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Multiple Receiver Monitoring with SDR

multiple receiver monitoring

Multiple receiver monitoring is the new normal with software defined radio. Here is how your SDR accomplishes this magic. 

My first experience with simultaneous use of multiple receivers was to simply line them up on the desk with a shared antenna. I did this for many years. My Ergo Radio Software was designed to control two receivers at the same time, local or remote. Over the years, many ham transceivers added a “dual watch” capability, where you could monitor two frequencies, usually in the same band.

Boy, have things changed with software defined radio. Today, most SDR users can run multiple, virtual receivers in the same hardware and software. Multiple receiver monitoring is now the norm, not the exception.

Engineers use three different techniques to enable multiple receiver monitoring. The most common is to provide multiple demodulators that you can place anywhere within your sampling bandwidth. SDR Console software uses this approach, regardless of which SDR is running.

So, for example, I can run my Perseus with a 1 MHz sampling bandwidth, and place any number of virtual receivers into this range. Even though it shares the common data from the radio, each VRX can select frequency, mode and other controls independently. If I sample AM BCB at 2 MHz, I can set up do multiple receiver monitoring across the whole broadcast band.

Similarly, with SDRPlay and SDRuno, I can sample say 8.192 MHz of radio signals and set up two completely independent tuners within this range, complete with spectrum display.

The only limitations with this first technique is that the virtual receivers must share the same antenna and gain, and virtual receivers must remain inside a contiguous sampling bandwidth.

Multiple Receiver Monitoring at the Next Level

With my Flex 6300 shown above, the second technique increases multiple receiver monitoring capability. The Flex 6300 lets you set up two independent sampling slices of 7 MHz anywhere in its tuning range. So, I could have one receiver monitoring AM BCB, and another monitoring upper HF. The Flex engineers implement this feature in hardware. You will find that the radio uses separate digital down converters to grab two streams of data from the front end. Again, though, I am limited to using just one antenna and gain for both. (The more expensive Flex 6700 lets you capture four spectrum slices with different antennas and gains.)

Lastly, the third technique is a dual or multi channel SDR. My Afedri AFE822x contains two receivers each with its own antenna and signal path. Using PowerSDR_mRX, I have two completely different receivers running in one program.

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