I passed my novice radio amateur exam in March 2013 and I registered the
PD4KH (pappa delta four kilo hotel!).
I passed my full radio amateur exam in March 2016 and I registered the callsign
PE4KH (pappa echo four kilo hotel!).
PE4KH on qrz.com
PE4KH on hamqth.com
I am usually located around maidenhead locator: JO22NC
In my project to receive amateur satellites with the rtl-sdr I noticed the sdr itself has a considerable frequency error as noted in Going full duplex with amateur satellites, part 5 : first test of the amplifier with RTL-SDR. Using the PI2NOS output frequency I ended up at an error of 54 ppm so I entered that in gqrx. But to be really sure there is a program named kalibrate-rtl available via GitHub - steve-m/kalibrate-rtl: fork of http://thre.at/kalibrate/ for use with rtl-sdr devices. I had some trouble finding the right way to use this program so I am sharing my steps here. First try to guess the error by using a known frequency such as a local repeater (especially when they mention using GPS to maintain frequency) or a broadcast FM station. First step with kalibrate-sdr is to scan for GSM channels which are strong enough. I noticed in later runs that I really need to add the first guessed frequency error, otherwise it will not find the GSM channels at all.koos@kernighan:~/radiowork/kalibrate-rtl/src$ ./kal -s GSM900 -e 54 Found 1 device(s): 0: Generic RTL2832U OEM Using device 0: Generic RTL2832U OEM Found Rafael Micro R820T tuner Exact sample rate is: 270833.002142 Hz [R82XX] PLL not locked! kal: Scanning for GSM-900 base stations. GSM-900: chan: 8 (936.6MHz + 724Hz) power: 67277.85 chan: 17 (938.4MHz + 606Hz) power: 36428.54Second step with kalibrate-sdr is to select a GSM channel to use for the calibration run. I selected channel 8 which looks quite active.koos@kernighan:~/radiowork/kalibrate-rtl/src$ ./kal -e 54 -c 8 Found 1 device(s): 0: Generic RTL2832U OEM Using device 0: Generic RTL2832U OEM Found Rafael Micro R820T tuner Exact sample rate is: 270833.002142 Hz [R82XX] PLL not locked! kal: Calculating clock frequency offset. Using GSM-900 channel 8 (936.6MHz) average [min, max] (range, stddev) + 169Hz [85, 251] (166, 49.119198) overruns: 0 not found: 0 average absolute error: 53.820 ppmAnd only in that step you get the output with the calculated frequency error. Update: Doing this calibration is also a good idea for the stick running the ads-b receiver. That came out to -30 ppm and using that factor makes dump1090 receive signals from greater distances.
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.
I was testing with noise on all radio bands with the LW-10 longwire antenna with tuner. I recently made the rope that hangs it out from the window a bit longer and I noticed the noise on the 10 meter amateur radio band had dropped a lot compared to the noise I experienced before and the noise on the antenna under our roof. In S-points: under the roof S8, with the 10/20/40m endfed S8, and with the longwire antenna S0. On bands with lower frequencies (higher wavelengths) noiselevels were high, up to S9+ on 80m with a rattling noise in it. But this sudden change on the 10 meter band made me think there could be a pattern so I measured how much more distance I could move the antenna away from the house and maybe get lower noise levels on the 20m band too. After adding 1.60 meter of rope and rehanging the antenna the noise level on the 20 meter band also dropped from S8 to S7. Not the biggest improvement but it's something. I'm now making some PSK qso's on the 20 meter band. At the S8 noise level this was getting impossible.
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.
Today I was scanning the bands to build an overview of noise / interference levels on each band and I came across the 60 meter band (5 MHz) which I can get tuned on my LW-10 longwire antenna. No idea how much power is eaten by the tuner and how much gets out but it works. I noticed some RTTY signals and those were within the part of the band I can access with my license. So I answered the CQ from DK7UY and we had a good contact. The 60 meter band is a recent addition for Dutch and other amateurs, only allowed since 3 december 2015. Around that date the WRC-15 conference happened where world-wide agreements were made about secondary amateur access to this band. And on 1 april 2017 the access for Dutch amateurs was limited to the agreed allocation.
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.
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.
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.
Recently I talked to a fellow radio amateur about my HF reception woes at home and he suggested trying the mini-whip antenna I built a few years ago as reception antenna, using an automatic switch to switch between the transmission and reception antenna. For the first test I used the mini-whip antenna with the HF downconvertor and an RTL-SDR stick that I bought to receive amateur satellites to check the signal on the computer. The further I move away from the house the better signal I get (less noise, more signals sounding like the amateur radio signals I want). I do notice that when I turn the gain on the RTL-SDR up (or set it to automatic gain) that there is a repeating 'ticking' signal which sounds just like the ticking interference from my own PLC tests. This could mean that a nearby neighbour has a PLC network without the notches for amateur radio. Or this is just an artefact of the high gain.
Earlier I had the Android application Ham Radio Prefixes - Android Apps on Google Play installed, but it needs some server on the Internet to look up callsigns and determine the country it is assigned to. Sometimes I need to do a lookup off-line, and I noticed fldigi and CQRLOG do that fine when the country data file is installed. So it can be done, I just have to find software that does this right. On ICQ Podcast Episode 234 - Portable Power Distribution and I heard mention of Pocket Prefix for Android which can be found at Pocket Prefix - Android Apps on Google Play and which works off-line. This was even mentioned on the podcast as one of the advantages. It even gives extra information when available, the given example is that prefix SV is for Greece but SV9 is specific to Crete. Or EA9 is specific to the Spanish enclaves Ceuta and Melilla which are located in Morroco (and therefore count as a contact with the African continent). It's a nice application, thanks to Derek Turner G4SWY!