News archive April 2017 - Koos van den Hout

Archive by year: 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | 2019 | 2020

2017-04-29 Using kalibrate-rtl to calibrate the rtl-sdr frequency 3 years ago
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: 36428.54

Second 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 ppm
And 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.

Tags: , , ,
2017-04-29 Going full duplex with amateur satellites, part 8 : No real contact yet 3 years 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:
MP3 media: 20170429 1858Z FOX-1a pass recorded by PE4KH in JO22NC (rightclick, select save-as to download)

Tags: , , ,
2017-04-25 Quest Management Inc (QSMG) pump-and-dump spam 3 years ago
It has been a while since I wrote about pump-and-dump spam (scam) but it's never been completely dead. It does seem there has been some action against it and spamfilters got better at recognizing it.

Today's winner I see is Q like in Quality, S like in Straight, M like Mary and G like Gold. The spammer is sure to never use QSMG directly to avoid spam filters.

The funny part is that a google search for QSMG directly brings me to Pump and dump spam: Quest Management Inc (QSMG) stock - Dynamoo's blog with a complete write-up of the multiple spamruns the last week trying to make some money from this type of fraud.

Tags: , ,
2017-04-24 Somewhat less HF interference by moving the antenna away 3 years ago
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.

Tags: , ,
2017-04-23 Going full duplex with amateur satellites, part 7 : Recording downlink audio 3 years 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.

Tags: , , ,
2017-04-23 New band in amateur radio: 60 meters (5 MHz) 3 years ago
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.

Tags: ,
2017-04-22 Going full duplex with amateur satellites, part 6 : First succes in reception 3 years 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.

Tags: , ,
2017-04-19 En nu is de MTU wel naar 1500 van de VDSL PPPoE sessie 3 years ago
Recent postte 'Coen' in xs4all.adsl een stappenplan om onder Ubuntu 12.04 de MTU van de PPP verbinding naar 1500 bytes te krijgen. Alle lof dus naar Coen, want met zijn stappenplan is het me wel gelukt en is alles nu doorgaand MTU 1500, wat minder issues zou moeten geven.
Na een gezellig avondje stoeien is het gelukt om dit met terugwerkende
kracht voor Ubuntu 12.04 op te lossen met een nieuwe pppd en pppoe versie.

Voor wie durft en bovendien wat Linux ervaring heeft hier de te volgen
stappen:

Nieuwe pppd builden:

mkdir ppp
cd ppp
apt-get source ppp
cd ppp-2.4.5/
wget -O debian/patches/zz_pppoe1500
"http://git.ozlabs.org/?p=ppp.git;a=patch;h=fd1dcdf758418f040da3ed801ab001b5e46854e7"
dch -i
dpkg-buildpackage -us -uc

[[ppp en ppp-dev installeren]]

Nieuwe pppoe builden:

mkdir pppoe
cd pppoe
wget -4
http://archive.ubuntu.com/ubuntu/pool/universe/r/rp-pppoe/rp-pppoe_3.11-0ubuntu1.dsc
wget
http://archive.ubuntu.com/ubuntu/pool/universe/r/rp-pppoe/rp-pppoe_3.11.orig.tar.gz
wget
http://archive.ubuntu.com/ubuntu/pool/universe/r/rp-pppoe/rp-pppoe_3.11-0ubuntu1.debian.tar.xz
tar -xzvf rp-pppoe_3.11.orig.tar.gz
cd rp-pppoe-3.11/
tar -xf ../rp-pppoe_3.11-0ubuntu1.debian.tar.xz
dch -i
dpkg-buildpackage -us -uc

[[pppoe installeren]]

Mtu op 1500 zetten: klaar!
Vanaf een losse client leek toch nog MTU 1492 gebruikt te worden, dus heb ik /etc/radvd.conf aangepast om expliciet MTU 1500 mee te geven:
interface eth0.3
{  
   AdvSendAdvert on;
   AdvLinkMTU 1500;
En dan de verdere opties. En dan werkt het inderdaad:
koos@kernighan:~$ tracepath6 ping.xs4all.nl
 1?: [LOCALHOST]                        0.018ms pmtu 1500
 1:  eth0-3.idefix.net                                     1.983ms 
 1:  eth0-3.idefix.net                                     1.858ms 
 2:  lo0.dr12.d12.xs4all.net                              17.910ms 
 3:  0.ae22.xr3.3d12.xs4all.net                           17.957ms 
 4:  no reply

Tags: , , ,
2017-04-14 Going full duplex with amateur satellites, part 5 : first test of the amplifier with RTL-SDR 3 years 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.

Tags: , , ,
2017-04-14 Going full duplex with amateur satellites, part 4 : amplifier built into the case 3 years 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.

Battery added for amplifier in metal case - KvdHout on FlickrBattery added for amplifier in metal case

Tags: , , , ,
2017-04-12 Trying the mini-whip as reception antenna 3 years ago
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.

