PD4KH Amateur radio - Koos van den Hout

I passed my radio amateur exam in March 2013 and I registered the callsign PD4KH (pappa delta four kilo hotel!). PD4KH on qrz.com

I am located around maidenhead locator: JO22NC

For now this page contains just the 'hamradio' items from my homepage.

Articles

Amateur Satellites
D-Star digitale amateur radio (Nederlands)

2014-07-27 (#)
This evening I tried another pass of the SO-50 amateur radio satellite. It wasn't as high as the afternoon pass, only 66⁰ maximum elevation. The experiences from the afternoon pass learned me to search around a bit for the downlink signal. I did not hear a lot of activity, it almost sounded to me like the transponder wasn't "armed" with the 74.4 Hz ctcss tone. This tone activates the transponder for 10 minutes, but to actually use the transponder you need to use a 67.0 Hz ctcss tone. Switching tones on the fly isn't easy when the FT-857 is controlled by gpredict, so I'll either have to control that via the computer assisted tuning (CAT) interface and rigctld or temporary switch to manual and use the memory in the FT-857 which has the different ctcss tone.

Browsing the rigtctl(1) manpage suggests a script which can set ctcss tones is quite doable.

2014-07-27 (#)
I soldered the cable for a stereo headphone on the mono phone output on the FT-857 this morning and went to listen for the SO-50 pass with tuning done by gpredict.

And I missed half of the satellite pass because gpredict has the 'preprogrammed' frequency and the satellite downlink frequency seems to be drifting away from this frequency, far enough to fall out of the FM receiver passband. I kept hearing nothing so I switched back to manual frequency control with the doppler-shifted frequencies preprogrammed in the radio and I found it again, somewhat shifted. I switched back to letting gpredict control the frequency but used the tuning dial on the radio to find the right spot, after which gpredict kept track of what I did. I still find this an awesome feature in gpredict, the two-way tracking of frequencies.

It was as busy as could be expected on an FM satellite on a Sunday afternoon pass with nice weather, so I could not find a 'hole' in which to call CQ or answer some call I heard. The headphones do help with hearing the audio from the radio, so a good thing I made that cable.

2014-07-26 (#)
I also managed to get CHIRP working with the Yaesu FT-857 radio. I had to RTFM: CHIRP does not use the normal CAT commands, it uses the clone mode of the radio.

2014-07-26 (#)
First thing to try with the new Yaesu FT-857 amateur radio: get it working with gpredict for amateur satellites. What gpredict can do is control the radio via rigctld, part of Hamlib to set downlink (receive) and uplink (transmit) frequencies automatically to the doppler-shift correct frequency. I bought a CT-62 USB cable for this which is the cable for the Computer Aided Tuning (CAT) interface on this range of radios with a FTDI based serial interface on the side of the computer. I added a new radio in gpredict with:

So I installed libhamlib-utils and tried to get rigctld working. At first it gave errors on communicating:
$ rigctld -m 122 -r /dev/ttyUSB0  -v -v
Opened rig model 122, 'FT-857'
ft857: error reading ack
ft857: error reading ack
And I found out the default baudrate of rigctld is 38400 bps and the FT-857 was set to 4800 bps. I tested first with 4800 bps and later changed the rate on the radio to 38400 bps and tested again. Now running:
$ rigctld -m 122 -r /dev/ttyUSB0 --set-conf=serial_speed=38400  -v -v
Opened rig model 122, 'FT-857'
The radio needs to be in 'split' mode so VFOa and VFOb can be set sepately and receiving is on the VFOa frequency and transmitting on VFOb.

Gpredict radio control set up for the FT-857 The good part, especially for SSB satellite work is that gpredict will follow frequency adjustments on the transciever and will track from the adjusted frequency. With the 'lock' function enabled (L button) this will also make the uplink frequency follow downlink changes. Change the (receiving) frequency on the transciever and the transmitting frequency will be updated accordingly. This should make SSB satellite work with one simplex transciever easier.

Sofar in tests without actual satellite communication things seem to work. Next is a test with SO-50 in FM mode, probably on the high pass I see coming Sunday afternoon. A test with an SSB satellite (first trying to receive) will probably be possible later this week with the Funcube-1 (AO-73). I found a gpredict trsp file for FUNCUBE from G0HWW.

