2017-07-24 Last night receiving ISS SSTV images 2 months ago
And a third night. I used the timed recording option of audacity, which in the current linux version does not offer the option to set in advance how to save the project. This time I 'only' recorded for 7 hours, and was able to save the project afterwards without needing a recover. But on reloading the saved project audacity complained about some internal error in it, and it still had the problem of assuming 44.1 kHz sampling while showing the project sample rate as 48 kHz. Anyway, images decoded from the audio and I even recieved a few new ones.
2017-07-23 Another night of receiving ISS SSTV images 2 months ago
On the night from Friday to Saturday I had the whole setup ready to receive more ISS SSTV images. And nothing was received since I had the antenna unplugged during Friday because of thunderstorms and forgot to plug it back in. So when I found that out I put a note on my desk with 'Antenna unplugged?' which can be a reminder to unplug it when I'm done or plug it in when I want to receive something. On the night from Saturday to Sunday I plugged the antenna in and let the whole setup run again like on the earlier run on Friday Received slow scan TV images from ISS while I was sleeping. To make sure I had the antenna plugged in I tuned to 145.750 MHz where I can hear a distant repeater faintly. Again audacity hung after the recording, and this time on recovery it had some issues with the saved project. At first I could see and hear audio of SSTV passes but qsstv could not decode anything. In the waterfall display of qsstv it looked like the frequencies were too low. I had a thought that maybe something decided the samplerate was back to 44.1 kHz so I simply speeded the audio of an image pass up by 8.8435% and suddenly it decoded fine. In the end I decoded 11 images from the ISS SSTV project. Numbers seen 8, 10, 9, 6, 7, 8, 6, 4, 5, 6. And 2 images from nearby radio amateurs who weren't operating according to the bandplan... but at least did not interfere with the ISS SSTV transmissions.
2017-07-21 Received slow scan TV images from ISS while I was sleeping 2 months ago
I read about the current ARISS Celebrates it’s 20th Anniversary through SSTV Event and noticed the planned times weren't really compatible with my day/night cyclus. I know, as a hardcore radio amateur I should be up at the weirdest hours for rare events but I also like my sleep a lot and my wife really dislikes alarms at weird hours. Automation to the rescue: I decided to record all of a night of ISS signals on the computer with audacity and decode images from it later. The computer adjusted the radio for doppler using gpredict. Since I don't have an automatic rotor for satellite antennas I used the VHF/UHF vertical. This may seem strange but the weakest signals from ISS are when it is right above the horizon (which is when the vertical has the best reception). And as noticed on earlier SSTV events that compared to other amateur satellites the ISS has a strong signal. So I left it running for a night and checked the results afterwards. The result was a 9 hour recording and audacity decided to hang after stopping the recording. I made a backup copy of the audio data just to be safe and restarted audacity. Luckily it recovered the project fine after restarting. With a recent version of qsstv I decoded the recorded audio and searched for ISS passes in the recording. The result is 13 decodes in one night. It turns out it received audio from a number of low passes that I did not see in gpredict because I have gpredict set up to skip low passes (those that don't come above a 20 degree angle above the horizon). But the strong signals from ISS make those show up in my radio anyway. Decoded and seen the numbers sofar: 11 (partially), 12, 9, 10, 9, 10, 9 (partially), 9, 7, 8.
2017-05-08 Going full duplex with amateur satellites, part 11 : Tried an XW-2A pass, heard vague signals, no contacts 4 months ago
This evening the only amateur satellite pass at a reasonable time was by the XW-2A satellite, part of CAMSAT XW-2 Satellites - amsat UK and I only heard weak signals which sounded like other radio amateurs tuning their transmitters/receivers but I never heard something like a voice. Or my own signal when I tried transmitting.
