We’re also pleased to start offering reprints that did not initially appear in IRCA’s DX Monitor, but are not easily found elsewhere. For example, we’ve obtained permission from the family of the late prolific author, Dallas Lankford, to organize and republish his out of print articles.
(if you’ve used the index before, you may need to refresh the browser page to see the latest update, dated December 2021)
A version of AirSpy’s popular SDR# software, showing the dark mode interface introduced in 2019. SDR# is always evolving, and the latest new tool is the Co-Channel Canceller.
It’s easy to take for granted the magical math that happens in Software Defined Radio. Occasionally though a breakthrough occurs which really grabs our attention, thanks to the hard work and bright minds of the designers behind the receivers and the software.
On the software side, the first series of “wow” moments happened for me in 2007-2008 when Nico Palermo of Perseus SDR fame expanded the program’s alias-free bandwidth incrementally from a modest (but impressive for the time) 100 kHz all the way up to the current 1600 kHz coverage.
The top-end 1600 kHz bandwidth was a game changer which allowed medium wave DXers the opportunity to record IQ-WAV files of the entire band for later review, analysis, and DXing. It’s even more impressive considering this expansion was done without any additional hardware or receiver updates.
What did Nico charge Perseus owners for this incredibly useful expansion of spectrum and waterfall bandwidth? Nothing! The program with its much improved features continued freely available to previous and new Perseus SDR owners.
Now in 2020, Youssef Touil, AirSpy’s hardware and software developer, brings a “killer feature” to his own SDR program named SDR#, for the benefit of medium wave DXers: the Co-Channel Canceller. The cost for this innovative tool? Yep, it’s a free addition to SDR#.
What are the benefits of the Co-Channel Canceller? This question is best answered by listening to three examples published by Youssef on his Twitter feed.
Read the descriptions below and listen to the brief audio files. In each example the Co-Channel Canceller is turned on and off a few times:
For the first example above, I suspect the 594 kHz station is Saudi Arabia’s Radio Riyadh, and the off-channel 596 kHz signal is Al Idaa Al-Watania from Morocco. It’s impressive that the 50 kw 596 station can be uncovered to any degree, as Radio Riyadh is a whopping 2000 kw!
In the AirSpy Groups.io forum, Youssef clearly illustrates the steps needed to initiate the Co-Channel Canceller. I’ve reproduced his screenshots below:
I’ve only just begun to explore the possibilities of the Co-Channel Canceller tool, but it holds promise of helping to reveal and identify hopelessly buried co-channel or adjacent channel stations. Not only does it work “live” in real time reception, it functions well with recorded IQ-WAV files too! Checkout the newest version of SDR# and give this new feature a try. I can imagine situations where this tool could be highly useful at times for the shortwave DXer also.
Thanks, Youssef, for this brilliant tool, which you’ve included free with the newest SDR# !
I encourage radio hobbyists to support AirSpy’s efforts to advance the state-of-the-art. The diminutive AirSpy HF+ Discovery receiver is not only a reasonably priced SDR to use with SDR#, it’s a top performer and a recipient of the World Radio TV Handbook’s Best Value SDR award for 2020.
Guy Atkins is a Sr. Graphic Designer for T-Mobile and lives near Seattle, Washington. He’s a regular contributor to the SWLing Post.
Many thanks to SWLing Post contributor and Ultralight DX enthusiast, Gary DeBock, for sharing the following guest post:
Nulling a local pest with dual FSL Loops
by Gary DeBock
After many dual FSL antenna experiments I’ve finally determined how to effectively cancel out QRM from a local pest that is off to the side (ideally 90 degrees different, but practical from 50 degrees to 90 degrees different) from a weak DX station, although I’m not quite sure of the theory behind this discovery.
This experiment was an attempt to cancel out QRM from a local pest, 950-KJR in Seattle, WA (35 miles/ 56 km to the north) and chase 950-KKSE in Parker, CO (1005 miles/ 1617 km to the southeast) during the early morning hours. The receiver was a basic (non-SSB) C.Crane Skywave, and two identical 5 inch ferrite rod FSL antennas were used. Please refer to the photo (above) to follow this description.
