Posts by 2E0ILY

    I am new to DATV and having only just, in the last few days, got a test card on the es hail satellite, and then a caption less video, I need to find a way to add stationary or scrolling text of at least my call sign and locator to existing videos I have on my PC. Most are in .mp4 or can be converted to .mp4 format.


    I am currently using a BATC Portsdown and the script for OBS from F1EJP to stream a video on my PC to the Raspberry Pi and then the networked Pluto SDR.


    My OS is Windows 7.


    Thanks for any info. Chris 2E0ILY

    For some reason my MiniTioune fed from a Megasat Diavolo LNB on a 1.8 meter PF dish has started to show the unhappy face and an average of 2.9dB LNA gain. The Diavolo is home modded to take a 25Mhz LO from a Leo Bodnar GPSDO. I tried putting the original Bullseye LNB back and get the same results. I realise I need to look at attenuating the LNB level, but meanwhile can anyone tell me if such a signal level can also cause a sudden rash of noise on the MiniTioune noise graph and a de-sensitising on low level signals?


    The thing I find odd is this level of LNA gain has seemingly only started recently. Maybe it's just atmospheric conditions, the impact of which on 10GHz is a bit of a mystery to me I'm afraid..


    Thanks.

    Thanks SWL-jsilva, appreciated.


    I have managed to find an Octagon quad outlet LNB that appears, as far as I can tell, to be the same as the one on a clear internet site. It shows how to modify it with photos. It's in Greece though and shipping is more than the cost of the LNB itself, but hey, you can't take it with you I guess [Blocked Image: https://forum.batc.org.uk/images/smilies/icon_e_smile.gif] I will open it with some trepidation when it eventually arrives, hoping in reality it IS the same. This is all probably easy to the more experienced here, but the first time is always the most worrisome :)


    Regards, Chris 2E0ILY

    I am wondering if you know where I can get, a dual output LNB ready to be locked to 25MHz up the coax? I have a single output LNB from QRO.CZ that works very well with their special Bias-T box and a 10MHz reference that I already have, down the coax? I want to be able to receive horizontal and vertical signals (SSB and DATV QO-100) at the same time, on the one PF 1.8 metre dish.


    If nothing is commercially available, what is currently available that might be modified to enable this please, with some published, clear instructions?


    Thanks and all the best from England. Chris, 2E0ILY

    I THINK I have fixed it. A very odd problem. I tried swapping the ethernet cable to a second port on the main satellite PC and suddenly I could transmit again. Why I have no idea. Why it has two ethernet ports I do not know, either, one is just marked Ethernet, the other IBM Ethernet.


    The Pluto, pre amp and PA are back outside in a box under the dish, so I can't say if basic USB connection for TX is also working again. I don't want to mess with it :) I then swapped the ethernet cable back to the original port on the main PC, and it is also working again there. Maybe the connector plug contacts were tarnished, who knows?


    I would like to know what was going on, as I am concerned it will occur again, but for now all seems OK and I have had two nice contacts just now.


    Sorry for the wasted bandwidth, I have wrestled with this for most of the day! :)

    Running SDR Console on two Win 7 64 bit PC's one a laptop, the other a desktop. Both RX'd and TX'd fine to QO-100 using both USB and ethernet connections to a Pluto SDR, locally and remotely. Suddenly no TX at all from the desktop, but RX is fine.


    A seemingly identically set up of SDR Console on the laptop triggers the Pluto to TX fine, via USB or remotely at the dish via ethernet and a USB to ethernet adaptor. The satellite hears the signal fine. I am testing the Pluto with a power meter on the output when checking the none working PC, it gives zero out. Laptop gives expected power. Same cabling used in both tests.


    I have spent hours on this, reloaded SDR Console, deleted and recreated definitions, everything I can think of. The laptop is old, slow and struggling, but it does at least work. The main PC has been fine for RX and TX for weeks, I am not aware of changing anything. Any words of wisdom as to what else to try please? Thanks!

    Hi,

    My proposal is to use the hardware solution (GPSDO) instead of software one as you have it.

    OK, thanks George. Now please DO NOT take this as me arguing or disagreeing with you, but that poses a question as to how these options might have people operating on two different frequencies from what they think. Those locked to a GPSDO for RX and TX and those locked to GPSDO for TX and the beacon, via the SDR Console for RX.


    Is this a genuine concern, or am I being unduly concerned? I assume most people consider to TX on a basic frequency, not something random, and as such if you assume they are on a "basic frequency" it's easier to tune them in with say 50kHz steps. But if they are not actually on say a 50kHz step, you then have to fiddle about, bringing properly into tune.


