Category Archives: Software Defined Radio

Guest Post: An Unusual Night for CB

Many thanks to SWLing Post contributor, Mario Filippi (N2HUN) for the following guest post:

An Unusual Night for CB

by Mario Filippi (N2HUN)

December 2nd was an unusual night for CB (Citizen’s Band) radio, as the band was open late (0030 GMT) when I turned on the President Washington CB radio just to see who was on. First stop was Channel 19 (27.185 MHz), the trucker’s channel, where the QRM was high, due to the skip from the many truckers on the channel. Earlier in the day this channel was very quiet as was the rest of the band. The fact that Channel 19 was pinning the S meter after dark was a big hint that the band might be open. And it certainly was!

Uniden President Washington AM/SSB Base Station

Being a CB’er from back in the 70’s (call sign KBN-8387), this band was my first serious introduction to two-way radio communication, and after 40+ years it’s still an enjoyable experience to listen in to the local, and sometimes DX chatter. For the most part the CB band mimics 10 meters, basically open during the day (except when sunspot numbers are low) and closed at night. That’s the usual drill, but Mother Nature doesn’t always go by the playbook and sometimes the band is opened at the darnedest times, sometimes even after midnight!

So this evening around 8:30 EST the President Washington CB base station was fired up and CB operators were heard in Maine, Illinois, and as far as Wisconsin, definitely what would be considered out of the ordinary range of CB, which is generally several miles. Now FCC rules still state that it’s illegal to communicate over 155 miles but it’s a non-issue when the band’s open. For the most part, AM is used on most of the channels but you’ll find LSB activity on Channel 36 (27.365 MHz). And when the band gets busy and crowded, you’ll hear LSB QSOs from Channels 36 – 39 (27.365 – 27.395 MHz) as sidebanders spread out among the channels so that they can work each other through the QRM.

To get a better idea of what the CB band “looks” like during a band opening, a spectral scan of the band (26.965 – 27.405 MHz) would be useful. This can be achieved using an SDR dongle, such as the version which is a diminutive broadband receiver with an analog to digital converter and covers from about 26 – 1670 MHz. Used in conjunction with an up-converter (from Nooelec), software such as SDR# (SDR Sharp) and a computer (Smartphone apps are available also) you’ll be able to put up a spectral scan of the band as well as hear what’s happening. dongle – a small broadband receiver covering all modes

Nooelec’s Ham It Up RF Upconverter expands dongle’s receiving range to the entire HF and MW band

As the old adage goes, “a picture is worth a thousand words” so tonight the SDR dongle, along with SDR# software was fired up to get an idea of how many stations were on during the opening. The antenna used was an S9 43 foot vertical, the same one I use for HF. Using the dongle, it’s an easy feat to visualize the entire CB band on the spectral scan, which is a plot of frequency (X axis) versus signal strength (Y axis). The top half of the screen is the spectral scan and the lower half is the “waterfall” which is a time lapse recording of the spectral scan.

Screenshot of CB Band (wide red stripe) during tonight’s opening.

Normally at this time of night a spectral scan of the CB band would be flat-lining, but as you can see there are plenty of stations conducting QSOs, with the stronger stations having higher peaks and more intense tracings on the waterfall. Seeing the entire CB band visually gives one lots of information such as what channels are active, how many stations are on, what stations might be running higher power (limit is 4 W AM, 12W PEP SSB output), whether outbanders are active or whether DX stations outside the US are partaking of the opening.

Over the years I’ve heard the CB band open beyond midnight and on a winter’s night during a snowstorm. Some openings have lasted for hours. Last year, using the mobile CB, operators from Europe, the Caribbean, and as far away as Australia were heard during my commute to work. At the opposite extreme some days all you’ll hear is ignition noise, hihi. It’s a lot like 10 meters and even a bit like 6 meters; you never know what surprises Mother Nature has in store. Spin the tuning dial over to the CB band and take a listen one of these days.