Step 1) Null out the pest station with the portable radio’s loopstick (away from the FSL antennas). Set the radio down in this nulled position, so that the pest station is as weak as possible, while ensuring that there is space to set up the FSL antennas to the back and side (see photo).
Step 2) Take the “Reception FSL” and use it to peak the pest station’s frequency, setting it up parallel to the portable radio as shown, at the position providing the maximum inductive coupling gain. This will temporarily boost up the pest station, which previously was nulled.
Step 3) Take the “Nulling FSL” and pretune the frequency to that of the pest station. You can do this either by adjusting the variable cap plates to match those of the “Reception FSL,” or by temporarily peaking the pest station’s signal in a position in front of the portable radio. After setting this frequency, set the “Nulling FSL” off to the side of the portable radio as shown, with the spacing identical to the spacing between the radio and the “Reception FSL.”
Step 4) Slowly and carefully tune the “Nulling FSL” until you hear the pest station’s signal take a sharp drop. This setting will be very sharp, but once you find this position you will have nulled out the pest very effectively, and if another station is on the frequency, it may suddenly become dominant, even if it is far away (like 950-KKSE in Denver).
Some MP3’s from this morning’s experiments:
950-KJR in nulled position with the portable only
950-KKSE generally dominant over the local pest KJR when the “Nulling FSL” is peaked
Fascinating, Gary! I don’t understand the dynamics of why this works, but it’s amazing that it does so effectively. I can think of two MW frequencies in particular where I could put a system like this to the test.
Tuesday, many of us in the shortwave and DXing community learned about the unexpected passing of our good friend and veteran radio reporter, Allan Loudell.
I got to know Allan via the Winter SWL Fest community. Allan attended every year and was well known for being not only wonderfully good-natured, the sort of guy who is liked by everyone, but also one of the most knowledgeable DXers on the planet. As a mutual friend recently noted, his knowledge of the domestic and international broadcasting scene was very nearly “encyclopedic.”
Dan Robinson (left) and Allan Loudell (right) at the 2020 Winter SWL Fest (Photo source: Dan Robinson)
I made a point of chatting with Allan each year at Winter SWL Fest. This year, we all noticed that he had lost some weight, but otherwise seemed fine and, as usual, in great spirits. He mentioned to me that he had been through months of medical issues and rehabilitation, but believed he was on a positive track. I only wish that might have been so.
It was among my favorite things to do at the Fest––and I got to enjoy this a few times–– to page through albums of QSL cards with Allan that he and other Fest attendees like Dan Robinson brought to share. Allan’s eyes would light up as he turned each page. Not only did he know each card and each broadcaster, but––if you asked––he could take you on a deeper dive into the nuanced history of each station.
Allan interviewing a young lady in the studios of WDEL. (Photo source: WDEL)
Clipped from the February 1994 issue of Pop Communications
As our mutual friend, Tracy Wood, put it: “[Allen] was a giant… radio was his life….and thankfully he shared his passion with us.”
Moreover, Allan was a longtime Delaware radio newsman, having spent 18 years with WILM and most recently 15 years with WDEL.
In a typical year, I make at least a couple of trips through the mid-Atlantic states, and each time I do, I tune to WDEL to hear Allan’s voice.
The subtext is plain: he was a well loved at the station and, indeed, in the community. The station included the following quote from Delaware Governor John Carney:
“I’m very sad to hear that Allan has passed away. I tell people that, in my thirty years of public service, I’ve developed a list––just a personal list of good guys and gals, people that were really good to work with…Allen was one of those guys…He was always very fair…He always covered his subject matter in a way that most reporters didn’t. And he used the radio media as a way of communicating, and having public officials like myself communicating, with the people that I worked for, the people in northern New Castle County. I particularly liked his show DelAWARE, because…he did, in very intense kind of way, various subject matter that got below the surface…”
Governor Carney continues:
“[Allen] was just a really interesting guy and a very real gentleman…and I enjoyed being with him…I know that the people in the WDEL, WILM listening area here in northern New Castle County and, actually, across our state now will miss his programming, will miss him as as a media person, and it’s sad to hear that he’s passed.”