    We have an expression in English, "being anal", meaning worrying about trivial matters and making too much of them. Am I being anal? :) Tell me straight George ;)

    Hi,

    My previous post regarding Doppler measurements... Link

    Thanks for the link, if I am honest some of that was a bit too complicated for me, but I get the idea 😀


    Would you advise I use the SDR Console lock to the middle beacon, or ignore using that and rely just on the LNB being GPSDO locked, as well as the Pluto for Rx? Thanks again everyone.


    Every day's a school day!

    If I tune to 10.489749895 I am dead on the middle beacon. So what's that 105 Hz off? All told, is that considered OK for a GPS locked LNB and Pluto? I really don't know what to expect if I am honest....

    Thanks for that, very neat! I have added an external reference lead to my Pluto c and connected my new Leo Bodnar. Worked flawlessly and very stable. So now ready for first QSO!

    How’s your rig going? Had any QSO’s?

    It seems to be working well, my main query is why, with the qro.cz sourced LNB, locked to the Leo Bodnar GPSDO, shows a frequency offset. For example, I tune to 10.489750 CW and the tune does not centre the beacon, it's pretty close, but certainly not spot on. I use the SDR Console software gizmo / trick to lock it to the beacon in the software. But with the GPSDO locking I wasn't expecting to have to do that, to be honest,


    I have had quite a few good QSO's and seem to get pretty good reports. If you fancy a schedule my email address is good on qrz if you no longer have it Phil :)


    Attached is how close the frequency is WITHOUT using the SDR Console software fix, but WITH the LNB LO GPSDO locked

    Hi I used a nano vna v2 and nano PC program.

    OK thanks for that Phil. I believe you asked a while ago if I had any photos of my modification removing the xtal oscillator and adding a feed for an external GPSDO reference? I had loaned my camera to someone but have it back now, so attached should be a couple of photos of the mod.

    I am glad you are confident it's fixed now, well done. I did wonder about rain drops de-tuning a POTY. They say the 3mm spacing between the plates is critical, so I can only imagine 10 or more raindrops between the plates must alter its resonant frequency and change the SWR. I wonder if a helix TX antenna suffers with raindrop de-tuning to the same extent, if indeed the POTY is significantly affected in this way?


    What are you using to measure the SWR of the TX antenna? I have no obvious means of doing this at all with the equipment to hand...

    I am experimenting with a ready modded LNB from qro.cz that can be locked to a 25MHz reference up the one RX coax to the LNB. It seems to work well, but there seems to be a frequency offset. I have, in the below the dish cabinet, a Leo Bodnar GPSDO with 2 outputs. One at 40MHz is an external reference to my PlutoSDR, and one at 10MHz that goes to the qro.cz combined injection box and BiasT. Inside this box from qro.cz I assume there's some form of multiplication up to 25 MHz. There's certainly a chip in there.



    However, in use, whilst TX frequency is perfect, (measured with a GPS locked, and in calibration frequency meter), the RX is off a tad, compared to the QO-100 beacons. I am not sure why and am currently using SDR Console's Geostationary Beacon locking ability to correct this. I had expected locking the LNB LO to a GPSDO would not require this, am I missing something here please?



    Thanks.

    The photo is not of my feed, but one I saw on QRZ and envied the engineering in it.


    2E0ILY your feed is not a standard POTY but one with a horn on the 10 GHz part, so get rid of all lenses. The horn is taking care of the illumination angle.


    G8PJH VSWR of 2.7 to 1 is really bad (return loss of around 7dB). While would result in 80% of the power radiated, it is very well possible that with such a mismatch, the output stage of the PA does not deliver its rated power (power gain is depending on proper matching). Typical return losses for POTY feeds are 17dB (VSWR 1.3). I assume you measure the output power with a attenuator and power meter so this will be close to perfect 50 Ohms but for some reason the POTY currently isn't.

    Hi Chris, You seem to be making more progress than me! How did the Pluto software external standard command go?

    I seem to be having problems with my POTY, vswr of 2.7 to 1.

    Did you buy your POTY fully assembled and tested?

    I did not need any command, I just made sure the firmware did not contain an offset from 40MHz. I did find a very comprehensive web page showing nearly all the commands, I think I bookmarked it, if I did I'll e-mail it to you.


    My POTY (I keep referring to them as a POTI for some reason...) came as a kit, I just checked dimensions and soldered it together.