2017-05-07 Going full duplex with amateur satellites, part 10 : Still no contacts, investigating AO-85 (Fox-1a) 4 months ago
Passes of amateur satellites aren't always at times that are compatible with other things happening. But the discussion about AO-85 on the amsat-bb mailing list also had some details about the satellite and I also found AO-85 Twist Trick and Other Hints - Spacecomms which explains:Apparently the epoxy caused a change in impedance which essentially “detuned” the antenna. It makes the bird appear deaf. A workaround is to twist the Arrow antenna 90 degrees when you transmit. That is, rotate the antenna until the receive signal is “peaked” and then rotate it 90 degrees when you transmit and back again to receive. The downside to this is if you’re working full duplex when you rotate the antenna 90 degrees to transmit you will often lose the downlink signal and not be able to hear yourself. In my experience I only have to do the twist trick in the beginning and end of the pass when the bird is farthest away. Another fix is to just use more power, but if you only have an HT that’s usually not an option.This, combined with the frequencies up and down being slightly different from the planned frequencies explains the weak signals I hear upon receiving and the difficulty I had getting into the satellite. This evening had a pass of AO-85 which did not leave me time to drag out the whole setup, but I was able to bring the arrow antenna and a handheld radio to check reception to see if the frequency was correct, including doppler correction. It was correct, but reception is indeed quite sensitive to the orientation of the arrow antenna.
2017-05-01 Going full duplex with amateur satellites, part 9 : Filtering the reception, in theory 4 months ago
I decided to share my woes of the receive side going deaf (receiving nothing) when I transmit with the amsat-bb mailing list, together with a description of the whole setup. The suggestion came from Eduardo PY2RN to not use a preamp and have filtering so the transmitted signal cannot get into the receiving side. I pondered this for a while and realised I already have a filter: the diplexer on the arrow antenna. So to receive on 2 meter and transmit on 70cm I connect the transmitting radio to the 70cm antenna and connect the receiving radio (the rtl-sdr) to the 2 meter antenna via the diplexer, and put a 50 ohms terminating resistor on the 70cm connector of the diplexer to make sure it still shows the right impedance. In a simple test this works, transmitting now has a lot less influence on the rtl-sdr (it's not completely gone yet). I haven't had a good satellite pass yet to try this out.
2017-04-29 Going full duplex with amateur satellites, part 8 : No real contact yet 4 months ago
This evening had a Fox-1A (AO-85) pass at a reasonable time so I decided to drag the entire setup outside and try my luck at a qso. Reception of Fox-1A was bad (maybe I'm somewhat off-frequency) and the major dissapointment was that the receiving side on 2 meter via sdr got deaf when I was transmitting on 70 centimeter. That's not supposed to happen, the whole reason for the full-duplex setup was to be able to hear myself on the downlink. Anyway, the recording of downlink audio went fine this time so there is a full recording of what I heard. It was a Northwest-Southeast pass which means it took a while before I heard anything because northwest is over the houses. Callsigns heard in this pass: DO3EXE, IZ5ILX, 9A2EY, IZ3KLF, Something with F2D I completely can't decode and "Mr Olla". My best guess would be a retry on SO-50, FO-29 or AO-73.
Listen to audio attachment:
2017-04-23 Going full duplex with amateur satellites, part 7 : Recording downlink audio 5 months ago
This evening I thought there would be a nice Fox-1A (AO-85) pass but gpredict on another computer showed totally different predictions. Pondering that difference made me suddenly remember AO-85 is still not part of the 'standard' set of Kepler data because it's close to some militairy satellite. The data is available through other sources, I use TLE | Amateur radio PE0SAT and updated from that location. The 'nice' AO-85 pass near 22:30 localtime shifted to 'way too late', so I looked for other satellites to at least try recording downlink audio. I saw passes of HO-68 and UO-11. So I created the whole setup with audacity recording audio. Using pavucontrol I adjusted the recording flow of audacity to record 'Monitor of Built-in Audio Analog Stereo' and indeed audacity was recording the same as I heard on my headphones. But no signal from the satellites was received. Checking the Amsat Oscar status page shows both haven't been heard by others either. So I recorded noise, but I recorded the right noise.
2017-04-22 Going full duplex with amateur satellites, part 6 : First succes in reception 5 months ago
Today I had time for a reception test and when I started collecting the amateur satellite reception gear I saw two upcoming passes, one of the AO-73 Funcube and one of the AO-85 Fox-1a satellite. The AO-73 Funcube is an 'inverting transponder' which converts an LSB uplink to an USB downlink with space for multiple contacts at the same time. By default gpredict selects the center frequency where I heard PA3HDG calling CQ but hearing no answer. Sorry, I did not have the rest of the setup to transmit that answer. The AO-85 Fox-1a is like an FM repeater in space so it should be easier to receive it. But I heard nothing, which was
most likely due to the satellite being in a part of the sky where the hedge is in the way.due to the fact my data about that satellite wasn't updated: it's not in the default sets. Updating from a trusted source of extra kepler data TLE | Amateur radio PE0SAT showed a shift in pass times of more than 60 minutes. Anyway, first success in reception. Next steps: recording the received audio with audacity and adding the transmitter to the mix to be able to make actual contacts. At least the concept I imagined with the rtl-sdr stick as receiver so I can work full-duplex works.
