Posts by pe1hzg

    my TX frequency drifts several hundred Hz over the course of a QSO. Nothing serious for CW/SSB operation, just a bit annoying, but not the best for digimodes. The culprit seems to be the 432/28 transverter from transverters-store.com .

    People who recently made QSO with me (Hi Remco!) have probably noticed the same behavior - there are some very polite people on QO100 who did not comment to me when they needed to adjust the RIT more than 500Hz over one QSO.


    I very much would like to use 10m in my setup because I need some really really long cables (to avoid trees) and 70cm doesn't work very well over more than 50m coax (unless the coax is expensive, and even then; I want to use RG58 for this).


    I've ordered some ADF4351 boards and I'm planning to replace the LO chip with a GPS-locked 404 MHz signal, so everything is GPS-locked.

    I'm now waiting for the boards to arrive from the East and will report if I get them to work (PLL should be clean because reference is divided by 5 and VCO would be divided by 202; so the PLL noise should be good, hopefully)


    The Ukrainian transverters aren't bad for the money, especially the ones for 6m and 4m, but you putting a 70cm antenna on one is probably not a good idea. As step-up for 13cm QO100 it doesn't matter much (For sat work, Dr Karl explained to me, many years back, that these signals "es versendet sich". which wonderful German I leave untranslated).
    But using it by itself on a 70cm antenna would put it next to Baofengs and similar kit you probably should not measure at.


    And unfortunately, Elecraft's 70cm transverter has issues too, you may want to read NT4RT's story at https://www.evernote.com/shard…r%2BUpgrades%2Bby%2BNT4RT


    GJ

    Folks,


    Apologies for this message, I will probably repeat some of it as the event gets closer....


    The 3rd full weekend in October, 18-19-20 october 2019, Scouts all over the world will use hamradio to meet other scouts in an annual event called JOTA (Jamboree On The Air).


    Now that QO100 is functional and easy to use, a number of JOTA stations are planning to be QRV on the bird that weekend.

    In my area, JOTA is a big thing (with almost 15 JOTA stations in our city alone!) and I know that several of them are working on getting gear ready for QO100 for that weekend.


    QO100 has a lot of advantages for us. We don't depend on solar activity for propagation on the bird (condx are normally poor in October, no solar activty means that even 20m is a challenge), QO100 has an impressive range and "talking radio over satellite is cool".

    With a dynamic range of 20dB and signals roughly the same strength we might be able to do QSO's that non-experienced ears may be able to listen into and enjoy.


    One of the objectives, apart from connecting scouts world-wide, is to interest young people in technology. We normally have several stations to make contacts (which is always under control of a licensee), but we also do games with radio, children solder an electronic kit, it is lots of fun. Stirring interest works, in our group alone we have a few licensees, people who got inspired to get their license as a result of JOTA.


    For the regular users of the bird, you may find that things are a bit more busy that weekend. I hope we can all co-exist in harmony, QO100 has plenty of bandwith. We will use temporary stations, so perhaps something might not be quite right; if our signals are have issues, please point it out and be patient, these weekends are quite chaotic.

    You may find an operator who does not have as much experience as a regular user, please have some patience and consider that it is likely that some future licensee is listening in on the QSO.


    We also want to make contacts with many and far locations so we can show what fun hamradio is. If you hear us call CQ, please do answer, and perhaps have a few questions for the scouts ready.


    This is also a great opportunity to make children aware of what satellites are. I hope the artwork people of AMSAT-DL will be able to provide high-resolution images of some of the cool pictures on the website so we can use them for posters and show-and-tell.


    I look forward to meet you all that weekend and hope it will be fun and inspirational to all.


    73, Geert Jan PE1HZG

    Perhaps I should write down my recent experiences modify-ing SR-3602mini LNB's.


    The SR3602 comes in various versions; my earlier description was using the "SR3602 ACE" version, where modification was relatively easy because only a top lid had to be removed and the PCB (including the ESD-sensitive input ports) remained protected during the upgrade.

