Seamless SDR Freedom – Unlock Your Radio’s Full Potential

You may have already been using the YAESU FTDX10, which is the most popular HF/50MHz radio in the world. On the other hand, due to the lack of RF output support capabilities of FTDX10, you may feel restricted to use SDR receivers such as SDRPlay, AirSpy, RTL-SDR, HackRF and software like SDRuno, HDSDR, SDRSharp, GNURadio (e.g.: Gqrx) as well. To address this issue, we introduce a unique solution by designing a high impedance signal probing product, FTRX-10, to help ham radio operators utilise their YAESU FTDX10 with full SDR functionality.

FTRX-10 utilises an active high impedance current-feedback probing technique to probe the HF/50MHz RX signal path of FTDX10. Due to the high impedance nature of the unit, it doesn’t introduce any insertion loss. Therefore, there are no adverse effects on the radio side in terms of signal quality. In this method, there isn’t any 3dB insertion loss as in the power splitting approach to probe the signal.  You can see the connection diagram in Figure 1.

During the development phase, we first characterised the dynamic range of the HF/50MHz RX path of the YAESU FTDX10 in terms of both voltage and frequency. We extracted this information, used it to define the design specification of the unit, and finally developed the proof of concept designs with the help of SPICE simulations. In these simulations, we took into account both the signal integrity and amplification characteristics. With the help of a DDS-based signal generator (30kHz to 120MHz, @980mVpp), we analysed the signal quality both in the time and frequency domains.

FTRX-10 has been designed with components from reputable distributors, such as Digi-Key in order to maintain the highest level of component quality. (e.g.: U.FL-SMA extension).

FTRX-10 does not compromise the radio, requiring any invasive operation such as soldering and/or mechanical modifications (e.g., drilling). These unique features provide the operator with the flexibility to remove FTRX-10 at any time without any hassle. You can see the installed FTRX-10 in Figure 4.

Figure 4: Installed FTRX-10 to FTDX10.

TESTING AND VALIDATION

As we mentioned before, we applied variable test signals in order to simulate extreme conditions. Although FTDX10 can operate within the frequency range of 30kHz – 75MHz (up to 500mVpp), we conducted our tests for ranges varying from 30kHz to 120MHz (@980mVpp). We make sure that the unit has a flat frequency response for this range. Our tests also cover SSB and DRM demodulation on actual HF band conditions. Testing the CAT control synchronisation with SDR software has been done by OmniRig with SDRUno.