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The past few days, I have noticed higher than usual noise levels, generally on the lower frequencies, and particularly on the longwave band, including the 285-325 kHz DGPS band, where I run nightly SDR recordings, to later process the data and decode and detect DX DGPS stations using my Amalgamated DGPS app.
Thinking back to what new electronics devices have been added to the house, two came to mind, a new cable modem, and a new ethernet switch. The switch is up here in the shack, so it seemed to be a likely candidate. The switch is a D-Link DES-1008E 8-Port 10/100 Unmanaged Desktop Switch. It uses a mini USB port for power, using either the included AC adapter, or power from a USB port. When I installed it, I decided to not use the AC adapter, but rather a USB port on my UPS, figuring it was better to not add yet another potentially noisy switching power supply to the mix.
The test was easy, I just unplugged the power to the switch. Sure enough, the noise vanished. Great, the switch is a RFI generator. Or is it? As another test, I plugged it into a port on a USB hub. No noise. Hmm… so it seems that the noise is indeed from the USB port on the UPS. I did not notice any increase in the noise floor when I got the UPS a few months ago, but It’s something I should look into again, just to be sure. The UPS is a CyberPower CP1350PFCLCD.
Here’s a waterfall from the SDR, showing the DGPS band, 280-330 kHz. You can see where I changed the power to the switch from the UPS USB port to the USB hub, the bottom part of the waterfall is when the switch was still powered by the UPS (click to enlarge it):
I still have a noise source just above 305 kHz to hunt down.
Update
I decided to see what I could do to improve things, and reduce the noise floor.
Here is the baseline, after no longer powering the switch from the UPS:
First, I relocated the AFE822 away from the computer and rats nest of assorted cables behind it, powered from an HTC USB charger:
The squiggly noise around 305 kHz vanished!
I then switched to an Apple USB charger / power supply, as their products tend to be a bit better made:
Another improvement, the overall noise floor is a bit less now.
But can we do better? I then switched to an older USB hub for power to the AFE822, that I thought might be better filtered:
I then changed to a linear supply plugged directly into the AFE822. I don’t notice any obvious improvement? Maybe it even looks like a little more noise? Difficult to tell. You can see a DGPS station popped up on 304 kHz while I was switching things around, between the last two tests, it was likely Mequon, WI.
Thank you for sharing this, Chris! I find a wideband spectrum/waterfall to be such a useful tool for tracking down sources of noise. Not only can you “see” the noise, but you can measure its bandwidth and identify what portions of the dial it affects.
Hi there, here is the second set of reception videos for my transatlantic MW DX catches using the 200 metre Beverage antenna. Most of the signals originate from the United States and Canada, however, there is also a catch from Mexico – XERF La Ponderosa – which is a personal first and another from Bogotá, Colombia – Verdad Radio. I hope you enjoy them. Please do not hesitate to contact me if you would like further details regarding the Beverage design and/or construction. in the meantime, thank you 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.
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.
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 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 http://fyngyrz.com/beta.zip
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.
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!
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:
RSP1: https://youtu.be/xBGHB0oMXHU
This morning, SDRplay Limited announced the release––and availability––of their second generation software defined radio, the RSP2.
Regular SWLing Post readers will note that I’m a pretty big fan of SDRplay’s first SDR, the RSP, or “RSP1,” as I’ll now call it (I published a review of the RSP1 in July 2015). To me, the $129 RSP1 has been the best wideband receiver you can buy under $200 US. Its HF performance, in particular, is sincerely impressive at this price point.
Introducing the RSP2
So what’s the RSP2, and how does it differ from the original RSP?
In a nutshell, here’s how SDRplay describes the difference between the two:
“The RSP2 delivers a significant number of additional features which result in a higher spec for specialist amateur radio users as well as benefits for additional scientific, educational and industrial SDR applications.”
In a sense, the RSP2 gives the enthusiast and experimenter access to more receiver parameters and control, opening it to a wider array of possible applications. The RSP2 will also cover a broader range, from as low as 1 kHz to as high as to 2 GHz, and is designed with better selectivity across the spectrum. Enhanced selectivity will certainly benefit amateur radio operators and SWL DXers who might seek weak signals in crowded portions of the band.
The following list outlines the primary additional features of the RSP2 (via SDRplay’s press release):
10 built-in, front-end pre-selection filters, with substantially enhanced selectivity
Frequency coverage extended down to 1 KHz
Software selectable variable gain Low Noise Preamplifier
2 x SMA Software Selectable 50? RF ports (1.5 MHz – 2 GHz)
1 x High Impedance RF port (1 kHz – 30 MHz)
Built-in software selectable MW /FM notch filters
Highly stable 0.5PPM TCXO trimmable to 0.01PPM
24MHz Reference clock input / output connections
4.7V Bias-T option (on one of the software selectable antenna inputs)
RF screening within a strong plastic case for the standard RSP2
A Rugged metal box version – the ‘RSP2pro’
The RSP2 has a total of three antenna ports: two SMA and one Hi Z for optimal LW/MW/SW performance
For the moment, the RSP2 only works with SDRplay’s own application, SDRuno. But SDRplay is already working with developers to make the RSP2 compatible with HDSDR, Gnu Radio, CubicSDR, and SDR Console. I appreciate that although the RSP series has an excellent free proprietary application (SDRuno), it was nonetheless developed with many open-source applications, also free, as well. This level of compatibility and support makes SDRplay rather unique among SDR manufacturers.
SDRuno running the RSP2 (click to enlarge).
Of course, SDRuno is a great application in its own right, and pairing it with the RSP2 will provide you with out-of-the-box calibrated RF and S meters. So far I’m very pleased with native SDRuno features like virtual receivers, embedded time code, spectrum display options, and streamlined design.
