2018-04-16 Building my own balun, part 5: First tests of the result 4 days ago
big common mode choke in the mix makes the combination show better SWR curves (still not what I want) but with the frequency with the best SWR still too low. This suggests (to me) two things: I need more windings on the ferrite core and less extra wire length from the core to the connectors. Time for a rebuild.Read the rest of Building my own balun, part 5: First tests of the result
2018-04-04 Building my own balun, part 3: First work on the case 2 weeks ago
The first work on the balun case was placing the SO239 socket. This included drilling a hole in the case of the right size and at the right position. Figuring out where to put it was mostly influenced by the fact that the ferrite core has to be placed inside the case and I wanted the SO239 socket, the ferrite core and the output terminals not all jammed together. So the SO239 socket was not going to be in the center. For this my new caliper was a useful tool and I measured the inside size and the wanted location of the socket. And I figured out I could drill a 16mm hole and the SO239 socket would fit inside while leaving enough room for the mounting flange. Holes were drilled and things worked out fine, so the SO239 socket is now mounted. After checking the future location I realized I will have to mount the balun with the SO239 socket facing downwards because the antenna cable is quite heavy. This has to be taken into account with the next steps. Other parts of this project:
2018-04-04 Building my own balun, part 2: measuring the 'old' balun 2 weeks ago
tested the SARK100 antenna analyzer from Linux. The 10 meter band dipole probably moved a bit or something else changed.Read the rest of Building my own balun, part 2: measuring the 'old' balun
2018-03-19 Building my own balun, part 1: idea and parts needed 1 month ago
I was considering hanging a dipole antenna outside. This would need a balun and I realized that I have a good outdoor-capable balun hanging in the attic. It's a Fritzel 1005 1:1 current balun which is good up to 300 watts power. I am not going to use 300 watts under the roof close to other equipment and the balun there does not need to be rain proof. So the idea was born to build a smaller balun for use under the roof and have the Fritzel balun available for outdoor use. And last Saturday was a hamfest (radio onderdelenmarkt Rosmalen) so I had an idea of things I wanted for this project. Parts needed for a current balun:Read the rest of Building my own balun, part 1: idea and parts needed
The various collections of electronics parts only missed the SO239 socket and a case. Those were found at the hamfest for a nice price. The choice of design is a current balun or a voltage balun. I had to do some searching to find a good comparison between the two, and DX engineering has one at Baluns: Choosing the Correct Balun - DX Engineering which has:
- A ferrite core with the right specifications
- Wire with enamel coating
- An SO239 socket
- Terminals for connecting the dipole wires
- A caseCurrent baluns, rather than voltage baluns, should be used whenever possible. Current baluns provide better balance and often have lower loss. Current baluns, especially 1:1 ratio baluns, tolerate load impedance and balance variations much better than voltage baluns.Some searches found good explanations of building your own baluns, I found a very clear explanation at VK6YSF project page. So I'm building a current balun, and when it's finished enough to test it I will measure how it is doing. I have the tools like the SARK100 antenna analyzer that I can control from Linux and a dummy load so I can check everything.
2017-09-08 I built a common mode choke 7 months ago
After the problems with the laptop controlling the radio when I participated in the SCC RTTY contest 2017 I decided to build a common mode choke. This is a filter that should keep the radio frequency signals at the side of the antenna. Based on the simple design with a piece of PVC pipe with 8 windings of Aircell-7 coax I still had lying around. The PVC pipe was donated by a fellow radio amateur who had it in his junkbox. I drew a pencil line on the pipe, decided where to drill holes for the coax cable (using a 16 millimeter drill) and where to drill holes for tiewraps to hold the coax. After drilling the holes it was a matter of winding the coax correctly, mounting the cable with tiewraps and soldering the connectors to the cable. In the first testing the filter worked fine, completely stopping the interference to the keyboard of my "shack computer" and even reducing incoming noise on the 10 meter band.
2017-09-08 I finished the linked dipole and tested it 7 months ago
I realized today I never wrote an article about finishing the linked dipole kit I bought a year ago and started making my own dipole from Linked dipole portable HF antenna kit. I used the SARK100 antenna analyzer to test it on each band: first 15 meter, after that 20 meter and I finished with 40 meter. I did 15 and 20 meter on two separate meetings at my radio club and 40 meter in a park near our home. As mentioned by others you need to take the time to tune this antenna to the right length. Each band took me about 2 hours which turned out to be what I could do in one evening at the radio club. The proof is always the first contact and that happened when I brought it on our holiday to Germany and Austria. The tree behind our tent at the campsite in Austria was not high enough to support the 40 meter length of the antenna but I just set it up for 20 meters and that worked fine. It's remarkable how forgiving this antenna is after tuning. I just set up something resembling an inverted V and my radio found it near perfect, very little reading on the SWR meter. First completed contact was with a radio amateur at the same campsite so that wasn't very hard. I did hear a Dutch radio amateur using a serious amplifier to try to reach me but lacking output power he did not hear my answer. Anyway, project officially finished.
2017-07-03 Reboots of the FT-857 radio 9 months ago
The last week I had a problem with the FT-857 radio rebooting when I started transmitting in digital radio modes (PSK31 or JT65). The reboot showed as the radio giving the standard beep and the display and backlight switching off and on. Searching for clues suggested that some form of radio frequency interference would probably be the source. So I wondered what I changed recently around the radio and remembered I changed something in the power distribution to have connectors available for powering my SARK100 antenna analyzer with a 12 volt battery. Reseating all those power connectors and fixing some wires seems to have stopped the problem.
2017-05-22 I bought a SARK100 antenna analyzer 11 months ago
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, build it and measure / adjust it until it does what I want. It's a good thing I can easily calculate linked dipoles at Various tools for SOTA purposes. My plan is to build a 15-20-40 meter band dipole. The selection of bands is because outdoors I will use less digital modes and 40 meters is the longest size for a dipole that is usable to set up. The angle of the dipole and therefore the height of the centerpoint also has an influence on the antenna. But I don't know how high the tree will be, so I will have to make a guess.
My sark100 antenna analyzer
2017-05-14 Upgrading the home network to shielded/foiled cable (s/ftp) 11 months 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.
2017-04-29 Using kalibrate-rtl to calibrate the rtl-sdr frequency 11 months 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: 36428.54Second 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 ppmAnd 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.
2017-04-14 Going full duplex with amateur satellites, part 4 : amplifier built into the case 1 year 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.
2017-04-12 Trying the mini-whip as reception antenna 1 year 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.
2017-03-29 Going full duplex with amateur satellites, part 3 : metal cases 1 year 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.
2017-03-26 Going full-duplex with amateur satellites, part 1: introduction and I bought the hardware 1 year 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.Read the rest of Going full-duplex with amateur satellites, part 1: introduction and I bought the hardware
2017-03-17 Soldeerstift vervangen van soldeerstation 1 year 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.
2016-11-27 Finished the homebrewed QYT KT-8900 programming cable 1 year ago
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.
Homebrewed QYT KT-8900 programming cable
2016-11-24 Creating a programming cable for a QYT KT-8900 with some soldering 1 year ago
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.
QYT KT-8900 radio with homebrewed interface cable, CC-BY-SA
2016-11-17 De zoektocht naar niet-storende LED lampen 1 year 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.
2016-11-06 One source of interference found: osram halotronic htm 70 transformers 1 year 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.
2016-09-09 First part of the lightweight outdoor radio antenna: the balun 1 year agoOlder news items for tag electronics ⇒
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