Tag Archives: Software Defined Radio

Medium wave SDR spectrum with over 20 transatlantic signals: a quick tour

 

Tour of a medium wave spectrum with over 20 transatlantic signals

Hi there, I thought some of the readers of SWLing Post might be interested in a review of a MW spectrum with multiple transatlantic signals – all with audio. This is one of the recordings I took with the 200 metre Beverage antenna and although I haven’t properly counted, I believe it generated about 50 catches that were either personal firsts or best-ever receptions. You will note that this video is nearly 20 minutes long, whilst the recording is only just over 5 minutes, thus to capture the signals listed below and demonstrate audio to you, it was necessary to effectively ‘rewind’ a few times. I haven’t annotated the video, however, the stations I’ve paused on to demonstrate audio are listed below. There are actually more catches in this spectrum, but hopefully the video will give you a good idea of propagation on the morning of 10/10/16 and the effectiveness of the Beverage/Elad FDM DUO combination. Also note, I didn’t have time to fully optimise the demodulation settings, so for example, I haven’t used AM SYNC in this demonstration. Individual videos of all catches, with optimised settings appear on my YouTube channel Oxford Shortwave Log. I hope you enjoy it! Recorded in Oxford UK on 10/10/16 at 02:00 hrs UTC. Thanks for watching and I wish you all great DX!


590 kHz VOCM Saint John’s
600 kHz CBNA Saint Anthony
620 kHz CKCM Grand Falls-Windsor
660 kHz WFAN New York
710 kHz WOR New York
730 kHz CKAK Montreal
750 kHz CBC Radio 1 Bonavista Bay
790 kHz WAXY (presumed)
800 kHz VOWR
970 kHz WBGG
1010 kHz CFRB Toronto
1030 kHz WBZ Boston
1130 kHz WBBR New York
1190 kHz WLIB New York
1280 WADO New York
1390 WEGP Presque Isle
1400 kHz CBC Radio 1 Gander
1440 kHz WRED Westbrook
1510 kHz WMEX Boston
1520 kHz WWKB Buffalo
1570 kHz XERF La Poderosa, Mexico
1580 kHz HJQT Verdad Radio 1580 kHz, Bogotá, Colombia
1610 kHz Caribbean Beacon, Anguilla
1660 kHz WGIT Puerto Rico


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.

Chris tracks down sources of radio noise

spectrum-waterfall-sdr

Many thanks to SWLing Post contributor, Chris Smolinski, who shares this guest post from his blog, RadioHobbyist.org:


Yet Another !&*%$! Noise Source

by Chris Smolinski

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):

pmuv3bc

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:
qormmpg

First, I relocated the AFE822 away from the computer and rats nest of assorted cables behind it, powered from an HTC USB charger:
kljq7ef

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:
goyrdt4

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:
k0e8eaw

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.

ocsavij


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.

Follow Chris at RadioHobbyist.org.

Oxford Shortwave Log: transatlantic MW DX catches with 200 metre Beverage – part 2

verdad-final

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.

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

worspectrum

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!


elad

 

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.

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

afe822x_bnc_pcb_640px

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 http://fyngyrz.com/?p=915

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.

Download the Mac beta (Windows version coming soon) of SdrDx: http://fyngyrz.com/beta.zip
If you have not used SdrDx before or recently, first download the stable version, and run that: http://fyngyrz.com/SdrDx-AA7AS-Light.zip
SdrDx page: http://fyngyrz.com/?p=915

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.

wn9t4nm

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!