Current SDRuno users will note the different antenna and filter options with the RSP2 which works natively with the latest versions of SDRuno (click to enlarge).
SDRuno installs very easily and provides a plug-and-play experience. It does have a modest learning curve, but SDRplay has an excellent owner’s manual and “cookbook” available to help you set everything up the first time.
Preliminary impressions of the RSP2
SDRplay sent me a pre-release RSP2 (the base model, not the metal box “Pro” version) to evaluate and provide the company with feedback.
I installed SDRuno and put it on the air only this past week. In truth, as I’ve been traveling and must be on the road again this coming week, I prefer not to comment, at least in depth, on the SDRplay’s performance as I’ve had comparatively little dedicated time with the unit.
Yet I have had the RSP2 on the air a few hours of casual listening, and find that it performs as I would expect: low noise characteristics and sensitivity that seems to be at least as good as the RSP1, if not a bit better. I’m looking forward to a side-by-side with the RSP1 running an install of SDRuno on my laptop!
I must say that I’m very pleased with the RSP2’s Mediumwave/FM notch filter. It happens that a local daytime 45kW AM broadcaster in our area is having transmitter issues which send wideband spurs across the entire HF spectrum; but at night, when the station lowers its power levels, the RSP2’s MW notch filter effectively mitigates the noisy signal. I imagine this filter will be a welcome addition for listeners living in RF-dense environments.
When the RSP1 was first introduced, it retailed for $149. As the economies of scale worked in their favor, SDRplay lowered the price to $129. The new RSP2, meanwhile, is expected to retail at approximately £130 (excluding taxes), or $169 US (excluding taxes). Quite a value, in my opinion: at $169, you’re getting a lot of SDR for the price––and an effective SDR application, to boot.
But if you already own an RSP1, I wouldn’t necessarily rush out and grab the RSP2 just yet. Of course, if you like the added features mentioned above, or if you’d like an inexpensive SDR with no less than three switchable antenna ports and a MW/FM notch filter, $169 is a bargain and about the same level of investment as a good modern shortwave portable.
As for myself, I’m happy to see a mom-and-pop community-supported company like SDRplay continuing to innovate for our hobby. I’m pleased to support them, and am truly appreciative that they also support our SWLing Post. This is a win-win, in my view; I’d be pleased to support more such companies.
Again, check back here as I plan to compare the RSP2 with the RSP1 and several of my other SDRs.
I plan to take the RSP2 with me on my travels this week. Time permitting, I might even pair it with my recently acquired PK magnetic loop antenna for some spectrum gathering and testing.
In the coming weeks, as my schedule permits, I’ll post updates here on the SWLing Post, including audio comparisons with some of my SDRs. If interested, bookmark the tag RSP2.
For more information about RSP2 pricing and availability, check out SDRplay.com.
Today, we released version 1.1 of SDRuno, specifically for RSP. New features include a calibrated power measurement facility, an SNR meter and automatic S-meter calibration. There are many additional improvements and fixes. To find out more about all the additional features, documentation can be found on:
Paul Jones and Mike Ladd have worked tirelessly to get the new features documented in an updated version of the SDRuno Cookbook: http://www.nn4f.com/SDRuno-cookbook.pdf
Other SDRs can also use SDRuno with a new increased bandwidth limit of 2.5MHz.
Many thanks to Jon Hudson at SDRplay for sharing this info!
Many thanks to SWLing Post contributor, Mark Fahey, who shares the following:
It’s been a fun weekend getting the first two remote modules for the Spectrum Project MK2 together. These modules tune into and then digitally preserve broadcasted human communication; music, discussion, culture for future generations to study and ponder.
This initial version of the hardware provides 0-30MHz with four (simultaneous) independently configured receivers that are controlled remotely from anywhere on the planet. The first of the modules will be installed near Vladivostok in Russia’s far east and the second is planned to go to one of the “stans” in Central Asia, most likely Kazakhstan.
The hardware includes a KiwiSDR 0-30MHz SDR 4 channel receiver AM LSB USB CW FM plus GPS for precision timing and location information. A BeagleBone Green is the CPU and the compact 100KHz-30MHz active antennas we are using are precision built by RA0SMS in Irkutsk, Siberia, Russia.
(Note to fellow SDR geeks – the WinRadio Excalibur running on the iMac [above] is not part of the remote system – it just happens to live on my assembly bench).
Remote Module #1 prior to sealing.
This first generation is built to connect to a wired internet connection and power supply. The hardware includes a KiwiSDR 0-30MHz SDR 4 channel receiver AM LSB USB CW FM plus GPS for precision timing and location information. A BeagleBone Green is the CPU and the compact 100KHz-30MHz active antennas we are using are precision built by RA0SMS in Irkutsk, Siberia.
Remote Module #3 and later will support solar power and a 4G/ LTE connection so the devices can be located anywhere on the planet that has reasonable cell phone coverage.
Remote Module #2
This is Remote Module #2 sealed and ready for connection to a network and power supply. The hardware includes a KiwiSDR 0-30MHz SDR 4 channel receiver AM LSB USB CW FM plus GPS for precision timing and location information. A BeagleBone Green is the CPU and the compact 100KHz-30MHz active antennas we are using are precision built by RA0SMS in Irkutsk, Siberia.
Remote Module #3 and later will support solar power and a 4G/ LTE connection so the devices can be located anywhere on the planet that has reasonable cell phone coverage.
This is simply amazing, Mark. I can’t wait to try out the receivers in your Spectrum Project MK2 once they’ve been deployed and implemented. We’ve talked about this concept before, but what I love about Mark is he simply pulls the trigger and makes it happen as soon as technology has made it possible to implement.
Mark: please keep us posted with your updates!
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