2017-04-14 Going full duplex with amateur satellites, part 5 : first test of the amplifier with RTL-SDR 5 months ago
For a first test I looked for the first reasonable pass of an amateur satellite and tried to recieve the morse beacon of HO-68. I have received signals from HO-68 before, but this pass I heard nothing. I tried a stable regular local source on the 70cm band : the PI2NOS repeater and noticed after a while the frequency display in Gqrx was showing 430.100 MHz where the (GPS stablized) frequency is 430.125 MHz, so the RTL-SDR I use is somewhat off frequency. Maybe in a next test things work better.
2017-04-14 Going full duplex with amateur satellites, part 4 : amplifier built into the case 5 months ago
Today I had some time to work on the metal case for the amplifier I bought for receiving amateur satellites. I've never been good at metalwork but I think I did ok. First I made sure the place I wanted to put the holes was chosen correctly, taking the size of connectors into account. Especially with metalwork it's "measure twice, cut once". Next I drilled holes with a drill for metalwork (HSS) and used a file for metalwork to make the holes bigger. I visited the local electronics shop to get a small switch for switching the battery power on and off and added a hole for the switch. In the end the amplifier and the cables are mounted inside the case and there is a bnc connector for the Arrow antenna on one side and an SMA connector for the cable to the RTL-SDR stick on the other side.
2017-03-29 Going full duplex with amateur satellites, part 3 : metal cases 5 months ago
I was looking for a metal case to put the low(ish) noise amplifier in and maybe the RTL-SDR. The RTL-SDR should also be shielded from the amplifier and from the computer as both RTL-SDR and computer cause their own signals. The first cheap source of metal cases I could think of was old cigar boxes. Altoid tins are not available here. So I asked someone who I know who smokes cigars who had a number of old metal cigar boxes. Next step, finding the way to get the right holes in the boxes for the SMA and BNC connectors, and for the USB connection to the computer. Ideal would be to lend / find a punch for those holes.
2017-03-26 Going full duplex with amateur satellites, part 2 : Installing Gqrx SDR software and the first tests 6 months ago
With the hardware available it's now time to test the first part of the software setup: whether I can have running software defined radio. To (re)install Gqrx I followed the instructions at Install Gqrx SDR on Ubuntu Linux. The first 'sudo apt-get purge --auto-remove' steps removed a lot of software and the latter 'sudo apt-get install' steps added newer (or maybe the same) versions. But I was glad to do a full reinstall, I have had weird problems with gqrx versions before. The laptop on which I am doing this has had an install of gqrx before, but was upgraded from Ubuntu 14.04 LTS to Ubuntu 16.04 LTS in the mean time, so a clean reinstall seemed a good idea. I plugged in the RTL-SDR stick and checked whether no drivers were installed, which was indeed still correct. The kernel messages:[156490.915435] usb 2-2: new high-speed USB device number 7 using xhci_hcd [156491.111136] usb 2-2: New USB device found, idVendor=0bda, idProduct=2838 [156491.111141] usb 2-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3 [156491.111143] usb 2-2: Product: RTL2838UHIDIR [156491.111145] usb 2-2: Manufacturer: Realtek [156491.111147] usb 2-2: SerialNumber: 00000001To make sure the drivers aren't loaded, I have a /etc/modprobe.d/local-blacklist.conf with:blacklist dvb_usb_rtl28xxu blacklist rtl2830 blacklist rtl2832 blacklist lirc_devTo test it with the 'minimal' setup I started with just the RTL-SDR and a simple antenna, and Gqrx. Enabled remote control in Gqrx and added a radio 'gqrx-sdr' in Gpredict with host 'localhost' and port '7356' (default for gqrx remote control) and Radio type 'RX only', PTT status 'none'.
