Using the RTL-SDR as a Panadapter for the IC-751A

A panadapter is a device that connects to a standard hardware radio and allows you to visually see the RF signals on a waterfall. Since SDR’s run on the PC, they naturally have the ability to display a panadapter screen, and most software like SDR#, HDSDR and SDR-Console already provide this. The RTL-SDR can also be used to add panadapter capabilities to a regular hardware radio. 

Gary Rondeau has been using the RTL-SDR as a panadapter for his IC-751A, which is a high quality ham radio transceiver. In his first post, Gary shows how he connected the RTL-SDR in a block diagram, and then shows how he interfaces the RTL-SDR and IC-751A together using HDSDR and the Omnirig software.

Block diagram showing the RTL-SDR as a Panadapter with the IC-751A and HDSDR.
Block diagram showing the RTL-SDR as a Panadapter with the IC-751A and HDSDR.

In his second post he shows a comparison between decoding JT65 and JT9 signals directly from the IC-751A audio output, vs via the RTL-SDR & HDSDR panadapter connection. His results show that as long as there is sufficient signal level, the RTL-SDR as a panadapter can match the performance of the raw IC-751A audio output, even producing less signal splatter on strong signals due to the pure numerical vs analogue mixing strategies of SDRs vs analogue radios.

RTL-SDR (top) vs raw audio from IC-751A below. RTL-SDR has a wider bandwidth, and less splatter at 2200 kHz when the strong signal came in.
RTL-SDR (top) vs raw audio from IC-751A below. RTL-SDR has a wider bandwidth, and less splatter at 2200 kHz when the strong signal came in.

Finally, in his third post he shows some more benefits of using the RTL-SDR as a panadapter, including rapid SSB tuning, RFI identification and signatures, helping work a pile up, monitor SSB net while working PSK on the parent radio, monitor the JT65 & JT9 band while working PSK – or vise versa and finally leave the radios on and monitor PSK, RTTY, JT65 & JT9 traffic for PSK Reporter.

3 comments

  1. Steve

    Is this possible with the IC 746 Pro? I have a soundcard and a laptop to use in conjunction with the transceiver and RTLSDR. Can this be explained in simple terms – I’m not an engineer so I need this information at a Radio for Dummies level.

  2. G1RNB

    Hi AF7NX,

    I don’t know how you tapped the IF from reading but to improve this – must have- upgrade with minimal signal chain disruption you could add:

    RF transformer from the IF tap that is optimized for the IF Frequency range and matches to signal chain impedance for minmal disruption.

    Two stage low noise pre/buffer amp >10dB gain – 1dB NF @ IF fx.

    Tight bandpass filter such as 3 stage Chebyshev to match IF pass-band (external to radio).

    I did this with my Ft-950 using an Funcube Dongle pro+.

    If you like experimenting and building like I do then this was a fun project with a great outcome.

    Bigger and faster FFT display than almost any radio available, HDSDR in fullscreen.

    If you are eager then:

    Galvanic isolator
    External low noise power supply to dongle – not USB power.
    USB RF dampening.
    Metal can enclosures with ground plane.

    Probably my first advice would be to align all the oscillators and filters in the Icom…as it is 30 or so years old.
    Regards

    All good fun…er

    G1RNB

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