Posts by pe1hzg

    I apologise for what should be an ignorant question, but I have R'd the FM, S'd the FW and still have no answer:


    I am using SDR console to monitor the narrowband transponder of QO100, meeting the requirement of monitoring my own transmissions and the transponder in general.


    This works fine if I only start SDR console w/o starting a receiver - the resulting spectrum screen does what I need and more.


    However, once so often it is desirable to start a receiver on SDR console. However, if I do, the new receiver always starts on LSB and I need to switch it to USB.


    The only way to avoid this is to disable LSB mode completely. I don't want that; I want LSB mode to be available just not used when I start a "new receiver". Hence my question: how to I control the startup mode of a new SDR receiver?


    The only thing I did find was someone asking this in 2019, with Simon Brown answering "I am busy". That is 3 years ago, I hope a solution exists now.


    73, Geert Jan

    I mad some modification (bypass) at my PE1CMO Transverter in order to use my SDRPlay RSP2Pro SDR-Receiver at the LNB-Entry point to see the whole SAT scope on my PC with SDR Radio COnsole v3.0.9 and to avoid TX-interference while I'm sending in full SAT duplex mode with the ICOM IC-9700.


    Modification

    At the LNB-Entry point of the transverter use an 1nF capacitor and a 220 Ohm resistor in sequence and then connect the SDRPlay.


    Apologies for resurrecting an older thread, but I tried this SDR-tap on the CMO transverter and there is a problem.

    The default configuration of the CMO transverter kit is for a 70cm backend transceiver for TX and RX (I use SDR console as bandscope and to monitor my signal)
    Wolfgang's transverter has a special configuration (70cm up, 2m down) and the modification works there.


    The default CMO transverter configuration has a low-noise PLL generating 307.5 MHz that is used to mix 739 MHz from the LNB to 432 MHz for the transceiver. There is switching and attenuation but there is no absolute isolation between TX and RX path.


    The problem is that when the 70cm backend transceiver generates RF, the 432 MHz mixes with 307 MHz resulting in a strong signal on 739 MHz at the port connecting the LNB. That signal is very strong, it blocks the input of the SDR receiver.


    I have fixed this by, during transmit, switching off the DC power to the 307 MHz oscillator. By removing the 307 MHz LO, the strong 432 MHz signal doesn't mix to 739 MHz and SDR monitoring now works. Using a transistor to short C87 (with a series resistor, please!) and the oscillator stops.


    I still use a dualport-LNB but I no longer need the 2nd LNB port for monitoring


    73, Geert Jan PE1HZG

    what noise floor level are you getting with this down-converter ?

    This fully depends on the LNB, the cable length, etc, since the g0mrf PCB does not do any active amplification, only a mixer.

    Keep in mind that the noise figure if your receiver is defined by the first stage (hence, the LNB), not your receiver.


    If the noise increases when the mixer is connected, then the level is high enough. You may want to add an attenuator to the path to your receiver, especially since direct-sampling receivers like the 705 don't do so well with a very high background noise level.

    Hello everyone,


    In the weekend 15-16-17 october 2021 there will be the annual Jamboree On The Air.

    This is a global event where scouts will use amateur radio to talk to other scouts, but also to hamradio in general.


    For many it may be the first time children see and use amateur radio.


    Because of the quality of the radio connections, a number of JOTA stations will be using QO100.


    I hope we will some good QSO's that will leave good memories.


    I hope that stations from countries that we don't hear every day, will be available. Keep in mind that every QSO can be a "where-is-this-country" and similar considerations. We are building future hams here, in the group I assist several Scouts did manage to get their license.


    If there is a JOTA QSO, you may expect some questions people normally don't ask, like about living conditions in your part of the world. Some kids need to speak using a radio transmitter, or are asked to speak in English or German which they did learn at school but typically have not used much. You know how your own school language learning went.


    You may also find that perhaps operating practice is less, or a station makes a mistake. Please have patience and guide, considering you're teaching potential future hams. They will not operate without supervision but people are trying and, let's face it, how cool is it to run a big radio transmitter with lots of knobs, all by yourself?