2014-07-25 (#)
For a while I have been considering my wishes for a more elaborate amateur radio. What I want to do with it is continue and expand the use of amateur satellites, and try to get into PSK31 on HF, starting on the 20m band. So a list of must haves and should haves arose: all-mode, portable, computer assisted tuning, HF support, 2 meter and 70 centimeter and an increas of power from 5W.

Adding it all up and looking for a reasonable price I ended up considering the Yaesu FT-857(D). It's in the middle between the FT-817 (too low power, still 5 watts) and the FT-897 (too heavy: 3.9 kilograms). And a reasonable pricetag, were other amateur radio brands have nothing comparable or at a much higher pricetag. I went looking for a second-hand one and when we got back from holiday a nice one (FT-857 with DSP and installed filter, and a remote control+DTMF hand microphone) showed up from Communicatie Centrum Venhorst - Hilversum and I bought it. Picked it up this week, and I am learning using it. I listened to SO-50 this evening using this radio with a lot of wires on the table in the backyard.
Radio setup
Radio setup - FT-857, PC power supply for 12V, laptop, Arrow antenna: ready for amateur satellites
It was clear I also need headphones to listen to amateur satellites on this radio so I'll get the parts to connect a headphone soon. Cables for computer assisted tuning and interfacing to a computer sound card are already ordered.

This radio also allows me to access SSB satellites, so I'll have to learn how to do that.

The good news about the SO-50 pass: there were QSOs going on, the person just calling CQ and never listening to the answers was missing.

2014-07-24 (#)
Yesterday evening I gave it another try to make a contact via the SO-50 satellite. It was hard since someone was trying very hard to work the satellite with 95% transmitting and at most 5% not transmitting which did not leave much room for an answer. I heard that person loud and clear with a repeated and somewhat bored "CQ satellite" and testing noises like whistling, but I never heard a callsign! Pass for SO-50 over my home location JO22NC

Trying to answer that person didn't work (clearly he had a reception problem somehow) so I just started calling CQ on my own when he left a gap. Someone answered but I had a hard time understanding the callsign, I think it started with a D (German callsign) and I am sure it ended with BBE (Bravo Bravo Echo). Looking up the callsign options on QRZ showed me the most likely candidate is DG0BBE so I e-mailed him to confirm.

During our holiday in Denmark I also tried to work a few SO-50 passes. Being on a campsite with a wide open view in all surrounding directions should make things easier for lower passes which I skip at home. I tried a pass with a 55⁰ elevation and one with a 62⁰ degree elevation and I heard the satellite loud and clear. The downside was someone was whistling and calling 'o la', probably the same person as I heard here at home. And another downside is that with lower passes the distance is a lot higher and therefore my 5 watts on VHF don't make it across the FM receiver on the satellite.

I also had a look at possible LituanicaSAT-1 passes but in Denmark those all stayed low to the Southern horizon.

Update 2014-07-25: DG0BBE mailed me back, I was right I heard him, but he made a very valid point the QSO was not valid: in a QSO at least call signs and a signal report need to be exchanged. In amateur satellite work a locator is also good to have.

2014-06-22 (#)
Friday evening I recorded the Amateur Radio on the International Space Station (ARISS) contact between the International Space Station in space and Focus Camp, Candriai, Italy / Euro Space Center, Redu, Belgium. I used the Arrow satellite antenna on a tripod and my Commtel com225 scanner to tune in to the downlink signal since that scanner has both an internal speaker and a line output for a tape recorder.
Recording ARISS contact
Recording ARISS contact - Laptop, recording ARISS contact, scanner, Arrow satellite antenna on tripod
Recording ARISS contact
Recording ARISS contact - Laptop with gpredict, backup radio, scanner tuned to 145.800
I had a bit of a problem setting up my laptop to have the input in line input mode, but after I fixed that I was able to record audio from the scanner while listening. The results didn't turn out very well, the antenna was in our backyard between houses which means houses are always in the way of weak signals until the object is right overhead. And the antenna is quite directional on 2 meter, so an azimuth/elevation rotor would have helped a bit in getting the best signal.