Thank you so much, Mario!

Only a few weeks ago, I noticed on my SDR’s wideband spectrum display that the 11 meter band was very active.  I started listening around and was absolutely amazed at how organized some of the nets were and how reliable skip was. Signals were blanketing all of the eastern US and even into the west. Sometimes I think there are openings on the 10 meter band, for example, but there are so few users there in comparison, no one notices. The CB frequencies are pretty much always active, when conditions are favorable for DX, everyone instantly notices!

Many might not realize that even their portable shortwave radio can tune the CB frequencies. Thank you again!

Oxford Shortwave Log: transatlantic MW DX catches with 200 metre Beverage – part 1


Hi there, a few weeks ago I posted a couple of medium wave DX catches with the Elad FDM DUO and newly constructed 200 metre Beverage antenna. Since then (and following my trip to Brazil) I have uploaded several more catches, some of which I would like to share with you. It has become evident that the Beverage’s low-gain but high SNR properties resulted in a huge increase in the sensitivity of my entire set-up and as a result. I have achieved numerous personal firsts on the medium wave band, coupled with many other signals that I can only describe ‘best-ever reception’. If nothing else, this endevour has underlined the importance of utillising the best antenna possible for your particular circumstances. We’ve all read at some point, how, in many respects, the antenna is more important than the receiver – and these catches demonstrate how absolutely true that statement is. All of the reception videos were captured using the Elad FDM DUO running on a home-brew battery-pack and connected to the Beverage via a 50 Ohm input transformer.

Below is the first set of reception videos, most of which are signals from East Coast of the United States. However, there is also an absolutely booming signal from WGIT Puerto Rico into my QTH in Oxford UK. Part 2 will follow almost immediately, but in the mean time thanks for watching/listening and I wish you all great DX!



Clint Gouveia is the author of this post and a regular contributor to the SWLing Post. Clint actively publishes videos of his shortwave radio excursions on his YouTube channel: Oxford Shortwave Log. Clint is based in Oxfordshire, England.

Holiday Deals: SDRplay RSP1 and RSP2 availability and Cyber Monday at HRO


The SDRplay RSP2

Many thanks to SWLing Post contributor, Ken Hansen (N2VIP) who writes:

HRO stores are taking delivery of the new SDRplay RSP2, and having a great deal on the original SDRplay RSP, now on sale for $119.95.

HRO link to SDRplay RSP2 selling for $169.95:

HRO link to original SDRplay RSP selling for $119.95:

Thank you, Ken! Click here to read more about the RSP2 and here for a great review at



In addition, HRO has a wide array of products in their “Cyber Monday Savings” event.

Click here to view HRO’s sale.

New Beta version of SdrDx allows for AFEDRI AFE822 two input phasing


Many thanks to SWLing Post contributor, David Goren, who shares this tip from Chris Smolinski at Black Cat Systems:

If you have an AFE822 Dual Channel SDR, and a Mac, run, do not walk, to the SdrDx website, and download a copy of the beta version. It now lets you phase the two inputs, much like using an external phaser such as the MFJ-1026. Great for nulling out another station, or noise/QRM. I have some descriptions of how to do this, along with some recordings, and the relevant links, in this HFU post. I believe a Windows version will be out shortly.

Chris’ post on the HF Underground goes into more detail and includes audio samples:

A few months ago, I picked up an AFE822 dual channel SDR, one of the reasons was to experiment with using it as a phaser for MW DXing. It was a bit of a daunting task, having to essentially write an entire SDR app. I then realized I could instead write a “black box” app that sat between the SDR and the SDR app, which would take the pair of I/Q channels from the SDR, and adjust their relative amplitude and phase, and combine them into a single I/Q channel, and send that on to the SDR app. I played around a bit with that, and was quite impressed with the results. I passed on the general idea to the author of SdrDx, who has implemented it in a beta of the app, which is nice because now it is all self contained, rather than having to use my kludgy app in the middle Grin

There’s gain adjustments for each RF input, as well as a phase control, an invert switch to flip the phase 180 degrees, and switches to zero either of the RF inputs, useful when first roughly setting up the gains.

