Category Archives: Software Defined Radio

North American and European medium wave signals into Oxford, UK

Hi there, I’ve been rather preoccupied of late, initially with the brilliant Tecsun PL-310ET and latterly with the even more brilliant Eton Satellit. However, in the background (as always), I’ve been trying to catch transatlantic medium wave DX. My listening schedule is broadly based on shortwave DXing during daylight hours – when I’m not at work of course, typically a Friday afternoon or at weekends – and always with a portable. Evenings usually start off with a tune around the tropical bands, followed by setting up the Elad FDM DUO to run some medium wave spectrum recordings overnight. In the past few days though, my daylight DXing has been bolstered by my NooElec RTL-SDR and ‘Ham it up’ upconverter. I bought the device over a year ago and after some initial exceitement, it quickly became quite obvious that I needed a reciever with a bit more ‘oomph’! However, it’s actually proving very useful to view signals on a  spectrum, even when I’m conducting most or all of my listening on a different (i.e. higher performing) receiver. Ultimately, the RTL-SDR is always going to be a compromise, with relatively limited sensitivity, but because by it’s very nature it has excellent selectivity, overall it’s a reasonable performer. My particular RTL-SDR performs quite well if a decent antenna is employed with it, such as a longwire or the Wellbrook ALA1530 active loop.

Anyway, back to the medium wave DX. In the past month or two, I’ve copied a number of stations from North America, with really nice signals, including WRCR Rampano – New York, WFED Federal News Radio – Washington DC, WENE – Endicott and WUNR – Brookline from Newton, Mass. I’ve also recorded a lovely interval signal from RAI Radio 1, Milano and further European signals from Magyar Radio, Budapest and Radio Slovenija 1, from Ljubljana. During the past 18 months or so of DXing, I have been mostly ignoring signals coming into Oxford from the continent. However, that changed a little after I stumbled across the RAI Radio 1 interval signal, which complete with the rather rousing Italian National Anthem, inspired me to dig out some more European DX. I’m actually finding European DX quite rewarding, particularly because it feels new again – not surprising since I haven’t listened to Europeans on medium wave for any length of time since the 1980s. I hope you enjoy the reception videos – embedded video and text links follow below and I wish you all the very best DX. 


Click here to watch on YouTube

 

Click here to watch on YouTube

 

Click here to watch on YouTube

 

Click here to watch on YouTube

 

Click here to watch on YouTube

 

Click here to watch on YouTube

 

Click here to watch on youtube

 

Click here to watch on YouTube

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.

The new Elad FDM-S3 SDR: screenshot of the entire FM broadcast band

Click to enlarge.

Many thanks to SWLing Post contributor, Rafman, who shares this tip via the Elad Yahoo Group where Elad engineer Franco writes:

Today I can show new hardware capabilities of FDM-S3:

24.576 MHz I/Q stream and you can see the whole 88-108MHz FM Band sampled.

The FDM-S3 is equipped of USB-3 controller…

Here a screenshot:
https://www.dropbox.com/s/uxlfi…/FDM-S3_FM_BAND_24MHZ_1.png
new info will come in next weeks.

73, Franco IU3ADL

Wow–the entire FM broadcast band! I bet recording that would burn through a 1 TB hard drive in no time! Can’t wait to try it!

As SWLing Post readers know, I love the FDM-S2. Very happy to hear the FDM-S3 is in the works.

We’ll post updates from Elad as they’re released. Follow the tag: FDM-S3

FM Notch Filter for SDRPlay RSP1

RF filters are used (as the name implies) to filter/remove the frequencies you are not interested in and/or let frequencies you want pass . They come in lots of types. For example a band-pass filter lets the signals in a frequency range to pass through it and rejects/attenuates other frequencies. The opposite of band-pass filter is a band-reject or band-stop filter (also called a notch filter) which rejects/attenuates signals in a specific range and lets other frequencies get through the filter. Lots of different filters are used in SDRs and traditional radios. For example AM low-pass filters (only let frequencies lower than 1.7MHZ or so pass) or band-pass filters for various ham radio bands.

One of the popular use cases for a notch filter is in the FM broadcast range (88-108 MHZ in most parts of the world)

When you live near a powerful transmitter, it can affect the operation of your receiver in other near frequencies (or overload your receiver’s front-end), but I didn’t want the notch filter for this reason. I’ve got a SDRPlay RSP1 (among many other SDRs) which due to its architecture, has some images of FM band in the UHF range (for example in 330-350 MHZ). In fact they’re the images of the product of LO harmonics and FM frequencies.

You can temporarily move/shift the frequency by changing the LO frequency which does not remove them, but moves them around.

Another method to remove these images is using a band-stop filter.

This is the filter I’m using (Thanks to my friend Amirhosein Hasanpur who designed and built it):

Here you can see the effect of using a FM notch filter on my SDRPlay RSP1:

FM, without filter:

FM, with filter:

UHF (images) without filter:

UHF (images) with filter:

Here’s a link to a Zip file containing the PCB (in Protel), schematics (pdf) and S Parameters (pdf):

https://www.dropbox.com/s/l98kylrofohgqxf/SWLing.zip?dl=0

Note: Like any other SDR test/review, the results depend on lots of different parameters (various gain values, LNA, antenna, software, etc). These pictures are captured with the same conditions just to show the effectiveness of this filter and your milage will definitely vary, but expect a similar outcome. If you live close to a powerful transmitter or use LNAs, you will receive some signals, even when using the filter.

