News items for tag electronics - Koos van den Hout

2016-11-27 Finished the homebrewed QYT KT-8900 programming cable 2 months ago
Homebrewed QYT KT-8900 programming cable, CC-BY-SA
Homebrewed QYT KT-8900 programming cable
I finished the homebrewed QYT KT-8900 programming cable by using tiewraps to clamp the two pieces of cable together and using heatshring tube to cover the wires and pack it all together.

More about Creating the homebrewed QYT KT-8900 programming cable and instructions for building a 3-pin programming cable for QYT/BTech/others and the KT-8900 FAQ at Mikklor.com.

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2016-11-24 Creating a programming cable for a QYT KT-8900 with some soldering 2 months ago
QYT KT-8900 radio with homebrewed interface cable, CC-BY-SA
QYT KT-8900 radio with homebrewed interface cable, CC-BY-SA
I bought a cheap 2m/70cm mobile/base radio, a QYT KT-8900 which has the special feature of being very small but still able of putting out 25 Watt on the 2 meter VHF band and 20 Watt on the 70 centimeter UHF band.

The display looks a lot like my Wouxun KG-UVD1P, complete with battery status indicator which is not much use when the radio has a constant 13.8V feed. The menus are quite similar, so this is probably not a coincidence.

I bought it via aliexpress and it got shipped at a reasonable speed to my house. In the original listing was mention of a programming cable, but it showed up without one. I asked the seller about this and directly a baofeng programming cable was shipped to me.

But, the QYT KT-8900 has a different programming interface, just a 3.5 millimeter plug with ground, rx and tx data. So I found a very good resource for chinese radios which has the answers: 3 PIN Programming Cable for a BTech, QYT, etc Mobile which has the right pinout. I just cut the Baofeng cable to get at the gnd, rx and tx wires.

Next I had to wait for a cable with the right 3.5mm connector to show up. The connector in the back is sunk into the case and the 3.5mm connectors I had in the junkbox did not fit. But a broken PC speaker set wanted to donate a cable with 3.5mm connectors that were slim enough. Next trying the result with chirp radio programming software under Linux. And suddenly I could copy a list of channels I had and upload it to the radio in 5 minutes, which is a lot faster than manual programming where getting more than one channel programmed in correctly under 5 minutes is hard, see for example Programming Repeaters into the QYT KT8900 Mini Dual Band Mobile Radio Review - AF5DN - Youtube.

At the moment the cable looks very experimental. Now it has been tested I will use tiewraps and heatshrink tube to make it sturdier and make it look a lot better.

As a radio it's ok, but not ideal. I was testing with meetnetwerk baretta - hobbyscoop and the antenna on the roof for 2 meter and 70 centimeter and noticed I had pulsing audio of the output frequency of PI2NOS on the Baretta frequency. Pulsing audio is a known problem in this radio, see KT8900 FAQ at miklor.com but I have no channels with receive CTCSS.

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2016-11-17 De zoektocht naar niet-storende LED lampen 3 months ago
In onze keuken hadden we 5 spotjes met halogeen lampjes achter een dimmer om zo op het werkblad goed licht te hebben. Toen kort na elkaar 2 van die lampjes stukgingen was de conclusie dat er binnenkort wel meer stuk zouden gaan en dat dit een mooi moment was om aan LED lampen te beginnen.

Ondertussen zijn er dimbare LED lampen die ook halogeen spotjes kunnen vervangen. Alleen was de gedachte in mijn achterhoofd natuurlijk of ze dat ook kunnen zonder radiostoring op te leveren.

In de Electron, het verenigingsblad van de Veron heeft recent een stukje gestaan van een radio amateur die na eerdere storingen geen storing meer had na het vervangen van goedkope LED lampen door Philips LED lampen. Ik heb het er dus op gewaagd en 5 philips LED lampen gekocht, type LED Spot 8718696483824 van Philips, GU10 fitting, 4W (vervangt 35W) dimbaar, warm wit.