I am quite impressed with how well it is working. As an example, here is a recording of 1680 AM from earlier this morning. I toggled the invert on the phase control a few times, so you can hear reception flip between the two dominant stations on that frequency.

This is going to be really nice for MW DXing. SdrDx is for both Windows and the Mac. If you’ve been considering getting an SDR, this feature alone in SdrDx is reason enough to get an AFEDRI AFE822. If you do buy one, be sure to let Alex of AFEDRI know the reason is because of SdrDx, we need to support the authors of third party SDR apps we use, and let the hardware manufacturers know how important they are.

The URL for the SdrDx page is

The download link for the beta (Mac only right now, once this is confirmed to be working well, I am sure he will update the Windows version) is

Some more tests, this time on some local Graveyard channels.

1230, getting rid of WRBS:

1240, getting rid of WJEJ:

How to use the phasing adjustment with SdrDx, an AFE822 SDR, and your Mac.

Download the Mac beta (Windows version coming soon) of SdrDx:
If you have not used SdrDx before or recently, first download the stable version, and run that:
SdrDx page:

Familiarize yourself with SdrDx if you have not used it before. You need two antennas of course, one plugged into each of the AFE822 inputs.

To use phasing:

Click on the PHA button, turn on Dial Channel Phasing Mode. Click OK to close the window.

Click the Run button to get the SDR into Run mode. Tune in whatever MW frequency you want to use. Ideally one with two stations you can hear at the same time. Graveyard channels are great for this. Be sure to put the SDR center frequency offset from that. For example if you want to null 1300 AM, make the center frequency 1305 or something like that. Or the I/Q imbalance will cause problems.

Click the PHA button to open the phasing window again. You want to keep it open now.

Make sure the Invert checkbox is off, the Both Channels On radio button is on. Set the Phase slider to the middle, both Gains to zero, far left.

Adjust the first Gain slider to bring the signal level up to a reasonable level. S9. S9+10, whatever you want. Make a note of it.

Click Chan A Muted

Now adjust the second Gain slider to bring the signal level up to where it was before with the first RF input. The goal here is to make the signal levels about the same, so you can begin the process of nulling out one of the stations, with some chance of it working.

Click Both Channels On now, so you have both RF inputs active.

Adjust the Phase control, until you notice a dip in the signal strength. Try to get it centered in the dip as close as possible.

Then adjust one of the gain sliders, I usually use the one with the largest value to make things easier, to increase the dip in the signal strength.

Then go back to the Phase control, and try to increase the dip. You may now notice the dominant station starting to be nulled, by listening to it.

Then, like washing your hair, lather, rinse, repeat. You have to iterate back and forth many many times. Eventually, if your two antennas produce different enough signals for the two stations, you will be able to null it out. There are cases where you cannot null out one station, because the antennas produce the same signal for both of them. So nulling out one also nulls out the other. But this is rare.

You can click in the invert checkbox, and reception should switch to the other station. Listen to some of my recordings to hear this in action. You are changing the phase by 180 degrees when you do this.


Most impressive, Chris!  Wow–I think this feature alone could make the AFEDRI AFE822 an invaluable tool for the mediumwave DXer. Those audio samples are amazing!

SDRuno tutorial videos

SDRuno running the RSP2.

SDRuno running the RSP2.

Jon Hudson with SDRplay recently noted the following tutorial videos in an SDRplay discussion forum. Since I’m also trying to learn the ropes of SDRuno, I thought I’d share this here on the SWLing Post.

Jon notes:

These video guides are very helpful for newcomers to SDRuno and the RSP1 or RSP2:


Especially when used in conjunction with the SDRuno Cookbook from Paul and Mike: