Posts by G4SDG

    Although the Limi Mini has a connector for external reference I believe that it is necessary to move (with a soldering iron) a zero ohm surface mount resistor in order to be able to use it. I don’t feel confident doing this so use mine with the internal reference and it drifts a small but annoying amount during each over as the Lime warms up.


    73 Chris

    Hello David,


    The filtered amp with good gain is a much needed item. I've dabbled with a few uplink options for QO-100 from on Day #1 an SG-Labs U/C, Spectrian amp and a 25 turn helix to the current set-up of a Lime-Mini, MHL21336 and "8W" Wifi amp to a 90cm off-set, and along the route I tried the "Easy-100" modular system with ADL5350 mixer and a handful of low power modules and WiFi amp. The MHL21336 works well but does get warm (OK - hot) and my version of the 5W DJ0ABR amplifier was a few dB short on expected gain. I have three "8W" WiFi amplifiers and none of them get produce more that 4 watts saturated and one of them was 4dB less gain than the other two. Overall, gain in the middle section has generally been a problem.


    Ole OZ2OE - I checked my Lime Mini and saw similar jumps in the output settings especially in the 80-90% area. Quite apart from this hardware problem I think that SDR Console would be easier to use if it had Up/Down buttons rather than a slider. Perhaps my old fingers are having trouble using the mouse with enough sensitivity!


    I've got a problem with my analyser so I haven't been able to check the output spectrum.


    73 Chris

    Hello Nicolas,


    How long is the cable between the LNB and what type of cable is it? Is there anything else in that path - a DC power inserter? Or are you peaking the antenna by looking at the NB beacon using a laptop very close to the antenna?


    73 Chris G4SDG



    Hello Nicholas,


    I believe that with a correctly pointed 80cm antenna and reasonable receive system you should be able to see the transponder noise floor and once you see that then the uplink S/N as "seen" by the transponder is largely the limiting factor. There is a thread here QSB on the beacon signal? where the measurement of the beacon S/N using SDR Console is discussed. Bandwidth settings have an impact on the figure but for his settings Peter DB2OS said 38dB S/N was usual for the lower beacon once you see the transponder noise floor. That's what I see with my 60cm with an unmodified Goobay GL202 LNB.



    73 Chris G4SDG

    Hello Ole OZ2OE,


    I will try out your tests on my Lime-Mini to see if my results are similar. How have you got the two tones set?


    When you mention 90% drive, is that with your SDR Console "Drive" configuration for the Lime set to the default spread. With mine like that the 90% equates to just over 6dB backed off from maximum.


    73 Chris

    Regarding SDR Console and the LimeSDR-Mini, I don't understand why changing the TX Antenna actually changes the output level when there's only one transmit port but it does. I'm using the latest Console software version. I checked my setup with a power meter yesterday and Band 2 is 11.5dB lower than Band 1. Selecting Auto did give the correct output.


    73 Chris G4SDG

    I'm using a LimeMini with SDR Console and when I recently updated the software my output power dropped right off by 10 or more dB. As I'm not transmitting that often I didn't immediately connect the two things and spent a while looking for hardware problems. Eventually it turned out that the wrong transmit output was selected in SDR Console and going back to TxAnt: Band1 restored my power level.


    73 Chris G4SDG

    Hello Peter,


    I was running a much older version of SDR Console (3.0.9) and just comparing the power in the beacon and with the same bandwidth of noise floor next to it for a rough ratio. I've updated to 3.0.18 and using the SNR function get the same 38dB as you.


    73s Chris

    That's quite weak, even for a 60cm dish.. perhaps you are on a side-lobe or the window is metalized and has attenuation. Make sure you have AZ/EL optimized in several iterations, also don't forget the tilt/skew of the LNB.

    6dB variation seems a lot.. Unless there is heavy rain or big clouds, I see almost have no variation.. the CW beacon is 38dB over the noise (in SDR console) here on a 80cm dish..

    How are you measuring that 38dB Peter? I don't see that on my 90cm but I do see the transponder noise floor so I must be doing something wrong with SDR Console.


