Last year in October, I have been active from a QTH in Gran Canaria with the same portable setup as I used in Iceland. The position on the island (locator IL27DT) and the QSO partners are shown in the two images below.
The following table summarizes the results. I am quite surprised how good this little setup performs. As can be seen from the number of QSOs, I ended operating mostly on the 10m band due to the good conditions.
When booking a trip to Iceland, the idea emerged to become QRV on some HF bands in digital modes using my (tr)uSDX. As I did not want to take excessive luggage with me, the precondition was that the additional equipment has to be as small as possible. After some investigation and experiments, the following setup was used.
Hardware Setup
The TRX was of course decided beforehand to be the (tr)uSDX with the high band option (20m and up) for the antenna not to be too large. It is powered by a powerbank capable of providing 12V via USB PD and the necessary trigger device.
(tr)uSDX with 3D-printed housing combined with the Raspberry Pi and cabling.
The computer was also a simple decision: A Raspberry Pi 4 with 4GB of RAM with a small 3d-printed housing. It is powered from a different power bank directly with 5V via USB-C.
The hardest decision was the antenna, as antennas on the HF bands are typically large. In the end however, the decision was the obvious choice to use a linked end-fed antenna. It can be tuned by opening the respective connections. The center of the antenna is elevated with a telescopic fishing rod to about 4m height. Longer rods would of course be better but have a packed length that goes beyond the size of my suitcase. The connection between the TRX and the antenna is made using roughly 5m of Airborne 5 cable.
The full setup with powerbanks, Raspberry Pi, (tr)uSDX, soundcard and USB PD trigger board.
For display, I used my Android tablet that connected to the Raspberry Pi using VNC. Additionally, the tablet’s internal GPS receiver was used to provide the time reference for WSJT-X via an SNTP app. The necessary WiFi connection was established over an access point opened by the Raspberry Pi. This enables maximum flexibility and comfort by putting the equipment outside and operating the setup from the inside.
Preparation and Exercise
After everything was put together, I used a weekend trip to test the equipment under realistic conditions. The first test was conducted at the Illerursprung (Locator JN57dk). After calling CQ as DC6GF/P, I was a bit overwhelmed by the response and also by only being able to use the touch display. So sorry to all who received weird messages from me at that day! In the end six QSOs from a not so optimal location within a valley were a big success for me.
Tourist information board at the Illerursprung.
The next test was operating from nearby the Fellhorn summit (Locator JN57ci). There I struggled with difficult lighting conditions and usability issues of the VNC client together with the desktop environment that would switch to a different desktop when touching in the wrong place. Returning to the right desktop was unequally difficult. In the end I achieved only two QSOs.
DC6GF waiting for the next QSO near the Fellhorn summit.
The last test with a refined end-fed antenna was conducted directly from my garden. As everything worked well, this setup was the final one and could be packed for the trip to Iceland.
On the Air as TF/DC6GF
On Iceland, operation was planned from four different locations where we did not stay at a hotel but at cottages where there was some space outside to place the antenna. The locators I operated from were HP94sg (7th June 2023), IP25sg (11th and 12th June), IP05am (17th June), and HP85pa (18th and 19th June).
View from the QTH in IP25.The setup at IP05.The QTH in HP85 with the antenna mast mounted to the wooden fence of the cottage.Evening at the HP85 QTH.
The number of QSOs varied strongly between 6 QSOs on two days from HP85, and 75 QSOs on two days from IP25. Highlights were some QSOs to Japan and Brazil. ODX was PY5EJ in GG54 with a distance of 10418km. Impressive how far 4W of RF power can go! Overall I achieved 107 QSOs (43 on 20m, 37 on 17m, and 27 on 15m) with 105 individuals from 27 DXCC entities. I put some overview graphs below. Please excuse the poor quality and German localization but I think the main information is visible.
QSOs from HP94QSOs from IP25QSOs from IP05QSOs from HP85
Conclusion
Operating from not so usual locations proved to be a lot of fun and a great experience. So whenever the occasion comes up again, I will definitely try again.
Some time ago I ordered a (tr)uSDX kit and assembled it according to the video instructions by Manuel (DL2MAN). The assembly itself went quite smooth. However, the tuning took some time and although there were no real surprises, some information for success was hidden in the depth of the discussion groups. So I thought summarizing them here might be helpful.
Tuning the Filters
Tuning the filters is already explained quite well in the video tutorial. For reference, here are the actual filter curves I achieved after tuning. I indicated the passband with a wide blue line at 0dB and the first harmonic with a wide red line at -40dB.
