Posts by MM0TWX

    It worked like a charm, Martin. On th one hand, you are very kind and I thank you. On the other, Kuhne may have saved a lot of trouble by writing "CR only" instead of just "CR" in the manual! HI. Thanks again and 73.


    I tried unsuccessfully to connect to the MKUP 2424B by using a Silicon Labs CP201x USB to UART Bridge configured as COM4. Not knowing the version of the firmware in my unit, I tried both the 115200 and 9600 Baud settings. No joy - no communication whatsoever.

    Grateful for any advice.

    73 Pete MM0TWX

    Dear forum,

    I was wondering if it is possible and appropriate to post a short ad for QO-100 pre-owned components.

    Thank you.

    Thanks again everybody for sharing your ideas. As I suspected from the beginning, the issue was with SDR Console, and Chris G4SDG put me on the right track. BUT, there is a big BUT... Changing TX ant to Auto, the system now draws one additional amp when transmitting, which is right. However, after that, if I switch to any other TX ant I get the same result... It looks like changing TX ant the first time "switched" something either in the dongle or in the software, and now whatever the TX ant setting, i get the same output. Super-bizarre. And, I NEED to get around to measuring RF.

    @G0MRF The F1OPA module alone draws 89 mA. When switching on TX on LimeSDR and gradually increasing drive, nothing happens until about 50% drive, and then current draw from F1OPA goes DOWN (!), 70 mA at full drive.

    G4SDG. Thank you for the heads up. The Console is a great piece of softwre, but can be a pain to use (mine freezes two or three times per session anyway...). Concerning TX power, how will I be able to tell, not having a power meter of any sort for 2.4? Please remember I am using a LimeSDR mini, which only has one antenna connection for TX and one for receive. TX ant does not seem configurable.

    Hello everybody.

    Please appreciate that my technical knowledge is limited and I have no microwave experience at all.

    I have been putting together a QO-100 system centered around a LimeSDR mini. The receiving part works fine. The transmitting part doesn't. The LimeSDR does transmit (checked with 145 MHz receiver) but no real power comes out of the 2.4 GHz system.

    The TX chain begins with the LimeSDR, followed by a 100 mW F1OPA amplifier, followed by an EDUP "8 watt" final and a filter finally into a dual patch.

    The EDUP amplifier has the TX modification, so when powered is permanently switched on TX.

    Since I don't have either a 2.4 GHz receiver or a power meter, my investigation is limited to measuring current drain.


    1. F1OPA and EDUP amplifiers draw 380 mA on standby. This is entirely due to the EDUP standby current drain, as per specifications.

    2. Putting LimeSDR in TX, current draw only goes up to 410 mA.

    3. Disconnecting the EDUP from 12 v supply, current drain goes to 0 on standby. It would appear the the F1OPA standby draw is very low.

    4. Putting LimeSDR in TX with only F1OPA module connected to 12 V supply DOES NOT change the 0 current draw.

    The only conclusion I can draw is that, although the "on" led is lit, the F1OPA module is defective. The 30 mA increase in draw under TX conditions is - I think - the attempt of the EDUP circuit to amplify the minuscule power coming from the LimeSDR.

    Is there any other explanation?

    Thanks in advance.

    Pete MM0TWX

    Just for information, I tried the 60 cm dish outside, on a clear day. SDR Console's snr meter now says 24 dB on the CW beacon. However, copy on SSB signals is possible but not very comfortable. At my latitude, 60 cm is evidently not enough.

    Apologies for my abysmal ignorance.

    Where is it best to place a 2.4 GHz bandpass filter? Before or after the "el-cheapo" PA? at the end of the chain.

    Thank you in advance.

    Thank you all for your inputs. Concerning the low signal, I believe it's partly due to double glazed widow, and possibly interference with the lobes from the window's metal frame. For me it was a success to hear anything at all!

    Concerning fading, clouds and rain could be an explanation, for we have a lot of that in Glasgow...

    Hello. I am a total newcomer to microwaves and QO100. I started experimenting with the RX part of the system before I try to transmit. At the moment I use a small dish (60 cm) behind a window. The beacon is about 12 dB over noise, so I am quite happy. I am waiting for a 110 com dish, and things will be much better.

    The big question I have is that I notice quite some QSB on the beacon signal, with as much as 6dB range and a pattern not unlike what you could see on HF. I have clear line of sight to the satellite, the dish is indoor, and I really do not understand how that could happen.

    Any wisdom from the experts?

    Thanks in advance and 73.

    Pete MM0TWX