Category Archives: Software Defined Radio

A very simple mod for your PowerMate controller

My Powermate USB sporting a white rubber band grip.

My Powermate USB sporting a white rubber band grip.

After publishing the post about my PowerMate USB controller, Mike Ladd replied on Facebook:

“Do what I did a couple of years ago and add a lobster claw rubber band to the [PowerMate] tuning wheel.”

In case you’re not familiar, Mike is referring to the thick, wide rubber bands that are placed on lobster claws to hold them shut. Mike included the following video; you can see that the rubber band fits perfectly around the top of the tuning knob, giving it a little extra grip.

https://www.youtube.com/watch?v=gtlDMSpaj4c

This same type of rubber band can often be found in the produce department of grocery stores as it’s used to hold bunches of broccoli, asparagus and other produce together.

Many thanks for the tip, Mike!

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Using synchronous detection and notch filter to eliminate het noise

WinRadioExcalibur-VOG-Notch

The lighter shaded side of the AM carrier indicates a lower sideband sync lock. (Click to enlarge)

A few days ago, I tuned to 9,420 kHz and found a relatively strong signal from the Avlis transmitter site of the Voice of Greece. The broadcast was quite clear until a heterodyne (het) tone popped up out of nowhere.

I checked the spectrum display of my Excalibur to find two steady carriers located about .5 kHz off each side of VOG’s AM carrier. I assume this may have been a faint digital signal centered on the same frequency as VOG.

The noise was annoying, but SDRs (and many tabletop radios) have tools to help mitigate this type of noise.

The het tone was originating from both sidebands of the VOG AM carrier (see spectrum display above). I had planned to use my notch filter to eliminate the noise, but I had two carriers to notch out and only one notch filter.

VOG AM carrier

Synchronous detection to the rescue… 

The simple solution was to eliminate one of the carriers using my SDR’s synchronous detector which can lock to either the upper or lower sideband. In this case, it didn’t make any difference which sideband I locked to because both had similar audio fidelity and were otherwise noise free. In the end, I locked to the lower sideband, thus eliminating the het in the upper sideband.

Next, I enabled my notch filter and moved its frequency to cover the annoying het carrier in the lower sideband; I kept the notch filter width as narrow as I could to preserve VOG’s audio fidelity. You can see the notch filter location and width in the spectrum display above (the notch filter is the thin yellow line).

I should note here that the great thing about using an SDR–or tabletop receiver with a spectrum display–is that you can see where the noise is. I was using my WinRadio Excalibur, but pretty much any SDR in my shack could have handled this task.

The results? No het tone and I was able to preserve the great audio fidelity from the Voice of Greece broadcast!

Here’s a 3.5 hour recording I made after cleaning up the signal. I believe at one point in the recording, I switched off the notch filter to demonstrate how loud the het tone was:

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Android tablet SDRs?

Image: screen grab from SDRtouch video

SWLing Post reader, Philip, writes with the following question:

“I want to know if you are aware of any good shortwave receivers that can be used on an Android tablet.”

I am aware of the Android SDR application, SDR Touch (see image above), but have never used it so I can’t comment on compatibility with the various SDRs on the market. I know that SDR Touch is compatible with devices that support USB host mode–but you may need to do research to see if your Android device and potential receiver are compatible. I believe most SDR Touch users connect their device to RTL-SDR dongles.

Readers: Please comment if you have any suggestions for Philip. I’m also curious if anyone has had success pairing an Android tablet to an HF-capable SDR.

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Hamfest find: Griffin Technology PowerMate Controller

GriffinPOwermateUSB

A few weeks ago, I attended the WCARS hamfest in near Waynesville, North Carolina. I walked out of that hamfest carrying way more goods than I had intended to purchase (more on that in a future post–!).

One of the best bargains I found was a Griffin Technology NA16029 PowerMate USB Multimedia Controller. The seller is a friend; he was trying (and succeeding) to push off a lot of his gear on me. We were actually in reverse price negotiations at one point–as he kept discounting prices, I was trying to raise them.

Knowing I’m an avid SDR guy, he insisted I give this Griffin Powermate controller a go.  I purchased it for $5 after I believe he had offered it for free (yes, the results of reverse negotiations).

I took the controller home assuming it would be cumbersome to interface with my SDRs–what a poor assumption I had made! It was a breeze: simply install the driver, and launch its associated application. The software makes it very easy to associate PowerMate controller actions with keystrokes and other PC functions.

PowerMate 8132015 54232 PM

There are a surprising amount of functions this simple knob performs:

  • Rotate clockwise and counter clockwise
  • Press down and rotate clockwise and counter clockwise
  • Press down once
  • Press down and hold

I set up the PowerMate to control my WinRadio Excalibur as follows:

  • Press and hold launches the WinRadio Excalibur application
  • Rotating the knob tunes up and down
  • Pressing down and rotating increases and decreases bandwidth
  • Pressing once toggles the volume mute

PowerMate-ExcaliburThe PowerMate is a brilliant piece of kit!

It has enhanced my user experience with the Excalibur. Soon, I’ll set it up to work with my Elad FDM-S2, and SDRplay RSP.

