Automatic antenna tuners are expensive, manual antenna tuners are slow. So it has been a long time I dreamed of making my own automatic system.
As this year I was following a raspberry pi class and we needed to make our own project I decided to finally try to make this automatic tuner.
Summary: – Forward and reflected power are measured with a Boxa Swr bidirectional coupler combined with an ADC – SWR is calculated in the raspberry pi and displayed on an LCD – When SWR is to high an alarm is sounded in CW – after pushing a button the capacitors and the coil in the tuner are reset to 0. For the capacitors I use 2 servos, for the coil I use a stepper motor. All mechanical connections are made using 3d-printed parts. The reference point for the stepper motor is made using an infrared port. – next is the tuning operation: — the ‘transmitter’ capacitor is sweeped over it’s full range and swr is measured every degree. Then this capacitor is returned to it’s best position — next idem for the ‘antenna’ capacitor — sweeping operation is repeated for maximum 4 times, if the SWR is below 1,5:1 then tuning is stopped. If SWR is above this limit then the coil is moved to the next setting and the sweeping is repeated – built in securities: — all alarms on the LCD and in morse code — alarm when SWR is to high — alarm when tx-power is to high for tuning — coil/stepper can not be switched when there is rf-power
Remarks: – no tuners have been harmed in any way for this operation! – Was the raspberry pi the best choice for this? This could probably have been done using some microcontroller instead but the class I followed wat not arduino or esp 32 🙂
Due to the lowering in price and the low GBP vs EUR exchange rate I finally decided to offer myself a SunSDR2pro. I know, the SunSDR are not produced in the UK but the price in the UK was about 15% lower than in the rest of the EU.
These are my findings trying to start the transceiver:
23+ years in ham radio for now and I feel a complete beginner! This is so completely different from the ‘knobbed’ transceivers I have used in all those years.
first things first, installing the software. I downloaded version 1.1.2 from the Expert Electronics site.
Next came trying to connect the transceiver to the pc. It should be possible to run the transceiver over the LAN/WAN but for simplicity I chose to connect the network cable directly between the transceiver and the pc.
the user manual says to configure the pc network card so it gets its IP number via DHCP. Well… this does NOT work for me. Of course Google is your best friend and I found this Youtube movie made by ML&S explaining how to set up the pc to the correct fixed IP-address.
After watching this movie I could let the software connect to the transceiver. Finally the spectrum and waterfall screens came to life. TIP: set your PC to a fixed IP adress in the 192.168.50.*** range.
after some fiddling and attaching a small test wire to the antenna connector I could listen to the different broadcast stations in WFM. You have to start somewhere 🙂
Now was the time to connect a microphone to the rig… but alas, a complete flea market in the attick but no microphone that can be connected directly. It was getting pretty late at night so I gave up and went to bed.
still no microphone in stock so time to try something else: can I get the CAT interface to work with my DXlab logging software? No luck, DXlab’s commander gives ‘COM4 already in use’. So for some reason the SunSDR is blocking some of my COM ports. A quick search on Google and on the SunSDR forum does not yield a solution so I started a new thread on this forum.
I really need Commander to have my remote antenna switch choose the right antenna. Without Commander running all my coax cables are connected to ground.
Vassil RN6LHF the developer of the SunSDR has replied to my question. I should use the latest version of the software. And indeed v1.1.3 RC7 solves my COM-port problem. TIP: always use the latest version of the software!
So time to connect a real antenna to the rig and listen around on HF.
A quick trip to the shop today yielded me a computer headset I could connect to the MIC1 port of the SunSDR.
New problem found: the jumper cable from mini UHF to PL259 works OK but the adapter plugs I purchased separately can not be tightened correctly on the transceivers connectors. I guess I’ll have to send them back to the supplier.
After connecting my LDG AT-200ProII it’s time to try a qso and, eureka, I manage to work a belgian station on holiday in EA on 40m.
To get some decent power out in SSB using the computer headset I had to set the mic gain to maximum and compression pretty high. But that should probably work better once I get the correct interface cable to connect my Heil Pro-Set 4 to the SunSDR.
The transceiver gets pretty hot even in RX. The internal thermometer indicates 46°C at this moment. According to the user manual this should be ok. I prefer to have my electronics running cooler. So lets see if I can find a suitable ventilator in my junkbox.
Last weekend we made our yearly ‘pilgrimage’ to the Friedrichshafen HAM RADIO in Germany. For the last few years there were always 4 of us, Andy ON7TS, Luc ON7KZ, Jan ON4KB and me. As Jan had to cancel at the last minute there were only 3 of us this year. (Jan, we missed you!)
For me it was the 18th year in a row and I can say I have seen a steady decline of the rally over the years. Every year there are less vendors at the flea market and at the ‘new’ market. I guess there are a few reasons for this: the prices for the rental of the fairgrounds and the competition of the internet sales.
This year there were only 2 halls of flea market with the second hall filled about 60%, last year it was 3 halls with the third hall filled about 50%. The following well known companies did not come back to the fair this year: Conrad, Classic International, Kabel Kusch etc. The room these companies took last year now seemed to be taken over by companies selling toy helicopters, handbags and even *very* cheap riflescopes…
Last weekend Jan ON4KB, Luc ON7KZ, Andy ON7TS and me went to the hamradio in Friedrichshafen (16th time in a row for me). The fair was a little disappointing, no real new things to see this time (apart from a 44m €28000 tower from Japan…). Moreover it seems there will soon only be a couple of companies left in Germany to sell hamradio gear.
The most positive thing is however that this time (for the first time in many years) we received a warm welcome at the UBA booth. Could it be this depends on the people being at the booth at the moment we arrived?
Next year the fair will be from june 23 till 26. Probably we’ll be there again.
The most important thing is however that, still not being on the air from my own shack (or from the car I bought last year), the virus hit me again during the trip. I’ll try to get my antenna’s up on the tower (HF) and probably the mobile rig in the car (VHF/UHF) in a few weeks!
If you haven’t made any arrangements to go to The Ham Radio in Friedrichshafen yet, the time is coming! Dates this year are June 22 to 24!
This year I’ll be there again for the fourteenth (yes 14) year in a row! This year we will be travelling with Jan ON4KB, Tim ON5HC, Erno ON6RK and Luc ON7KZ.