I passed my novice radio amateur exam in March 2013 and I registered the
PD4KH (pappa delta four kilo hotel!).
I passed my full radio amateur exam in March 2016 and I registered the callsign
PE4KH (pappa echo four kilo hotel!).
PE4KH on qrz.com
I am usually located around maidenhead locator: JO22NC
My amateur club Veron A08 call PI4UTR has a really good clubstation with multiple nice antennas. In an environment with a lot less interference than I have at home. Last Tuesday I used the clubstation to make a few connections and got some nice calls in the log, adding two new countries. VP8LP on the Falkland Islands and CE2ML in Chili.
The HF linear amplifier I bought had one missing link: the control cable to signal when to start transmitting. I first looked for such a cable at Hamshop but the cable was not available anymore. Further searching found the right cable at 8 pin linear amp switching cable for Yaesu FT-817 FT-857 FT-891 FT-897 FT-991 - TechnoFix UK and ordered it. It came in, so time to test it in the upcoming weekend.
After the SCC RTTY contest in August I decided to plot the number of amateur radio contacts again. Clearly visible are months with contests I participate in. And the influence of the summer holiday. before, before, before
Last Friday I had time available for outdoor radio and the weather prediction looked nice. Fellow radio amateur PA5Z had time available too and joined me. We cycled to the local park and found a nice spot for some radio, complete with a bench available to sit and run the radio. First decision was which band, because changing the band after raising the linked dipole means having to take it all down again. It was a tough decision between 40 and 20 meters, both looked not too promising. We decided on 40 meters. I also extended the mast and tie-wrapped the balun of the linked dipole to the mast (three segments below the top) before getting the mast upright. This worked nicer for me on an earlier setup. The downside is that we had to be very careful in where the guy-wires and the dipole wires are around the fiber mast to avoid tangled lines and twists. And the right way to lengthen the mast is twisting the segments to lock them together. With two people it is a lot easier to get the mast straight and it looked very nice. Soon contacts were made, but after a few tries I received a report that the audio sounded like I had RF interference. I heard this remark before at the end of my testing the mast at Trintelhaven and this time I found out what the problem was: the lead-acid battery I was using was running low and when the voltage drops from 12.0 to 9.6 volts on transmitting the output gets distorted. The fix was to lower the output power, a local radio amateur who we contacted was willing to help test this and confirm my theory that the drop in voltage was causing distortion. Eventually it started to rain a bit, the batteries started to get depleted even at lower power and we decided it was time to pack up and go back home. A nice day for radio, I ordered a new battery to replace the failing ones and I'll be doing this again some day!
Outdoor radio, picture by PA5Z
As planned and prepared for I participated in the SCC RTTY contest this weekend. I was aiming for 100+ contacts but due to local interference and not very cooperating propagation those did not happen. In the end I made 83 contacts, 2 on the 40 meter band and 81 on the 20 meter band. I entered in the 'single operator 20 meter' category which was the most fitting for me. That does mean the 2 40 meter contacts only count for log checking. Interesting things that happened: I got YV5AAX in the log. This has happened before in RTTY contests. But I do see YV5AAX from time to time in FT8 but never made a contact in that mode. I guess the station uses different antennas for contests. I also worked several US stations but I don't think those have resulted in a new US state for my statistics. The new amplifier was working fine although I noticed the fan control and fan in the power supply stopped completely when I transmitted RTTY in the 10 meter band. This was not a very big problem this time as there was no propagation at all on that band. But it will have to be fixed before the next contest. With this amount of power I can work almost all stations that I can decode. That is a nice improvement!
Today I set up the fiber mast against the back fence of our yard and used it to raise the endfed wire antenna as a vertical, with the coil between the 10/20 meter and 40 meter parts of the wire a few segments beneath the top of the fibermast. This works ok. Interference on the 10 meter band is nearly gone, interference on the 20 meter band is about the same. What is also interesting is that this setup gives more balanced results on the pskreporter map. With the endfed antenna from the roof to the end of the garden the results are that most of what I receive is to the east of me. With the fibermast and the endfed as a vertical the reception is more balanced and I see more North and South America. There is a downside: with even the slightest bit of wind the top of the fibermast starts to move a bit much. So to keep this setup safe for a weekend I would need to do something with guy wires.
