Posts by DF1QE

    Some LNBs need a VERY clean powersupply.

    In case that most of the LNBs have internal voltage regulators at 6 volts (like 78L06) , one can power the LNBs with voltages down to 8 volts. (which also keeps them nice cool)

    So it's possible to use 12 volts from the rig and filter it in an additional voltage regulator to 8 / 9 volts for example 7808 or 7809

    This gives a very clean LNB supply.

    And don't forget the capacitors at the regulator.


    Armin DF1QE

    Hello Oscar 100 friends !

    It has been a while that I was active here since my publications of LNB Mods, IndoorTCXOs and Converters.

    Meanwile some hundereds of my developments were rebuild by other hams.

    But that does not mean that I was inactive ...

    My own Station works fine, but what me disturbed were the many small boxes, TCXO, 2m converter, ATV converter, LNB supply and so on ...

    So I developed a "AllinOne-Interface" which can be used for all kinds of RX possibilities together with a modified quad LNB.

    All in just one 160x100x30 mm box.

    It contains :

    1. A flexible regulated LNB Supply with 12 an 18 V

    2. An excellent indoor reference TCXO with 25 or 27 MHz

    3. A 2m converter for receiving the NB-Transponder

    4. An ATV converter for the WB-Transponder for receiving ATV with an original SAT-Receiver

    5. A filtered output channel with H/V switching for connection of an SDR-Stick for monitoring

    All inputs and the ATV output are filtered with very sharp SAW filters wich results in a very good signalquality.

    So you have 3 several RX Path at the same time with just one box.

    I made a complete report of building instructions, including shematics, layout, placepan, mechanic plan, partslist and many more for rebuilding it on your own.

    You find it at :

    Sorry, it's german only up to now, but "deepl" helps and the shematics and layouts are "international" :)

    I hope you find it useful and I wish you many success with it.

    best 73s :)



    I don't think the lowpassfilter is a matter if the LNB sychronises or not.

    As DH2VA already wrote, the PLL synchronizes best with a high (but not to high) slew rate.

    But the signallevel matters in some LNBs a lot.

    Usually the x-tal oscillates with a level of around 0.5-1.0 Vss.

    If you drive it externally with more than 1.0 Vss, some LNBs don't like it.

    Then the DC-Level on the OSC out pin drops very low and the AC curve gets limited at ground or a frequency doubeling occurs.

    You can easyly test that by inserting a potmeter (around 100 Ohm) as a voltage divider in the REF line.



    I also recommend a low- or bandpassfilter. Else you "spread" your whole shack with a ladder of 25 MHz harmonics if your cables are not well screened. And your neighbour will like it :-)

    (In our region there is a loved radio broadcast on 100 MHz)

    But another question :

    Does not all Oktagon LNBs use 27 MHz reference ?


    Armin DF1QE

    Hello Sat Friends !

    After modification of lots of Single- and Twin-LNBs for external LO input and the use of them I found it uncomfortable to have only one IF output.

    So I decided to modify a Diavolo Quad LNB for external LO, which gives me 3 simultaneous IF outputs now.

    I use one for the NB-Transponder converter, one for the WB-Transponder converter, and one for a SDR-Stick.

    I wrote a complete modificationreport in my Forum for you.

    You find it at :…lnb-f%C3%BCr-externen-lo/

    Hope you find it interesting.


    Armin DF1QE

    Hello Sat-Fans !

    Based on a discussion, after I described my 739 to 144 MHz converters, whether it is possible to make a converter to 28 MHz, I did some experiments, and found out that it IS possible.

    So came out a converter 739 to 28 MHz that really works fine.

    I called it the "NB-Konverter tiny28 V1.0"

    You can find the description at :…-0-739-mhz-auf-28-27-mhz/

    I build up two versions, one for 28,5 MHz for use with regular shortwave receivers, and one for 27 MHz for use with CB-radios. The CB-version is nice for monitoring the beacons and for outdoor use for alignment of dishes and LNBs.

    Sorry, the description is german language only, but there are many pictures, shematics and layouts so anyone might find it interesting. In other case "deepl" helps.

    For me it was a very nice experiance to tune over the OSCAR100 with the old analog "flyheel" of my Trio JR599 and to tune the SSB-Signals with no digital steps.