The PowerMate software allows you to set up multiple configurations, so it’s easy to call up a configuration based on the SDR being used (since mine have unique hotkeys).

The good news is a new PowerMate is only about $32 via Amazon.com.

I’m quite tempted, in fact, to buy a second unit to use with my laptop and to serve as a spare.

While looking up PowerMate pricing, I noticed more complex multimedia controllers on Amazon; I’m curious if any Post readers have experience with other models.

Seems to be a very affordable way to enhance your SDR user experience.

Click here to view the PowerMate on Amazon: http://amzn.to/1MmyxkC

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The SDRplay RSP now has gapless coverage

SDRPlay-RSP (1)

Jon Hudson with SDRplay has just informed me that they’ve released the latest version of the SDRplay RSP’s API and EXTIO which, among other things, removes the previous frequency gap between 380 MHz to 420 MHz. This is brilliant news for those of you who need continuous coverage from 100 kHz to 2 GHz.

RSP owners can download the new API and EXTIO on the SDRplay website.

Click here to read about other improvements, included with this API/EXTIO update, on the RTL-SDR blog.

Click here to read our recent review of the SDRplay RSP.

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Radio Serbia International recording and final farewell

Location of Serbia (green) and the disputed territory of Kosovo (light green)in Europe (dark grey). Source: Wikimedia

Many thanks to SWLing Post reader, “Mutezone,” who writes:

“I want to share a link to a video of Radio Serbia International’s English service recorded on the 4th of July 2015…

[…]I have been monitoring for RSI during the last week of July but got nothing. I have also been monitoring 6100 kHz after the July final date of transmission as according to RSI’s website, there are “Pirates stalking Serbian short wave” due to the termination of the station. However I have not received any odd transmissions on this frequency at the moment.”

Thanks for sharing this recording/video and, especially, for capturing RSI’s interval signal.

I was unable to hear RSI’s final broadcast on July 31, 2015.

If any SWLing Post readers managed to record RSI’s final broadcast–in any language–please contact me so we can add it to the Shortwave Radio Audio Archive.

Regarding the end of Radio Serbia International (or International Radio Serbia), the following final post was published on their website. I’ve included the full note, for archival purposes, in case the RSI website goes offline in the future:


The End of Radio Yugoslavia – International Radio Serbia

RadioSerbiaThanks for sharing the recording and for including a few minutes of the RSI interval signal. RSI was always a difficult broadcaster for me to catch here in North America, though I heard them a number of times via the University Twente Web SDR.

Dear friends, Radio Yugoslavia – International Radio Serbia, ceases to exist on 31 July 2015. For you, our faithful listeners from all over the world, and also for us who have worked on this radio, the only consolation would be the fact that this only state short-wave station in Serbia, which has existed for 79 years, will be remembered as an efficient and reliable promoter of Serbia worldwide. No one has ever presented valid reasons why this media, of rich tradition, range and staff potentials, and with big plans until yesterday, should cease to exist. Unfortunately, the assessments not based on arguments were louder than serious analyses and recommendations of experts, professionals and numerous listeners that the world radio service is necessary for Serbia, that it presents the country worldwide in the best manner possible and that no serious state will renounce such an effective diplomacy.

Our significance has been confirmed by the letters of thousands of listeners from all over the world. Some listened to us because of our information programmes, some because of economic topics, while many got to love our country, Serbia, because of its tradition, beautiful and interesting landmarks and the rich heritage they were acquainted with by listening to International Radio Serbia. Regardless of your affinities, you have all told us that you were listening to us because of our objectivity and the possibility of hearing us at any time and everywhere, for such is the power of short waves.

The Serbian government, however, believes that the closing down of Radio Yugoslavia – International Radio Serbia – is a justified move. Regardless of the fact that the state of Serbia is in an economic crisis, that each saved penny is precious, that many citizens have been rendered jobless, that new work positions should be opened, it has become unclear to the very end why the only state short-wave station has suddenly become too expensive after 80 years. We are, however, certain, that Serbian citizens, taxpayers, who have financed us for all these years, would have decided differently had they been asked to.

What remains, after all, is the pride we feel because of the history of our radio as well as the hope that the voice of Serbia will reach our listeners wherever they are.

Thank you, dear listeners from all over the world, for having trusted us all these years! Radio Yugoslavia – International Radio Serbia now greets you and signs off.

Source: http://voiceofserbia.org/content/end-radio-yugoslavia-%E2%80%93-international-radio-serbia#sthash.rvvWUjgx.dpuf

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The Siru Innovatios SDR20 adds new features

Siru-Innovations-SDR20-1

Many thanks to Jarkko Mäkivaara with Siru Innovations who writes with the following update:

We have added some new features to our SDR20 portable radio!

Please see the video [below] for a demonstration of the following features:
* Smooth zoom in FFT/waterfall view
* Adaptive menu
* Frequency memory with snapshot pictures of signals
* Sliding effect between views
* Keyboard beep
* FM broadcast receiver
* Example of Ham radio transceiver with Narrow-FM mode
You also might got the email sent out Today where this is in HTML format.

https://vimeo.com/134605242

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