    These SR3602-ACE are very sensitive, have a lot, a lot of conversion gain and if I can find some more, I would buy them; I gave away my spares to allow someone else to get on the bird.


    What aliexpress now seems to offer is the "SR3602-mini" which is a different beast. You have to watch closely to see the difference; typically the different type is on the box in the picture.


    Mechanically the mini is very different. Hans PE1CKK has described how to modify them: http://www.hybridpretender.nl/25MHz%20reference.pdf. Please check the pictures there.


    The mini gives a few new challenges.

    Electrically it is similar to the other SR3602; 3567-chip, 25 MHz xtal (not value-stamped on my units), and the usual trick with the 6V stabilizers, the combination diode and the voltage divider to divide H-pol, V-pol, or port-off.

    Mechanically the unit is very different however.

    First, the F-connectors are attached to the lid but soldered to the PCB. You must remove the plastic putty and then un-solder the F-connectors to remove the lid, which is awkward.

    Second, the components are on the "bottom side" of the PCB, accessing that makes the vulnerable RF input probes accessible because if you left the PCB to access the components, you lift the probes which are now ESD-unprotected. The LNB I modified is now a lot less sensitive and I think I ESD-damaged it during my experiments. I don't know if my modification causes the impact or me causing ESD damage but it is something to note.


    Modification is very similar to earlier PE1CMO-recipes: replace stabilizer with parallel resonator (150nH, 270pF), remove xtal, remove capacitor xtal to gnd, add series resonator (another 150nH, 270pF, now in series) between F-connector and xtal input (see PE1CKK for port to use), and adjust voltage divider to make polarisation work again as described earlier. Also, remove capacitor at input of stabilizer or you will short the 25MHz reference carrier.


    I do find the mini less sensitive than the ACE version (tried a new one, for which I had not voided the warranty yet) but I don't know if that applies to all 3602-mini LNB's. Experiences?


    I also note that many aliexpress sellers now push the SR220 instead of the 3602 but few pictures of the innards exist. Has anybody tried those?


    I might try some more, once the shack temperatures has fallen a bit so that my solder doesn't spontaniously melt,


    Geert Jan

    The reason the dummy-load is spec'd up to 500 MHz is that the construction adds capacitance and inductance whose influence gets bigger with higher frequency.

    Without measurements it is hard to define what the actual deviation of the dummy-load is.


    But, you can also use the high frequency to your advantage. Some types of coax cable (think RG58) have a "high loss" on high frequencies. By connecting the dummyload via a long length of RG58, part of the power is dissipated (lost) in the coax and if you use the 500 Mhz dummy-load to terminate the cable then reflections from the dummy-load are also attenuated by the same lossy cable.


    Kusch doesn't specify RG58 on 13cm but on 23cm they list 64 dB per 100m. Extrapolating 23->13cm should be another 15 dB. Practially, 10m cable would yield roughly 8dB.


    In short, if you use a long run of crappy coax (the crappier the better!) to connect your dummy you will probably be fine. Note that cable loss is dissipated, so don't wind the cable, run it loose over the floor.

    It doesn't, if you do it right, that is, the circuit you're using to filter out the 25 MHz reference doesn't put a load on the 739 Mhz signal. Keep in mind that the coupling happens using a series resonant circuit that gives a high impendance except at the resonance frequency 25 MHz.


    But, even a little attenuation does not hurt. Keep in mind that the input of the LNB defines the noise figure (and you're not touching that) and these things have a lot of gain (30-50 dB I read somewhere, not sure if this is right).


    In any case, even if you'd load the 739 MHz a bit, there is plenty of signal and you probably won't notice.


    At the same time, the original reference crystal oscillator smears signals a bit, but using the reference signals are sharp. Expect clarity of the signals to go up, depending on the stability of the xtal oscillator this can be quite a bit.

    Converters for QO100 are a bit difficult. The AMSAT-DL converter is sold out right now, I think we have seen the discussion on the forum.


    A while back, Dave G0MRF published a converter circuit in Oscar news. That design has been picked up and is now available: http://transverters-store.com/qo100_converter.htm


    I don't have a relation with the seller but thought I should point out other possibilities I discovered.


