Posts by G4KCM

    Well each to their own but I stand by my opinion. Some earlier words on the forum regarding 2.4GHz RX maybe of interest...

    2,4GHz transmission check

    Not to ignore the original topic completely... I would also encourage any one wishing to operate QO-100 to have their own 10GHz receive capability. It is not difficult to achieve especially now with the popular SDR console software from G4ELI carrying out frequency drift correction.


    I think it could be interpreted that in the case of the U.K licence it requires that your “Radio Equipment” be capable of receiving on the frequency upon which transmission takes place. I’m not a lawyer but the language, to me, in conjunction with the rest of clause 7 of the licence conditions implies that it is the licensee’s equipment that should be receiving and not that of a third party.

    “7(6) In order to reduce the likelihood of causing Undue Interference, the Licensee shall ensure that the Radio Equipment is capable of receiving Messages on the same frequencies and with the same classes of emission in use for the transmission of Messages by the Radio Equipment.”

    Besides the above offline monitoring of the stations transmitter into a dummy load should go some way towards reducing the number of poor quality signals that have been appearing.

    Personally I would not consider transmitting without being able to hear my own signal locally. QO-100 is not a piece of test equipment and using it as such cannot do anything to enhance the reputation of the amateur radio community in the eyes of the satellites owners.


    I have actually left the bias 'as is' because I do want to try the DATV transponder at some stage. Just about got the setup as I want it now but I'm sure that won't last for too long!

    Thanks Dave appreciate the good words, I do indeed key the bias via the PTT. Overall I’m a bit further down the line with the Spectrian now. Have applied the VK4OE ’snowflake’ which has taken it to 30W. Added a decent fan and using the embedded sensor (duly converted to Celsius) wrapped it with a PID loop to modulate the fan PWM. Also added an option for USB PTT. The amplifier now plays nicely with the LimeSDR mini and SDR Console.

    Yes indeed it works great, I just did the upgrade last night. Been doing some 'snowflaking' on my Spectrian 30W PA which now really gives 30W @ 2.4GHz. So, now along with some additional heatsink, an Arduino based PID fan controller and thermal protection I'm hoping that I might be able to try getting a signal through the QO-100 DATV transponder one day soon.

    Mike that's absolutely fair comment, it's just a lack real estate on the SV1AFN pcb. So in this case it will be a regulator soldered to the brass origami which will also compensate for supply variations.

    The thing that's griping me a bit presently is the number of operators I see showing systems using Lime / Pluto / HackRF as prime movers with broadband "Far East" amplification and no stage filtering i.e. Lime / Pluto-> Broadband amp -> WiFi Amp. Which pretty much relies on the antenna as the system filter. Ok it's heading out to space but..! Am I being a bit old fashioned?!

    I'm learning KiCad so hope to be able to add something to the community in due course.

    I really do want a CNC milling machine! But... was just thinking that it would be a good exercise in filing and fitting to make an aluminium enclosure with hand tools :)

    With the Gali 84+ most heat seems to be dissipated in the resistors setting the 100mA bias current when it is run from a 13V supply. As I intend to fit it in the case with my Spectrian amplifier I will install a 9V regulator so the bias resistors can be adjusted accordingly and make it run cooler.

    I had a CW filter switched in on SDR console so the G4JNT s/w wasn't getting the full picture, now with a 2.8kHz SSB filter, settings as per DB8TF's and Peak -> CF and tracked I'm getting 51dB and 17dB.

    I also am no expert in this matter. I'm using a 1.2m Gilbertini offset dish Octogon LNB and a LimeSDR mini here and measuring the CW beacon using SDR Console I get 34dB on the steady carrier and 84dB @ 1 Hz and 49dB @ 2.5kHz using Andy's software.

