Thank you to Joseph IT9YBG for submitting his article describing how he has made an RTL-SDR based panadapter for his TECSUN PL660 portable shortwave radio. The post is a series of pictures that show how Joseph was able to open the PL660 and connect a coax cable to the IF output, and mount the connector on the plastic cover for easy access. He then connects that IF output to the RTL-SDR via a 10pF capacitor.
The result is that Joseph is able to receive the IF output of the PL660 at 451 kHz in SDRUno with his RTL-SDR Blog V3 running in Q-Branch direct sampling mode. He notes that although the IF bandwidth from the PL660 is small, it is possible to decode digital signals by passing the audio demodulated by SDRUno into decoding software.
Over on his YouTube channel Tech Minds has uploaded a video where he tests out a cheap US$90 automatic antenna switch with DC-160 MHz range that he purchased from Chinese goods retailer Banggood. An automatic antenna switch like this is required when wanting to use an SDR such as an RTL-SDR as a panadapter with a transmit capable radio. The switch will automatically switch the SDR to ground when transmitting, so that high power does not enter the SDR via the shared antenna and destroy it.
In the video Tech Minds shows how to set the switch connections up and then demonstrates the switch in action with a Yaesu FT-991A and SDRplay SDR. He notes that this cheap Chinese version is actually built better than the MFJ-1708 antenna switch which until recently was the only commercial option available. It is also half the price.
PANADAPTER For Any Radio DC - 160 MHz SDR Antenna Switch
Over on YouTube "Gadget Talk" has uploaded a useful video showing how he set up an RTL-SDR V3 based panadapter system to use with his traditional amateur radio. The setup involves utilizing an antenna switcher which allows him to transmit with the RTL-SDR connected to the same antenna. The switch grounds the SDR during transmission, ensuring that the RTL-SDR is not overloaded with the transmit signal.
In the video he also shows how to set up the HDSDR receiver software and the HRD Rig Control software for controlling the hardware radio through the software and vice versa.
Rodrigo's system consists of an IF tap amplifier+filter board that is connected to an internally mounted RTL-SDR. The RTL-SDR is internally connected to the FT-991A's USB hub which had to be upgraded from a 2-port hub to a 4-port hub as the 2-ports were already in use by the CAT and Audio features. This required the stock USB hub IC to be replaced with a hot air rework station.
Everything is mounted inside the radio chassis itself, and the end result is a neat solution with no external wires, hubs or dongles that has essentially turned the FT-991A into an SDR. Plugging in the single stock USB cable from the FT-991A results in the standard CAT and Audio interfaces showing up, as well as the RTL-SDR.
What's also interesting is that Rodrigo makes use of the GPIO pins on our RTL-SDR Blog V3 to enable the RX_EN, BPF and BYPASS switches on the IF tap board. This allows for a cleaner solution as no external switches need to be installed.
The entire project is open source with schematics and the BOM provided over on the GitHub, and excellent documentation is available on the project's Wiki.
Turning FT-991A to a REAL SDR: Embedding a SDR Panadapter INSIDE the radio, no extra wires!
Over on GitHub user mcogoni (Marco/IS0KYB) has recently released a new program called Pepyscope. Pepyscope is a simple and fast panadapter application that is designed to be used with direct sampling capable RTL-SDR's such as our RTL-SDR Blog V3 units. Like other panadapters you simply connect the IF output from the hardware HF radio into the input of the RTL-SDR. Then Pepyscope gives you a waterfall display that helps users to easily visualize the spectrum.
Pepyscope is open source and runs on Linux PCs. So far Marco has tested Pepyscope with a KENWOOD TS-180S (single conversion with IF at 8.83 MHz) and an RTL-SDR v3. He has also uploaded a demonstration video on YouTube.
PEPYSCOPE: a simple panadapter for Linux and the RTL-SDR in direct sampling mode
The uBITX is a US$129 HF SSB/CW QRP transceiver kit that works from 3 MHz to 30 MHz with up to 10W TX power. It's a fully analogue radio, but it can be combined with an RTL-SDR to create a panadapter display thanks to a tutorial released by KD8CEC.
The method requires that you use the custom CEC firmware, or modify other firmware, as this appears to change the output frequency at the tap point. The tap point is made accessible by soldering on an extra SMA connector for the RTL-SDR to connect to. The rest of the work is entirely performed in the uBITX software manager, Omni-Rig and SDR-Console V3.
The Freqshow software is an RTL-SDR compatible tool for Raspberry Pi devices that can render live spectrum and waterfall displays. It is designed to run on portable touchscreens that plug into the Raspberry Pi. We've posted about freqshow a few times in the past.
The additional features are many. Additional features include: Full resolution zooming, I and Q Swap, 9 different pre FFT windowing functions to choose from. Center frequency offset or shift. PPM correction for the RTL2832. FFT averaging or FFT peaking. Easy frequency up and down from main screen. Easy Scale adjustment from main screen.
On YouTube he's also posted a video that demonstrates the software in action when running on an Adafruit 2.8" and Pi Foundation 7" TFT capacitive touch screen. Dan uses the software as a panadapter for his ham radio.
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.
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.
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.