    Also, I wonder if the same converter can be used for the WB converter (10491 - 9750 + 595 = 1336 MHz)?


    73, Geert Jan

    Quote

    Thanks for that nice antenne - next challenge to make it water and winter restistance.

    What I currently have is a RND 455-00198 (available at Reichelt in Germany). I am unable to measure to the last dB (can someone please do these measurements?), but empirical shows no loss and it doesn't heat in the microwave.


    To install the POTY, you need a 22mm hole (10 GHz pipe), a hole for the SMA for 2.4GHz, I have not weathered those yet, but the box itself is IP65.

    And, to attach the POTY, 4 M3-screws and rings is sufficient.


    Attaching pictures for inspiration





    Talking about Microphones, how about Headphones with 6.3mm jack plug?

    We will have our QO-100 station with DL50AMSAT running at the AMSAT-DL booth at the HamRadio2019 in Friedrichshafen. The noise in the hall will be very high... any recommendation?

    I think it will be very noisy two ways: you audio transmitting, and but also the sat signal will not be understood well with much background. One of the cool things with QO100 is that almost all signals have 15-20dB s/n and about the same signal strength, making them very easy to understand. But the ham-made QRM in the messe will kill that.


    I wonder if there are people with an airplane license on this form who can make a recommendation or two..

    does anybody know where at the receiving chain (before the receiving mixer) a sdr rx can be connected in parallel to the transverter solution from Rene?

    The schematic shows ("EVT 739 TP") but at least the unit I have doesn't have that point provided at the exterior box.


    But, not to worry: if you insert a 3dB-splitter between the LNB and the LNB input of the CMO-box, you can make your own SDR output. The LNB has plenty of gain and unless you use a very loooooong cable, it is OK to steal 3dB antenna signal.


    Two things to consider. Several things are called "splitter", I have good results with something like this, available from the typical hardware shop:

    Keep in mind that, to have these work for "us", they must pass DC, 25/27 Mhz, and the 739 MHz signal. If you use a multimeter to measure between ports, you will see that all three ports are DC-connected and have a low resistance between them.

    If your unit has 75 or 150 ohms DC resistance between the ports, then it uses resistors instead of a transformer -> in the bin

    And the much nicer ones with F-connectors don't pass DC either so -> in the bin.

    You can get adapters between F and belling-lee, which is what this splitter uses.


    If you open one of these you will see that you can also make one of these yourself using a ferrite bead and some windings. But, as cheap as these are you can't go wrong.

    Make sure the IN port goes to the LNB, the OUT ports go to CMO-box and the SDR. Isolation between OUT ports is 30dB!


    And please make sure you put a DC-blocker (capacitor, 100p-1n) on the port going to the SDR so that the 5V DC doesn't get shorted out in the SDR receiver.


    Tip: the NB-transponder uses vertical polarisation. According to lyngsat.com, the 10818 transponder (22000-5/6) carrying BBC news also has vertical polarisation. Before I modified my SR3602 duo LNB (see elsewhere on this forum) so I could use the 2nd port for a sat receiver, I used a sat TV receiver tuned to BBC news on this transponder to adjust the dish - QO100 is just a little more south.

    If you do this, it is VITAL to use a DC blocker because the LNB from Rene has been modified for 5Vdc and the typical sat receiver supplies 13-18V on the LNB port.


    EDIT: After posting this, I realised that you are in Germany and the British 28.2 sat position may not work for you depending where you are. The splitter still works, whether you can receive 28.2 depends on how far west you are.

    Let me add my experiences modifying a Starcom SR-3602.


    I'm a satisfied user of the PE1CMO transverterkit, which comes with a SR-320 that has been modified. Modifications include changing the powersupply from the onboard stabilizer to the low-noise power supply of the CMO kit, and to use the 25MHz reference from the same CMO kit instead of the internal crystal.


    But, the SR-3602 is a twin LNB, and I could use the other LNB port for the WB transponder, or as an aide to point the dish (over here, the British 28.2 position is usable and close).

