DX-Patrol "Groundstation" not Full-Duplex!

  • hello, I am a french hamradio, new on this forum

    is it possible to write in french ? or only in english ? I can use a translator...


    I own this DX-Patrol Ground station and I would like to share my experience with this converter

    In France, many hamradios use the F6BVA converter which is also half-duplex converter :

    https://f6bva.pagesperso-orang…V3%20QO100%20complete.pdf


    and aniway, if you are using an FT-817 or an IC-705, these transceivers are not duplex !


    73s from F1FCO, south of France

  • the new documentation (by ON4IQ) is online : https://www.dxpatrol.pt/files/QO-100GS_1.pdf

    with pictures and description of the PTT

    on the simplified diagram in page 4, you can see that only the synthesizer ADF4351 switch beetween RX and TX

    apparently no switching of RF 432 input / output between RX and TX

    median beacon of QO-100 is 10.489,750 MHz

    to receive it on 432,750 MHz, OL of LNB must be on 10.057 MHz

    10.057 / 390 (internal PLL of LNB) = 25,787 1795 MHz x 64 = 1650,379 487 (PLL of the Ground Station)

    in transmission, for the same frequency, tx must transmit on 2400,250 MHz

    for a radio (FT-817 or IC-705, or other...) on 432,750 MHz, OL must be on 1967,500 MHz


    in the Ground Station, internal PLL must switch beetween 1650,379 487 and 1967,500

    to be checked with a sniffer and a spectrum analyser with high precision ( external 10 MHz reference)


    I am going on vacation with my portable station but on my return I will take precise measurements


    about the supplied LNB , it is a "standard" LNB of DX-Patrol

    if you inject 25 MHz, output is on 739,750 MHz

    if you inject 25,787 1795, output is on 432,750 MHz


    it would be necessary to do "reverse engeenering" to modifiy frequencies (control with a PIC ?) and external connection for a RX on other band than TX (1289 / 432 by exemple)


    I have already changed the PICs 12F675 on DOWN Converter and UP Converte MK3 of my DX-Patrol to get frequencies that suited me on my IC-9700


    to be continued...

    F1FCO

  • It is a very basic diagram 😀, I voluntered to rewrite the manual, and in v1.2 you will find clear indication that it is simplex station , and as per amsat request the operator must be able to rx his own signal (websdr or seperate downconvertor).


    I am inprocess to make a modication available to add the extra RX on other band 28 144 or 1296. Just awaiting one more part to test run it, and see how easily it fits in the box..

  • I am kind of saddened by this discussion. It is easy to fault someone, but it will result in bands that are empty and perhaps that is not what we want.


    The duplex discussion has been done before on this forum.


    Personally, I don't think that "monitoring one's signals" must mean listening to one's own signal when transmitting.

    You can easily recognize the stations that listen-to because hearing your own voice with the sat delay makes you stutter:

    you cannot .... speak well .... while you .... are hearing .... your own .... voice.

    Many of these stations also respond 1 kHz off or more when they respond to a call.


    For me, monitoring means just that, monitoring. Seeing if someone tries to break into your QSO. Seeing if LEILA is asking attention. Monitoring the signal levels.

    And for that, watching one's signal via some SDR spectrum thing is fine.


    A simple approach I've used often is to have a laptop that shows the Greenhilly WebSDR page. With proper font size and a but of scrolling the page can be used as a transponder scope. And when enabling the signal strength plot (on "slow") you can really monitor your own signals. This isn't bad: broadcast stations use remote receivers to monitor their signals.


    When you cannot / do not want to use Greenhilly for monitoring, there are several approaches still. I have a Megasat Diavolo twin LNB and use one port to receive and the other just gets 12V and I use SDR console with a RTL-SDR dongle to monitor the signals.


    Another approach is to tap the receive port signal and feed it to the SDR dongle. Unfortunately, with the DXpatrol that results in a few issues: 1. on the DXpatrol unit, the clock on the LNB is switched off when the unit is transmitting so the LNB does not function during transmits; 2. one needs to look at the frequencies for conflicts.


