Upconverter for QO-100

  • Hello everyone!

    I've seen some people using a downconverter similar to this downconverter (check block diagram)! I've designed

    it considering IU8CRI and SV1ELF work .

    I'm not expert at all so I don't know if what I'm thinking for a homebrew upconverter will work!

    If I generate a 2.4ghz freq via an adf4351 signal generator and mix that freqeuncy with an IF from my IC-7300 (on 28/50 etc mhz), and add some amps and BPFs will it work for transmitting on QO 100 ?

    Has anyone done something simillar? I don't even know if it can be done but I hope you will be able to give me some advices.

    (also any suggestions for the downconverter's block diagram will be really helpfull)

    73 DE SV9RYG

  • Thank's for your quick replies.

    Due to the fact that in the current block diagram i use adf4351 signal generator

    I thought it would be cool to use it for mixing also the current TX IF with 2.4ghz and

    transmitting that way! I had the idea from a facebook from someone who claims that

    that's the way he transmits on 2.4ghz but he didn't reply to my message for further information.

    I actually have not at all experience on microwaves haha that's why i posted this thread just to check

    if this thought could actually work somehow!


  • Hi,

    Just for the history my first QO100 transmission was with a laptop controlling a ADF4351 at 2.4 GHz , two amplifiers producing 3W and a homebrew helix powered from two lead acid batteries !!!

    So it actually can be done?

    Due to my low budget and the downconveter using adf4351 and the fact that I have only HF/50/70 radio (IC-7300)

    I hope that I can do it all in one box using the same adf4351 for RX/TX generating freq (controlled from arduino and possibly having

    an external reference) and some relays changing the "RF paths".

  • Hi,

    The only point that is under investigation is if available 2.4 GHz filters are drop image from 70 MHz IF from your 7300. Also ADF4350 can be used that costs less. In your block diagram you mention 100 MHz GPSDO but usually are 10 MHz. ADF4350,1 require 25 MHz that are required also for LNB if drived externally. A GPSDO can be build with Arduino using Lars design.

    UPD: The filter I use is not suitable . LINK this it seems OK.

    UPD2: see also this LINK

  • Hi,

    The only point that is under investigation is if available 2.4 GHz filters are drop image from 70 MHz IF from your 7300.

    Hello folks,

    interdigital filters would do that but probably would not help with a low budget rig, unless one is capable of building one homebrew.

    I use this interdigital filter from ID-Elektronik to successfully run a BU500 up-converter with an IF of 50MHz.

    Vy 73

    Holger ‚Geri‘, DK8KW

  • Hello again and thanks for your answers!

    Sorry for my late reply but I've got a lot of studying for my exams this June.

    I checked all your replies and last night I designed this block diagram for a QO-100

    up/down converter! I got some ideas from IU8CRI,SV1ELF,BG0AUB,SV9OFO and checked also a lot of

    similar projects in this forum and on FB groups. I think it will work just fine even without an external

    reference from the beginning, but with a modified PLL TCXO LNB. I ordered some componnents from ebay

    and I'll start experimenting with this project and I will keep you updated for more infromation but mostly

    with even more questions haha!

    I would be glad to hear your comments and suggestions for this block diagram!

    ( I will build each part seperatly first RX and then TX and after I check that everything works fine

    I will put them all together)

    73 de SV9RYG

  • Using in4148 to do RX/TX switching, the isolation degree is about 24DB insertion loss of 6db... A special microwave switching diode might be better.

  • I was thinking of HMC-213 frequency mixer! Any other suggestions for a mixer?

    I think I will change RX to TX path with 1n4148 diode though, it seems much more

    safe than realys, although I was thinking of something like this circuit .

  • Hi,

    I have mesured the V PtoP at UHF 1 W and it was about 300 mV. I replaced them with BAT85 and it was about the same.The danger is that if PTT line is disconnected you will burn the circuit ...Nice ideas about mixers. I used MAX2671. PCB is available. I measured 50 dB down two tone test at -22 dBm output.A nice solution is also ADE25MH but it is not found cheap at eBay any more .... SV9RYG have you think to go to an SDR solution like Pluto ?What solution do you think about GPSDO ? Have you seen the Lars GPSDO? It is easy to get 25 MHz from it for ADF4350/1 and LNB.Any way how do you think to get 25 MHz from GPSDO? It is a critical point and some solutions does not work !!!

    I hope good results in your exams !!!

  • I will make so experimens with 1n4148 and BAT85 and I will choose then.

    Actually I thought about pluto/lime etc full duplex sdr solutions but I want

    a PC free solution . GPSDO will propably be the last part I will check because

    of their high prices but I'm pretty sure I'll try something homebrew based on

    LARS gpsdo controlled by an arduino. Though I have no idea yet about how I could

    get the 25mhz ext. reference (via the GPSDO ofcource, but how?!), but I'll do my

    research on it by the time everything else is tested!