    Flo is correct, it would be good to use and "independant" piece of software such as Andy's to compare results across the many different configurations being used on QO-100. Time to read the manual 8|

    Hi Claudio,

    I use a LimeSDR mini for both RX & TX with SDR Console software, using however windows 10 it works fine. I would try to see if the Limesuite software loads under Win 7 as that updates the LimeSDR mini's firmware. The driver and software installation is though detailed here

    Whilst I can't comment much on Win 7 I can add some comments on the LimeSDR mini and an external clock.

    The external clock in the mini is actually applied by physically switching R59/62 i.e. a hardware modification has to be applied and the switch from internal clock to external cannot be made by software alone. A connection has to be made to a U.FL on-board connector. So it's not very straightforward and needs some fine SMD work.

    Doing some tests with Lime Suite the mini seems a bit 'picky' regarding the external clock values it runs with and I ended up using 40MHZ which is the same as the internal VCTCXO, having done that another problem manifest itself as the mini then fails the stock quick tests and calibrations (I noticed also that the SDR console log threw errors as well). The errors relate to the fact that the mini's VCTCXO is, it would seem, 'exercised' by the DAC providing it's control voltage and expects to see a corresponding change in the VCTCXO's output frequency, a reasonable test to be applied to ensure overall functionality but clearly with the internal oscillator disconnected cannot take place.

    I ended up restoring the original hardware link to the internal VCTCXO and trimmed its 40MHZ output by means of a loosely coupled and GPS locked service monitor whilst adjusting the DAC via Lime Suite. The final value is then written to the mini and persists. I would though say that a degree of luck is needed to hit the right frequency as the DAC resolution is quite coarse. This I see is already documented in the Myriad Discourse forum where a possible substitution of the DAC is suggested it would though require also that the software is rehashed accordingly.

    The LimeSDR mini mini works great for me with no problems at all and the internal VCXTO is proving quite stable once trimmed it is though a quite coarse adjustment as has been commented on in the Myriad Discourse. Some have replaced the DAC with a higher resolution device but that means a rehash of the firmware as well. If i experience any drift or need ultimate precision I will swap the resistor again but for now it is fine and SDR console with the new beacon lock trims out any discrepancy.

    Hope this helps and I hope someone can comment regarding Windows 7 and limesuite.

    Best 73

    Clive, G4KCM

    Clive, this design from DB4UM needs to be pinned. high gain and decent output power, excellent.

    Achim, it's $9.70 for three if you can wait for the slow delivery. With Fedex it's about $33. For three four layer boards that's not bad. Only slight hiccup is that it will need hotair or an oven to solder which may make it difficult for some. Will leave it to you to do any pinning in the forum as I haven't a clue how to. It would be nice if it had a SAW on the front end but it does roll off.

    73, Clive

    Rather interestingly I purchased a similar board a while back and was less lucky. It was labelled as 50Mhz - 4GHz and when I tested it at 2.4GHz I discovered that I had actually purchased an active short circuit i.e. it consumed 100mA and had no gain! The device was labelled as a Qorvo SPF5189Z but for sure was not.

    I take the view with the Chinese modules that you pay your money and take a chance, thus far I have been more lucky than unlucky so with this I just smile and carry on. I will put a 'real' device in it one day :)

    73 Clive

    Achim, I do agree re the overall cost. I tend to 'browse' the shared area of OSH Park and grab a few things if I use them for a PCB to try to minimise the impact of carriage fees.

    The end result is that I have a couple of spare filters to try with Chinese options and one which was grafted on to a SV1AFN Gali-84+ amplifier board that works nicely between the LimeSDR mini and Spectrian PA.

    Not very pretty but it does the job for now!

    73 Clive

    Nice to know that that those filters work as advertised I was thinking of getting one but then I found a PCB in the OSH Park shared area that the SF2124E fits on... Link

    As you can see it was originally intended for the UHF filter but the SF2124E has the same footprint. A word of caution... it really needs hot air or an oven to solder as there isn't really enough copper pad for a soldering iron. Quite a cheap solution though as the PCBs were $1.35 for three plus of course shipping etc.

    73 Clive