    I did see the feed in the below photo on the QRZ page of DJ8EI, which to me as an engineer was like looking at some page 3 bird to others ;) I an=m curious as to whether it uses an LNB a all? It sure looks a nice bit of kit,


    I have no obvious means of measuring SWR unless I fit the SG Labs amp and measure on the voltage output connections for forward and reflected power.


    Now, what has confused me, and God knows, it's not hard to do that, is the diagram showing the feed point distance for the POTY, and how that might change with no lens. The second drawing, described as "phase Centre". Having a prime focus dish several people told me to not use a lens. Indeed, adding one dropped the RX signal substantially. I intend experimenting with moving the POTY entrance hole nearer and further away from the dish.

    I am now able to have QSO's via the satellite, but I am only using Pluto to Analog Devices CN-0417 preamp to POTI, so very low power. I get reports varying from S2 to S7, but this is using a 1.8 metre prime focus dish. I was amazed to be heard at all via SSB. Initially I tried an AM carrier and looked for it on the Goonhilly web SDR. I was surprised to see it, and reasonably strongly, too.


    But I have since been told that I should be much stronger, I don't see how though, I took painstaking trouble setting up the dish, my only doubt is I set the POTI aperture exactly the same distance from the centre of the dish as it was on the original manufacturers set up. So it's the same dish to aperture of the feedhorn as the original LNB was. I am having to presume that is still correct...?


    I was also told a dish of this size should show a reception of the middle beacon much stronger than I see here, too. I am sure they said -30 to -25 dBm, which sounds very high. I am seeing about --50 dBm at best, but I have no idea if the SDR Console "meter" needs calibrating, or even if it can be. The one in HDSDR I use for HF is calibrated against an in calibration signal generator, so I know that's pretty accurate for HF.


    I have spoken to a few saying they are running 200mW and I hear them +20, but when I look at their set ups on QRZ they have a 20 Watt PA in the chain ;) If 200 mW is giving a 59+20 they might as well sell the PA :)


    I managed to temporarily knacker the Pluto somehow, but to my amazement brought it back to life with the recovery tools. It was whilst I was installing v0.33 firmware, not sure what occurred, but it lives to fight again!


    I have now locked the Pluto to a 40MHz output from a Leo Bodnar GPSDO, and the Bodnar's other output channel locks the LNB to 25MHz, that all went well EXCEPT when I first removed the xtal oscillator form the Pluto's PCB and soldered a coax and SMA bulkhead connector, the Pluto stopped working. I thought I'd killed it somehow, but I had been very careful. Eventually I probed the incoming reference signal pad with my `scope and there was nothing there at all. Turned out my Chinese cable with pre attached SMA, sold as Teflon, was NOT Teflon at all, and had melted internally when I soldered it, shorting inner to braid. I threw it away and up made up my own assembly, with good Teflon coax and a branded SMA, and all was well.


    All good fun...



    I'd be curious as to what strength people hear the middle beacon on various sized dishes.


    Good luck Phil!

    Hi Chris,

    thanks for introduction.

    If you decide to change the oscillator, don't put it back to the original pads. It is much better to have a thermal isolation. I used a very small board just to solder four wires to the original place. There is a whole, closed to the solder pads. Stick the wires though to have the oscillator free hanging below the main print. Temperature influence of the main board is reduced. A little fan above the heat sources can be helpful too. Otherwise a "Leo" is much better of course.

    For removing the original oscillator use two irons and some more tin around the chip. The lead free tin is horrible. Turn the irons to more heat and you will remove the Chip within seconds.

    73
    Andreas

    I will be using a Leo Bodnar GPSDO as the reference once I remove the xtal oscillator, so that should not be affected by temp changes in the box? Thanks Andreas. Chris, 2E0ILY.

    Thank you Andreas and Detlev for your replies, much appreciated. Andreas, I edited my post, my name is Chris, sorry! I should add a sig I think!


    Unfortunately Mouser sent me an earlier Rev. B so I will have to do surgery on the PCB. If I get the oscillator off OK I may attempt to solder a u.FL connector pad to the board as I have seen done on some Google photos. I have the connector pads and some suitable short coax links, SMA female bulkhead to u.FL.


    I have successfully fitted SMC oscillators of similar size to new PCB's in the past, but I tend to be a bit unlucky REMOVING such things leaving the PCB in a reusable state ;) Having seen how bad the stock oscillator is for such demanding usage as ours, I need to just go for it and see what happens. Thanks again.


    Best regards, Chris Wilson.