For 20m, I was not able to put the notch high enough in frequency to reach the desired stop band with the number of turns given in the instructions, so I removed one turn. After that I had to struggle to move the notch down in frequency to fit the stop band. In the end I succeeded but as one can see from the graph, I could have left the coil as it was because the additional suppression is marginal.
Tuning Rshunt
After tuning the filters, I wanted to tune the efficiency of the amplifier but could not reach more than about 68%. After some digging through the forum, I found the solution in the quite low Rshunt value setting in my firmware. It was set to 17, where a setting of 19 is more reasonable for my setup. After that, I was able to tune the efficiency in the desired region above 75%.
The procedure to determine the correct value for Rshunt is quite straight forward:
Measure the receive power consumption PRx of your (tr)uSDX. I reduced the output volume to the point where the current did not decrease any more for lower volumes.
Measure the transmit power consumption PTX and the RF output power PRF.
Compute the efficiency by eff = PRF/(PTX-PRX).
Tune Rshunt to match the computed efficiencies over the different bands to the displayed values.
I took measurements over all bands and was able to match the measured and the displayed efficiency quite well but not perfectly which cannot be expected from the small device.
Tuning the Efficiency
After setting the correct Rshunt value, tuning the efficiency for the lower bandy went as described in the video tutorial. For the 20m band however, the output power was quite low and the efficiency also not very good. So I removed one turn from the coil and was also able to achieve about 4.5 to 5W of RF output power at a decent efficiency.
Using it with WSJT-X on a Raspberry Pi
In order to successfully use CAT control on Linux, you have to execute the following command to successfully access the interface:
stty -F /dev/ttyUSB0 raw -echo -echoe -echoctl -hupcl -echoke 38400
The command has to be executed before accessing the interface but it worked as well while WSJT-X was already running. Before the command, the CAT control failed, after the command, everything worked as expected.
Summary
Thanks to DL2MAN and PE1NNZ for this great device!
Important Links
The original posts from the forum, where I found the information given above:
Yesterday a new tool arrived that was still missing for my radio station: A CW paddle made by Filipe, CT1ILT. Now I have no more excuse to not start practicing CW. I wonder how long I need to be ready for my first CW QSO.
Since winter 2022, I started to bring DC6GF on air again from my new QTH. After a long pause from amateur radio activity, I decided to become QRV on shortwave for the fist time.
Equipment
Radio
Tuner
USB sound card and PTT adapter.
The TRX I use is a IC-706MK2G that I used exclusively on 144MHz until now. The tuner matches the capabilities of the TRX regarding power and the digital interface was improvised from existing components, packaged in a 3D-printed housing. It contains the sound card and the RS-232 interface for PTT control, both attached to one USB port using a small hub. The antenna I use currently is a GPM-1500 but a better one is already available. However, as some adaptions are required, it will be installed after some other projects are done. The cable between the tuner and the antenna is a 7mm type from Messi & Paoloni.
Achievements until now
Since my first QSO mid of march 2022, the QSO count in FT8 and FT4 is nearly 1000 and I reached 106 DXCC countries including New Zealand which is about as far as it can get from my QTH. 89 of them are confirmed via LoTW. I also set-up an E-QSL account, however, I did not manage to upload my log.
Lessons Learned
For most experienced operators, these findings may be obvious but from my short time of activity, I learned the following:
Propagation predictions are about as accurate as the weather forecast. You have to be on the band to see how the propagation actually is.
Especially on weekends, QRM is the most important limiting factor to reach the DX station. Although the band may seem empty, there are tons of other stations near you you do not hear (or see in the waterfall).
As a result from the previous point, FT4 sometimes is the better choice for low power stations compared to FT8 just because the FT4 frequencies are not as crowded as the FT8 ones.
Split operation is an important capability for successful FTx operation. If you answer on the same frequency, chances are very high you are not alone and neither of you is heard. If you answer on a different frequency, the chances of being copied are much higher.
The (my?) IC-706MK2G changes its output power significantly over the NF frequency band. Highest output power can be achieved between 1500Hz and 2500Hz.
Things to do…
The following things are on my short term agenda:
QSL cards are ordered. As soon as they arrive, I will try to have the last 11 missing countries confirmed to apply for the Digital DXCC.
Find out how to configure E-QSL to accept my log from CQRLOG.
Learn CW. A paddle by CT1ILT is already on its way.