But I do have audio of some of the answers. I edited the audio to lower the noise audio level and the recording is limited to the part where I succesfully recorded audio. The voice of the astronaut sinking away in the noise at the end is a bit of a "Major Tom" moment.

2014-06-14 (#)
A pass of the radio amateur satellite SO-50 this morning in which I concentrated on the probable shift in downlink frequency. It turned out the shift is probably not more than 5 kHz (my radio has no 2.5 kHz steps). I tried calling CQ but no answers.

In general I am noticing now that usable passes are rare at the moment. With my limited setup and other things taking my time I have a lot of wishes for a usable pass: elevation must be over 70⁰ and the pass must be at a reasonable time in the evening or on a weekend day with no other plans. I'm not a nightowl like a lot of radio amateurs seem to be. So the week in which I made my first satellite contact with GS3PYE/P was quite special: there were 2 passes in that week matching all requirements for both locations.

2014-06-09 (#)
A bit more luck on a LituanicaSAT-1 pass Saturday evening: this time I could understand at least one callsign. Hearing a known callsign helps: it was Peter Goodhall 2E0SQL. I tried answering but this failed. A mail exchange later confirmed I heard him calling so at least I heard it all right.

2014-06-07 (#)
Success: I made a contact via SO-50 with PD5DJ. This was on a high (88⁰ degree elevation) pass of SO-50. The output frequency of SO-50 seems to have shifted a bit so I had to select the 'next' downlink frequency earlier than gpredict was showing them.

I will send a card via the QSL bureau to PD5DJ, this is my second amateur satellite radio contact.

2014-06-06 (#)
There are great things happening at the moment: the NASA ISEE-3 satellite from 1978 is going to pass earth again in August 2014. Due to budget cuts and cleanups at NASA they decided to not do anything with the satellite. International Cometary Explorer - Wikipedia.

The first signals from this satellite were received in March: AMSAT-DL and Bochum Observatory Detect ISEE-3 Transmitters - Space College and since that moment people have been busy with it. The satellite was supposed to be switched off but it wasn't completely switched off and it receives enough solar power to overcome the lack of energy storage. A project was started named the ISEE-3 Reboot Project - Space College to get in touch with the satellite again and control it to make the course correction to return to the original orbit. With crowdfunding this project was able to get started quickly and the project received the control keys from NASA to be able to command the satellite. The first commands were succesfull: Happy Dance Video: First Successful ISEE-3 Commanding - Space College when the satellite was ordered to send more telemetry data.

I'm following this story as I think it's great: commanding a satellite that has been in space for 36 years. The amateur radio angle is that recent developments in amateur radio have made this possible: the kind of specialized equipment that was needed in 1978 is now done with software defined radio and really good amplifiers.

2014-06-05 (#)
Around midnight last night there was a pass of LituanicaSAT-1. After my earlier attempts and the announcement it would switch off the transponder at around 01:00 UTC on 5 June I decided to give it a go at this late hour. Original announcement: LituanicaSAT-1 FM Transponder Active until June 4 - amsat UK.

I did hear traffic but it was very hard to understand callsigns (so I couldn't respond to a callsign I just heard) and I got no response to calling CQ.

So not much luck in working this satellite, but at least I heard it this time.

2014-06-02 (#)
I was looking for options for a pre-amplifier to amplify the incoming antenna signal for receiving amateur satellites in the 70cm band (430-440 MHz). Commercially available units seem to be quite expensive like this one: DBA 270 Duo-Band-Preamp. 2m + 70cm - SSB for 298 euro.

A cheap option seemed to be Low Cost 440 MHz Receiver Preamplifier Kit - Ramsey Electronic Kits for US dollar 9.95. Oh, and US dollar 57 for shipping it to the Netherlands. I'll skip. Other options sofar seem to be quite expensive or require SMD soldering. I decided I have enough problem seeing normal soldering with a magnifying glass so I'll skip SMD soldering for now.

A cheap but not ideal trick is (ab)using a cable TV amplifier: those include the 70cm band because they include everything from around 88 MHz to 1000 MHz. I found this suggested at KickSat Ground Station. So I walked into the local electronics store and found a cheap cable TV amplifier with a special sticker "does not support digital interactive TV" which means it doesn't support the returnchannel. Good, just a simple amplifier. The specific impendance in cable TV networks is 75 Ohm and I want 50 Ohm so that will probably have to be fixed too. It came with a small power supply which will be replaced with a battery like in the kicksat page.

