• Hi people.

    My new construction and design "full duplex" transverter to operate via HF TRX.

    Based on frequencies mixing. 2 separated VCO units, each one controlled by single PLL & reproduce single frequency. Basic control program for PLL2 may changed by re-calculation of counters value, there may working on any amateur HF-band from 3,5 to 28 MHZ.

    The design allows the use of SDR dongle and an external reference OSC in range of 8 ~ 20 MHz. design does not include driver stage for transmitter path. Every chnge required re-programming PLL controllers.

    In attachments seams partial construction. At last tested PLL's lock after debuging firmware for burning controllers. Repeated experience with PLL's lock gave a positive and identical result.

    All stages of design maded by my self , from idea, include program writing and burning controllers , loop filter calculation, pcb routing, parts ordering and soldering.

    Total box size 100x56x24mm.

    Now partial explane about block diagram.

    Main synth lock VCO at 1660,5 MHz, second PLL do it at 949 MHz. PLL1 serve downconvertion operation for product of 711,5 MHz. By the way this frequency will change final downconvert to any HF band. Mixer connected in those manner not given so mutch on 2609 MHz, also LPF 720 MHz disable it, especially IF max range is 1500 MHz.

    Next converter is 1660,5 MHz mixed with 711,5 MHz. This point serve RX or TX mode. If mixer M2 is "shorted", no product of up conversion can run trouth this path - there M1 receive signal from LNB and mixed product going to the owner TRX.

    In TX operation mixer M2 is up converter (IF port at input) with 1660,5 MHz and product of M2 - 711,5 MHz. Last converter based M1 mix transmitter carrier from TRX and product of M2. Here i'm set power attenuator from TRX to prevent damage of mixer M1. Maximum saturated power to RF port is 0 dBm.

    Input-output path's signals distribution diveded by diplexer - LPF for LNB in and HPF for PA's driver.

    Abouth harmonics or products from mixed signals.

    949 x 2 = 1899.

    1899 + 711,5 = 2609,5.

    949 x 3 = 2847.

    1660,5 x 2 = 3321.

    1660,5 + 711,5 = 2372.

    711,5 x 2 = 1423.

    1423 + 949 = 2372.

    711,5 x 3 = 2134,5.

    There is no product of combinations above is close to 2400 MHz.

    About x-harmonics of 28 MHz not discuse.

    Even i'm not shutt down PA and driver in RX mode, nothing to amplify bacause mixer M2 is "shorted". In any case, port's short technics used in frequency doublers based mixer.

    Final stage will have BPF for 2400 MHz, but i not support any PA, also not support BPF/LPF for the range.

    Both VCO's choosed with low RF output power, to prevent high level radiated power into system. For PLL' f-in port low power arround -3 ~0 dBm found in working windows range. Actualy real RF power of VCO is lower than datasheet value.

  • Hi 4Z4LS,

    thank you for sharing your ideas.

    I am not sure I understand how you can operate with that unit full-duplex.

    In addition how do you plan to deal with the suppression of your local oscillator and your image frequency of the 2.4 GHz upconverter.

    You will need a very high Q filter to get to an acceptable level (min 60dB suppression !?).

    In receive mode I propose to switch off the driver stage and the PA as you will otherwise generate additional spurious emissions due to your frequency generation scheme.Kind regards



  • Hi, 4Z4LS

    Also I wanter how you can archive suppression of Lo and image. A less complicated Lo could be a ADF4350. Do you have capability of external frequency reference from GPSDO? You have an amplifier before the LPF at 2.4 and you amplify also the 739 signal.

    George, please see head of theme after additional explane for all questions. Later i will set schematics diagramm, now is in "crude" form, even though the PCB is ready.

    Actualy i'm not amplify 739 MHz signal from LNB, also i have not switch over 20 dB attenuator to the TRX, because RX signal so strong and must be attenuated. TX out is amplified to get some level after mixing and filtering stage.

    Actual schematics have possibility for external OCXO source (it written before) 8~20 MHz range. You can see it clear in the picture of outside PCB "BOARD7". Now in use separated 10 MHz XTAL's for each REF of source - only for my experiments and testing.

    ADF435x - not shure is less complicated, that my point with PLL's. First all you have not program in simple form to make few steps : calculate new value of counters in PLL, change parameters of source, compile & burn micro with HEX file. I spend a lot of time for program form to set 4 parameters and compile it. this was take a time. Now progam is tested and actualy i can can reproduce any single carrier from each PLL.

  • Hi

    I don't understand it.

    It's either very very good TRV or only good TRV, I'm not sure.

    Is this TRV already working? You can make an appointment for connectivity?

    Sorry, I want to understand this construction.

    1) What is "Full Duplex" here?

    2) How do you want to suppress the differential mixing signal (TX)?

    3) The receiver's signal goes through the transmitter's attenuator -20dB?

    4) Will the system I have made simpler not work? (screen2). What is the difference?



  • Hi Artur!

    Full duplex in sat range is not exact,name of, but it's mean TX and RX modes run via same path - AERIAL of OWNER’s TRX. May be is not exact name , but is it. RX signal from LNB is really strong,so 20dB pad is not a problem. Few radioamateurs add cable to rerduce signal level up to 40 dB! If you compare,many constructions include attenuator on RX path to reduce a lot of power from LNB. In that case sensetivity still at desired level. Supression of conversions or unwanted products. Because in every point or in every mixer is single frequency signals,try to calculate where you can see unwanted products.

    My oldmen teacher (RIP few years ago), was teach me 35 years .ago and i really remember many lessons and themes, but one geniuos phrase i'm remember perfect: "every RF circuit will working ideal on the paper even mistakes is in".

    I will explane you all part and part from this design, and because this project is totaly my from first block diags up to synth calc include phase noise,loop filter, program and other blocks. Also, you can immaginary about fantastic parts, but if you have not compact, low power consuption and RF level VCO, your project will on paper only.

    Off course i can make any manupulations with frequency sources, multiply, divide, add or substruct, but first all i need choosing parts with cost-efficiency line. In thats case must to see what's market have too.

    If i talk about design for HF transverter, in any case it must to give to owner working (by request) in one of HF bands from 3,5 to 28 MHz.

    I will attache screenshots of Appcad 's run spurs of mixer. I open scale of 5-th product of every mixer combinations.

    Now about choosed parts - my opinion is VCO from Maxim series MAX262x & VCO from Alps E-D07A.

    Now show me please VCO for 720 MHz mid range with same parameters. Believe me, I testing market before making first step.

    You are change my circuits, but have not parts. I receive 711,5 MHz by product of 1660,5-949 MHz. In the next mixing stage I’m add 1660,5 to 711,5 MHz, there additional TRX freq of 28 MHz will give 2400 MHz. To change final product to desired HF band, I reprogram & lock PLL 949 MHz to 935 MHz e.t.c. For working on 20 m band, mixing must to give 2386 MHz. Also other ranges of HF.

    It’s good or not I don’t know. Now I wait for mixers, so important parts is tested – PLL lock and software test.

    I hope that you have all answers for your questions.