Final note: this issue is solved in the newer version of SDRPlay (RSP2) : it has software-selectable notch filters for FM and MW broadcast frequencies.

Mehdi Asgari, the author of this post, is a regular contributor to the SWLing Post. Mehdi lives in Tehran and is an active member of the EP2C amateur radio club.

Visualising shortwave band activity throughout the year

This article originally appeared on the London Shortwave blog.

24-hour shortwave spectrum image, showing activity for a single day in the first week of February 2017 (©PA3FWM, Twente WebSDR).

As many of my readers and followers will already know, these days I mostly enjoy listening to shortwave radio via the outdoor spectrum captures I make in my local park. Although I have built a system that helps me deal with urban radio interference at home, some of the weaker signals still can’t make it through the indoor noise. Since I have a limited amount of time for making outdoor trips, capturing entire portions of the spectrum allows me to record a lot of shortwave signals simultaneously, which I can then explore individually at a later time. However, these trips still need to be carefully planned because the time of the day and the time of the year both affect long-distance signal propagation, and do so differently depending on the frequency range. For example, signals on the 16 meter band are usually at their strongest during the daylight hours, whereas the 31 meter band is at its busiest around sunrise and sunset. Because my current portable recording set-up allows me to capture only 10% (3 MHz) of the shortwave spectrum at any one time, I decided to carry out a systematic exploration of activity on the shortwave bands to help me time my outings so as to capture as many signals as possible during each trip.

Capturing the shortwave spectrum out in the field with a portable SDR set-up.

Luckily, I didn’t need to make any of my own measurements for this. For over a year, the wide-band WebSDR at the University of Twente has allowed its users to see what the shortwave spectrum has looked like over the past 24 hours in a single image. More recently, however, the creator of the service, Pieter-Tjerk de Boer PA3FWM, has opened up his spectrum image archives, so it is now possible to see the past conditions of the bands on any single day in the last two years. Intrigued by how band activity changes depending on the time of the year, I created a timelapse animation of these images by taking two from each calendar week and lining them up in sequence. With Pieter-Tjerk’s kind permission, I share this animation below.

First, a really fast version to illustrate the broad effects the time of the year has on peak activity times across the bands:


 Click here to view on YouTube

The X axis represents the frequency and the Y axis is the time of day, starting at the top. Conventional wisdom about band behaviour can be easily confirmed by watching this video: the 60m, 49m and 41m bands are mostly active after dark, with the 60m and the 49m bands being generally busier during the winter months. The 31m band is most active around sunset, but carries on all night until a few hours after sunrise. The 25m band is active during sunrise and for a few hours afterwards, and around sunset during the winter months, but carries on all night during the summer. Peak activity on the 22m and 19m bands is also clustered bi-modally around the morning and the evening hours, though somewhat closer to the middle of the day than on the 31m and the 25m bands. The 16m band is mostly active during the daylight hours and the 13m band is quiet throughout the year except for the occasional ham contest.

It almost seems as though someone positioned in the middle of the image’s right edge (corresponding to noon UTC) is shining two flashlight beams on the bands in a V-shaped pattern, and is changing the angle of this pattern depending on the time of the year: wider in the summer and narrower in winter. Here’s a slower version of the animation that shows some finer week-on-week changes:


 Click here to view on YouTube

Thanks to this data being made freely available, visualising and understanding these dynamics will help me schedule my spectrum capture outings in the weeks and months ahead.

A quick view of my shack in Oxford, UK & recent transatlantic medium wave DX

Someone recently described my shack in Oxford as ‘an impressive mess’…. and that really is just about the most positive comment I’ve ever received regarding my listening post! So, my apologies for displaying the mess in public, but in response to having been asked many times by subscribers to Oxford Shortwave Log to ‘share my shack’, here it is, well most of it at least, in all it’s unadulterated glory.

 

The primary reason however for this post is to share my most recent transatlantic medium wave catches using the brilliant Elad FDM DUO and Wellbrook ALA1530 magnetic loop antenna. This excellent combination continues to pull in really nice DX, although not so much very recently as propagation has been fairly rubbish. However, since early to mid December, the dynamic duo have managed to pull in a number of transatlantic medium wave signals, including Radio Rebelde, Cuba on (670 and 710 kHz), KVNS Texas, CHIN Radio, Toronto, WFED Washington DC, WWNN Health and Wealth Radio, Pompano Beach, Florida, and huge signals from WMEX Boston and WWKB Buffalo, New York. Embedded reception videos and text links follow below and in the mean time, I wish you all great DX!


Click to watch on YouTube

Click to watch on YouTube

Click to watch on YouTube

Click to watch on YouTube

Click to watch on YouTube

Click to watch on YouTube

Click to watch on YouTube

Click to watch on YouTube

 

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.