Many thanks to SWLing Post contributor, Bill Hemphill (WD9EQD), who shares the following guest post:
My First DX Contest
by Bill Hemphill, WD9EQD
Being a recent new member of NJARC, this is my first time competing in this contest. I have always been a big fan of BCB DXing and have recently got back into it – especially with the amateur radio bands being in such poor conditions. The acquisition of a couple of Loop antennas plus two Panasonic RF-2200 radios have just enhanced my enjoyment.
For the contest, I used two completely different radios. First was the RF-2200 and second was a spur of the moment creation.
The RF-2200 was its usual good performer. While the RF-2200 has a beautiful built-in rotating bar antenna, I enhanced it with the 27” Torus-Tuner Loop Antenna as made by K3FDY, Edmund Wawzinski. I think I had picked this antenna up at one of NJARC’s swap meets. So I wish to thank whoever it was that was nice enough to bring it and sell it at the meet. I have really enjoyed using it. With this setup, I was hoping that I might be able to pull in Denver, Salt Lake City and maybe even a Mexican station, but it was a complete bust on them. But I did have a nice surprise in receiving the Cuban station Radio Enciclopedia on 530 in addition to the usual Radio Reloj time signal station. Following is photo of it in operation:
Originally, I had thought that my second contest entry would be done with a 1962 Sony TR-910T three-band transistor radio. This radio has a fairly wide dial along with a second fine-tuning knob which would be a big help. I would have again used the 27” hula-hoop antenna.
But I made the nice mistake of running across Dave Schmarder’s Makearadio website:
Dave’s site is a wonderful resource for creating your own Crystal, Tube, and Solid State radios as well as Audio Amplifiers and Loop Antennas. While going down the rabbit hole of his site, I ran across his Loop Crystal Set, #19 Crystal Radio:
It was a really nicely constructed, nice swivel base.
I replaced the tuning capacitor with one that has a 6:1 ratio.
At this point I started thinking that I could create something similar with my loop.
I randomly grabbed a diode from my parts box. Not sure what the exact model is. (I later found out that it was an IN-34 which is what I was hoping it was.) Then quickly soldered the diode, a resistor and capacitor to a RCA plug:
I then proceeded to use some jumper cables and just clip it to the tuning capacitor on the antenna base:
The RCA plug was then the audio out (I hope) from the radio.
I quickly realized that I did not have a crystal headset or any headset that would reproduce any audio. So I used an old Marantz cassette recorder to act as an amplifier. Fed it into the mic jack and then tried to listen to the monitor out. Bingo – I could pick up or local station on 1340 really weak.
So I then fed the audio from the Marantz into a Edirol digital recorder. Now I was getting enough audio for the headphones plus could make a recording of the audio.
At last I was receiving some signals. To boost the audio some more I removed the resistor from the circuit.
I found out the I could only tune from about 530 to 1350. I probably needed to clip the lead on one of the loop turns, but I really wanted to see how it would do at night. I spent several hours and was just totally amazed at how well it performed and how good the audio was. The hardest part was when there were very strong signals on the adjacent frequency. What I found really interesting was that it was not linear in its tuning. At the low end of the band the stations were more spread out than at the higher end. This made tuning fairy easy at the low end and very touchy at the high end. I was able to hear a couple of Chicago stations along with Atlanta and St. Louis.
Here’s photo of it in action:
I have created an audio file of the station ID’s heard with the diode/loop radio. The audio file is on the Internet Archive at:
I had a lot of fun in the contest and especially enjoyed trying something really different with the diode/loop radio. Now I have a whole year to try to think up something really creative for next year’s contest.
Absolutely brilliant, Bill! I’m so happy to see that your ham fest homebrew loop has served you so very well in a contest. I love how you pulled audio from your homebrew, make-shift diode radio as well–using your audio gear in a chain for amplification obviously worked very well.