Here you can find current and archived information from our company regarding our products, services and events.

  • 2022


    Please take note of our new price list!

    Unfortunately, inflation is not sparing our company. On the contrary, small companies are once again particularly hard hit. Many electronic components, now also "simple" things like passive or mechanical parts, can only be procured for a high surcharge or not at all.

    Nevertheless, most of our devices are still available in the short to medium term! However, please plan ahead for the rest of the year!


    Many thanks to all visitors of our booth at the Ham Radio 2022!

    We were very happy to meet old acquaintances once again and welcome new interested parties! It is amazing how well known and appreciated our devices have become!



    RAP1: Active preselector 0.5 - 30 Mhz.

    Prototype, series production from approx. Mid-July 2022.


    RAP1B: Version with integrated antenna control unit for RLA4

    The RAP1 is a combined inductive / capacitive coupled 2-channel bandpass filter with fully electronic tuning. There are 3 switchable filter modules with 1:4 tuning range each: 0.5 - 2.0 MHz; 2.0 - 8.0 MHz; 8.0 - 30 Mhz.

    Each module has a finely switchable capacitor network for tuning in minimum 10 kHz steps. All switching is done by reed relays, opto-MOS relays and high linearity CMOS analog switches. No capacitance or switching diodes are used.

    This can contribute significantly to improving reception (no sheath currents on the antenna cable, less interference, insensitivity of the cable routing, safe (natural vibration-free) operation of active antennas, etc.).

    In addition, the RAP1 has an adjustable attenuator for attenuating very strong antenna signals. Attenuator and amplifier are also used to automatically correct the passband attenuation of the RAP1 according to the current tuning (attenuation of the bandpass filters). This varies depending on the frequency and the filter module used due to different losses in the filter elements. The control adjusts the attenuator appropriately in each case so that the passband attenuation is largely independent of frequency. In some cases, even negative attenuations, i.e. amplification, can be set.

    The RAP1 can also be equipped with an integrated control unit for RLA4 antennas. In this case, remote feeding and adjustment of the reception direction of the RLA4 antennas are possible without additional control. All current receivers of the RDR5x series can remotely feed the RAP1 and automatically tune the frequency along.

    The frequency setting is done only with a rotary knob without any further manual band switching or range selection. The internal control takes over each switching operation according to the set frequency. Tuning is possible in steps of 10 kHz, 100 kHz or 1 MHz (shifting the cursor to the desired position of the frequency display).

    Adjusting the RAP1 can also be done wired remotely via the cable from the receiver (remote power supply also possible, otherwise at the device with 9 ... 15 V). Furthermore, the RAP1 has a WiFi transceiver for wireless remote control via a WiFi network and the Internet (if the WiFi network has access to the Internet).

    What selection values does the RAP1 offer? It is not intended to filter out individual narrowband transmitters (that is what the RX is for!), but mainly to relieve the RX from strong transmitters and interference far away in frequency. Especially modern RX (SDR, Direct Digitizing Radio Receivers) offer excellent selection characteristics in close range around the reception frequency, but suffer especially from strong signals in the far range (high sum signal of broadband antennas -> clipping of the ADC). On the other hand, these receivers can often display a wide frequency range ("panorama adapter", spectrum analyzer). This characteristic should not be suppressed too much by the preselector.

    The RAP1 was therefore developed as a broadband design with a bandwidth of approx. 10 - 20 % of the reception frequency. This allows good attenuation of signals lying far away with simultaneously low attenuation around the reception frequency. This means that the spectrum in the neighborhood of the signal just received is still easily visible (e.g. an amateur radio band). In addition, the need for constant retuning is greatly reduced for small changes of the reception frequency. Typically, one can "crank" over the SSB and / or CW segments of an amateur radio band without having to retune the preselector.

    The following images illustrate the selection characteristics of the RAP1. They were recorded in broadband on a digitally generated broadband noise ("shaky" curve) in real time on a RDR55 equipped with 4 units of 16 bit ADC.


    Setting 0.5 MHz: The filter curve lies at 500 kHz at the left side (setting below 0.5 MHz: low-pass filter up to 500 kHz).


    Setting 30 MHz: The upper side is strongly limited by an additional high-pass filter.


    The 3 individual bandpass filters are designed in such a way that above the highest tuning frequency (2.0 MHz, 8.0 MHz, 30 MHz) there is an additional notch filter for steepening the upper slope.


    New software version 1.3 available for RDR52!

    The Vx13 software contains some minor bug fixes and an enhancement of the Bluetooth driver (automatic connection to audio devices when the RDR52 is turned on).

    Please also observe the new operating manual!


    New firmware v8.0 for the antenna control units RSW3 and RSW4 is available (each in the software tab of the antenna web pages)!

    The updates allow the display brightness to be adjusted to suit the environment. They can be loaded into the devices with the Windows remote control software RLFA (new: version 04) via a WiFi connection.

    Please also observe the extended operation manual (each in the "Documentation / Software" tab)!


    The updated manual and a first software update for the RDR52 are available!

    The update contains minor functional enhancements and improvements in operation as well as bug fixes of the first version v211.


    New price list.

    Unfortunately, we too now have to adjust the prices of our devices due to sharply increased procurement prices (“chip crisis”) and considerable inflation. Since we were still able to buy smaller quantities of the most expensive IC (FPGA of the RDR5x devices) at tolerable prices, the new list is initially valid until stocks are exhausted. After that we have to recalculate the possible conditions.

    We thank you for your understanding and despite everything, we wish you a lot of fun and great reception success with our devices, which are completely handmade in Germany!


    New loop antenna amplifier version "4J" now in all variants of the RLA4!

    The new RLA4J amplifier was specially designed for the RLA4G/GS. This antenna is specified for frequencies up to 30 MHz. The amplifier includes advanced filters for attenuation above 30MHz. In particular, the constantly increasing interference from broadband services such as DAB/DVB or mobile communications can easily cause interference in amplifiers with a higher bandwidth in the vicinity of transmitting antennas. The 4J amplifier is significantly less sensitive to these disturbances than the previous types.

    Due to the installation in the smaller antennas RLA4 D to F, their upper limit frequency now drops to 30 MHz (previously specified up to 54 or 71 MHz, with some sensitivity also up to several 100 MHz). Individual circuit boards for self-construction of loop antennas are now also being delivered as version 4J. Please note the changed data sheets for the RLA4J board and RLA4 D - F antennas.

  • 2021
  • 2020
  • 2019
  • 2018
  • 2017
  • 2016
  • 2015