Saturday, February 24, 2024

My Ham Radio Upgrade Is Close to Ready to Implement

Back in December I started the story of upgrading my ham station to allow it do much more than just what the radio allows, by upgrading the computer and putting a Software Defined Radio (SDR) in line.  Yes, relying on a relatively cheap SDR (an Airspy R2) instead of the much more valuable HF to 6m radio that's the heart of my station.  The Airspy SDR and the software that guys are using gives a tremendous advantage.  It allows you to monitor (in this case) seven different frequencies across the ham band you're tuned to, while the receiver itself only allows you to listen to two frequencies. 

Consider this display:

The SDR is running on seven different frequencies.  Some of them are conventional Single Sideband (SSB) voice (50.125 and 50.140 MHz); most of them are the modern digital modes (50.313, 50.260, 50.275, 50.318, and 50.323 MHz).  As the operator, we can listen to SSB voice audio, or CW (Morse code - CW is for Continuous Wave - none of these are tuned to frequencies where CW is more commonly used) and run several instances of the software used for the digital modes.  An important thing to know is that I still have only one transmitter so it's impossible to have more than one contact going at a time; the advantage of this is that it replaces listening all day to one frequency and not hearing the guys 100 kHz away in the same band. 

The hardware that I've needed to acquire to implement this is depicted in this drawing, which I've revised about a billion and six times and am now just about ready to put it in place.  

This started out as a way to determine how many and which kind of cables I needed to get and then became more involved.  The key piece of hardware is an SDR Switch from; the specific one pictured here is his 0 -70 MHz RXin RXout Switch.  The box on the top left is what I call the back panel, which is all low frequency control signals in and out using RCA connectors, also called phono plug connectors.  The biggest box on the top right is all BNC female connectors.  My various notes there are reminders to myself about what cables I have, the four BNC male to BNC male cables I needed to buy or build (and did), the adapters I need in various places and so on.  In a few places I note the existing cable used.

The obviously professional radio drawing at the left is from the user manual for my main rig, an Icom IC-7610.

The last piece I needed to get for this was the LNA - in the square box between the Front Panel and the Splitter at top right.  I bought a kit from Down East Microwave, a relatively well-known VHF to microwave accessory seller.  It was all surface mount components, but they weren't the tiniest of the standard packages and I thought it was relatively easy to build.  I wouldn't recommend it if you've never done surface mount soldering.

This is close to ready to integrate into the station now, except for two little things.  The 12V DC wire to the switch; Anderson Power Poles to RCA Plug, and put a phono plug on the power wires on the LNA.

EDIT 2-25-24 at 0900 EST:  The first link in the post wasn't working and I didn't test it before hitting the Post button. 


  1. Nice.

    How are you handling audio levels on the rig/computer on receive? (I'm assuming you may have a mixer to a set of speakers for the various sources...)

    Plus can you record the "output" of the Airspy to the computers SSD/HD for later analysis and playback?

    1. I'm not sure I understand that well enough to answer.

      The audio interface between digital modes on the computer and the radio is currently done by a standalone little box called a SignaLink USB. That's both for transmit and receive. With the new setup, the big radio's receiver isn't used, just the transmitter. The seven receivers seen in the picture are on the computer and will demodulate there. In the case of the digital modes, that's pretty much a no-brainer. It produces audio that the digital mode SW uses. In the case of voice modes, I think the software, SDR Console, demodulates it and drives the computer's speaker/headphones.

      There's no audio mixer; I select which receiver I want to listen to on the computer and that output goes to either the speaker or digital software. I think I can run multiple instances of the digital software and pick which one I want to read.

      SDRConsole is one area I've been unable to test because it depends on having the hardware working. I can't really test the software without this hardware, and can't really tell if the computer decision was right until I can run the software. I could sorta half-test it, but not enough to be confident.

  2. SiG, an interesting setup you are going to have.

    I have a question regarding your IC-7610. I am considering saving up for one. A friend loaned me his IC-7300 when I was having problems with my TS-570D. I set up the 7300 in my shack and used it a little. It was great on SSB but I found the CW to be "uncomfortable" to my ears. The 7300's CW seemed harsh whereas the TS-570 sounds better and a lot like the older all analog rigs even though it does go through a low frequency digital IF/DSP. What does CW sound like to you on the 7610? I don't know anybody locally that has one.

    BTW, the problem with the 570 was oxidation in the radio antenna to tuner connections, which I didn't have in the 7300 because I had moved the jumper cable from one radio to the other and to a different tuner. I went through and redid the connections on all radios, like we used to do on problem connections for missile and aircraft cables at LTV 35 years ago.

    1. I need to start by saying I'm probably the worst person to ask. I've known people who objected to radios that all seemed fine to me. I suppose I've got "tin ears" as we used to say. (nah, I got two, not tin)

      I think the 7610 sounds fine. I typically set my CW filter to 500 Hz and rarely go with narrower, but I have. Being a band sampling receiver, everything takes place after A/D conversion, so it has features to adjust things on the fly. I know virtually nothing about the 7300, so I don't know how many of those things it has. I like the way Icom's noise reduction sounds, compared to others I've heard. The DSP filters are mathematically more like rectangles, flat across the top and then the signal drops like a rock as you tune off it, while crystal filters typically had several dB of ripple.