Posts by DL5CN

    Hallo,

    the LimeSDR Mini has three thermal sources. To reduce thermal drift, the board is mounted upside down on a big plate of aluminium. The plate has the same size as the Laptop I use for portable operation. All the other components like USB-Hub, sound card, power supply, USB-Relay, PTT-Interface, PA and some connectors are mounted on this plate too. The thermal capacity of the plate helps to avoid fast change of the LimeSDRs TCXO. Between the Lime and the Aliminium plate there are a little milled peace of aluminium and silicon thermal pads. This is for levelling the different hights of the Lime-Chips and thermal coupling.
    At least, the TX-Frequency changes a bit with the environmental temperature beeing outside. Adjusting this once at the beginning of a session with XIT of the Console will give sufficient stability.



    The upper cover, normal carrying the Laptop is removed. The lower floor gives room for extensions. At present there is a 12V-power supply for the Laptop. The complete radio is running with 12V too.



    Here is the LimeSDR Mini mounted upside down. No need for a fan. The hight of the board is fitting with the USB-Hub left.

    73s
    Andreas

    Hallo,

    if someone is talking about the occupied bandwith, don't forget the intermodulation distortion. This is (some times) much more than 2,8 KHz.
    Use the audio equalizer to correct the frequency response. Individual voices require adjustment. A frequency response of 6 dB per octave is recommended in the literature. Most of the signals show too much level closed to the carrier. The goal is a well balanced spectrum inside the SSB-Filter.

    Use the compression to reduce signal dynamic. Even with low signal to noise it is important to have a level control.
    Peak clipping avoids overdriving amplifiers and reduces Intermodulation.
    All this is possible with the SDR Console what I - and so much more users appreciate very much.....

    73s
    Andreas

    Hallo Mike,
    I think, there is no need for copper. The idle current is around 800 mA. With rf the current reaches approx. 5 A. If one interrupt the supply to the idle current circuit, the standby mode is easy. This can be done disconnecting the copper on the lower left side below the huge electrolyt capacity C136. Then the idle current is off complete. The PTT-switch on can be done with electronic, there are a few Milliamps flowing only. I like "high side switches" for example BTS4140 from Infineon. They have a control input pin. Pulling it to GND, the input supply is given to the output pin.


    With the normal doherty operating no dangerous heating can be seen. The transistors are not at the same mechanical hight as the print. It's recommend to resolder before mounting. With a good thermal connection like "Artic Silver" or similar, save operation with an aluminium cooler is possible. With driving power around one to two watts, the output is more than enough for NB-operation with very good linearity.
    73s
    Andreas

    Hallo,
    mit dielektrischem Material zwischen Patch und Reflektor kann man die beiden Dips, die sich bei einem Patch ergeben
    sollen, abgleichen.




    Ich hatte leider nur 0,5mm Material und damit sind die beiden Resonanzen zu hoch. Das Ganze funktioniert wie ein Puzzle.

    Im S11 Plot ist die Verschiebung nach unten, symmetrisch um die Betriebsfrequnz herum, zu sehen. Das dieeletrische Material sind eilig zugeschnittene FR4-Stückchen.



    73
    Andreas

    Hallo,

    I did a new Dualfeed-System for a friend with some new ideas. Mill a brass tube. There is no need to reduce the outer diameter of the rocket but removing the lense flange. Clean it with sand paper. The brass tube has a new flange to carry the lense. All three parts can be sticked together. No loss in LNB because all is original.



    Solder the patch and the reflector disk to the tube. One can mill 3mm (plus copper thickness) shoulder to the tube to get the right distance between the patch and reflector. Don't forget to drill the "feed hole" when both parts are fixed flat together with a srew before soldering. In this case, the reflector disk hole has a reduced diameter to stay on the shoulder.




    This is the ready LNB. It gives a compact unit and can be mounted with the most dish equipment.