This evening I tried several things to improve my chances of actually receiving anything other than the loudest stations in the upcoming SCC RTTY contest. First try was with a borrowed receive loop indoor and using an HF upconvertor, an rtl-sdr dongle and gqrx as receiving software. This did not work for digital modes: letting wsjt-x (FT8 software) 'listen' to the audio output of gqrx gave no decodes. Interesting detail: looking at the right piece of spectrum for FT8 showed that the frequency wasn't 100% stable, with frequencies slowly changing. Touching the rtl-sdr gave a bump in frequency. Another attempt was with the loop indoor and reception on the FT-857D radio. Reception of a strong SSB station seemed somewhat better on the loop, but I heard no improvement of weaker stations. So I moved the loop outside to the end of the garden and layed a long cable back to the radio setup. This made interference worse! It was already dark so this was not related to any solar panel setup, but some other source of interference on HF. The loop is supposed to receive less local interference but I could not get it to do that this time (it did work for SSB some other time).
The HP DPS-700 GB power supply adapted to feed the linear amplifier has no own internal fans so I connected a recycled 50mm PC fan. Which runs at full speed which is a lot of noise. I ordered a 12 volt fan control module on-line so it can run slower and keep the noise down a bit. I'll probably replace the current fan with an 80mm PC fan and set a low minimum speed. The air has to move as the power supply has no internal fans and is quite good at a thermal shutdown. But as long as things don't get warm it would be nice to reduce the noise as this was very noisy.
The reason for making the HP DPS-700 GB powersupply deliver a somewhat higher voltage and lots of amperes is that I made the decision to buy a HF linear amplifier. With such a device I get more output power on HF bands which should increase my chances in radio contests. I have been looking at new and secondhand linear amplifiers for a while. Since this market is dominated by US customers most amplifiers will give 1000-1500 Watts output power at a serious price. The legal limit here in the Netherlands is 400 Watt unless I request a special license which will never happen since the radio station is surrounded by other houses. But there isn't much on offer below 400 Watt output power. I found RM Italy which sells linear amplifiers for CB and radio amateur use at more reasonable amounts of power and at a better price-point. I selected the RM Italy HLA300V plus which should give 300 Watts on HF bands. I bought it online and it arrived fast. After soldering some cables to the power supply I was able to use it and it works as intended. On the 20 meter band and 10 meter band it works with the endfed antenna (which can take 400 watts). On the 40 meter band it goes into protection mode instantly. It turns out the amplifier is quite sensitive to SWR problems, the endfed gives a 1:1.5 SWR. Maybe I can improve this a bit, the resonant point is below the 40 meter band. Giving it 5 watt input power in digimodes will make 5 of the 7 output power LEDs light up. To get it to light up 5 LEDs in SSB mode I need to give it 10 watts power in that mode. Propagation wasn't great this weekend so I spent most time in FT8 mode. With the help of the new amplifier I was able to get two new countries in the log: V51MA in Namibia and 9G5AR in Ghana. The receive side is currently a different story. Interference levels are at an all-time high. The way I currently get reception for FT8 is by using the UTwente WebSDR for the receive side and feeding the audio to WSJT-X. With the delays and audio-processing introduced by the WebSDR I still get better and more decodes than from the local receiver. For contesting that setup is not going to work. Most contests have a rule that all equipment for a contest station has to be on a limited area. For example the upcoming SCC RTTY contest has the rule:All operation must take place from one operating site. Transmitter and receiver must be located within a 500-meter diameter circle.I'm looking into using a receive loop to have less interference on reception.
At a hamfest a scouting group was offering a HP DPS-700 GB power supply for the nice sum of 5 euro. A quick search with google found information about the pinout so I bought it. This is a power supply that can deliver 56 Ampere at 12 Volts, and the 12 Volts can be adjusted upwards somewhat. As usual with projects like this the power supply lived in the stack of projects for a while, but today I got around to testing it. Finding the pinout again was a bit hard, but I found the pins again at HP DPS-700GB 80mm fan shroud - Thingiverse which includes the simple modification to make the output voltage go up. As this power supply has no internal fans and will stop fast due to internal overheating if not cooled, I set it up with a recycled computer fan. Power supplies like this will always be active in systems with enough fans to push air through the whole chassis. The first test gave me 12.1 Volt. After adding a 1.5 kOhm resistor it went to 13.27 Volt. In theory the maximum current may have dropped as a result of this modification, but my best guess is that it can still deliver 50 Ampere. Update: More about this power supply and the different types seen in the wild: Increasing voltage on DPS-800GB A / ATSN-7001044-Y000 K1000 / HSTNS-PD05 for amateur radio - PA0FRI