Some soldering work on the HF convertor kit for the rtl-sdr stick today. I noticed I haven't mentioned the progress of this electronics building work yet.
HF active antenna kit PCB printed side.The main board of the HF active antenna kit (a mini-whip, based on the excellent work by Roelof PA0RDT has done) is finished. Soldering the antenna-plate to the amplifier has failed sofar: soldering two bigger areas of copper together with a soldering iron designed for electronics work fails. And a small inductor between antenna plate and amplifier might be a good idea too reading the design, it would improve reception above 20 MHz where I want to have a listen to the 10 meter amateur band too (28.000 MHz - 29.700 MHz). There is also an indicator led included which I will solder in place once the print is tested and ready to be mounted in a housing (PVC pipe seems to be quite popular for this). I plan to mount the led in such a way the housing doesn't have to be opened to check the status.
HF active antenna kit PCB component side.
HF upconvertor kit PCB printed side.Next soldering project is the HF upconvertor kit. I'm working on it at the moment, finding time for soldering and working very carefully. Not careful enough: the kit contains one length of wire for winding 4 coils and I found out at the fourth coil that I took a bit too much wire for the first three ones. Time to visit the electronics shop again, to get wire for winding coils. I checked the collection of parts at the radio club but there was no winding coil wire of 0.8mm. I ordered the kits from Van Dijken Electronica, a Dutch shop in electronics, quite popular with amateur radio hobbyists.
HF upconvertor kit component side.
And yes, it's more difficult than first thought to take usable pictures of printed circuit boards.
- Bouwpakketje actieve antenne 10 KHz - 20 MHz(max 30 MHz) Kit mini-whip antenna
- Bouwpakket HF converter voor de rtl sdr sticks DC - 65 MHz Kit HF convertor
I took some pictures of the PA0FBK coax antenna in full action.
Ik heb er nog geen metingen aan kunnen doen maar de zelfgebouwde PA0FBK 2m/70cm portable coax antenne doet het in ieder geval beter op 70cm dan de standaard spriet van mijn Wouxun KG-UVD1P portofoon. De antenne is duidelijk gevoelig voor van alles in de omgeving: ophangen in de buurt van actieve LCD schermen leverde ook al heel slechte resultaten op, en een eerdere test hangend aan een verfroller-stok die van metaal bleek was ook al geen succes. Het toekomstig gebruik is dus duidelijk aan een lijntje de boom in of op een andere manier vrij ophangen ver van allerlei storingsbronnen. En nog iets van tijdens het bouwen: voldoende licht op de werkplek is nuttig. Ik had een keer 's avonds aan het op lengte maken en strippen van coax gewerkt en toen ik het resultaat goed bij daglicht zag wist ik dat ik al wat dingen over ging doen.
Misschien een interresant project om een 2m/70cm antenne te bouwen die makkelijk uit het raam kan hangen: PA0FBK's 2/70 portabele coax antenne. Ik kwam onder andere een foto met positieve beschrijving tegen van PD1JMB. 2m and 70cm Dualband Antenna according to PA0FBK - DL8KDL (engelstalig) geeft nog meer informatie en heeft zelfs serieus er aan gerekend. Ik ben meestal niet zo goed in mechanische dingen, maar dit ziet er uitvoerbaar uit, zeker als ik wat versteviging aan de connector maak. Ik ga ook zeker een ophangtouw er aan maken.