    I know I've requested the same last year, and then "nothing happened". For the Dutch stations, the tuesday before the JOTA the Dutch government changed the Corona rules and any and all mitigations we had made, became null and void. This year we hope to get some activity, in narrow-band or perhaps even on the wideband transponder.


    For us the focus will be on the saturday including saturday evening.


    I hope we will have an enjoyable weekend on the bird and perhaps some fresh hams in future years. Thank you for your understanding!


    73,


    Geert Jan PE1HZG

    During JOTA: PA1PTP/J

    With a good soldering iron you can apply a big blob of solder on the surface of the crystal and continue heating it up until it comes off.

    And do so with the PCB out of the casing (mind the antenna pins - ESD sensitive!)

    If you try this with the PCB still in the case you will find that the casing cools enough that the solder won't melt.

    This PCB material is a pretty good heat conductor.


    And keep in mind that leaded solder has a lower melting point. So you can "wet" the pads with old solder to mix old with new to reduce the melting temperature.

    I found I was able to reproduce the "non lock" with an eval board, and I have a theory of what is happening


    Looking closer at the datasheet of the ADF4351, it seems that "programming the registers" does more than just load values it it, a number of circuit selections happen inside the chip while the programming process is happening. This is why the registers must be programmed in a certain sequence: R5, then R4, then R3, ... last R0.


    If there is no reference frequency during the process then it will fail.


    If you power-up the adf4351 with a reference, then remove it, then connect it again, the PLL will lock. The problem is if the PLL is that if the PLL is programmed when the reference frequency is missing, the programming doesn't seem to work.


    My suggestion would be to make sure that your programming includes correct programming of the Lock Detect output, then change the programming of the 12F675 so that after programming you wait a bit, wait for Lock Detect to go active, and if not, re-start the programming process. I have not tried it, but your "touch the MCLR" suggest this will work.

    I'm nervous about the "touch MCLR" comment. Does this pin have a pull-up resistor?

    Hi Roberto,
    If you do not connect the 10MHz, power on, see that the PLL doesn't lock, then pulse the MCLR on the 12F675, does the PLL lock then?


    I've made something similar, but with attiny13, it can be found elsewhere on this forum. I don't have the problem you have: PLL always locks when 10MHz is connected.

    The uplink uses circular polarisation so the line-up does not matter.


    That is not true for the receiver which is vertical for the NB transponder and horizontal for the WB transponder. For this reason, the angle of the LNB *does* matter. What makes things worse is that unless your azimuth is 180 degrees, your view to the sat will be squinted. For this reasons, for optimal performance, the LNB must be twisted a little bit. You can use sites like dishpointer.com to find the "LNB skew".
    Note: there is an easier way: it is easier to find the null of the signal and the max is 90 degrees away. So, turn the LNB to "null" the signal (for instance, beacon), then turn the LN exactly 90 degrees CW or CCW and you are set.


    The 3rd issue is the distance between the base of the POTY and the black plastic carrier of the dish. I think your POTY sticks out much too far: I think it should be flat (but someone please correct me!). You will run into two problems if you do things this way:

    1. the SMA connector is in the way. From the picture I think you have a TRIAX dish. Instead of the plastic bracket, metal brackets do exist and those just need a small bit filed away and then the SMA connector goes.
    2. The edge of the POTY base plate may interfere with the pipe that carries the LNB. LNB brackets assume a diameter of 40mm, and the POTY pipe is 22mm so you use a spacer. BAMATECH has spacers that are off-center which solves this problem

    Hope this helps!

    When I cannot depend on long-term stability of the setup, long enough stable to let a GPSDO do it's thing, I now use a OCXO like https://www.ebay.com/itm/283995359041


    It is a OCXO, the casing gets warm, but the thermal mass isn't big and the temperature / frequency stabilizes stabilizes in 90 seconds.