    If the upper bracket gives no room for the S-Band-Cable, take a metal bracket. The picture shows my own feed with heavy Cellflex cable. The transition to SMA-Surplus-Cable is fixed with an alu bracket


    By the way, rockets with 25 MHz TCXOs are extremly stable. No fast changes in the final frequency can be observed like it was with 27MHz from Connor Whinfiled mounted in Octagons.

    There is only little change with outside temperature which can be easily regulated with SDR Console.


    Many Thanks to Simon in this way ! He did a great job all over the year. We appreciate this very much.


    Finally, the feed is a compact unit. It can easily be changed and compared with other antennas, probably a helix.

    73s, have fun
    Happy New Year to all "Helians"

    Andreas

    Hallo,

    es gab schon mal einen thread zum Thema.
    Ausgehend von zwei grundsätzlich verschiedenen Typen von LNBs muss man eine Linse vor dem
    zylindrischen Hohhleiter der "Rocket-LNBs" als Alternative für die Ausführungen mit angegossenem
    Rillenhorn sehen. Die "Raketen" sind schmal gehalten, für die Anordnung auf einer Multifeed-Schiene.


    FEW RULES FOR LNB CHOOSE


    Sprich, beide LNB-Ausführungen haben identische Strahlungsdiagramme, geeignet für kommerzielle Spiegel.
    Ob offset- oder zentralgespeist spielt keine Rolle, entscheidend ist der f/D-Faktor, ein Maß für die Krümmung.

    Die "Rocket-LNBs" lassen sich meiner Ansicht nach leichter mit einem bündig aufgeschobenen Cu-Rohr für eine Patch-Antenne oder eine Helix kombinieren, ohne den HL des LNB zu verändern. Die Linse befindet sich auf einer kleinen Messingscheibe, die vorn auf dem Cu-Rohr aufgelötet ist.

    Beim Versuche, die Wirkung der Linse zu erkennen, ist ein breites Spektrum, über den Transponder hinaus,

    hilfreich. Dann erkennt man, daß sowohl ein Vorwärtsgewinn als auch eine Absenkung des (am Spiegel vorbei) aufgenommenen Hintergrundrauschens entstehen. SDR# mit einem RTL-Stick erlaubt eine breite Darstellung des Spektrums.

    73
    Andreas

    Hallo,

    nice collection, it helps.
    I would like to add some mechanical hints. The rocket types have no horn but a lense to correct the radiation pattern.


    The original waveguide has a litte flange to fix the lense. This can be removed with a lather. The outer diameter of the waveguide must be reduced a bit and the inner diameter of the 2mm copper tube must be slightly increased, in this way that both can be sticked together smoothly. Now you can decide using a patch or a helix. Fixing the lense again, there is brass washer soldered to the copper tube.
    Milling the lnb is possible when prepare a wood cone with the inner waveguide diameter.

    To combine a horn type lnb with a patch is more difficult.

    Part of the horn is removed. This gives a flat flange. The brass flange is fixed with 3 screws and soldered to the copper tube. The input of the copper waveguide has no pretection and correction of the radiation pattern. A lense can fill this two requirements.

    Have fun....
    73s
    Andreas

    Hallo,

    I milled a little brass ring which is soldered to the copper tube. The ring fixes the lense.
    Brass can be found in the plumbers junk box.
    From my point of view, the diagrams from DD9FJ above show an effect I could see also. The increasing of the gain is less then the reduction of the background noise. The diagram gets smaller when using the lense and there is less noise receiving beside the dish. As a result the SNR is higher.
    This can be seen more clearly, receiving the NB with a wide spectrum display.
    So, the lense works as expected.

    73s
    Andreas

    Hallo,
    there are two types of LNBs tested here. OCTAGON OTLSO which has two indepedend LOs and Rocket LNBs VENTON and Red Eagle. Both work with 7,5 Volts. The Rockets can be combined now even with a patch or a helix.

    Reducing the diameter of the LNB-Waveguide and increasing the copper tube a bit it can be sticked together smoothly. I prefer SMA-Connectors to feed the S-Band-Antennas to avoid mechanical collision with the LNBs and the mounting clamp. That's why the backplane of the helix shows a corner connector. At the front of the tubes is a small ring of brass to fix the lense again.