Unlicensed mobile radio (walkie-talkie like use) in Europe is possible with PMR446 devices which operate on frequencies between 446.0 MHz and 446.1 MHz. PMR446 was introduced in 1998. The original PMR446 standard gives 8 channels where FM analog audio is used. Using CTCSS or DCS codes extra options to distinguish users of PMR446 are available. But these are more 'calling certain users' options than real privacy, a radio scanner tuned to the PMR446 frequencies can receive all users. Analog PMR446 radios are quite cheap nowadays: when I browse conrad I can find a simple set of 2 PMR 446 radios for Eur 19.99 Audioline portofoon PMR-15 (Conrad Electronic). A begin of privacy comes at a price: the lowest price for a (single) PMR446 radio with 'scrambler' and a description which suggests extra software is needed to program that scrambler is Eur 135 Midland PMR portofoon set G14 (Conrad Electronic) or Stabo PMR portofoon Freetalk com (Conrad Electronic) or Eur 205 for the PMR-zendontvanger Kenwood TK-3301E (Conrad Electronic) which is advertised as 'professional' which is visible in the price. Diving into a manual shows that the scrambler has an 'on' or 'off' setting, which makes the given privacy limited to "can't be heard on a standard scanner" but a determined listener can determine the scrambling system and listen in. A newer development is Digital private mobile radio 446 (DPMR 446) which uses frequencies between 446.1 MHz and 446.2 MHz, not overlapping with analog PMR446. There are 16 channels with FSK (frequency shift keying) in a 6.25 kHz wide channel (half that of analog PMR). I can find exactly one device supporting digital PMR446 on sale: the ICOM IC-F4029SDR professional digital license free transciever and the price I see is 180 UK pound which is also a 'professional' price. The 'digital' part of DPMR could allow for real encryption, but for as far as I can find it is not implemented, and searching for details about this I find: Draft amended PMR446 ERC_DEC(98)25 which states:a)that it is not recommended that applications requiring encrypted speech should be used with PMR 446 radio equipment;It would seem (to me) that adding strong encryption on digital PMR446 wouldn't be too hard, but the standard doesn't have space for it (at the moment). There are options for group codes (just like ctcss or dcs codes in analog PMR446) but it is possible for a (specialized) scanner to ignore all those. ETSI TS 102 490 technical specification: Peer-to-Peer Digital Private Mobile Radio using FDMA with a channel spacing of 6,25 kHz with e.r.p. of up to 500 mW.
In the weekend I had some more time to play with rtl-sdr, the cheap software defined radio using rtl2832u based receivers. I tested with coupling rtl-sdr and gnuradio companion using a fifo, so I can do experiments 'realtime' and not with (huge) capturefiles. This works, which enabled me to listen to FM radio. I'm still looking what the minimum and maximum frequencies of the Fitipower FC0013 tuner are, but my guess is that the range might also be near 64 to 1700 MHz. The good news is also that there are the first signs of a gnuradio block for this receiver on the site above, which means I can use it directly in gnuradio and retune it on the fly.
The Noxon DAB USB stick I got as a cheap DAB/DAB+ experimenting device has hidden powers. A big part of the 'cheap' is because this device leaves all of the work to software. If I understand the discussions about the Noxon correctly, there are drivers to receive dvb-t signals with the same stick. Most development for the linux driver seems to be on the dvb-t side too. I came across a webpage which puts this all in a new light: The whole device turns out to be a wideband tuner and an analog to digital convertor. Software has to do the rest. And now someone has written that software. Some clever thinking and discussion started by Antti Palosaari turned into rtl-sdr, a software defined radio using the RTL2832U chip. Together with my other thoughts about software defined radio where I thought about receiving and decoding D-STAR ham radio signals with for example a funcube dongle this means I already have a software defined radio. Time to capture some I/Q data and learn about gnuradio. The rtl-sdr software has already been used to receive Tetra signals (frequencies UHF 380 MHz .. 476 MHz) and GMR signals (satellite phone, L-band 1600 MHz). So I guess 70cm D-STAR should not be a problem. Update 2012-03-21:Played with this, and I managed to receive an FM radio station and decode the stereo audio from it using the grc (gnuradio companion) rtl2832 to fm scripts mentioned here. Hearing a bit of radio received and decoded by hardware which absolutely wasn't sold to me with that capability is fun. Everything gnuradio is all new to me so most of the time I have no idea what I'm looking at and the noise in the Noxon stick is causing issues as usual. Update 2012-03-22: Played some more, and added the plot. And I heard audio from some of the stronger stations. But I still have serious noise issues, even when moving the usb stick away from the computer with a long usb extension cable. As you can see in the plot there is not much difference between the noise level and a strong local station. The wideband FM receiver module available in gnuradio companion couldn't even decode the signal at 93.8 MHz (Slam!FM Noordbrabant) in the captured data.
Simple FFT (spectrum analysis) of data coming from the NOXON dab usb stick. Works in the VHF FM broadcast band, I can see various signals and verify their frequencies. With stronger stations I can use the wideband FM decoder in gnuradio and get audio. Click for full screen capture from gnuradio FFT.
This evening I hooked up the radio scanner to the UHF TV antenna to see if using that might get me one of those '35 cm pirates' which should be active in the 856 - 862 MHz and 865 - 868 MHz ranges which is UHF TV channel 69/70. So the preamp should work.It took a bit of searching through the junkbox to find parts for a cable to get from the output of the UHF TV antenna (through the power inserter) which is a Belling-Lee connector (as shown in the picture) to the input of the scanner which is a BNC connector. My guess is these transmitters would be active on a Sunday evening. But, the only thing I heard in wide FM mode was a wireless headset.