    If there is a lot of interest in this project I can offer some smiprofessional PCBs and a package of the "uncommon" components.

    best 73 and stay healthy

    Armin DF1QE

    Hello George !

    and the 25 MHz is clean

    Yes I agree .... IF it's clean and not any kind of digital signal ....

    But why always work with minimum components ?

    Are we chinese ?

    Shouldn't we as technicians not better try to optimize components ?

    1 or 2 chokes and 2 or 3 capacitors should not burst our ham budged.

    If I would build such an amplifier for myself it would have a high level MMIC, a regulated power supply with EMV components, a double Pi low pass filter at the output, and may be a damping regulator at the in- and/or output, and sure a tight metal case with good sockets.

    Is that to much for ham radio ?


    Armin DF1QE

    But keep in mind to add a lo-pass filter after the last Amplifier to keep the signal sine form and not to "send out" harmonics.

    25 MHz x 3 = 75 MHz (security Band) and 25 MHz x 4 = 100 MHz (Public radio Band).

    Also you may disturb yourself in the SAT IF.


    Armin DF1QE

    Hello Sat Fans !

    Meanwhile several types of Diavolo Twin LNBs appeared in the market.

    I named them V1, V2 and V3 in order of the appearance in my Workplace.

    For V1 and V2 I already wrote modification reports and posted them here earlier.

    Meanwhile I found out that V3 is the oldest one, then came V1 and V2 seems to be the "up to date" one.

    I got several requests about V3, which I thought it was out of the market, but they were still sold, especially on Amazon.

    So I wrote a modification report for V3 too.

    BTW: V3 is completely different to V1 and V2.

    Here is a list for all Diavolo modification reports I wrote :

    V1 :

    V2 :

    V3 :

    All Pages are german language but there are lots of photos and shematics so it will help all.

    In other case "deepl" helps.

    Hope this was an interesting information for you.


    Armin DF1QE

    Somehow my entry from September disapeared, so I post it again :

    After my Oldschool Converter project I developed and build an other tiny converter 739 MHz to 144 MHz based on some earlier publications I found in the net.

    It works excellent for receiving Oscar100 NB transponder with a 2m RX.

    I wrote a complete report and building instruction for it.

    You can find it at :

    Sorry, german language only.

    But there are lots of pictures an shematics also for download so everyone should it find interesting.

    In other case "deepl" helps :-)


    Armin DF1QE

    PA3FYM : Hi Remco !

    That's why I wrote "new (?)"

    But ok, let's say : you won :-)

    Anyhow, there is some difference.

    As I saw in your Twitter picture, you just disconnected one side of the x-tal and directly connected it to the F-socket.

    I don't think the x-tal works optimal this way.

    I did some experiments until the x-tal was in optimal resonance.

    In the Diavolo quad I modified, I even mounted a variable C to "tune" the x-tal.

    But to all of you who did that before : Why did noone post it here ?


    Armin DF1QE

    DL5MGD Hi Andreas !

    Uhhh, not a good idea ...

    The x-tal needs this capacitive load to work on the right frequency.

    And actually the coax input needs a termination, at least a nearby one ...

    Ok, if you didn't implement the resistors, you have the high capacity of the coax on one side of x-tal,

    but then you need at least half the capacity (6p) on the in pin to get the x-tal in a good resonance.


    Armin DF1QE

    Sorry Remco, I cound not resist this wordgame in the subject :)

    So Folks, here's a new (?) idea for injecting an external TCXO, which I successfully tested.

    Just leave the x-tal where it ist, disconnect the LO out pin of the PLL-Chip, and inject the external LO at the x-tal.

    I tested succsessfully this method with 2 Diavolo Twin V2 and one Diavolo Quad V2.

    This method has some advantages :

    you don't have to remove the x-tal

    you can easily go back to internal LO (original)

    the external LO signal will be filtered by the x-tal

    easy to implement

    so many advantages :)

    The value of R1 in my shematic determins the sensivity and optimal level of the external LO.

    With 820 Ohm at a RT320M chip it is optimized for 1Vss LO input.

    For other levels you should make your own experiments.

    The value of R2 in my shematic depends on which impedance and coax cable you use.

    68 - 82 Ohm is fine for 75 Ohm systems.

    47 to 56 Ohm is fine for 50 Ohm systems.

    But this value is actually less important.


    This method is not useful for (older) NXP chipsets.

    Therefor you better take a look at Remco's Subject : other-method-to-inject-external-ref-into-lnb


    Armin DF1QE