Het licht is inderdaad serieus anders dan van halogeen lampen, dus ze alle 5 tegelijk vervangen was een goed idee. En de storing is minimaal, pas als ik heel dichtbij kom met een kortegolfontvanger krijg ik een storing binnen die net zo goed via de electriciteitsdraden kan komen.

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2016-11-06 One source of interference found: osram halotronic htm 70 transformers 3 months ago
Recently I noticed one source of radio interference on 40 meter was the lighting in our bathroom. There are two sets of lights in the bathroom, one with a switch which causes heavy interference and one with a dimmer.

The lights in the bathroom are all 12volt based and the transformers are in a weird corner above the bathroom, but accessible for me. So I found out the "osram halotronic htm 70" electronic transformers (the specs read like switching power supplies) are quite audible on the 40 meter band. The other two a lot less than the switched one. Time to complain to Osram and/or replace them. The Osram Halotronic HTM 70 specifications at Osram say the maximum length of the wire after the transformer is 2 meters to keep RF interference below acceptible levels, I am not completely sure the complete wires until the lamps are shorter than that, so it may also be an installation fault.

Searching for "osram halotronic htm 70 interference" finds this interesting bit: Installation LED Leuchten in Spanndecke with:
Aber auch wenn "nur" der Meßwagen der Bundesnetzagentur vorbeikommt und Deine Konstruktion kostenpflichtig stillegt, kommt wenig Freude auf.
The German Bundesnetzagentur is a lot stricter in finding and stopping interference to amateur bands.

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2016-09-09 First part of the lightweight outdoor radio antenna: the balun 5 months ago
Sotabeams balun After building and testing the Sotabeams dummy load I had time to work some more on the ordered parts. The main part of the order at Sotabeams was parts for outdoor antenna building: an antenna centre and 1:1 balun and linked dipole portable HF antenna kit.

The HF antenna kit does include parts for a simple centerpiece/balun but I decided to get a separate balun that should make these things easier and/or sturdier.

The balun build was doable, but soldering coax on the connectors gave a bit of a problem as the solder did not want to flow on those connectors very well. Maybe clean them next time or even sand them a little to make that easier.

Next part will be the rest of the HF antenna for which I will need an antenna analyzer and time outdoors in the daylight.
Read the rest of First part of the lightweight outdoor radio antenna: the balun

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2016-09-06 Je draadloze microfoon is prima af te luisteren 5 months ago
Draadloze microfoon, bron http://www.publicdomainpictures.net/view-image.php?image=2905 Vandaag was ik op een plek waar regelmatig draadloze microfoons gebruikt worden bij presentaties en/of grote vergaderingen. Er was recent een probleem waarbij geluid van andere gebruikers van het gebouw te horen was op de geluidsinstallatie, en dat bleek na wat zoeken ontvangst van de "verkeerde" microfoons te zijn.

Er ging toen ook een lichtje op dat draadloze microfoons prima af te luisteren zijn, wat in deze omgeving niet altijd een prettig idee is. Met een scanner die wide-fm en een groot bereik aan UHF frequenties aan kan is het prima mogelijk naar analoge "Program Management and Special Events" (PMSE) microfoons te luisteren.

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2016-09-04 De slimme meter uitlezen 5 months ago
Slimme meter uitlezen De slimme meter die meer dan een maand geleden ons huis in kwam wordt nu constant uitgelezen en de resulterende gegevens worden opgeslagen in rrdtool databases van het electriciteits- en gas gebruik.

Uitlezen van een seriele poort vanuit Perl bleek niet makkelijk stabiel te krijgen te zijn. Uiteindelijk heb ik maar een oplossing gekozen/geleend van iemand anders: een stuk python wat cu aanroept: P1/P1-python-cu.py at master · sanderjo/P1. Dit script zou nog iets robuuster zijn als het de CRC controleert, maar dat is dan een wens voor een toekomstige versie.