IEC-169-2 connector, picture by Colin from Wikimedia commons (CC-BY-SA license)
Fun with rechargeable batteries: two GP NiMh 2300 mAh batteries. One spent months in my MP3 player, sometimes playing stuff. The other was sitting in a drawer. When the battery in my MP3 player stopped I wanted to change to the other one, but that one was empty enough too that the MP3 player would not boot. So self-discharge takes more out of the batteries than my MP3 listening I guess.
Ik heb van het weekend eens voor de aardigheid een proefexamen radio amateur novice gedaan. Zonder enige studie vooraf een score van 27 van de 40, om het te halen is een score van 29 nodig. Blijkbaar is er genoeg van mijn MTS electronica blijven hangen. Op specifieke radio techniek en de regels moet ik nog wel het nodige studeren als ik een licentie zou willen halen.
Seen today: #twatch Open Hardware Networked LCD Screen - Slashdot Hardware. Quite tempting! Affordable (USD 45) and it can do cool stuff. By default it displays real-time topic trends from Twitter on an LCD. But with a bit of playing with LCDproc it can also show system statistics, RSS feeds, mail notifications, and more such as ... METARs.
Hope someone of the LCDproc development team picks this up soon: Although the page assumes there is a way to redirect a serial port to a network stream in linux this is a bit harder.
Finally I counted a few light pulses with the one-wire counter. No big circuit with the Velleman MK120R kit but just a photodiode and a resistor hooked up to the counter module. I got the idea from looking at the schematics for the Hobby Boards 1-Wire Lightning Detector. The counting circuit is a phototransistor (in an optocoupler) and a resistor. With a bit of tweaking on the resistor I eventually got the counting circuit to count 2 light flashes from a flashlight. With some more tweaking of the resistor value I think I could count red flashes from the electricity meter.
I also installed the lightning detector under the roof. But it is too close to the wiring of the house I think: sofar all counts are related to me being in the attic and turning on the light. In a 'real' setup I think it needs to be away from the house. Something to keep in mind for the project sundial weather station.
The parts came in but I still can't make the MK120 receiver work as detector for LED light. From looking at the schematics carefully I think the receiver is tuned to the sender. What I want is quite simple: just detect on/off state and convert that to connecting or not connecting +5V and a counter input. Maybe some variant of the Infrared remote control extender circuit can do the work. The LM324 opamp in the Velleman design can be fed with +5V so maybe it is simple to go from a small current (light on a photodiode) to +5V. But this means it is not going to be an 'out of te box' working circuit. Oh well, my electronics knowledge is slowly coming back from way deep...
No local source for a photodiode which is sensitive to visible light. Time to shop on-line for a photodiode which is sensitive to red light, which will be listed as 650 nm, is directional and can deal with the amount of red light from the electricity meter LED. Reading specsheets for photodiodes is also new to me. I found a webpage with lots of explanations about LEDs and calculations. But, ordering a component on-line which costs less than a euro is a bit silly, with probably a lot more costs in shipping and handling. Conrad just charges extra for too small orders.
I finished soldering the Velleman MK120 receiver I will use for detecting the lightpulses from the electricity meter for the one wire electricity measuring project. I think that is the first soldering of a circuit board since somewhere around my electronics education which finished in 1989 and I did it right! The circuit works as designed: it needs a strong infrared signal to not send out a signal via led and buzzer. I did not solder the buzzer because eventually the signal needs to go into the 1-wire counter and buzzing sounds from the cupboard under the stairs might get irritating fast. After checking whether the circuit board worked as designed I swapped the inputs on the comparator like in the 1-wire electricity monitoring design by Jon00. I did not cut traces and solder wires, I used the IC holder to set up 2 crossed wires to the pins of the IC.
I decided to start monitoring the electricity usage in the house. Using 1-wire sounds the most logical to me as I am already using that to monitor temperatures. I found a description by Jon00 using a MK120 Velleman Kit which sounds quite compatible with my level of electronics knowledge and my budget. So I went to the local electronics shop, Radio Centrum and bought the Velleman MK120. I asked about a 1-wire counter but they don't sell 1-wire equipment (yet?). Well, a counter is something I can order from Hobby boards. Probably together with some other 1-wire stuff to make it an interesting order.
Small update on the GSM as GPS project after playing for a while with a phone and a datacable.
It's that time of year that you can play with my christmas lights again. [ link dead ]