Tapping into a Ham Radio’s Potential with SDRPlay

Software-defined radios are great tools for the amateur radio operator, allowing visualization of large swaths of spectrum and letting hams quickly home in on faint signals with the click of a mouse. High-end ham radios often have this function built in, but by tapping into the RF stage of a transceiver with an SDR, even budget-conscious hams can enjoy high-end features.

With both a rugged and reliable Yaesu FT-450D and the versatile SDRPlay in his shack, UK ham [Dave (G7IYK)] looked for the best way to link the two devices. Using two separate antennas was possible but inelegant, and switching the RF path between the two devices seemed clumsy. So he settled on tapping into the RF stage of the transceiver with a high-impedance low-noise amplifier (LNA) and feeding the output to the SDRPlay. The simple LNA was built on a milled PCB. A little sleuthing with the Yaesu manual — ham radio gear almost always includes schematics — led him to the right tap point in the RF path, just before the bandpass filter network. This lets the SDRPlay see the signal before the IF stage. He also identified likely points to source power for the LNA only when the radio is not transmitting. With the LNA inside the radio and the SDRPlay outside, he now has a waterfall display and thanks to Omni-Rig remote control software, he can tune the Yaesu at the click of a mouse.

If you need to learn more about SDRPlay, [Al Williams]’ guide to GNU Radio and SDRPlay is a great place to start.

15 thoughts on “Tapping into a Ham Radio’s Potential with SDRPlay

    1. It depends on the end result.

      At the first IF, it shows you up and down from the frequency you are tuned to. So you can see a nearby empty frequency without having to manually tune the receiver. But traditionally, that was limited to a small range away from the centre frequency, and each has its use. I remember an article in “Ham Radio” magazine about 1972 where someone built a receiver that tuned 500KKHz at a time, and a converter for each of the HF ham bands. Each band would be tuned in turn, but done fast enough that one could see each band at the sane time. The oscilloscope was a tv set modified to be a low frequency oscilloscope, and multiplexing so all the bands were on screen at one time, one above the other.

      Michael

  1. That is way awesome and really in excellent detail! Thanks for sharing Dan… and Dave!

    I know for me the SDR’s have opened my mind up to radio more and really aided in learning the history more regarding radio, electronics and electromagnetic theory since I find that for the investment… the older equipment operates with better quality. Then to be able to interface the older equipment with the new is really exciting. I mean… to take a $10-20 US RTL-SDR even and interface with tuning by the radio is way fun… especially with improved quality. Seems touchy feely rewarding.

    I wonder if this is a way to get the youth in the U.S., U.K. and elsewhere into electronics more since in the U.S. there seems to be the gaming and software addiction that I feel is causing oversight to health, safety, welfare and well being interests and concerns that are more required for longer term (even perpetuity) advanced domesticated complex large population survival business?

  2. I have been doing this type access for a second receiver for a long time now. The small cludgy band display scope on the icom 706 and other radios has long seemed a joke and a waste of time and memory space on the radio that might have been used for better purposes. I have been playing with SDRS now for 5 or 6 years the SDR Play is a fantastic bargain for an out of the box item I love mine, but I would not be where I am today with SDRs if it were not for the little $12 dongles for dvb tv the a super cheap way to get introducedone to SDRs. For a third the cost of the great SDR PLAY and a little fun in building you can have just as much fun buying one of the dvb stick and circuit boards with kit of parts off of eBay for less than $30. I say go for it yout will have a ball and learn a lot for a small investment even a child can afford. It reminds me of my time with old military surplus radios back in the 1960s. C Ya 73 WB4IVG Laurin

  3. I have been doing this type access for a second receiver for a long time now. The small cludgy band display scope on the icom 706 and other radios has long seemed a joke and a waste of time and memory space on the radio that might have been used for better purposes. I have been playing with SDRs now for 5 or 6 years the SDR Play is a fantastic bargain for an out of the box item I love mine, but I would not be where I am today with SDRs if it were not for the little $12 dongles for dvb tv the a super cheap way to get introducedone to SDRs. For a third the cost of the great SDR PLAY and a little fun in building you can have just as much fun buying one of the dvb stick and circuit boards with kit of parts off of eBay for less than $30. I say go for it you will have a ball and learn a lot for a small investment even a child can afford. It reminds me of my time with old military surplus radios back in the 1960s. C Ya 73 WB4IVG Laurin

  4. Dave, KD2C, sells a little circuit board for this purpose, called the HUP-RF board, based on the design that used to be sold by G4HUP, SK. It’s has a high-Z input that won’t load down the rig’s RF input, and a follower stage to drive the 50 ohm input of your SDR. The kit includes everything you need, including an SMA connector to bring the tapped RF out of your rig. I’ve been using one in my TS-590 to drive my Nooelec Han-It-Up based SDR, and it works fine.

  5. This is called a: “Pan-Adapter” which is short for panoramic spectrum adapter. A spectrum display of the receiver’s IF band. Since the noise figure of a real spectrum analyzer is high compared to even a run-of-the-mill receiver, a good pan-adapter will see things down in the weeds that a spectrum analyzer will not.

    Anyone have any comparisons of this SDR solution with a decent spectrum analyzer set up as a pan-adapter on a sensitive receiver? What is the effective noise floor comparison?

    1. This is not a pan adapter because it’s connected before the mixer so he can use the Yaesu on one band and monitor a different one using the SDR; in other words unless I missed something, it just allows him to use the same antenna for both receivers without being forced to add any external circuit to disconnect the SDR when the Yaesu is transmitting. A pan adapter should be connected after the mixer but before any filters so it could follow the main receiver tuning but also allow the monitoring of a several megahertz wide spectrum even when the radio is set to demodulate very narrow bandwidth signals. Both are interesting mods to make, and they’re very different in nature so that one could connect to the same HAM rig a pan adapter and 3 or 4 other SDR like in this article to allow monitoring of what the main radio is tuned to along with other bands, all at the same time.

  6. Recently connected an RTL/SDR nano stick to the IF of the FT-897. There is room enough in this radio and a female mini-USB cable runs to the back where the connector fits exactly in the vent hole near the power connector. On HF you can view the entire band you’re on, fantastic.
    I even added a USB hub with a soundcard internally connected to the Data-jack, a USB-TTL board for CAT and a small USB memorystick with the software and drivers so you carry it always with you.
    There is a lot to be done with these radios. With the ever getting smaller boards from China and smaller space there are possibilities enough!

  7. Good afternoon everyone,
    Dave here (project author) of the featured project. Apologies for not commenting I wasn’t aware the project had been featured on Hackaday as I originally posted the project as a Instructable.

    Many thanks for all the comments, I will cover a few questions :
    – The Yaesu service manual is freely available on the web – it is very detailed and has a full block diagram and schematic.
    – The design of this LNA originates with Dave G4HUP who has sadly passed away.
    – As has been pointed out this arrangement is not a pan-adapter as the tap point is before the first LO mixer. I simply wanted my SDR to see the same antenna as the Yaesu and this seemed like an ideal method.
    – The SDR is fixed to the side of the Yaesu with 3M doubled sided foam tape.

    If anyone has any questions please fire away : dtrewren@blueyonder.co.uk

    73!
    Dave (G7IYK)

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