    As to the latter problem: in my station (based on the praised PE1CMO kit) the LNB gives 739 MHz out and there is a separate PLL to convert 739 MHz to 432 MHz using a 307 MHz PLL. So it was easy to add a 739 MHz tap and that is what I have. However, in my case, the transmit signal (also on 432 MHz) was leaking on the receiver and was mixed with the same PLL signal to (also) result in 739 MHz. I spent weeks puzzling why I had this big signal on SDR console during transmit: was the 13cm overloading the SDR? In my case, the leakage of the 432 MHz transmit signal, over the TX/RX relay, over the mixer, gave a big signal on 739 MHz (credits to Rene CMO for the clue!).
    On my setup, I mitigated this by disabling the oscillator of the 307 MHz signal during transmit.


    Unfortunately, the DXpatrol unit has some challenges here. The LNB clock disappearing during transmit is not helping. The LNB outputting directly to 432 MHz is not helping either because it is very hard to keep this signal out of the receive chain. So, self-monitoring may be a challenge with this unit


    Should DXpatrol consider an upgraded design that does not have these issues (perhaps with a "739 MHz out" connector, which my PE1CMO unit has now) then the unit would be even more attractive. But the current unit can be made to work - just watch Goonhilly when you operate and you're done.

  • Actually the lnb still get its 12v in RX, but another LO In freq instead of the 25MHz goes above 30MHz (not at same level, bleed through the pin diode switching)

    I had a simple approach to the thing, add another source of LO to the LNB, which doesn't change on TX, so plain simple fixed one.

    (its just PIN diodes for rx tx switching, D4 going to C15 and IC1 divider and 25/30Mhz out to LNB LO input , the LNB LO input needs to be swapped to the other LO source.



    Only thing is that me using 432MHz also on 2nd receiver as IF (same rx freq as TX freq on transmiter) wasn't an brilliant idea...

    (but I do hear my voice :-o )


    But the next thing will be adding a dxpatrol downconverter PCB in the box, so that in RX i can use 1296/144/28 as IF.

    You could add a basic downconvertor with plain 25MHz source and get the 739MHz for your sdr rtl stick. Or find a small sdr radio with panoramic display (still looking for a decent one) e.g Malachite Malahit for one of the above mentioned IF freq's.


    The dx patrol PCB will nicely fit in, just need to drill the extra holes in the backpanel. And I can choose to run the RX on 28/144/1296 (duplex radio), or go simplex and use a websdr, by swapping the LO output to the LNB , or even add a relay with front panel switch for the LO.

  • Our colleagues, who are always welcome, shoot themselves in the foot if they disregard our rules (duplex operation). Why? Example: Today a station called me with a completely incomprehensible modulation. This is typical for simplex operation, because the OM did not hear back its modulation and a QSO was not possible. These are then the OM's who, completely frustrated, want to sell their QO-100 equipment again.

  • Calm down everybody...

    It doesn't matter which equipment you use to join the QOMs, try to make sure that your uplink signal is ok and if you are sure that you have a nice,clean and not to strong signal them it is (in my opinion) not nessecary to monitor your signal in realtime.

    BUT if other QOMs tell you that you signal is not ok then try to find the fault and fix it as fast as possible!

    It's just basic hamspirit 😀

    73s DB8TF

  • The reason many people don't work full duplex is because there is no radio that can work full duplex. For example: 9700 and so on... But WebSDR is a great tool to check your downlink. I always check my signal with WebSDR at the start of the first transmission.

  • You don't need a full duplex radio. I work with my old Kenwood TS-711 + 811 duo in full duplex. If you add a SDR dongle to your simplex radio you are also duplex. WebSDR is ok, if you have a fast VDSL line and router. I think the reason of not working full duplex is the echo. I work since more than 30 years with satellites now, for me is my echo normal "business".

  • ...."there is no radio that can work duplex"....