    73 Chris

    As I understand it the LEILA system ("LEIstungs Limit Anzeige" or Power Limit Indicator) for QO-100 is ground based and will just generate a siren to remind users to decrease their uplink power. That would be similar to the space-based AO-40 system and in those days we didn't have such easy access to spectrum and waterfall displays.


    I don't believe that it's operational at the moment, but if it is then it's rather forgiving sometimes.


    Chris

    I got around to measuring the unit today and mine has around 11dB gain. Saturated output power is 35.3dBm (3.4W). Output did look reasonable at 3W driven by my SG Labs transverter.


    Now to work out why my 1980's vintage SSB Electronics transverter is only producing 18dBm which is a bit light to act as a driver.


    I've not found any other "cheap" WiFi boosters and will probably just stick with this one, but perhaps bypass the output switch and place the unit at the antenna. I've got two Spectrian modules but have other plans for those!


    73 Chris

    Hello all,


    My EP-AB003 "8W" amplifier works but only has 11.5dB gain as opposed to the claimed 17dB so I get +29.1dBm out for +17.6dBm in. At the moment I don't have more drive available to see if I get more power output for more input. Lack of output power seems to be a common but not universal complaint about these units.


    Anyway, I took the lid off and have noticed that there are some suspicious white blobs of what looks like foam on some pins of the device associated with the output combining and also two pins may have a solder bridge:



    Is the white stuff just flux residue or were those areas not actually soldered? I assume(!) that the white blobs at the two corners of the device are not actually pins so only the middle left hand side blob is important. I'm going to need to buy a much finer soldering iron, steadier hands and better eyesight if this needs reworking :(


    Does anyone know what the device is? I searched on the "2031 1RNT" but couldn't find anything relevant.


    73 Chris

    According to one internet vendor selling these boards the pin outs are:


    1, Temperature output = 10MV/ degree F.

    2, PTT = +12V To enable all 3 power FETs.

    3, Drain current monitor for Q1. 1 volt out/amp of drain current.

    4, Drain current monitor for Q2. 1 volt out/amp of drain current.

    5, Ground.

    6-10 are no connection.


    See also link and link for some further info.


    I had my first QO-100 contact using one of these into a 25 turn helical antenna but as I'm not interested in video it's much easier with 2W from my converter straight into a dish.


    I didn't bother adjusting the Spectrian bias (I can't remember what the standing current was now) but there's some info here.


    Good luck.


    73 Chris

    Has the telemetry changed recently? Initially using AO40rcv I could decode the page with the message from Bochum and then later from Qatar but now the programme is not locking up at all. Last night I also thought I could hear some intermodulation on the beacon from a strong SSB station.


    73 Chris

    My 25 turn helix was based on this design (eg http://www.amsat.org/articles/g3ruh/117.html) and uses a square aluminium tube. I should have explained that the 5 turn feed is for single band only, in fact a reworking of my AO40 feed as the original helix had fallen of while “in storage” and I couldn't find suitably thick wire to make a new one. Originally the 15mm tube had been just to the rear to support the reflector and ended flush with it but in the reworked version I used a longer pipe to additionally support the helix. The pipe is not acting as a 10GHz feed.


    I suspect that the 5mm tube used for the helix might present too much blockage for a dual band feed and I'm making a patch feed instead with the 22mm feed for 10GHz and a dielectric window from a Rocket LNB.


    Thanks for the calculations. Once done I'll make some proper measurements of feeds and the 25 turn helix all using the same power level.

    I've used 5mm (3/16" actually) outer diameter copper brake pipe for a 25 turn helix antenna and also a 5 turn feed for my 90 cm off-set dish. I had my first Es'hail 2 contact with the 25 turn helix but had to use a Spectrian amplifier too at about 30W. With the 90 cm dish I can run an SG Labs transverter on its own (probably only 1W) into about 9m of 3/8" Cellflex with about 2dB loss and get a reasonable signal off the satellite. The transverter SWR indicator is green but I've not got around to actually measuring the match.