Vervolgens sla ik de output van dit script op in /var/run/telemetry/smartmeteroutput. De keuze voor /var/run is omdat ik niet elke vijf minuten op de SD kaart van de raspberry wil schrijven. Ik heb dus ook /etc/rc.local aangepast om een /var/run/telemetry met als eigenaar user telemetry te maken, er worden daar meer meetgegevens neergezet voor verdere verwerking in statistieken. Het telemetry concept wat ik gebruik is het verzamelen in ASCII leesbare vorm van meetgegevens op systemen waarna deze opgehaald kunnen worden door een verzamelaar die ze gaat importeren in rrdtool databases (of andere verzamelingen). Omdat de verbinding tussen het te monitoren systeem en de verzamelaar als onbetrouwbaar gezien wordt (sommige systemen waarvan ik meetgegevens verzamel zitten achter een hikkende wifi verbinding) worden de meetgegevens lokaal opgeslagen met een tijdsaanduiding in de bestandsnaam en worden ze in rrdtool geimporteerd met deze tijdsaanduiding.

Het script wat de meetgegevens van de slimme meter verwerkt moet er tegen kunnen dat er soms velden ontbreken. Ik heb er voor gekozen uiteindelijk de dag- en nacht tellerstanden afgenomen en teruggeleverd (meetwaardes 1.8.1, 1.8.2, 2.8.1 en 2.8.2 in de Dutch smart meter standard) als 'verplicht' te tellen en de overige meetwaardes als 'optioneel'.

Uiteindelijk komen er dan mooie grafieken uit. De conclusie die ik eerder trok dat uit energie meetwaarden per kwartier prima af te leiden is wat bewoners doen is nog steeds valide. Uit grafieken over langere termijn is ook keurig af te zien wanneer we op vakantie waren.

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2016-09-01 I built a RF dummy load 5 months ago
I ordered some parts for building a lightweight outdoor radio antenna. But while ordering I had a look around and noticed the BOXA-LOAD 50 Ohm RF Dummy Load - Sotabeams, a kit for building a dummy load. So I ordered one in kit form, with enclosure.

Boxa load dummy load A dummy load is for testing radio circuits, it gives the radio the ideally matching load since radio transmitters ideally expect a 50 ohm resistive load. A dummy load does not convert the electric energy into radio waves, it just converts the electric energy into heat in the resistors.

I currently have an RF power meter on loan which I could use to test the dummy load so the dummy load was the first project to build and test.

Boxa load dummy load Building was no problem with the very clear instructions given by Sotabeams. And after building it I tested it and found it perfect as designed with no reflected power. The maximum power input is 20 Watt which it can handle for 1 minute and will need to cool down again for 10 minutes.

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2016-08-23 Over op de slimme meter 6 months ago
Ondanks mijn privacy-bezwaren tegen de slimme meter heb ik er voor gekozen deze wel te accepteren toen netbeheerder Stedin kwam met de melding dat ze er een wilde plaatsen.

De plaatsing duurde een stuk langer dan verwacht omdat er ook iets aan de ophanging van de gasmeter moest veranderen en de dag/nachtstroom schakelaar de monteurs nog in verwarring bracht. Maar toen was er eindelijk een slimme meter die kan helpen het energiegebruik veel nauwkeuriger in beeld te brengen.

Ik heb hierin natuurlijk wel mijn principes gevolgd en heb zo snel mogelijk een slimme meter kabel om de P1 poort uit te lezen besteld zodat ik de meetgegevens aan de binnenkant kan verzamelen, op mijn eigen server via een Raspberry Pi in de meterkast. Ten opzichte van de eerdere metingen met behulp van de YouLess is de vooruitgang in ieder geval dat ik nu ook de gasmeter kan uitlezen en de stroom per fase kan meten. Slimme meters zijn altijd dubbeltarief (dag en nachtstroom) en meten apart afgenomen en teruggeleverde energie.