    I've done tests comparing with a GPSDO, doing lissajous tests at power up, but after 90 seconds this really is "plenty good enough" for SSB use (my whole station, not DXpatrol btw, is GPS-locked).


    I would recommend to put the PCB+module in an enclosure for additional thermal isolation in case of e.g. wind.


    Nevertheless, it was frightening to see how much work Leila had to do now that she is back in operation. Some stations seemed to ignore Leila completely, maybe because they can't do full duplex? Others even felt disturbed.

    This morning I had Leila trigger on signals that (confirmed on some WebSDR's) were clearly below beacon level.

    I made some signals myself to measure (signals that never triggered Leila before) but even signals 5dB lower would trigger it. So, Leila wasn't deaf, it was having morning temper issues.


    I should note that, at this time, the Goonhilly WebSDR cannot be used for beacon signal levels because the beacons are significantly below level (compared to the middle beacon at least). Right now, the middle beacon measures -72.4 dB. On the same Goonhilly, the lower beacon measures -80.1dB and the upper beacon -80.7 dB. So, the lower and higher beacon measure 8dB below the middle beacon.


    Looking at the IS0GRB WebSDR, the middle beacon is -70.2dB, the lower beacon -71.5 dB, and so is the upper beacon.

    This is how I remember the signals from a few months back .

    That (relatively) matches my own signal measurements, and that means the Goonhilly WebSDB cannot be used to qualify signal levels. This problem started after fix of the recent "GPS lock" issues; in any case, it makes the "signal measurement" thing a lot more complex.


    Another issue is that if one sends a carrier, Leila zero-beats on the carrier. If the carrier is made using a SSB radio, then Leila is outside the passband of the radio and I can't even hear it; it is 300 Hz below the low-end of the SSB passband.


    I would appreciate not having another "full duplex" discussion. There clearly are a number of other issues at play here too. It is volunteers who are keeping all this alive and Corona makes working on these things even more complex. Who is without sin throws the first stone!

    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.

    Let me re-visit this, because when I ask in a QSO, it turns out that people did monitor their signal levels when setting up, but generally no longer monitor afterwards:


    When working over QO100 NB transponder, one's signals are not supposed to be stronger than the lower CW beacon on 10489.500.

    And the AMSAT-DL website strongly pushes the Goonhilly WebSDR.


    Until recently, the CW beacons (10489.500 and 104900.000) had a signal strength of typically -70dB, and the middle PSK beacon was typically -73dB. Signals raising above that would be yelled at by Leila.

    The signal strengths have roughly the same levels on the Italy WebSDR, and my own equipment gives the same (relative) signal levels.


    However, recently, the strength of the CW beacons on the Goonhilly WebSDR have dropped significantly and are now -80dB. This only applies for the CW beacons, the PSK beacon as well as user signals have normal signal level.

    Signals have normal levels when measured over the Italy WebSDR, or on my own receiver.

    Only the CW signals are weaker, and only over the Goonhilly WebSDR!


    I have measured over days to make sure it's not a weather issue - it isn't. And to the best of my knowledge all three beacon signals are made from the same earth station. If weather would be obscuring, then I'd expect all signals to be weaker - they aren't, only the CW beacons! - and if the Bochum / Doha ground station would be covered by weather, then all three beacons would be weaker, on all receivers - they aren't, ONLY the CW beacons, and ONLY via the Goonhilly WebSDR.


    If people can confirm that would be grand. I've included screenshots of my measurements of 10489.500, 10490.000 and 10489.750; note that the signal history indicates that the signal strength is constant.


    Clue appreciated!


    I found your signal even more useful than expected, while testing link margin during a thunderstorm. I know I lost at least 15dB at its worst, and that happened while the streets were still dry. I could "see" the thunderclouds drifting towards the sat path. When the rain started, signals went up ;-)


    Using WebSDR, I saw that my own signals were not attended as much which is strange (2.4 is the max water absorption frequency ?!?)


    Having longer signals at a level would be useful. "zero" is short to measure.


