News items for tag electronics - Koos van den Hout

2017-05-22 I bought a SARK100 antenna analyzer 5 days ago
My sark100 antenna analyzer
My sark100 antenna analyzer
In september 2016 I ordered a balun and a linked dipole kit from sotabeams with the idea to make a lightweight dipole antenna for outdoor use. But there is one very important ingredient to making a dipole: you need an antenna analyzer to get the dimensions right to have optimal reception and transmission into a resonant antenna.

I could borrow the antenna analyzer from the club just like I did for measuring my 2m/70cm portable coax antenna but after reading about the (cheap) SARK100 antenna analyzer I decided to buy one myself. One good review I found is It finally arrived! My SARK100 from China. This analyzer seems to be a serious case of an 'open source' design being picked up by the Chinese electronics manufacturers and sold in high numbers. I bought one for a reasonable price at an aliexpress seller that had good reviews and orders before.

It arrived today and the first tests look really good. First I measured my dummy load (to get an idea of how it was doing as an analyzer) and after that the 10m/20m/40m endfed antenna that was hanging outside anyway for the EU PSK DX Contest 2017 that I participated in. This antenna isn't perfect (as visible in the picture) but it does the job.

So now I have to find the time to design a linked dipole as I want it and to go outside and make it all happen.

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2017-05-14 Upgrading the home network to shielded/foiled cable (s/ftp) 1 week ago
I was looking at on-line offers of shielded/foiled network cable and found out it's not that expensive anymore. And with the 'keystone' connectors it looks like it's not that complicated to make neat and very well shielded connections.

But it's always a good plan to check the local electronics hobby shop. We still have one in the center of Utrecht: radio centrum where they had 1 meter and 2 meter patchcables for a very nice price (competitive with on-line shops) right up for grabs. So the first set of short cables that are always in use for gigabit are now s/ftp category 6 cables. I hope this improves radio reception.

I still think I will order longer cable and keystone connectors and holders for the longer cables.

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2017-04-29 Using kalibrate-rtl to calibrate the rtl-sdr frequency 4 weeks ago
In my project to receive amateur satellites with the rtl-sdr I noticed the sdr itself has quite a 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 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.
        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.

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2017-04-14 Going full duplex with amateur satellites, part 4 : amplifier built into the case 1 month 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

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2017-04-12 Trying the mini-whip as reception antenna 1 month 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.

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2017-03-29 Going full duplex with amateur satellites, part 3 : metal cases 1 month ago
I was looking for a metal case to put the low(ish) noise amplifier in and maybe the RTL-SDR. The RTL-SDR should also be shielded from the amplifier and from the computer as both RTL-SDR and computer cause their own signals.

The first cheap source of metal cases I could think of was old cigar boxes. Altoid tins are not available here. So I asked someone who I know who smokes cigars who had a number of old metal cigar boxes. Next step, finding the way to get the right holes in the boxes for the SMA and BNC connectors, and for the USB connection to the computer. Ideal would be to lend / find a punch for those holes.

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2017-03-26 Going full-duplex with amateur satellites, part 1: introduction and I bought the hardware 2 months ago
I still want to get active on amateur satellites again, but the main reason is that the amount of work per contact is a lot more than for example in a digimode contest. But I still want to make those 'special' contacts, especially when the amount of local radio noise on HF is bothering me.

One of the most important improvements in making contacts on amateur satellites is working 'full duplex', meaning receiving signals while transmitting. The expensive way to reach that goal is buying a second amateur radio capable of receiving in FM and SSB modes in the 2 meter and 70 centimeter amateur bands and having computer aided tuning so gpredict can control the receiving frequency.

The less expensive way to reach that goal is using software defined radio. The good news is that Gqrx SDR can be controlled by other software which as the page shows is intended for remote control by Gpredict. All I needed now was reception hardware. Since the first RTL-SDR device I bought is always in use for receiving ADS-B signals from airplanes I decided to buy another cheap one to get me started. So it was on the shopping list for a recent visit to a hamfest.

At the hamfest I found a RTL-SDR stick with mcx connector and an mcx to bnc cable. But the same guy also sold cheap low(ish) noise amplifiers with SMA connectors and a 9V battery connector for power. So at one of the booths selling cable assemblies I found an mcx to male sma cable and a female sma to bnc cable, and a male to male sma cable.

The plan is to put this all together in some metal case to shield the lna from the outside world. Maybe also shield the amplifier from the RTL-SDR stick so it won't pick up any extra noise.

Should this work it would be possible to think of an upgrade with better SDR hardware and/or a pre-amplifier at the antenna side.
RTL-SDR stick and BNC cable - KvdHout on FlickrRTL-SDR stick and BNC cable
LNA and extra cables - KvdHout on FlickrLNA and extra cables
Read the rest of Going full-duplex with amateur satellites, part 1: introduction and I bought the hardware

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2017-03-17 Soldeerstift vervangen van soldeerstation 2 months ago
Een tijd geleden heb ik een soldeerstation gekocht van Velleman, een Soldeerstation keramisch 48W VTSSC30. Die gebruik ik ook regelmatig naar alle tevredenheid.

Tot recent het steeds meer moeite ging kosten. De conclusie was uiteindelijk dat de stift aan het verslijten is, wat heel logisch is. Ik was even bang dat ik niet zomaar een losse stift kon krijgen, maar na dat ik deze gekocht had via Conrad blijkt die ook via Radio Centrum verkrijgbaar: Soldeerpunt 1,6mm Velleman VTSSC10/20/30/40 soldeerstation.

Stift vervangen, probleem opgelost. Grappig is dat volgens de Radio Centrum website de originele meegeleverde stift 1.6mm is terwijl ik in het overzicht van Velleman soldeerstiften bij Radio Centrum zie dat ik de 2mm versie had. Misschien moet ik nog eens een 0.8mm punt er bij kopen voor klein soldeerwerk.

Update: Radio Centrum zit dicht bij de winkel waar ik koffie haal, dus ik kwam er langs en heb gelijk een 0.8mm punt aangeschaft. Gelukkig hebben we nog een echte electronica winkel in Utrecht.

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2016-11-27 Finished the homebrewed QYT KT-8900 programming cable 6 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

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2016-11-24 Creating a programming cable for a QYT KT-8900 with some soldering 6 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 but I have no channels with receive CTCSS.

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2016-11-17 De zoektocht naar niet-storende LED lampen 6 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 6 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 8 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 8 months ago
Draadloze microfoon, bron 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 8 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/ 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 8 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 9 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) -

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

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