Posts by DL6DBN

    Hi friends,


    I must apologize for not being there yesterday. During the first test my PC crashed with a faulty JS8call process after aview minutes of listening. And I didn't get the system running anymore yesterday evening. I'm so sorry and hope we can conduct the next test session for the next JS8 QSO party.


    73, cu

    Frank DL6DBN

    Hello!
    I'm glad to see some interest in conducting a new attempt of JS8CALL on QO-100. What about using the monthly JS8 QSO Party as the next date?
    It'll be from Saturday, November 13 th 19:00 UTC until Sunday 14th 19:00 UTC. Probably it could be helpful to limit the activity time on QO-100 to a shorter period to increase the probability of finding each other.
    So hw?

    Hello Digimode Users!


    I'd like to conduct a trial of the FT8 derivate mode JS8 via QO-100.


    JS8 is a low power, low bandwidth "ragchew" mode based on the well-known FT8 modulation scheme of WSJT-X. Instead of a rather fix and pre-formatted minimalistic QSO style, one can exchange messages of free content, including information like your names, QTH, rig and weather info or whatever you like. Imagine it like an RTTY or PSK machine with enhanced demodulation and operation capabilities.


    Beside the more human kind of conversation possible with the JS8 mode, it has the advantage of so-called "heartbeats". They are a kind of beacons showing you are qrv and willing to qso. These heartbeats can automatically be acknowledged by those listening. And JS8 offers depending on SNR and propagation four different speeds from 8 to 40 wpm in time slots of 30 s down to 6 s with bandwidths between 25 and 160 Hz.


    JS8 is handled with the free program JS8Call by KN4CRD and it's available for the following platforms:

    Windows 10 (seems to work down to XP)

    Mac OSX 10.11+ (x86_64)

    Desktop Linux (deb)

    Raspbian (RaspberryPi, armv7, deb)


    http://js8call.com/


    Like with the NB-Digimodes on HF a coordinated frequency is very helpful to get in contact. As there is no recommendation for JS8 on QO-100 yet, I suggest 10489.548 MHz (Uplink 2400.048 MHz) USB in the NB Digi section of the bandplan as many HF frequencies for JS8 are ending with an 8.


    So, if you are already familiar with FT8 and WSJT-X and you like to know more than grid locator and signal report about and from your QSO partners, then give JS8Call a try. I'll be listening the next days and weeks on 10489.548 MHz, whenever family and QRL are giving the time.


    73 es cu

    Frank/DL6DBN

    Yes, it would be nice and fun, though in times of SDRs, spectrum displays and waterfall diagrams, there probably won't be a technical need for it.


    For those not knowing what the ZRO test was: A station started to transmit in CW with beacon level equaling to ZRO level 0. Then the power level was reduced in steps of 3 dB increasing the achieved ZRO level by 1. So a ZRO level of 7 means 21 dB received signal range via the transponder.

    The DATV signals are much stronger than some SSB signals

    Aren't WB and NB transponders transmitting in different polarizations? So with one receiving chain switched to WB polarization, I'd expect a decreased NB signal by several dB.


    And yes, SATSAGEN is a great tool, saying it already as a beginner in its usage. Thank you. 73

    Problem (hopefully) solved.

    I detected the IC YS1802 of the step-down converter close to the 12 V socket became very rapidly very hot, even in BIAS. Maybe the thermal contact to the heat sink was bad. With a little pushing of the pcb and retightening of all screws the interruptions became less. After attachment of a small additional heat sink on top of the IC I couldn't discover any transmit interruptions so far. The final check on-air will follow this weekend.

    73, cu on QO-100

    Hallo Thomas,
    ja, es freut mich auch, nach der "Babypause (er ist jetzt 16) und Baupause" allmählich zum Amateurfunk zurück zu kommen - vergangenes Jahr KW, dieses Jahr QO-100 und in der Zukunft auf neuem Dach vielleicht auch wieder mit Rotoren die umlaufende Satelliten.


    Regarding the booster: I use the one with the spiral heat sink. But neither during my transmissions nor while in BIAS I detected any significant warm-up. In case of a kind of thermal protection I expect some heating of the sink/case before the protection gets active. Maybe thermal coupling of the semiconductors to the heat sink is bad (or doesn't really exist at all) and the amplifiers heat up to fast without any heat dissipation. But to look at that requires disassembly of the PCB, which I tried to avoid so far. I thought, I can detect or close-in to the failure with some measurement and a circuit diagram.


    So any idea by anyone?


    tnx es vy 73, Frank/DL6DBN

    Hello!

    I'm not new to the sat business but new to QO-100 and the GHz (except receiving AO-40). I started testing with ADALM PLUTO, the suitable AD "20 dBm booster", the EDUP "8W" PA mentioned above and my old 65 cm AO-40 S-Band prime focus dish. I was surprised getting a carrier signal back 4 to 6 dB weaker than the beacons. I expected a much weaker signal, knowing the PA should be driven with at least 3 dB more input power.


    But I discovered a signal interruption caused by the WiFi PA (the 20 dBm out of the AD booster only produced a steady - but much weaker - signal). 1st I assumed the VOX might not be well triggered with the low input. So I modified the PA to continuous transmission and shorted I/O switches as described in links above. The good news, shortening the RX/TX switches increased the level by 1 dB. The bad news, the signal interruption remained as above.


    I discovered that the pulses shorten with increased requested output power. But even without any input signal the PA switches ON/OFF (Status LED) after several seconds only being in BIAS. I tried different, more powerful power supplies, to exclude supply failures, and different antennas (helix, patch, wifi, dummy) to exclude matching issues. Nothing changed.


    Has anyone observed a similar behavior? Are there some protection circuits of the PA known (current, temperature, TX time), which may be too sensitive and hit the transmissions? Or is even a circuit diagram available to close-in the failure?


    tnx es vy 73, Frank/DL6DBN