Posts by G0MJW

  • Mounting of POTY on dish, SWR high, how to fix?

    I would go with the wrong frequency. If there is 20W going out and not a lot back it's got to be going somewhere. The coax is short I assume, not 50m of RG213! Dish should be brad enough at 2.4 GHz to be aligned. Why don't you check the LO is correct with the SDR ?


    Mike

  • Mounting of POTY on dish, SWR high, how to fix?

    Bill


    I think the problem here is getting information out of you as to exactly what the set up is is quite difficult. If you need help tell us exactly what the end-end configuration is and then we will have a chance of understanding what might be wrong.


    For example your earlier comment about SWR getting better after you moved the feed back does not make sense. Moving the feed should not significantly impact VSWR. We later find out there is a 20W PA in line, but I recall the LED is on the transverter - so where is this VSWR being measured? Is there also an LED on the amplifier? I don't think there is. Therefore you have now a good match from transverter to amplifier which is useful but does not relate to the feed. That amplifier does have forward and reverse power monitoring. This should tell you if you are getting the correct power out and what the reflected power is. Measure these voltages. Compare with the manual. Tell us the result.


    Mike

  • ADALM-Pluto

    The pluto does not hold the settings unless you configured it to in that config file. Normally the router will assign the same IP to the same MAC address, unless you told it to do something different. This is usually the best way to ensure the IP remains the same.

  • Mounting of POTY on dish, SWR high, how to fix?

    If the dish has not been moved since the LNB and the feed is in the same place - exactly the same, not higher or lower then you are probably pointing correctly but it is only a 60cm dish so you will need to run a few watts to see a reasonable signal. If the transverter is only the 2W one and if you are losing some power elsewhere it might not be enough. Also you have to really check you are on the right frequency which is hard to do with no test gear.

  • Mounting of POTY on dish, SWR high, how to fix?

    Bill - seems like you need to tune the antenna. You can't realistically do that without test equipment. How did you acquire it?


    Hopefully someone near you can help with test gear. You also, once tuned need to pay attention to the focus of the dish and where the antenna mounts. That might require mechanical work to the feed arm. Nothing difficult.


    Mike

  • RX sig strength 7 db lower with POTY

    We don't know because you don't tell us the focal length of the dish. Assuming it is a standard 0.6 or so use the Rexolite lens, the lens from a rocket type LNB or the 3D printed lens from HB9VQQ. Make sure it is accurately at the focus.


    Mike

  • TS-2000 und SG-Lab Transverter

    Quote from DH2VA

    For the sake of completeness: AMSAT-DL also uses TS-2000 at its ground stations in DL and Qatar thanks to the generous support of Kenwood and JAMSAT. Since these devices are hard-wired to us, we have 'killed' the transmitter belonging to the receiving branch by removing the corresponding control line in the device.

    My solution to the TS2000 spike is to apply a negative ALC voltage to the ALC input. This disables the transmitter. The ALC is allowed to come up on TX, but only slowly. This eliminates the spike but also cuts the first few 100mS or so of transmission. Not so good for CW operators, fine for SSB. However, you still need to take care between quiet audio and loud audio. An attenuator in line is a must.


    W6PQL produced a PCB for this and I think he still does.


    Mike

  • Good cop, bad cop...

    Would we send 73s in CW?


    There is a problem in with assumptions on bandwidth as not all driver radios have SSB filters able to meet a 2.7 kHz limit.


    So why wasn't the limit set to be compatible with the "standard" 300Hz-3.4kHz ? It's not as if there is a lack of bandwidth available with the extension to 500kHz.


    Rec. ITU-R BS.640-3 might have been more sensible.


    "The upper limit of the audio-frequency bandwidth (-3 dB) of the transmitter shall not exceed 4.5 kHz with an attenuation slope of 35 dB/kHz and the lower limit shall be 150 Hz with lower frequencies attenuated at a rate of 6 dB/octave."


    However that is for SSB broadcasting and even though QO-100 is a broadcasting satellite, amateurs don't broadcast.


    ITU Report M2478 which although related to the 6m allocation, does mention the bandwidths required for narrow band modes (CW/SSB/Digimodes) to be between 500Hz and 3kHz depending on the mode. So for 6m at least maximum of 3kHz.


    Then there is the handbook: https://www.itu.int/dms_pub/it…HDB-52-2014-OAS-PDF-E.pdf which is where I assume the 2.7 kHz comes from though the definition of SSB:


    SSB – Amateur single sideband suppressed carrier telephony has virtually replaced double-sideband amplitude-modulated telephony in the amateur service. The emission symbol is 2K70J3E, although there is some use of narrower and wider bandwidths. SSB is used on frequencies from 1.8 MHz through 47.2 GHz.

    So we see where it comes from and there's not hard and fast number. Most radios people might try to use from the (Yaesu, Icom, Kenwood, Elecraft) have filtering to 2.7 kHz or less at -6dB anyway.

  • TS-2000 und SG-Lab Transverter

    Regrettably Andreas is right, it really is nearly all of them. The safe assumption is to assume there is a spike and take measures to prevent that being a problem. Otherwise you will keep the pre-amp suppliers happy with repeat business.


    Mike

  • MiniTioune V0.9 beta optimised for QO-100

    It is an approximation to the level of signal above the noise. To improve it, improve your receiver. Bigger dish, better LNB. Compare with others to make sure your setup is operating effectively. You will need a large dish for DATV, at least 80cm and preferably 1.2m.


    Mike

  • The new Icom IC-705 is (NOT?) ready for QO-100

    Indeed - what would be good would be a IC705 with just a few milliwatts output and fully duplex and full coverage. Not impossible. Several SDRs already do that, they just lack the filter banks and integrated computer that generates the look and feel of a traditional radio. Then a bolt on amplifier would allow whatever was needed, from 1mW to 1kW. This will be an unpopular statement but I think the IC-705 is disappointing. The fact it can't do duplex means it is essential to have a second RX for the linear satellites. Even if Icom don't produce an update we can be sure someone in China will and it will be considerably cheaper with "good enough" performance for most people and yet bad enough performance to annoy VHF weak signal operators. Icom missed an opportunity, let's hope they fix it.


    So to the point. There has been several times now "I know my frequency comments". We don't have to just know our frequency but also our power and if not listening or looking at the waterfall of the downlink how do we know if we are not too low or too high power? I can imagine "I know my power" comments. Well, evidence seems to suggest far too many clearly don't know their power and ignore Lila as they don't hear it. Remember, the owner of the transponder probably doesn't care if you drift or have a poor signal, or trample on top of someone else, but they absolutely care when someone sends too much power. Too much too often and it will be switched off. So lets be clear about this. If you are not operating QO-100 duplex, you should not be operating at all, period.


    Mike

  • The new Icom IC-705 is (NOT?) ready for QO-100

    It is really important to actively monitor your downlink, not just to be able too. When I mentioned this in the UK there was a lot of pushback. Out of the bad signals I see, almost none of them are from people using SDRs and almost all of them from people operating simplex. The IC705 is an SDR so hopefully it will be good, but I fail to understand why ICOM did not make the radio duplex! It makes no sense. The IC9700 is almost the same price and must have much in common in its design and is duplex.


    Mike