Posts by dj0abr

    ok thanks, that makes sense. So if I choose 1/4 than only one quarter is used for video. This is why my TX buffer is filled up to 99%.

    It also explains why 9/10 gives the best results in my local transmission over only 5m distance,

    Friday is my free day, so time to hobby! As guinea pig #2 built the 'Radioclub 't Gooi' (PI4RCG) MMIC amplifier however, deviated a little from the original design (didn't had all the parts, so the junkbox is always my best friend ; -) and used two TQP3M9009's as driver MMIC's (original design uses two SBB3089z's). My MMICs have more gain and hopefully all will be stable! Amp has to be tested of course...

    that looks really good ! Please think of a PTT input to switch off the quiescent current during RX.

    thank you for answering my questions,

    Heiner, a test with 2000 kS/s worked fine too,


    For 333 kS/s:
    G0MJW : that did the trick. I reduced the input resolution to 640x480 and the picture was fine.


    An additional improvement was to change the FEC to 9/10.
    Can anybody explain what this FEC setting is doing ?

    With 1/2 I still have some blocks, with 9/10 the picture is clean.

    With some other FEC settings (i.e. 1/4) the TXbuffer fills up to 99%.

    I am trying to get a DVBS2 TX running with Pluto.
    In general it works, but the video quality is very bad.


    PC: Win7, Intel i7 16-cores, 16GB ram

    Pluto: all hacks installed, second core activated
    Pluto connected via USB or ETH (makes no difference)

    Software: DATV express, 333 S/s

    Cam: 1920x1080p webcam


    Receiver: SF8008

    RX signal strength: 99%


    When I receive videos (333 S/s) via QO100 from other people using pluto, all looks fine, nice quality.


    When I directly (not via QO100) receive my own signal, generated by pluto, there are strong artifacts and blocks. These blocks are "pumping" every second, the picture gets very bad and then improves a bit during the next second. When objects in the video are moving, I see only blocks and extreme artifacts like the tail of a comet.


    Please can anyone post the settings of the datv-express menus, or has another idea what I could try to improve quality ?


    73, Kurt, DJ0ABR

    Hi Thorsten,

    if you drive it with a single carrier up to compression it will draw around 1,5A. When used with an SSB signal usual for QO100 its below 1A.


    DL1ZU , bitte wende dich an dl1ev@gmx.de, er hat einige Platinen vorrätig.


    The BLF2425M9L30U is available at digikey from stock. No.: 1603-1067-ND


    vy 73, Kurt, DJ0ABR

    today we built the full PA equipped with all boards,


    the board in the middle is the (already released) 10W-PA. Right of it is the prototype 30W booster and at the left is a small universal board with an attenuator to fit the input to the 50mW of the Amsat TX mixer.


    All boards can simply be screwed to a cooler, but we did an aluminium box, just for fun. The red plug is the 24V supply (2A max) and the black plug is the PTT input.


    The 10W-PA followed by the booster has these data:


    Output: 26 watts Peak

    Input: 10mW (for full output, nice to be used with an SDR)

    Gain: 34 dB

    Efficiency: 48%


    in my case I have put an 10dB attenuator in front of the PA, so I need 100mW for full output.

    This small board (in the picture on the left) has pads for up to 5 SMD components (0603 or 0805). It can be used as attenuator, filter or whatever is needed.


    The RF lines of all boards are at the same position, so all boards can be easly stacked together with a solder bridge. Alternatively SMA connectors can be soldered to each board's input and output.


    I have ordered a couple of these filter boards and also the booster, should arrive end of this week, as usual you may contact Ernst (dl1ev@gmx.de) if you need empty boards.


    Best 73
    Kurt, DJ0ABR

    it took some time to get the new PCBs, but they arrived this week.


    The first board which is finally released is the 10W amplifier.