    I didn't want to adapt the supplied SR-320, prefer to keep it as received from Rene (so I have a "good" reference), also I wanted to get some experience making these modifications.


    Via aliexpress I bought 4 SR-3602's cheaply, if we were to ruin one during my experiment it would be no big loss. At time of writing, I indeed succeeded in ruining one in the process.




    To begin, the electronics is very different from the SR-3602 Remco PA3FYM described earlier. Note that the PCB is only half-size of the diecast box and the very RF-way to bridge the space between the edge of the PCB and the F-connectors (several cm!).


    Incidentally, the plastic enclosure of the LNB has a sticker with type and serial number. On my LNB's, all four have the same serial number.


    In contrast to other reports, the lid is not screwed-on but held with glue. Cut through the glue, use the tip of the knife to lift the bottom left corner and you can lift the lid.


    On the PCB there is a 25 MHz xtal (thankfully the same frequency as the shippedSR320), and one receiver chip (RDS 3567E) that feeds both IF ports. PE1CMO described the circuit earlier and it is the same here: on-PCB choke to isolate the IF signal, 78L06 stabilizer and various capacitors. The output of both 78L06's are combined with diodes to supply the receiver chip.


    During tests with the LNB un-modified I had found that the right IF port (near the horn) already gives a good signal, but the left port (away from the horn) has some aurora-like instability, unimportant for television but it may affect our SSB signals. So, I will modify the right port for the NB transponder.


    To modify the power supply, remove the 78L06 (not easy if you don't want to damage the PCB) and replace this with a parallel resonant circuit of 150nH and 270pF with coil stacked on capacitor, using the pads of the 78L06. I had 0805 SMD's; if I would do this again I would use 1206 SMD's for this.

    The input of the 78L06 (on picture, mid and top connection of the right stabilizer) has a capacitor of 200nF or so, which I removed as not to attenuate the 25MHz reference signal.

    To the right of the stabilizer there is another capacitor, which I removed as well.


    The best way to do this is to do one modification at a time, then test if the LNB still works. More on that below.


    Second modification step is to replace the 25 MHz xtal with the reference carrier from the IF port (supplied by the CMO xverter). The picture shows the two crystal connections, the LEFT one is the input. In the top left of the PCB there is a trace that goes to the RIGHT pad of the crystal (formerly, output). I cut that trace, this is easier than trying to lift the crystal (it is hard to get enough heat on the xtal to avoid lifting solderpads). Moreover, as suggested by PA3FYM I wanted to use the crystal as filter towards the IF port. Unfortunately, I could not get this to work, but a series resonant circuit (again, 150nH and 270pF) between IF port and left xtal pad, made things work.


    So far so good, but in my case something unexpected happened. After modifying the power supply, the receiver chip would not work. Normally, connecting the LNB results in a significant noise increase, but no more after I had mod-ed the power supply circuit. It took me a while to figure this out.


    The IF-port circuit has multiple, different functions: power supply (which I had modified), IF output (not touching that), but in addition there is circuitry that makes the LNB switch H/V polarisation on 13V vs 18V, and change LO frequency if a pilot tone (22 kHz) is sensed.

    On the photo, right-below next to the receiver chip there are 3 resistors and a capacitor. That is the switching mechanism: 560k to input voltage, 63k to ground, and a series resistor of 1K towards the input of the IC.

    This circuit is a 1:10 attenuator: 13V input gives 1.3V on the receiver chip, 18V gives 1.8V. The 560k resistor is bypassed with a capacitor, probably to avoid attenuating the 22kHz pilot tone.

    When the power supply is changed to 5V, the circuit only gives 0.5V and it seems this causes the RDA 3567E to switch off. Fix is simple: replace the 560k resistor with an 180k resistor. I removed the capacitor at the same time, didn't want the 25MHz reference signal to confuse the receiver chip and everything started working again.

    I suspect this logic was added so that if an IF port is unpowered, no IF output should be on that port. Keep in mind that if one of the IF ports receives power, the receiver chip is powered because of the diodes after the 78L06.