    Is 0dB the beacon level? I don't think it is, but propagation is strange right now.


    I any case, this is useful, but perhaps t needs to be there structurally. Good stuff!

    Without wanting to play my own harp, see https://forum.amsat-dl.org/index.php?thread/2856-transverter-pe1cmo-and-kuhne-down-konverter/&postID=9489#post9489


    I don't know if Megasat has a good representation in the UK, the BRexit has caused a deep ditch to the mainland but let's keep the forum technical please!


    However, brand and type doesn't matter that much. Keep in mind that if you buy a certain type of LNB, and you order the same type 3 months later, you will likely find completely different electronics inside. In that regard, what does matter is to "buy a few at once". If you break one, you have learned the construction and the next one will be easier to modify\; you also have "one to look at" which I find, helps a lot.


    The key is to get a LNB with crystal reference. The good news is that these are cheaper than older models with DRO. My suggestion is you buy a few, open one, if it is a DRO-type, send the other ones back unopened. Personally I find it difficult to ind DRO LNB's these days; PLL is much more common

    Also, something that is not covered in that document, and I had problems with, is cutting the wiggly line going to the voltage regulators and adding an SMD inductor. That wiggle line is enough inductance to block the IF going into the regulators, but is not enough to block a 25M signal, and the decoupling caps at the input of the regulator were eating all of my 25M reference preventing the LNB from locking. Once I added an external inductor (820 nH IIRC) it locked just fine.

    The proper way, IMHO, is to make a parallel resonance circuit on 25 MHz. That will keep the reference where it is supposed to be.
    Personally I use 150nH and 270pF. Note that with SMD these can be "stacked" making it easier to find space for them.

    It is sunday afternoon and it shows, on the spectrum waterfall. Carriers come and go, drift all over the place, people calling "test... test".


    We've all seen it and we've all cursed it, but what is someone to do who just want to test his signals? Aren't callsigns not given not just out of disinterest, but also to avoid being called for QSO? If I want to test, where should I test?


    I wonder if it makes sense to set aside a small segment (20 kHz or so) just for testing. "if you must test, test in the test segment; no QSO in test segment",


    I guess most of us know that the most often used feature of a terrestial FM repeater is testing. "click-boing": doesmy radio still work? I think the same applies on our bird.


    I guess the good news is that the test signals most often happen during EU daytime. That means it's humans doing this, and perhaps these humans can be guided


    Just a thought,


    Geert Jan

    Actually, you can't use the TV splitter modelled because it does have filters in it (it has to, because otherwise LNB noise would interfere with TV signals).


    Strange as it may sound, the one you want is:

    This is "just a TV splitter" but if you open it, it actually has a transformer inside to do the impedance thing correctly. You will see that it passes DC on all three ports, so voltage supply for the LNB "just works". Disadvantage: this splitter uses Belling-Lee connectors, though adapters to F and BNC exist.


    Note that this splitter really is different from the typical "plastic" splitter which uses resistors. Check your ohm meter.


    I would like to stress that this works for the specific use case you have. NB and WB have different polarisations, so this trick can't be used to receive NB and WB on the same single LNB. For those cases, I recommend dual LNB's, I have good experiences with the Megasat Diavolo Twin LNB, giving me two independent ports can can do each polarisation as I want for the experiment du jour.


    Geert Jan

    While making adjustments to my station I must admit being guilty to triggering LEILA (I'm sorry, guys!).


    But, I found that I didn't hear LEILA, I only saw LEILA on monitoring. So I investigated closer.


    When sending a carrier, my radio sends a carrier on "carrier frequency" of the USB signal. Using USB means that the modulation will be above the carrier frequency.


    When LEILA triggered, I found it sends a carrier on the frequency it "discovered" and a lower frequency. That means the LEILA signal will be outside my filter, which explains why I didn't hear it.


    My question: why does LEILA use the "discover frequency" and a lower frequency for signalling instead of using a higher frequency so it would be in the passband of my receiver?