2014-05-27 (#)
Club evening at the Veron Centrum Radio Club and I walked into the radio shack and heard W1AW calling CQ on the 12meter band from New York. It was pure coincidence the radio was tuned to that frequency and I don't know who tuned it or left it in SSB mode. I checked DXHeat DX-Cluster but did not see W1AW spotted at that frequency. I should register at DXHeat so I could have posted my spot.

The reception of W1AW was mostly ok, sometimes fading a bit. I answered the CQ using the club callsign PI4UTR.

The W1AW callsign is doing a tour of the US states at the moment as the ARRL centennial qso party. It was fun to be a small part of this. The New York part is organized from W1AW/2 Operating Event Calendar - Rochester DX Association.

2014-05-26 (#)
An SO-50 pass came up this morning at 07:46 local time (05:46 UTC) and it looked workable: a maximum elevation of 85 degrees. So even in the busy morning schedule before work I tried working it, after preparing everything in advance to fit in the schedule. I called CQ and I heard F0FIG clearly and called him but no responses.

2014-05-24 (#)
I was able to buy a real Garmin GPS 18 LVC secondhand. It's now on the roof of our shed. The first thing I want to do is repeat my plotting of GPS satellite positions from $GPGSV messages and plotting of GPS satellite positions and signal strengths from $GPGSV messages measurements with data from this unit. After that has run for a while I'll configure ntpd to get the correct time from the GPS unit and the PPS signal.

And again, the resulting plot of gps satellite positions versus signal strength is not very helpful in finding out which part of the sky is obscured.

2014-05-22 (#)
I saw an announcement that Artsat1 Invader CO-77 aka ITF 1 was going to make a pass over Europe. I recorded it by having the laptop with the gpredict software also run audacity to record the audio from my handheld transceiver, so the audio isn't brilliant, but it's something. I reported the pass and the recorded audio to the Artsat team. This satellite is even in a lower orbit: the entire pass horizon to horizon was in 7 minutes. In the end I have 1 minute 40 seconds of usable audio, with everything the satellite offers: morse, the digitalker and AX.25 frames.

The voice says: "Konnichiha Uchu" which translates to Hello, space!.

Update: with fldigi I decoded the morse code:
*HELLO, SPACE*

Update: the pass was also recorded by PE0SAT and DK3WN: INVADER Digi-Talker active - DK3WN SatBlog including decodes of the AX.25 frames.

And the transponder file I used: /home/koos/.config/Gpredict/trsp/39577.trsp with:
[FM Downlink]
DOWN_LOW=437200000
MODE=FM
Now I have adding frequencies for an existing satellite covered, I wonder about adding an entire satellite.

2014-05-18 (#)
Weer een overgang van LituanicaSAT-1 waarbij ik geen succes had met contact leggen vanmorgen. Ooit gaat het lukken! De satelliet overgangen zijn momenteel niet op handige tijden, dus ik ben al zover gegaan om te zorgen voor een piepje om op tijd wakker te zijn voor een overgang om 08:25 lokale tijd.

Achteraf weer alles nagekeken op de radio, en daarbij ontdekte ik dat de geheugens die ik geprogrammeerd heb voor de LituanicaSAT-1 in wide-FM mode stonden. Uit de discussie op de Amsat-bb lijst begrijp ik dat wide-FM zeker een verkeerde instelling is LITUANICASAT-1 experience - Amsat-bb (nu niet meer gearchiveerd).

Direct gecorrigeerd, volgende kans beter dus.

De overgang van SO-50 aan het eind van de zaterdagmiddag heb ik goed gehoord maar het lukte me niet om erdoor te komen, volgens mij zat ik iedere keer dubbel met een ander. Ik hoorde haarscherp G0JMI over de SO-50 komen, maar terugroepen werkte niet. Een van de eigenschappen van FM is dat als een ontvanger twee signalen binnenkrijgt op dezelfde frequentie dat het sterkere signaal dan het andere signaal verstoort of wegdrukt.