    10W means, compression begins at 10W output. In SSB we can expect an average power of 2,5 watts and if a speech compressor is used up to 4 watts, which works well with many QO-100 antennas. Gain is 17 dBm. We built a couple of board and no additional tuning was required, all worked immediately, so you usually don't need any measurement equipment except a DC voltage/current meter.


    The board has a PTT circuit now. The quiescent current is only ON during TX. The requirements for a cooler are very low (in SSB only), a piece of aluminium or any other cooler is usually sufficient.


    The complete development documents are available for everybody for free. Please see here: www.dj0abr.de .

    A member of our local club, Ernst, dl1ev@gmx.de, has empty boards available. If you want to get a board, please write an email to Ernst and ask for board number: 10821.


    The next step is a 30 watt booster which can be connected between the 10W PA and the antenna. The prototype is already working, currently I wait for the final boards.


    vy 73
    Kurt, DJ0ABR

    Before doing the final layout, we started some experiments with the BLF2425M9. Mounted on a homebrew prototype PCB this Mosfet generated 22 watts out from 500mW input with almost 50% efficiency.

    (nice for use in portable 60cm dishes).


    The plan for the final PCB is now as follows:

    1) 2.4 GHz SAW filter at the input (as recommended for the Amsat TX board)

    2) MHT1008 amplifier

    3) LP filter

    4) --- CUT ---

    5) Attenuator

    6) BLF2425M9 amplifier

    7) LP filter


    at step 4) there are simply a couple of holes in the PCB, the PCB can be cut here into 2 parts. So if only the MHT1008 is needed, the PCB is broken at 4) and the other part is thrown away (the PCB is very cheap :-) ).

    If one needs both stages (i.e. for higher gain), then he uses the complete board with a gain of up to 34 dB.


    Some applcations (i.e. the Amsat Mixer board) need a gain of >17 but less then 34 dB. To adjust the gain to the needed value a simple attenuator (0,5 watts SMD resistors) can be mounted.


    This week we are doing the measurements with the BLF2425M9 board and also design the low pass filters.


    vy 73
    Kurt, DJ0ABR

    (Board have been sent to DO1CTL, DD0KP and ON6AJ)


    The last measurements were take in my Shack with very simple equipment.


    This week we have been invited by Rohde&Schwarz to measure the PA with calibrated and expensive instruments.

    The measurements were take by Alex, DG5RAQ and Johannes, DC1RJJ.


    This picture shows the max. output power with 12 volts supply.



    this is the spectrum (12 volts)



    12V was measured just for fun. The datasheet specifies 28V for this transistor, so the next pictures shows the 28v operation.


    The PA was driven with 25 dBm:



    and generates 10 watts output power. Supply: 28 volts and 0,709 amps (=19,85 Wdc). This is about 50% efficiency, thats not bad for a 2.4 GHz PA.



    this is the spectrum at 10 watts output. The measurement was taken using a power attenuator.



    the requirement for spurious emissions (> 1Ghz) is -50dB. We measured 40,88. If the antenna has at leat -10dB at 4.8 GHz then we can use it without any filter. Otherwise some filtering is needed.


    vy 73, Kurt, DJ0ABR

    I have the SF8008 also running with the Amsat Downconverter.

    Everything works fine when I select the channels manually.


    In the link to dd1ku is a reference to a channel-list: QO-100.tar


    This file is maybe old ? It does not work in my SF8008 because the channels are set to wrong frequencies and also to DVB-S instead of DVB-S2, DVB-S2 needs additional parameters which are not in this list.


    Is there an update to this list available ?

    I have prepared a couple of board, tomorrw we will measure if the input matching is the same for all boards.


    Taking measurements on 13cm is a realy challenge :-) One SMA <-> N adapter has 2dB loss, another identical adapter only 0.5dB.

    Also the temperature of the transistor has some influence on the input match.


    But these are only details. The most important thing is, driven with the Amsat-TX mixer it generates a couple of watts output and can be used for QSOs.


    I found one important issue: the maximum input power should never exceed 300 mW.

    With 400mW at the input I measured a degration of the transistor gain, so we have to be careful not to overdrive it.


