TX-only modification on commercial WiFi booster

    • Official Post

    The mail from DL4OCE is confusing, it implies that full duplex operation, always via QO-100, without modification of the EP-AB003 booster is not possible. Geri wrote:

    In my view the only valid reason to do this modification is when you want to reduce the power for whatever reason, for example to test low-power (below noise floor) data communication. As the HF-VOX switches only above a certain input power (in the range of 5 dBm), you can further reduce the input power only if you did this modification.

    To clarify the whole story:

    Input power without mod: 3.2 mW (5 dBm) to max 500 mW (27 dBm)

    Modification for low power < 3.2 mW (5 dBm)

    • Official Post

    yes. youre right, Johannes. I didn´t tried ssb yet. Thought its maybe a problem in ssb because the vox sensity and delay is to short in the unmodified pa.

    73s de Robert

    Yep, I think this was the reason of misunderstanding to modify or not modify.

    Ufff :)

  • 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

  • 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

  • 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

  • So just received the pa 8w today ,reading this post with my poor english i understand two diffrent opinions with the mod between the 4 and 5 contact for permantly TX mode in ssb .So ok with the heatsink i will doi it but do i have to do the mod or not at 4 and 5 contact?