Update: De LituanicaSAT-1 satelliet is ook weer uit transponder mode: LituanicaSAT-1 Telemetry Reports Requested - Amsat UK. Door onverwachte reboots is de satelliet weer terug in de instelling waarbij er alleen een telemetrie signaal is waarin digitaal de metingen aan boord van de satelliet verzonden worden. Misschien toch eens proberen die telemetrie te ontvangen.

2014-05-09 (#)
An interesting development in software defined radio for amateur satellite use: Controlling gqrx from a remote host - Gqrx SDR which allows gpredict to control the frequency, mode and audio recording of Gqrx.

I was wondering recently whether it was possible to record the right signal in Gqrx, correcting for doppler shift. Now this can be done.

2014-05-08 (#)
Momenteel weinig geluk met de amateur satellieten: de mooie hoge SO-50 overgangen zijn op tijden dat ik slaap of op mijn werk zit. En het lukt me nogsteeds niet om iets te doen met LituanicaSAT-1. Vandaag twee overgangen gehad volgens gpredict (met als het goed is de gecorrigeerde baangegevens) maar beide keren niets ontvangen via de FM transponder en niets via de baken frequentie. Nu lopen de berichten over het baken ook uiteen: op de ene plek wordt het beschreven als puur CW wat ik natuurlijk niet kan ontvangen met mijn radio, op de andere plek als FM CW waar ik in ieder geval piepjes verwacht op mijn radio. Of de LituanicaSAT-1 FM transponder aan staat is mij ook niet duidelijk, volgens een bericht van vorige week zou deze constant aan staan LituanicaSat-1 transponder remains on - Amsat-bb maar volgens een ander bericht is er nu een watchdog-reset geweest LituanicaSAT-1 reboot test - reports requested - Amsat-bb en dan kan ik me voorstellen dat de FM transponder niet automatisch ingeschakeld wordt na reboot.

Update: De radio zenders op LituanicaSAT-1 zijn momenteel helemaal gestopt om de accuspanning weer te laten stijgen volgens Re: LituanicaSAT-1 reboot test - reports requested - Amsat-bb (nu niet meer gearchiveerd). Ik denk dat een reboot nogal veel vermogen kost. De satelliet zal dus eerst wat rondjes in de zon moeten draaien voor er weer dingen ingeschakeld worden.

2014-05-05 (#)
Vandaag een paar satelliet momenten. Met de SO-50 satelliet lukt het me al beter om callsigns te verstaan. Maar ondanks proberen op passages vanmiddag en een vanavond geen reacties gehad. Dus wel conversaties van anderen gehoord, onder andere van PD5DJ die ook al reageerde op het onderwerp op zendamateur.com over callsigns verstaan bij satelliet overgangen waar PD5DJ ondertussen ook wat mooie foto's van zijn satelliet acties geplaatst heeft.

Ook kwam LituanicaSAT-1 een keer voorbij, maar daar hoorde ik helemaal niets van en kreeg ik ook geen reactie op mijn oproepen.

2014-05-02 (#)
Vanavond was er een overkomst van de SO-50 satelliet die redelijk te doen was. Ideaal is als de satelliet recht over komt, maar dat gebeurt natuurlijk niet al te vaak. Deze overkomst had als maximale elevatie 54 graden boven de horizon, waardoor de periode waarin ik een contact zou kunnen leggen redelijk kort was (ongeveer 5 minuten). Alleen waren die minuten gevuld met succesvolle contacten door andere radio amateurs waarvan ik het meeste goed kon verstaan. Een mooi moment om te luisteren en er niet doorheen te roepen.

Achteraf weet ik de roepletters die ik gehoord heb alleen niet meer, misschien toch eens een manier vinden om deze sessies op te nemen.

2014-04-29 (#)
I made my first succesful satellite QSO yesterday evening. I saw an upcoming SO-50 pass which was right overhead for me, northwest to southeast. This is the ideal direction for following a pass in the backyard. And there would also be a big overlap for when it would be in view from the Cambridge hams on Lewis Island, maidenhead locator IO68UL. That's a distance of around 1010 kilometers.

When I started to hear the satellite I heard some CQ's from different callsigns. I tried calling CQ myself once but heard no clear answer. The pass was reaching the zenith, the moment of the highest change in doppler shift. Then I heard GS3PYE/P in another contact. When that contact was over I answered with G S 3 Papa Yankee Echo, this is Pappa Delta 4 Kilo Hotel/Portable and heard the answer Pappa Delta 4 Kilo Hotel/Portable ... followed by noise.

