A Preamp for the SDR

preamp8Figure 1:  A preamp tossed together on a piece of proto-board. Click to enlarge.

The performance of the Soft66 Lite is alright for the price of a couple fast food dinners, so I’ve no complaints.  But, I thought maybe some shoes could help it get a better footing, and bring those sought-after WX faxes down to earth with more clarity.  I thought “Why not give it a shot?”

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SoC/SBC Boards for Ham Radio (2)

fldigi-on-pi2withcirrus44Figure 1: FLDigi is shown running on the Pi2, decoding a BPSK signal, using Cirrus audio.

The Cirrus adapter worked just fine on the Pi2, as can be seen in figure 1.0. I took the audio first from the “phones” jack of an old amateur radio receiver, and then from the sound card of a second PC running a browser webSDR page. This audio was connected via the “line-in” connector of the Cirrus adapter in the Pi2 box. In both cases the audio was very good, and was adequate to decode signals while using a only a moderate input level. The noise and spur levels were much less than on an i386 PC based machine I had used for FLDigi/ham activities in the past.

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Ham Radio on a Pi2

quiskplussdrhardwareplusraspberry-1Figure 1: Quisk running on the second “homemade” tablet, which use a Pi2 SoC SBC board. (Click to enlarge).

Some of the other posts on this site refer to my “homemade” tablet, which I subsequently outfitted with components for ham radio usage.  I recently built another “homemade” tablet, this time using a Raspberry Pi2 board for the computing power.

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Note: This author is not affiliated with the Raspberry Pi/Pi2. For information about those projects visit http://www.raspberrypi.org. “Raspberry Pi is a trademark of the Raspberry Pi Foundation.  Figure 1 contains elements of a desktop system and associated programs that have been released under a free software license (Copyright: LXDE team: http://lxde.org). As a derivative work, the respective part of the screenshot in Figure 2 falls under that same license. The full text of the licences may be found at http://www.gnu.org/licenses/old-licenses/lgpl-2.1.en.html.  Fig1 contains another program that has been released under a free software license (Quisk). As a derivative work of that program, the respective part of the screenshot in Figure 1 falls under the same license (GNU GPL). This site/author has no affiliation with the author of the Quisk program. The code and full text license for Quisk may be found at https://pypi.python.org/pypi/quisk/.

Simple SDR + FLDigi


Figure 1: The graphic shows the layout of SDR, as utilized by hams.  Click to enlarge.

I decided to utilize the simple SDR hardware by using Quisk as the SDR software, and FLDigi as the digital mode software. It was simply a matter of stopping the WSJTx process and starting FLDigi. The FLDigi software picked up the audio feed with no manual intervention. After launch, it presented itself in the Pulseaudio control app (pavucontrol) recording tab, as …

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A Second SDR for the Desktop

Figure 1: I liked the “Soft66 Lite” so much I decided I needed another for the desktop, in addition to the one purchased for the homemade tablet. For the desktop unit, a separate enclosure was needed.

These tiny little things are addicting! The enclosure was outfitted with a couple switches to do bandswitch duty, since (unlike the homemade tablet) there will be no GPIO to apply for that function. A big, clunky SO-238 connector was attached to the box, to accept the PL-259 plug from the antenna coax. And of course, holes were made for the audio and power connectors.

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Using Simple SDR hardware

wsjt-scrn1 Figure 1: The combination of the “Soft66 Lite SDR hardware, the Quisk SDR software, and the WSJTx digital mode software is displayed in the graphic (the WSJTx screen shows two CW signals).

The Soft66 Lite SDR hardware worked well with the Linrad SDR software, for copying CW signals or SSB signals on a variety of ham bands. While that was fun, I decided to take it a bit further, and use the Soft66 SDR hardware, the Quisk SDR software, and the WSJTx digital mode software to copy JT-9 and JT-65 style digital communications.

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A Shortwave Receiver for the “Homemade” Tablet

Figure 1: The “soft66 Lite” SDR (software defined radio) board. It’s a fun thing to build in a spare three hours, and even more fun to operate!

Recently I’d integrated a “homemade”  tablet into the station, for things like receiving weather faxes and BPSK31 transmissions.  I’d been using external receivers to do that, but mentioned that I really wanted to put a “shortwave” receiver board inside the tablet, for an all-in-one effect…

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