Category Archives: How To

Sproutie hears the Shortwave Shindig

SWLing Post reader, Dave Richards (AA7EE), made a short video of his regen receiver “Sproutie” tuned to the Shortwave Shindig Friday evening.

Dave writes:

“I was quite pleased with the fidelity. Of course, the skirts on a regen are quite broad, even though the nose of the selectivity curve is fairly narrow. The signal was a bit lower in level and noisier at the beginning of the show but by the time it got to this segment, it was a nice strong signal. Sorry – no S-meter here, so that is the best I can do!”

Dave, thanks for sharing this video! Sproutie did a brilliant job tuning in a program from across the continent. I’m also most impressed with Sproutie’s audio. Amazing!

Readers, click here to read a previous post about Dave’s home brew regen receiver, “Sproutie.” Also, be sure to bookmark Dave’s blog by clicking here.

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Pulling Radio Santa Cruz out of the interference

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I recorded Radio Santa Cruz early this morning around 05:00 UTC on 6,135 kHz using the TitanSDR I currently have under review.

Radio Santa Cruz‘s 10 kW signal from Santa Cruz, Bolivia, was very much audible here in North America, though RSC was competing with another station on-frequency at the time. Actually, Radio Santa Cruz was broadcasting slightly off-frequency–6134.8 kHz instead of 6,135 kHz. In this case, the fact that RSC was slightly below frequency helped me delineate the station’s audio from that of a competing station.

In the screen-grab of the narrowband channel from the Titan SDR (above–click to enlarge) you can see two distinct carriers spaced only .2 kHz apart (represented by the two peaks in the spectrum display and two parallel vertical lines in the waterfall display).

Here is what the audio sounds like in normal AM mode when we center on the Radio Santa Cruz frequency of 6,134.8 kHz:

You hear a hetrodyne and garbled noise from a competing station. Not pleasant audio.

If we change from the AM mode to eLSB mode (essentially, the TitanSDR’s version of synchronous detection on the lower sideband) we are ignoring all of the noise in the upper sideband, allowing the desired signal of RSC to pop out.

You can see in the screen-grab above that now only the lower sideband of the RSC signal is highlighted. Here’s a 21 minute recording:

Makes quite a difference!

It’s easy to see competing signals and interference on an SDR’s spectrum display, but if you hear something similar on your portable, try the techniques above to see if it clears up the signal.

If your receiver lacks a selectable synchronous detector, much of the same results can be gained by zero-beating (tuning in) the desired signal in lower sideband mode. Of course, if you have a receiver that lacks SSB mode, the best you can do is tune slightly below frequency in AM, in which case the results will not be as dramatic.

Conclusion? Listening in single-sideband or with a selectable sync detector might be all you need to dig a signal out of the interference.

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Two strategies to improve Sangean ATS-909X sensitivity

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SWLing Post contributor, Moshe, writes:

“I would like to share something I noticed about Sangean sensitivity issue:
As I own the ATS909, I noticed that with fresh set of regular batteries (1.5V) or it’s power transformer, it is very sensitive.
When the voltage of the batteries drops, so does sensitivity! Which means that if one uses rechargeable batteries (1.2V), the radio will be much less sensitive to begin with.”

Many thanks, Moshe! That is a very good reason to keep fresh alkaline batteries for the 909X, or to run it on a quiet power supply. Moshe is correct–fresh rechargeable batteries can’t deliver full voltage.

Several weeks ago, a reader informed me about a modification that increases SW sensitivity by adding a 4:1 impedance transformer.

Click here to download a PDF that documents the 4:1 transformer procedure.

Note that I can’t remember who shared the PDF and am not sure who was so kind to document the procedure with photos. Any additional information would be appreciated.

Have any readers performed the transformer mod on the ‘909X with success?

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Video: Chris reviews the Tecsun 2P3 AM radio kit

SSB for the non-technical

Video: Controlling the Elad FDM-S2 SDR with the HP Stream 7 tablet

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Many thanks to SWLing Post contributor, Guy Atkins, who shares the following video demonstrating how the Elad FDM-S2 can be controlled with the $99 HP Stream 7 Windows 8.1 tablet PC:

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Using the Elad FDM-S2 on the $99 HP Stream 7 tablet

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The HP Stream 7 Windows 8.1 tablet

Regarding the Elad FDM-S2, Guy Atkins comments:

“This week I bought an HP Stream 7 tablet from the local Microsoft Store for $99, and it runs my Elad FDM-S2 receiver great! This recently introduced tablet is the perhaps the lowest priced new computer with Windows 8.1. I can even record the entire MW band, and play back the WAV files without audio stuttering. CPU load is an impressive 11-12%. Once you add a small OTG USB adapter you can plug in a USB hub and attach a wireless mouse receiver, the SDR’s cable, and other stuff. I was recording to a micro SD card (the slot is a bit of a pain, as you need to remove the back cover of the tablet. Recording to a USB external HD or SSD may also work). I also had an AC adapter powering the USB hub, as the tablet’s micro USB port cannot supply enough current for the Elad SDR.

This will be a neat, very portable setup for camping DXpeditions and when I want to take the SDR right to the termination of a phased loop array antenna for adjusting nulls. I do that now, but it’s more of a hassle with a regular laptop.

I presume I’ll be able to run the Afedri SDR-Net in “LAN mode” also but I’ll need to attach a USB-to-LAN adapter to the tablet first. A LAN rather than a USB connection is required for this particular SDR to have the bandwidth to handle all of medium wave at once.

Here’s a review of the 7-inch, Win 8.1 tablet: http://www.youtube.com/watch?v=SoPNzx8bcVQ. Also, when you buy it for $99 USD it includes a one-year subscription to MS Office 365, that can be used on two different devices. That’s worth $70 in itself.”

Wow–thanks so much for sharing this, Guy.

I’m very impressed you can record the entire MW band to an SD card and playback without stuttering. The quad core Atom processor must have enough horsepower to cope with the incoming data.

This setup would be ideal for field recording then taking the SD card back to the PC for analyzing later on a larger screen.

As you use this set-up, Guy, please keep us informed about any tips or quirks you discover along the way!

I found the Stream 7 at the following places online:

Update: Check out Guy’s video demonstration of the Stream 7/FDM-S2 combo.

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