Germany we have Talk-Back-Voice-Receiver in every ATV-Repeater, nice Contacts for Non-ATV-Transmitting-Stations, making Tests and Comunicating very easy. If you see the Spectrum you have no Idea abt Parameters, you call on a fix Frequency and hear what going on.

    I totally agree with you.

    I have been working on ATV for 20 years now. Without talk back channel sometimes is almost impossible to work ATV, DATV even more. For example on our local ATV repeater we have option to mix audio from 144,750 to main sound carrier. Chat window alongside WB monitor SDR is ok, but is already overwhelmed with messages.

    Without talk back channel only big stations can take part on ATV, and receive-only stations can not contribute in the ham way.