Welcome on DL4UNY's Radio-Page!

...DL4UNY on 160/80...

I really enjoy working on the low-bands. No matter whether its DXing or Contesting, Low Band contacts always give me a special satisfaction :)
My standard rig on 160m is FT-1000D / FT-1000MP, a homemade kW amplifier, a top loaded 29m vertical with approx. 40 radials between 5m and 30m, 4-6 beverage antennas and a high impedance receiving antenna. During the past years I have tried many concepts such as coaxial (shielded) loop antennas, flag, K9AY, LZ1AQ-System, several short vertical with active impedance transformers (similar to the commercial HighZ-System) but I found the best solution with a modified LZ1AQ-System (more information below, I will call it Current Antenna) and my beverage antennas. Interesting is that the current-antenna performs almost as good as a 220m long beverage. A beverage antenna has a directional sensitivity, a small loop like the current-antenna is almost omni-directional. Comparing a directional and an omnidirectional antenna is not that easy, and I don't want to go deep into maths, so I compare justfield strength and noise of a DX station. And interestingly a current-loop must collect much more noise (from other directions) but during the last years I could hear about 90% of the far-away DX-Stations (such as JA, VK, PY, W6/W7... I'm not talking about UA9 or UN) on my current-antenna that I could hear on my beverage system. I only compare with stations I can not hear on my TX-antenna, of course. That means that an antenna that is 0.8m x 1.6m is almost equal to 4 - 6 beverage antennas between 180m and 250m length. Of course the active antenna has some disadvantages, it's quite sensitive to electromagnetic noise such as from poorly designed switched power supplies and therefore it must be taken care of filtering all outgoing signals from the shack to the antenna, so that the own noise wont reduce the antennas performance.

A bare PCB and a completed Amplifier

close up shot of the output transformer

Box with 2:1 transformer, input for Power supply and optional PTT (to switch Amp off during TX)

a single loop constrution for my city QTH in Munich

Double Loop (in parallel) for my main lowband QTH

The amplifier is designed for 120Ω symmetric output impedance, so it can be used with cheap and low-loss ethernet cable. Inside shack there is a 7:5 voltage transformer as a transition to 50Ω coaxial cable. I use a double loop (two old 700c bicycle rims) on my primary station, about 60 meters away from my shack. The amplifier provides enough gain and the loss of patchcable is lower than of RG-58 on the frequencies of my interest. For my city-QTH I figured out it's best to use only one bicycle rim. A second one only increases the noise and doesn't show and improvement for wanted signal reception.
Just message me in case you are interesed in purchasing a already tuned amplifier or parts.

Having more and more receiving antennas ends up in having more and more feedlines running from the shack to the antenna points. At some point of time I was tired of stumbling over 5, 6 or sometimes even more feedline cables running 'wild' through the backyard. My receiving antennas are only used during winter time, after farmers finished harvesting and got the field ready for the next year. As of that, burying cables for RX Antennas was not an option. So I decided to switch my receiving antennas remotely and, to add more flexibility, and integrated a W7IUV amplifier to be able to use low-power output antennas such as a K9AY or a shielded loop. To make it even more flexible, I wanted the antennas to be impulse-selectable with a micro controller or by simples push-buttons. Using a switch is the easiest solution, but push-buttons are more convenient. During contests from central Europe it happens that you can work JA and W/VE at the same time (our late evening) but on my switch-board there were another two antennas between the position of JA and W4-Antenna. Switching 2 directions after calling CQ ended up in switching 4 antennas. With push-buttons I can switch from any to any direction ;)
Design of the remove RX antenna switch and switchable amplifier

completed and tested boards

You can message me if you want to purchase a already tuned switch or parts of it.