You can assemble your own diversity reception system for medium and shortwaves for under $700. Entering the world of beamforming and interference reduction has never been easier.
With Cycle 25 on the upswing and summer arriving, you should consider a diversity reception system as your next radio project. Here’s a summary of how to build one. You can find all the details on this web site. My design features a city-lot size array of two wideband loops spaced 30 meters apart. Your key components are shown above.
First, your diversity receiver is as simple as getting the SDRplay RSPduo. You can run this standalone for listening, or interfaced with a ham transceiver using T/R switching and input protection. Second, your wideband loop antennas are easy to construct using the AAA-1C active antenna amplifier kit from LZ1AQ. Aluminum core PEX pipe easily forms into one meter diameter loops for connection to the amplifier. Finally, 75 feet of shielded CAT7 cable provides control and signals to the shack.
My original experiments used a single loop phased against my main ham antennas. In short order, I added a second loop and built a two element array of wideband loops. These can be switched between broadside and endfire patterns.
I have been dreaming about an active antenna diversity reception system since 1978 and an article by W5TRS in Ham Radio magazine. So, it’s taken me forty years, but I finally have one, and it works wonderfully.
Diversity Reception System – Bill of Materials
Starting from scratch, your total cost for a diversity reception system should be under US$ 700. Your major outlays are the RSPduo receiver ($280) and two AAA-1C amplifiers ($120 each or $240). Next comes some lengths of PEX-AL-PEX ($25 est.) and several shielded CAT7 cables ($40). Finally, add in another $100 for shipping, structural support and hardware. Fifty feet of PEX-AL-PEX does the trick for four loops.
If you read through my articles, you will notice I built all support structures using my 3D printer, but wood is an easy alternative. If you go to LZ1AQ web site, you can see pictures of how many hams mounted their loops. You can also find lots of videos online about diversity reception with RSPduo and other gear.
Is it worth it? I think so. For my money, a loop array diversity reception system is the way to go on an urban city lot. Find out for yourself.
Hi John, have you given up on the Afedri in favor of the RSPduo? I am more of an MW DXer and seem to remember you liked the Afedri more for that. I think I mentioned in the past that I have done a fair amount of phasing myself. I have several wideband Wellbrook phasers and have made numerous L/C based delay phasers as well as coax based phasers. Interestingly, my coax phaser which uses a Magic-T to combine the signals, has the most signal output and is almost completely free of common mode noise. So I am using coax based phasers mostly now.
Dave Aichelman N7NZH Grants Pass, Oregon
Still use both. Generally, Afedri wins on MW and RSPduo on SW. Read my articles on signal chain comparisons. Biggest issue with wideband loops is local MW overload on receivers that have wide open front ends, like the Afedri.
So you connect the antennas to separate channels on the RSPduo? How does the stronger signal get selected? Does the RSPduo use phasing for beamforming?
Yes. You can use the built in algorithm, but better to tune phase and amplitude manually. Yes. Will provide more information directly.