    Hey Guys, don't know if I should laugh or cry.
    Is it nessecary to talk about the Pluto again and again really? From my point of view full duplex means listening exact on the same frequency. One can see and hear stations transmitting very closed to or direct on used channels. Or finding their own transmit frequencies, scratching across the full transponder with full power. This is modern technique, horrible. I am sure, they have no spectrum displays and no duplex radios. I don't like to repeat all the other advantages of SDRs.
    But I like to repeat offering help and support if needed and or wanted. Radio Hams were always seen as open to future technologies. SDR is not future is present. I don't see any reason not to use it.

    Give you a kick and start....it is easy.

    73
    Andreas

  • Hi Andreas


    I used to use a Pluto. They’re very good, but I wanted to simplify my setup for portable use.


    My IC-705 has a spectrum display so I can see what’s happening on the band, and the GroundStation with OCXO and GPS Lock for both transverter and LNB, “should” make sure I’m RX and TX on exactly the same frequency.


    I’ll use WebSDR to make sure everything is golden, too.

  • Hallo Josh,

    ok, all is fine. And if you take care, the radio function ist satisfied.
    It is a pity that ICOM didn't go one step further to bring the 705 to duplex operation.
    A simple approach to a portable Radio is a Pluto followed by the AMSAT-6W-Amp.



    The rest is power supply and - if wanted - a GPS-RX. The rig is mounted with two clamps closed to the LNB holder.


    The only Connection is a Ethernet cable. And Power. 12V from a battery or from mains. With a short wiring to the Helix, 4 linear watts out of the amp are enough. As you see in the first picture with my dirty setup it can be done smaller still. A WEBSDR requires a PC. This is good to operate a Pluto too. In the field it is nessecary to have a sunshield. This is a disadvantage of modern displays not working in a bright environment.

    73
    Andreas

  • hello everyone,

    I have an IC-9700 that I use in my fixed station with a stabilized LNB (on 25 MHz), a DX-Patrol Down Converter and a DX-Patrol Up Converter. Both piloted by GPSDO.

    I modified the PICs 12F675 to receive on 1289.794 (by exemple...) and transmit simultaneously on 433.794

    There is no difference in frequency and full duplex is possible : I listen myself with about 250ms of delay (rise / fall time of radio waves)

    I will further improve my frequency accuracy by equipping my IC-9700 with the LeoBodnar kit.

  • Coming back to the DX-Patrol ground station that I use outdoors, there is a small offset of about 200Hz between transmit and receive.

    I think this is due to the fact that we cannot get EXACTLY the correct frequency when receiving with the ADF4351.

    The OL in emission is on 1967.500: no problem to obtain this frequency.

    OL in reception must be on 1650.379487: impossible to program exactly on an ADF4351

    a solution for this Ground Station would be to use a reception module like on the Down Converter: LNB with output on 739.xxx

    OL must be on 9750 MHz (25 MHz internally x by 390) and OL of the converter must be on 307 MHz for an output on 432.xxx or 557 MHz for an output on 1296.xxx

    a jumper to choose the frequency (if you have a simplex transceiver, like IC-705 or FT-817 or a duplex transceiver like IC-9700)


    maybe a 2.0 version of this ground station?

  • Hi all,


    I do not own nor intend to buy a DX-Patrol groundstation. This said, I would be disappointed seing an offset of 200Hz between RX and TX with a setup claiming to be GPS locked.


    In principle, the ADF4351 can be programmed to output the exact frequency for generating the LNB LO of 10057,0 MHz as required for an IF of 432,5 MHz. The trick is to calculate using fractions and not trying to solve the fraction.


    According to the datasheet, the output frequency of the ADF4351 calculates to RFOUT = fPFD × (INT + (FRAC/MOD))

    Assuming fPDF as 10Mhz, 1650.379487xxx MHz can be generated exactly (meaning exactly 64 * 10057/390) with e.g. INT=165, FRAC = 37 and MOD = 975.


    73 Jean DJ0VL

  • Don’t forget that there are three parameters affecting frequency that are outside your control.

    The accuracy of the satellites Local oscillator, and the Doppler shift on the uplink and downlink (which will be different and variable)

    You will always need to apply some RIT to achieve perfect netting.