    I didn't read anywhere about this arrangement on a forum so I hope this report helps.



    Other thing: I was worried that the lens of my POTY antenna would be damaged if the antenna would be dropped. I have now put the POTY in an enclosure RND 455-00198 (available at Reichelt in Germany), where I also ordered the SMD's. The enclosure doesn't seem to attenuate the signal and doesn't heat up in the microwave oven.


    Hope this helps,


    Geert Jan

    Hi,


    A couple of notes on my experiments resulting in my first QO100 QSO tonight. Not spectacular, but perhaps this story has one or two points that may help others getting their kit ready.


    I've started with the PE1CMO kit, which has been reported by others already to work very well, but I'll need to make the setup a little different since I plan to use this for Jamboree-On-The-AIR (JOTA) and the scouting hut is surrounded by trees blocking south, so the dish and transverter need to be at at distance - a distance big enough that a run of coax on 70cm is an issue. I also made a remote control box so I can see status from the scouting shack.


    Unfortunately, the dish I planned to use for initial tests could not be used since the disk mounting hardware was supplied incomplete by the sat shop - the shop will fix but not tonight. So, instead, I tried a 40cm "camping dish", that was sold by LIDL a few years back.


    Aiming the dish, small as it is, is an issue (it can't be pointed that accurately).

    To get a ballmark aim I connected a sat receiver, adjusted to BBC news (28.2 degrees, 10818, Vertical), so it uses the same LO and polarisation as needed for the NB transponder. Since the LNB supplied with the CMO kit is modified (5 volts instead of the usual 13/18 volts), I used a RF splitter and a DC blocker to the sat receiver so the sat receiver would not damage the 5V LNB. Given the wide angle of the small dish, when pointed to 28.2, pointing to 25.9 is not hard.


    The splitter had a surprise. I had bought a splitter with F connectors at a hardware shop, assuming it had the same arrangement as similar radio/TV splitters with belling-lee connectors, with a small transformer inside, but to my dismay the F-connector one has decoupling capacitors in the circuit so I cannot use it if I want to feed the LNB. The older belling-lee version was just a transformer though, so with some belling-lee->F adapters and the DC blocker in the path to the sat receiver, and the other port of the splitter to the CMO kit I could safely connect the 5volts-LNB Rene had supplied.

    (note that really cheap splitters actually are not splitters at all, they just have 75E resistors in there, but the metal belling-lee ones are actually pretty good certainly considering price. Use an ohm meter to verify!)


    Once I had TV signal, tuning to the beacons was relatively easy (note that the CMO kit uses GPS reference throughout, so there is little frequency uncertainty). Question: Would AMSAT-DL consider changing the lower beacon from SW to FSK? That would make aiming a lot easier still.


    I didn't want to modify the LNB that came with the CMO kit (it is a nice reference), and had ordered a few SR3602's before (very cheap at aliexpress). I had assembled a POTY antenna earlier, and had sawn-off and made-fit a SR3602 LNB for the POTY before, but wasn't sure the POTY antenna would work. So I connected another SR3602, unmodified, to try to see what it would do to my signals.

    There was a second surprise here: the SR3602 has two ports. The port in the back would make the SR3602 unstable (signals sounded like aurora), while the port in front was a lot more stable - it still drifted of course but at least the tone was constant. I tried this on two SR3602's and both had the same behavior, so be aware. (the "front connector" is closest to the horn, or where the horn was before it was sawn off).


    With the POTY antenna on the dish, I was able to receive on an unmodified SR3602 (albeit with drift and offset of course) so the POTY antenna did work as well. What was left was to connect the 2400MHz output of the CMO kit to the POTY, and then, even with just a 40cm dish, I could make carrier on the NB transponder.


    Once that worked I found an old friend on the band (hi Hendrik Jan!) called him, and the rest is history. I didn't even need to drive to full power and didn't need the 20W that the CMO kit can make was really too much even with the too-small antenna.


    I hope some of these comments are useful for others making their way to the band.


    73, Geert Jan