    In the short wave Amps, I simply put Zener diodes on the gate for protection. For 2,4GHz this is not possible due to the diode capacitance.


    Any idea how to protect such a circuit from being overdriven ?


    vy 73

    Kurt

    just did the first QSO with this PA with DK1KQ. He reported a good signal.

    120cm dish and the homemade dual band patch feed (according the NL and G document).

    The previous measurements were taken with a continuous carrier from a signal generator.


    In SSB the power is maybe half of that because we need linearity. With 24V and the Amsat board as the driver (abt. 50mW, maybe up to 100mW) the SSB output power was about 3 watts. This made an average signal on the NB transponder like most other stations are doing.


    The current board was just made to prove the concept. For a real PA a few things are missing, like a PTT circuit to switch on the quiescent current during TX only. Also I want to change the size of the board so it fits into the usual Tin cases.


    I will publish the PCB data this evening, mainly for people doing tests and measurements. If you want to use it for regular sat operation you should better wait for the next layout which is hopefully available in 10 days from now.


    Also, FR4 is not FR4, if a board is made from a different manufacturer, it may be required to check the input match.


    vy 73
    Kurt, DJ0ABR (DC1RJJ)

    as promised I give you an overview on the progress for building a low cost PA for es'hail-2 NB transponder.


    We have the prototype finished and tested. It is running fine.


    The total cost of material of the amplifier is about 20 Eur only.


    The performance data are:


    at 12V/850mA

    output power is 5 watts

    with 100mW input (nice fit to the Amsat TX mixer board)


    at 24V/680mA

    output power is 10 watts
    with 200mW at the input.


    You can read more detailed information here:


    English:

    https://www.helitron.de/dj0abr…sh/technik/sat/sat_pa.htm


    German:

    https://www.helitron.de/dj0abr/german/technik/sat/sat_pa.htm


    since this prototype works so well, we will continue with a second version including a PTT circiut and a few other parts. But we keep it simple so everybody can build it easily.


    If more gain is required (i.e. for SDR transmitter), simply two of these boards can be chained, giving a total gain of up to 34 dB. I have used two boards in series for the power tests because my generator has only 10mW max output.


    All parts are available worldwide from digikey or mouser.

    I have 4 PCBs left, if anyone wants to build it, just write me a forum-message.


    The part list, circuit and gerber data will be published on above web pages during the next days.


    vy 73
    Kurt, DJ0ABR


    super ! Danke für die Info,

    hab das Filter gleich bestellt da ich nächste Woche erste WB-Empfangsversuche machen möchte.


    Hab den TX und RX Mixer jetzt 10 Tage im NB Einsatz und bin außerordentlich zufrieden, spielt perfekt ! Ihr habt für uns tolle Platinen entwickelt.


    Nur ein kleiner Hinweis: für die TX Platinen habt ihr zu enge SMA Buchsen bestellt. Vielleicht die Stückliste mal checken. Aber mit einer Feile kann man sie erweitern dass sie auf die Platine passen.


    73 de Kurt

    thanks to all answering my request for building a low-cost PA for QO-100.

    We now have a small group of hams, and also access to R&S test equipment.


    We started the development beginning this week.

    Circuit and layout is ready, components arrived.

    Next week, when we get the PCB, we start assembling the prototype and testing.


    Designing the matching using PCB-traces was not easy, so there is a high risk that it maybe will not work as expected and we have to make some changes in the layout. We will see. If it works I will publish all documents to the community.


    More information end of next week.


    vy 73, Kurt, DJ0ABR

    PH2M , i know the circuit in your link. It looks good except one thing.


    What looks strange: L4 ... 10uH.

    These SMD parts (with 10uH) have self resonance frequencies of usually below 100 MHz. So it will be just a capacitor at 739 MHz and pull down the LNB's output signal through C5.

    And L5 with 10nH has no effect.

    I think L4, L5, C5, C6 should be recalculated.