I made a little yell which made my wife come out to see what was happening. But there was still the question whether my callsign got across and logged as a valid contact. That was answered minutes later: the contact was visible in the 2014 - Lewis Logbook - Camb-Hams DX blog. I will send a QSL card and request one.

2014-04-27 (#)
I had a look at creating a simpler QSL card which I could print with my own printer. I still want 4 cards per page. The earlier qsl card designs are nice and an inspiration for when I get around to having cards printed. But I want a few things different, like a mention of my amateur radio website http://pd4kh.idefix.net/, on the card. And space for notes about contacts. And when I use my own printer and heavy enough paper I want to print 4 cards per A4 page. Having 4 the same cards on one page meant wanting to use \LaTeX and a \newcommand so I define the card once and use it four times all of them on the same printer page. I found A QSL card backside made in LaTeX - DJ1YFK's Ham Radio Stuff which has a nice QSL card design in \LaTeX which I could use with some adjustments. This \LaTeX file defines the page size as 14cm*9cm landscape, the official size of a QSL card. I first tried changing this to an a4 page with 4 14cm*9cm \fbox in it, but this didn't give me the right result. I now create 4 pages of 14cm*9cm and create an A4 page from this with:
$ pstops -pa4 "4:0L@1.0(30cm,0)+1L@1.0(30cm,14.85cm)+2L@1.0(40cm,0)+3L@1.0(40cm,14.85cm)" qsl.ps qsl-4.ps
Which has about the right result: 4 cards on one page. No frames around the cards yet.

I use the coloured Veron logo, but it prints fine in grayscale on my black and white printer.

2014-04-23 (#)
I just noticed: LituanicaSAT-1 FM transponder test - Amsat UK which mentions an upcoming test of the FM transponder on LituanicaSAT-1 tomorrow April 24th between 13:30 UTC and 15:00 UTC. And I may be able to at least listen to one pass in that time period, there is a pass for me between 13:55 and 14:05 UTC with max elevation 47⁰. Would be really nice if the transponder would still be active the next pass since that will be at max elevation 84⁰.

After updating gpredict does know about the orbital elements of Lituanicasat-1 but not about the transponder. So I added that myself. The format of the .trsp files isn't very complicated, so I created /home/koos/.config/Gpredict/trsp/39571.trsp with:
[Mode V/U FM Voice]
DOWN_LOW=435175500
UP_LOW=145950000
MODE=FM, PL 67.0 Hz

Update: .. no signal. I received nothing and heard no response to my CQ. I notified the LituanicaSAT-1 team of my experience. Who quickly answered with the question 'are you tracking the right satellite'.
Which was indeed the problem: Gpredict had the name 'LITUANICASAT-1' for Norad catalog number 39571 but it is now 39569. I also renamed the transponder file to /home/koos/.config/Gpredict/trsp/39569.trsp. Searching for LituanicaSAT-1 finds a few more places where it is listed with Norad catalog number 39571 so I guess there has been a change in the listed information.

Using strikeout a lot so I hope I won't add to the confusion.

2014-04-22 (#)
Combining a websdr with fldigi gives me great views of PSK31 traffic, but this evening I also tried receiving APRS, with the audio routed from the java plugin to fldigi using padsp multimon. This crashes a lot, but disabling the scope helps, padsp multimon -s SCOPE. But the 2 meter signal from HF/VHF/UHF WebSDR at the Maxwell Foundation in Eindhoven was too noisy and had interference from other signals to decode anything. I have listened to 2 meter stations via this websdr just fine so I think this could work when the current interference is gone.

2014-04-18 (#)
Another ISS pass and I was already aware the orbit may be changing a bit since gpredict and hamsatdroid were disagreeing on the time of the pass.

And indeed, the ISS pass started around the later time from gpredict. I heard the AFSK data clearly. The signal from the ISS is strong enough that I can receive it most of the pass with the arrow antenna just pointing directly up. Maybe I can use this to record an entire pass and decode the AFSK data.

