Hardware Needed for TX

  • Hello,

    i am new on the forum.

    I have already assembled my RX part for the QO-100

    For DATV:

    Dish 80cm



    For Phone:

    Dish 80cm



    SDR New Gen. RTL2832

    I would like to try to go on air but i am a bit confused for what i need.

    Please anybody can suggest me which hardwares i need?

    I want to TX and RX in both mode: Phone and DATV just with one Dish.

    Please any help will be really appreciated

    73's de Enzo IK8OZV

  • Phone will be easier to start out with. I have what I consider to be a simple system, as yet on receive side it is very simple. 1 metre dish unmodified LNB and a SDR receiver from Ebay (Auzener) this is going to my laptop running SDR Console and I use the Digital beacon to lock the receive display and keep it steady.

    On Transmit I am using an old 2m multimode driving a BU500 up-converter, the converter is capable of 2 watts output and even with 7 metres of RG213 to the dish is enough to put a reasonable signal to the satellite. A bit of extra heat-sinking on the converter is really needed, I use a small fan to blow air across the fitted heatsink.

    You can drive the converter (as you can with many other up converters with a multitude of frequencies, either 28, 50 144, 435,MHz etc. You can reprogram the local oscillator of the up-converter to match your input frequency to come out on 2400MHz. I would always recommend a Band pass filter on the output of the converter no matter which one you use.

    To actually put your transmit signal into the same dish as you receive from I would recommend you build/buy a dual feed, typically a POTY (Patch of the Year). If you wish use a separate dish then it is also possible to use a helix antenna feed just for transmit, or build one around a satellite LNB for dual feed. That choice will be down to you either way will require some building skills or modifying skills for the receive LNB.

    If you can already do DATV, on another band the up-converter is capable of passing DATV signals from a lower band, and putting out on 2400, again the same as many of the converters available. If you can not generate DATV you will also need is a system to generate it such as software driving a lime mini, or Pluto SDR transmitter.

    Also a decent power amplifier will be required, probably one capable of at least 30 to 40 watts, or more at 2400 MHz. The reason is the extra power levels required for the bandwidth used in DATV, this is dependent on the SR rate used, the higher the SR rate the higher power amplifier is required.

    There is a big difference between peak power and average power used on DATV so a typical PA that can output 50 watts of pure carrier will only be around 12.5 watts on DATV. The amplifiers have to be highly linear for the modulation system and are normally used at levels of -6dB or -7dB from the 1 dB compression point of the amplifier.

    I hope this information has helped initially and I am sure other members will be along to offer other information soon.


  • Many of the converters need to have inputs attenuated. You can get the BU500 with some attenuation built in and that is what you have looked at so it requires 100mW drive. To go from 5 watts you would simply stick another attenuator in line from the TS-200 output and if my maths is correct you would need 17 dB of attenuation, so I would suggest a 5 watt 10 dB bought attenuator and then probably make a simple pi one made from resistors. Two 120 Ohm and one 47 Ohm resistor will give 7.3 dB so you can drive it with that, or, for a bit of safety margin use a 20 dB attenuator.

    I actually got the BU500 with out any internal attenuation, so from my 1 Watts output from a Standard C58 I actually added 36 dB attenuation. The reason I chose my BU500 is to be able to drive it from a hackrf One SDR transceiver directly as it's output is typically around -10 dBm to 0 dBm so 1 mW at max.

    A popular up-converter is the Kuhne up-converter. That will allow you to drive it directly with 5 watts and will give up to 20 Watts output from looking at the specs, but the unit was well out of my price range. But if you want a very simple to operate system and have the money, I would suspect this will be the easiest way to get on phone. As to DATV I am not sure about using the Kuhne, but again I am sure a user of the unit will chip in.

    There are also converters from Bulgaria, SG labs and one from the amsat shop the S-Band Transmitter Mixer for QO-100 (P4-A) is worth a good read up on.

    I would sit down with pen and paper and work out all your choices, include a few extra option you may not be considering yet such as portable operation or always fixed operation, i.e. use of batteries or mains etc. Phone is easy, I have managed to get that far even though it is still spread over my desk it works, DATV is taking me a lot longer as I rework cellular PA's for 2400Mhz, sort out required 28 Volt power 10 Amp supplies etc.


    Just to add, all this is from my perspective and budget and the fact I like to build things up rather than just buy in the goods, mainly because money is limited.:)

  • I really appreciate your helps but i still cannot make up my mind what i need.

    I have been on Kuhne site to have a look of the converter but honestly is a to high price for me.

    I would like to get something for less price if possible otherwise if i have to send higher i have to wait as my budget is low at the moment.

    It will be greatfull if i could see some picture also how the are assembled.

    I have seen about the bulgarian Transverter how you said but i have heard that i could not do both modes.

    I really appreciate if you can work out all my choices.

    Please can you pass me the links wher to buy the stuffs?

    If you can and want we ca continue off the forum.

    my email is vimone@alice.it

    Thanks once more

    73's de Enzo IK8OZV

  • Hi Enzo, I really would not like to choose which way you wish to go, it is a personal choice for you to make, you have to consider what radio gear you have, 2m or 70cm etc, if you have any DATV gear, what budget you have and how much you want to spend over what time period. I have more time than money.

    Lets see if anyone else come up with ideas and pro's cons of various set-ups.

  • It is more sensitive than expected. You can just about do 2Ms with 25W QPSK 1/2 rate FEC with a 2.4m dish. Lower rates 125ks QPSK 2/3 FEC and 66ks 8PSK 5/6 FEC require under 5W and 33ks 8PSK 5/6 FEC even less.

    Multiply these powers by 4 for a 1.2m dish. So 2MS 100W but 66K only 20W.

    Thus 333ks and 500ks are achievable with a Spectrian or similar PA and a 1.2m dish. Many are using 50W PAs and achieving good results with 333/500ks QPSK 2/3 FEC.

    Make sure your feed is true RHCP or you throw away 3 dB. That's like cutting the dish in half.


  • This was my home made POTY and I cut the LNB just before it started to flare and carefully used a file and emery until it would just slide into the copper tube. The leading edge of the LNB still had a taper on it so in effect there was a good transition from the tube to the slightly smaller diameter of the LNB. The joint was later sealed on the outside to stop water ingress with some enamel paint.

    I hope this is what you are looking for, if not let me know and I will delete it to stop any confusion, I am sure others will help.