    With the lenses I always expected more gain. It was'nt seen clearly. Looking to a wide spectrum, the difference between transponder noise and background increases. Probably the background noise gathering beside the dish goes dowwn with a smaller radiation pattern?


    This is a wide spectrum without the lense.


    Here is the same spectrum using the rocket lense. The reduced background noise can be seen in the waterfall also.



    Looking to the Datasheet of the TFF1017 the question appeared, woud it be possible to modify the loop filter. The result could be improved phase noise of the LOs.

    Of cours it is a very theoretical question and the transponder noise can be seen clearly above the LNBs noise even with a "normal" dish and the lense. SMD components are fare away from easy changing and experiments. But, may be....

    73s
    Andreas

    Hallo,

    I don't see the need to feed LNBs with 12V when only one polarisation is used. It can be reduced until the drop voltage of the regulator is reached. This helps to avoid unnecessary dissipation.

    73s
    Andreas

    Hallo,

    buying one piece of a 2,4 GHz-circulator in Asia means approx. 70 $ shipping and 25 $ money transfer.
    It seems to be not in the amateurs budget. One possible way could be sharing this when ordering more pieces....?

    What a pity.
    73s
    Andreas

    Unfortunately at mouser not in stock. Until now there is no response from UIY listed at ALIBABA.
    Not sure if they will sell me some parts.

    Hallo Heiner,
    thanks a lot. Didn't find this although some internet search.
    Below one Euro, unbelievable.
    I will see what happens.

    Thanks again
    73s
    Andreas

    Hallo,

    I am looking for a suitable 2,4 GHz circulator. At the output of the amplifier board there is a whole but the Chinese guys didn't place it.



    The amplifier works well, I am going to play with more patches and helix antennas and different cables also. Feeling better with an independent load....

    Any hints are welcome.
    Thanks in advance.
    73s
    Andreas

    DL9SEC
    The output of the TCXO is connected to Pin 11 of the TFF1017. Is there any recommendation, 11 or 12? I didn't care, it works.

    Interesting, both TCXOs, I assembled in two LNBs give an endfrequency shift of around 3 KHz. Probably it is useful to put an adjusting voltage of 1,5 Volts to AFC-Pin 1 of the TCXO.
    My goal was to test the modification of the LNBs. At least, a modified LNB is ok to play around with, doing demonstrations using scanners, little dishes and so on...

    Because of the internal 5V, there is no need to operate the LNBs with 12V. If vertical polarisation is ok, reduce supply to avoid dissipation and drift.

    73s

    Andreas

    Hallo,

    I just modified two Rocket LNBs. Carefully cut the Silicon to remove the board. The only pin to resolder is the output on the right side. Because of leadfree soldering it is not easy. Don't worry losing the crystal pads. They are not needed furthermore...

    Remove the crystal on the backside and place the TCXO 25 MHz. The new Chip is upside down with double sided adhesive tape and connected twice to GND. The output is connectet to one former crystal-via. Remove the capacities from Pins 11 and 12 of the TFF1017 Mixer/PLL. Connect Vcc somewhere to the +5V Bus (Pin 16 of the Mixer). The +5V is generated by the detector chip ZXNB4202. Take care not to squeeze the +5V red wire when closing the case.

    Enjoy the better accuracy. Don't mix it with the drift. This is done with SDR Console.





    73s

    Andreas

    Hallo,

    to say it more clearly, don't care about the beacons and the user signals to design a receiving system.
    Take care about getting the transponder noise above the system noise of the LNB.
    This is the only criteria.

    By the way, it is important to have the right radiation pattern of the LNB corresponding to the
    f/D-ratio of the dish. Commercial LNBs and dishes should work. Adding a patch to a LNB the feed is no longer a horn but an open waveguide. With a rocket-lense to my open tube nothing changed.
    This confuses me a bit. Further research has to be done.

    73s
    Andreas