I guess celestrak.com (used by gpredict by default) is better up to date than amsat.org (first option in hamsatdroid). Since hamsatdroid can also use the celestrak.com data I switched to this source. The fun part is that satellite names aren't the same. 'SO-50' according to amsat is 'SAUDISAT 1C (SO-50)' according to celestrak.

2014-04-18 (#)
A bit of searching later found the right incantation to make gnuplot adjust color based on a third value (signal level in my case). It isn't very complicated:
set size square
set angles degrees
set polar
set grid polar 30
set xtics axis 0,30
set ytics axis 0,30
unset border
unset param
set xrange[-90:90]
set yrange[-90:90]
set rrange[0:360]
set trange[0:90]

set title "GPS satellite tracks"
set xlabel "Azimuth"
set ylabel "Elevation"
set terminal png size 600,600
set output "gpsazelsig.png"
plot "gpsazelsig.dat" using 1:2:3 palette notitle
But the resulting plot isn't very helpful for my original question: in which direction radio signals are obstructed. There are some obstructions in the Southwest, but they are comparable to what is in the Northeast.

2014-04-16 (#)
I want to get an idea of the 'radio shadow' around our backyard to get a better idea of the minimum elevation to receive from and transmit to amateur radio satellites. Since there still is a gps receiver on the roof of the shed and the earlier ntp experiments aren't running at the moment I decided to stop ntp and log the $GPGSV GPS satellites in view messages from the gps unit. My idea is that the radio signals from GPS satellites get obstructed by houses at least the same as UHF signals, so a GPS satellite reception plot will be interesting. Something like the VisualGPS plot I made at a previous house with a different GPS unit. Note that the plotted satellite tracks are way outside the plotted contour which I recall was a nice approximation of the view during the test.

Now to get this data plotted with gnuplot in a polar plot. I found out the orientation of $GPGSV messages (true north is 0 degrees, east is 90 degrees, south is 180 degrees, west is 270 degrees) does not match the azimuth range available by the polar plot in gnuplot (0 degrees is to the right, 90 degrees is up, 180 degrees is to the left). And the horizon is 0 in $GPGSV messages and maximum range in gnuplot. Time for some perl massaging of the $GPGSV lines to gnuplot orientation:
#!/usr/bin/perl -w

use strict;

while (<>){
    chomp;
    if (/^\$GPGSV,\d+,\d+,\d+,([\d,]+)\*[0-9A-Z]{2}$/){
        my @fields=split(/,/,$1);
        while ($#fields>0){
            my $sv=shift @fields;
            my $elevation=shift @fields;
            my $azimuth=shift @fields;
            my $signal=shift @fields;
            if ($signal){
                warn sprintf "SV %d elevation %d azimuth %d signal %d\n",$sv,$elevation,$azimuth,$signal;
                $azimuth=90-$azimuth;
                if ($azimuth<0) {
                    $azimuth+=360;
                }
                printf "%3d %3d\n",$azimuth,90-$elevation;
            }                   
        }               
    }           
}       
And indeed we have data:
SV 33 elevation 27 azimuth 205 signal 38
SV 29 elevation 83 azimuth 100 signal 44
SV 31 elevation 48 azimuth 227 signal 45
SV 21 elevation 47 azimuth 169 signal 44
SV 25 elevation 29 azimuth 122 signal 41
And azimuth/elevation in a file that gnuplot can handle:
245  63
  8   9
283  40
226  44
326  64
The azimuth/elevation data, modified for gnuplot. And the next step is a gnuplot plotscript:
set size square
set angles degrees
set polar
set grid polar 30
set xtics 30
unset border
unset param
set xrange[-90:90]
set yrange[-90:90]
set rrange[0:360]
set trange[0:90]

set title "GPS satellite tracks"
set xlabel "Azimuth"
set ylabel "Elevation"
set terminal png size 600,600
set output "gpsazel.png"
plot "gpsazel.dat" using 1:2 notitle
Which indeed gives a nice plot of some recent data.

Main conclusion: this sirf star II gps is 'too good' for this application. For example, one measurement:
SV 5 elevation 4 azimuth 86 signal 37
Satellite 5 seen at an elevation of 4 degrees above the horizon in easterly direction with a signal/noise ratio of 37 dB. There are high buildings (4 floors) in the easterly direction so I think I'm seeing the gps receiver being way too good at this.