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2014-08-17 (#) 2 years ago
Some more work on the digimode interface for the FT-857 radio: setting it up on a real circuit board, to be built into a plastic casing. This time I heard a strange ticking sound when recording audio from PI3UTR but again it seems this clicking sound is a local problem normally filtered out from the audio path of the radio. When I picked up PI3UTR on the Wouxun KG-UVD1P radio I heard the same ticking noise. New respect for the audio filtering in the FT-857, but things like this make me question the digimode interface every time I'm testing it.
Radio data interface
Radio data interface, The interface in its case
The digimode interface is now finished, but now I need to test it with real radio signals. I don't have HF capabilities yet, and I did find PSK31 frequencies for 2m (144.610 MHz) and 70cm (432.610 MHz) but nobody answered a PSK31 CQ on those bands.

Update 2013-08-18: The whole setup together in a somewhat blurry smartphone picture:
Radio working
Radio working, PC with fldigi controlling the FT-857 radio sending psk31
And fldigi doesn't mind when I control this remote over the network.

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2014-08-16 (#) 2 years ago
Friday evening I had time to work on the 'digimode' interface for the FT-857 radio. I set up a breadboard with the audio transformers and started making cables from the transformers to the USB audio interface. Then I added the cable to the radio on the other side. All of the earlier mentioned interfaces had resistors to regulate the signal level so I started with 12K resistors between the radio and the transformer in the radio to computer audio path. This gave me a weak signal when recording the result with audacity on the computer so I switched to a 6k8 resistor which improved audio but it still wasn't great. So the resistor was replaced by a simple wire which gave me good audio when recording from the PA00NEWS transmission on the PI3UTR repeater. I did notice some low hum while recording, but I realized that was just the CTCSS tone on the repeater output. Normally this tone is filtered out when hearing the audio through the speaker of a radio.
Testing radio data interface, by Koos van den Hout on flickr
Testing radio data interface, The data interface for the new radio on breadboard for testing
Testing radio data interface with USB audio interface
Testing radio data interface with USB audio interface, The data interface for the new radio linked to the USB audio interface

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2014-08-14 (#) 2 years ago
The cable and parts for a 'digimode' interface for the new FT-857 radio are on their way. Such an interface will allow me to get audio from the radio directly into a computer and audio from the computer directly into the radio. This will allow digital radio modes such as PSK31, RTTY or AFSK. These modes allow bits (text, or databits) to be exchanged over radio. The simplest interface like FT-817 AFSK cable couples these directly but based on the advice of fellow radio amateurs I will use audio transformers to decouple the computer and radio and keep stray radio signals out of my computer and any interference from the computer out of my radio and I decided to use a cheap USB audio interface. What I will build is based on Digital VOX sound card interface but without the 'VOX' part and iPhone / Baofeng interface (schema) and El Cheapo AFSK (e.g. RTTY) USB interface (for FT-8×7) - remco.org.

Update: Parts have arrived, time to build something on a development board first.

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2014-08-02 (#) 2 years ago
Yesterday evening I tried to make some contacts during an SO-50 amateur satellite pass and twice the CT-62 USB interface to the radio crashed, with messages like:
Aug  1 20:33:15 machiavelli kernel: [48075.216289] hub 6-0:1.0: port 2 disabled by hub (EMI?), re-enabling...
Aug  1 20:34:45 machiavelli kernel: [48165.984146] hub 6-0:1.0: port 2 disabled by hub (EMI?), re-enabling...
I had to unplug and replug the cable every time to get /dev/ttyUSB0 available to rigctld again.

A few hours later the proverbial light above my head went on: EMI means electromagnetic interference, maybe transmitting quite close to the laptop is the problem.

So this evening I created the same setup and tried transmitting so I could attack the problem and see if some ferrite cores would help. The problem decided to not return, even with the CAT cable and the antenna cable laying parallel. I'm still going to use at least one ferrite core to try to keep the USB interface from crashing.

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2014-07-27 First try with the Yaesu FT-857 radio, gpredict and the SO-50 satellite 2 years ago
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.