2017-03-26 Going full-duplex with amateur satellites, part 1: introduction and I bought the hardware 6 months ago
I still want to get active on amateur satellites again, but the main reason is that the amount of work per contact is a lot more than for example in a digimode contest. But I still want to make those 'special' contacts, especially when the amount of local radio noise on HF is bothering me. One of the most important improvements in making contacts on amateur satellites is working 'full duplex', meaning receiving signals while transmitting. The expensive way to reach that goal is buying a second amateur radio capable of receiving in FM and SSB modes in the 2 meter and 70 centimeter amateur bands and having computer aided tuning so gpredict can control the receiving frequency. The less expensive way to reach that goal is using software defined radio. The good news is that Gqrx SDR can be controlled by other software which as the page shows is intended for remote control by Gpredict. All I needed now was reception hardware. Since the first RTL-SDR device I bought is always in use for receiving ADS-B signals from airplanes I decided to buy another cheap one to get me started. So it was on the shopping list for a recent visit to a hamfest. At the hamfest I found a RTL-SDR stick with mcx connector and an mcx to bnc cable. But the same guy also sold cheap low(ish) noise amplifiers with SMA connectors and a 9V battery connector for power. So at one of the booths selling cable assemblies I found an mcx to male sma cable and a female sma to bnc cable, and a male to male sma cable. The plan is to put this all together in some metal case to shield the lna from the outside world. Maybe also shield the amplifier from the RTL-SDR stick so it won't pick up any extra noise. Should this work it would be possible to think of an upgrade with better SDR hardware and/or a pre-amplifier at the antenna side.Read the rest of Going full-duplex with amateur satellites, part 1: introduction and I bought the hardware
2016-06-10 ISS SSTV MAI-75 image received 1 year ago
I had no advance warning but suddenly mailing lists and other places I find my amateur radio satellite news lit up with news of another round of slow scan TV (SSTV) images. I thought at first things would be over Friday evening but then the reports started again and I put the radio, antenna and laptop outside to record another pass and decode it. Reasonable decode, especially for the pass starting in the noise.
ISS SSTV June 2016 MAI-75 image recieved by PE4KH at JO22NC 20160610 at 1900 UTC
2016-04-23 Recorded a Tim Peake ARISS contact 1 year ago
This afternoon was a contact between Wellesley House School in Britain and Tim Peake on the International Space Station. So I decided to put the finished antenna rotor to good use since one of the triggers for building a rotor was getting my arms real tired on earlier ISS passes. And indeed, I had no problem with holding the antenna. But it still took a while before I heard anything and the signal was not very good.
Listen to audio attachment:
2016-04-15 ISS SSTV MAI-75 image received 1 year ago
And a chance to receive an image from the Russian 'MAI-75' project. Originally I had a lot of trouble decoding the image with qsstv and the author of qsstv helped me find the ideal workflow. Upgrading qsstv and using a 48000 samples/second .wav file helped. Earlier I played the audio in audacity and decoded in qsstv with pavucontrol setting the 'Monitor of builtin audio' as input for qsstv.
ISS SSTV April 2016 MAI-75 image received by PE4KH at JO22NC 20160415 1627Z
2016-04-14 Tried an SO-50 pass this evening 1 year ago
And while I had the amateur satellite gear out I checked for upcoming interesting passes and saw that SO-50 would pass right after the ISS pass between SSTV experiments. I tracked the pass and heard activity, mostly from IZ5TEP with F0DTV. I tried answering a few times, to IZ5TEP and in general but no contacts. The amount of interference was not as bad as I heard a few times last year but it was not perfect amateur satellite behaviour either.
Listen to audio attachment:
2016-04-14 ISS pass between SSTV experiments, nothing heard 1 year ago
I saw people post more images which seemed to be from the MAI-75 SSTV program. I tried a pass at 18:27 UTC but heard nothing. Checking the article ISS Slow Scan TV in April - Amsat-UK shows that the ARISS commemorative SSTV event ended at 14 April 11:35 UTC and the first MAI-75 activity was 14:45 until 18:00 UTC. The next MAI-75 activity is Friday 15 April 14:10 until 19:00 UTC.
2016-04-13 Two partial ISS SSTV April 2016 images received 1 year agoOlder news items for tag amateursatellites ⇒
In a later pass I received two partial images.
ISS SSTV April 2016 image 06/12 received by PE4KH at JO22NC 20160412 1920ZThe good news is that standing outside holding my Arrow antenna I did some serious thinking how the Arrow is going to fit on the antenna rotor. And I tested how reception is when I fix the elevation at around 20-25 degrees: fine.
ISS SSTV April 2016 imagereceived by PE4KH at JO22NC 20160412 1920Z