The good part is that I'm not the first one to think of this: GPS Skyline: A Panorama in 1.6GHz Microwave-"Light" which suggests I need to find the right cutoff value for my type of GPS unit.

2014-04-14 (#)
This evening had no high Saudisat SO-50 passes at friendly times but it did have a nice overhead ISS pass around 22:15 localtime. I noticed the AFSK signal later than I expected according to the azimuth/elevation calculated by gpredict and reception stayed fine when gpredict said elevation had dropped to about 1 degree above the Eastern horizon. There are high buildings in this direction, so I guess the orbit has changed a bit compared to the latest data I had. AFSK reception was fine, maybe I should try to record the outgoing audio somehow so I can decode it later.

I have programmed the ISS region 2 voice frequency from the ISS Frequencies - ISS Fan Club into my radio so I could hear voice communications or even try to make a contact when the ISS is overhead. Reading the Recorded ISS radio contacts - ISS Fan Club page shows some radio amateurs have been trying that for 2 years before succeeding so it won't happen easily.

2014-04-07 (#)
Trying to hear and work the SO-50 satellite as PD4KH portable has one downside: certain types of weather don't agree. The first pass this evening was really nice, straight overhead. But closer to earth there were serious rainclouds overhead causing a downpour so I opted to skip that one. A pass later in the evening started dry so I went outside. During the pass it started to rain again a bit so I had to dry my laptop after I was done! It was a low West-North pass and those are harder to follow from our house. But I did hear some voices and I think I understood at least one callsign, but checking the live oscar satellite status page shows no callsign matching what I think I heard.

Update 2014-04-08: Another nicely timed West-North pass, without rain this time. I heard some interference, including someone who decided that whistling at the satellite was a good idea. Probably taken directly from the "what NOT to do with amateur satellites" handbook.

The pages maintained by Mike Rupprecht DK3WN about amateur satellites have some realaudio samples of good and bad use of the amateur satellites: SaudiSat 41, 42, 50 - Mike Rupprecht - Amateurfunk Betrieb über FM Satelliten - Mike Rupprecht - Amateurfunk I don't agree with the quoted statement by LA2QAA in the last article of being proud of never using the "easy" FM amateur satellites. A more positive approach is needed in my opinion.

One "mental" switch I have a problem with: with the squelch completely open I hear noise when I'm either not listening to the satellite or the satellite is not in use by another amateur. With listening to "earth" FM repeaters at normal squelch settings I'm used to noise meaning that someone is trying to use the repeater but failing. This means pressing the transmit button when hearing noise on the satellite is a bit "unnatural" to me.

2014-04-02 (#)
I ordered and received an Arrow Antenna: hand held portable dual band 2m/70cm Yagi satellite antenna. It came in last Saturday afternoon. And now I constantly look at the amateur satellite trackers on my laptop and tablet to see when passes come up for satellites that I can receive in FM. First receiving: I don't want to be the proverbial alligator on the amateur satellites (all mouth and no ears).

Our house being in a quite built-up area means when the elevation doesn't get above around 20 degrees there will not be a lot of chance to receive the satellite.

What I am looking for is satellites I can receive (and work) with the FM handheld transceiver. I focus on Saudisat-1c, the International Space Station and Oscar-11. Oscar-11 is an older amateur satellite but I could be lucky with receiving telemetry in AFSK format.

This evening had an 'easy' pass of Saudisat-1c usually known as SO-50, straight over my head. The obvious upside is: no buildings in the way. The less obvious upside: a shorter distance to the satellite, less signall loss. With headphones to hear the incoming audio in both ears I was able to hear callsigns. I'm not sure I heard a complete QSO. What I learned was that the moment the reception is clearest (shortest radio path) is also the moment of the biggest Doppler shift in receive frequency.

I also had a reasonably easy pass Saturday evening. I reported both passes to the OSCAR Satellite Status page by KD5QGR.

Update 2014-04-04: This evening I heard the AFSK1200 noises from an ISS pass! Amazing how fast the enormous mass of the International Space Station flies across the horizon. In 6 minutes it passed from azimuth 218⁰ (southwest) to 80⁰ (north of east).

Items before 2014-04-02
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