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2014-06-02 A cheap pre-amplifier for receiving amateur satellites 2 years ago
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.

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2014-02-12 (#) 3 years ago
I decided to try aprsdroid on my android device. First and easiest should be to select the option AFSK via Speaker/Mic and I hoped it would work when the speaker and microphone of the portable radio are near the microphone and speaker of the android device. No luck: no transmitted APRS packet was found via aprs.fi call PD4KH and no incoming packet was decoded. I guess there was too much distortion and interference. I looked at the aprsdroid settings a lot since I noticed outgoing audio seems to be fixed at the highest volume, which can also be an issue.

In the video Get Started with APRS for only $30! - youtube.com video a simple cable from the android device to the radio is used, so it can be done.

Going for a solution like an Mobilinkd is more expensive, but maybe interesting in the long run when I want to do more with APRS. For now, an interim solution would be nice: building the right cable to get audio from the radio to the android device and back. I found the specs for such a cable at iPhone / Baofeng interface bouw en schema - PA4TW which can be adjusted for the android device and Wouxun. And PA4TW has used it for APRS in Aprs via porto en iPhone - PA4TW.

Old analog telephone equipment can be a source of 600 ohm 1:1 transformers, so I guess some old equipment will have to donate those when I go for such a cable.

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2013-09-23 (#) 3 years ago
De frequentie-upconverter die ik als kit had aangeschaft en in elkaar gezet is af genoeg voor de eerste testen. Dus de metalen behuizing dichtgemaakt met een elastiekje en eens testen.

Radio 10 am 828 kHz in SDRsharp Om het wat makkelijker te maken heb ik eens windows geboot en de rtl-sdr quick start guide gevolgd om snel signalen te kunnen decoderen en te zoeken naar de juiste frequenties. SDRsharp heeft een nette user-interface en je bent erg snel aan de gang. Er is vergelijkbare software voor Linux waar ik zeker naar wil kijken: Gqrx sdr.

De tip van van Dijken voor het testen van de HF upconvertor was om sterke AM omroepzenders te proberen. Een uitgebogen paperclip was niet zo'n goede AM antenne, maar ongeveer een meter draad uit de junkbox werkte beter. De eerste zender die lukte was Radio Maria op 675 kHz. De offset bleek ongeveer 5 kHz te zijn, wat niet slecht is voor een rtl-sdr en/of een HF converter.

Dus: beide kits werken! Even een goed moment voor mijn zelfvertrouwen in electronica in elkaar zetten: ik kan het nog en het werkt.

Daarna wat andere frequenties gezocht, onder andere kwam ik de audioloop tegen op 828 kHz AM dat Radio 10 (Gold) er mee stopt op AM en overgaat op alleen FM frequenties en DAB+.

Het mooiste is als straks de actieve HF antenne (mini-whip) ergens buiten gemonteerd is zodat deze beter ontvangt en de converter en rtl-sdr dan binnen (in de schuur) hangen. Als ik de beschrijvingen van rtl_tcp goed lees kan met een recente versie van deze software de hele aansturing (frequentiekeuze) ook remote over het netwerk.
Listen to audio attachment:
MP3 media: 2013-09-23 aankondiging radio10 op 828 kHz AM (rightclick, select save-as to download)

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2013-08-24 (#) 3 years ago
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
HF active antenna kit PCB printed side.
HF active antenna kit PCB component side
HF active antenna kit PCB component 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 upconvertor kit PCB printed side
HF upconvertor kit PCB printed side.
HF upconvertor kit component side
HF upconvertor kit component 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.

And yes, it's more difficult than first thought to take usable pictures of printed circuit boards.

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2013-07-28 (#) 3 years ago
I took some pictures of the PA0FBK coax antenna in full action.

PA0FBK Coax antenna: Hanging in our yard for testing. Works great.

Connected to transciever: PA0FBK coax antenna connected to Wouxun KG-UVD1P transciever

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2013-06-19 (#) 3 years ago
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.

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