Tags: , , ,
2017-04-10 Amateur radio callsign lookup on Android without needing Internet access 3 years ago
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!

Tags: , , ,
2017-04-06 Results from a powerfailure 3 years ago
Earlier today there was a local powerfailure. I noticed it while being connected remotely to my server at home, it stopped responding and stayed off-line for a while. I checked the website of the electricity distribution network and it showed a local powerfailure.

Initially my reaction was a bit of interest in how low the radio noise levels would be when I could try the radio at home. By the time I got home power was back on so I never found out.

Some systems at home had to be started by hand, but eventually everything was up and running again, with new kernels booted. Everything came up fine including PPPoE to the outside world.

Later in the evening I noticed the old weatherstation in the shed which measures the temperature and humidity inside the shed seemed inoperational. Checking that weatherstation eventually led to a diagnoses that the 12 volt powersupply for that weatherstation had failed. It was only delivering 7.2 volt. To disconnect that weatherstation for diagnosis I completely shut down the shed computer ritchie. After that it did not come up again. Power came up and the harddisk started spinning but nothing happened after that.

So I also took that computer in for diagnosis. Connected to a keyboard and monitor everything came up fine. Disconnected from the monitor nothing came up.

Slowly it dawned on me that this might be related to an issue which I had read on the PC Engines Alix.1d page :
BIOS update

* beta various updates (release MFGPT timers)
* beta fix VGA DDC issue (boot hang)
Which seemed to be the problem which suddenly started acting up for me which it never did before. But the BIOS clock was also reset so I guess the whole setup was erased and I just did not notice because the default settings were good enough to boot anyway and ntpd sets the clock soon after boot. A simple solution would be a BIOS upgrade.

But preparing a CF card to boot freedos seemed a long way to flash the bios so I tried it via the Heavy Duty Boot pxeboot environment which booted FreeDOS nicely on the alix.1c but it rebooted as soon as I started SB.COM. I guess sb.com searches for bios images on C:\ and the FreeDOS floppy image is A:\

In the end I searched for a workaround and found mention in PC hangs up when no monitor attached - Ubuntu bug #243257 of a wire between pins 12 and 7 in the VGA connector. A piece of wire was bent and inserted into the vga connector and now the weatherstation computer ritchie boots up again.

Next plan is to do the BIOS upgrade via flashrom: In searching for information about the Alix 1.c bios upgrade I'd like to do I came across mention of flashrom.

Tags: , , ,
2017-04-03 I participated in the EA RTTY contest 2017 3 years ago
This weekend after the antenna installation was done I had some time to participate in the EA RTTY contest 2017. I only participated on Sunday afternoon on the 20 meter band so I entered in the SO20 DX category.

The end result was 35 QSO's (contacts). Less than the results I had in the EA RTTY contest in 2016 but I had less time and energy available.
Read the rest of I participated in the EA RTTY contest 2017

Tags: , ,
2017-04-02 (It took a while, and a lot of help from a fellow radio amateur who has climbing gear. Now on my roof...) 3 years ago
Google+Koos van den Hout : It took a while, and a lot of help from a fellow radio amateur who has climbing gear. Now on my roof: a nice 2m/70cm antenna. Diamond X-30N, painted grey to make it stand out less against the average grey sky.
2017-04-02 Antenna for 2m/70cm up on the dormer roof 3 years ago
Antenna mounted on dormer roof
Antenna for 2m/70cm, Diamond X-30N, mounted on roof of dormer
Parts for mounting the Diamond X-30N which I bought in October on the roof were collected in the months since October and it was finally clear enough weather for a fellow radio amateur with lots more climbing experience and the right gear to climb on top of our dormer and install it.

There are rubber granulate pads on the roof to avoid damage, a metal frame sold as a mount for satellite dishes to which the antenna is mounted, 4 concrete tiles in the mount to weigh it down on the roof. The coax enters the house alongside a chimney.

After the work on the roof it was good to drink a beer to celebrate and afterwards I routed the cable further to my shack.

The first fast test was calling CQ on a local 2 meter frequency and someone from my radio club answered immediately.

The second big test was participating in a radio roundtable held on Sunday evening. This went fine, net control at a distance of somewhat over 30 kilometers gave me a 55 report (audio readability 5 and signal level 5). So the antenna is clearly doing what it is supposed to do. It's also nice to see the base noise level on the 2 meter band is near zero.

Tags: , ,


, reachable as koos+website@idefix.net. PGP encrypted e-mail preferred.

PGP key 5BA9 368B E6F3 34E4 local copy PGP key 5BA9 368B E6F3 34E4 via keyservers pgp key statistics for 0x5BA9368BE6F334E4 Koos van den Hout
RSS
Other webprojects: Camp Wireless, wireless Internet access at campsites, The Virtual Bookcase, book reviews
This page generated by $Id: morenews.cgi,v 1.46 2019/10/20 15:42:02 koos Exp $ in 0.030011 seconds.