What to do about SDR?

For quite a while now, I’ve been thinking about what I should do about software-defined radio (SDR). For one thing, I’d like to write about it here on KB6NU.Com. For another, I’d like to learn more about it – how it works, what’s available, etc.

I”ve decided that short of writing a book about the topic, I’m not going to try to write something comprehensive, but instead just little bits about SDR as I come across them. So, with that in mind, here’s some SDR stuff that I’ve come across recently.

  • DVB-T Mini DongleDVB-T Mini Digital TV USB Stick Dongle. Based on an exchange of e-mails on the AMRAD mailing list, I recently purchased one of these little dongles. Apparently, a bunch of AMRAD members purchased this unit at a recent hamfest, and they’ve all been having fun with them.Unfortunately, it looks like I purchased the wrong one. This design is not supported by the commonly available SDR software. The dongles that are supported use the Realtek RTL2832U chip, so look for that before purchasing.

    Coincidentally, one of the guys here in Ann Arbor, purchased a FunCube Pro dongle at Dayton and brought it down to the museum Saturday. It costs significantly more ($150), but it will tune 150 kHz to 1.9 GHz. It will be fun to compare the two.

  • SoftRock, Peaberry. A couple of months ago, I purchased a SoftRock Lite II kit from someone who hadn’t gotten around to building it and decided that he was probably never going to get around to it. Well, of course, I haven’t gotten around to building it yet, either, but I do hope to get to it sooner rather than later.I have since come across the Peaberry line of kits. The Peaberry SDR V2 kit looks interesting. For $150, you get a multi-band SDR transceiver.
  • RTL-SDR.Com. This blog covers a wide range of topics including how to receive all kinds of different transmissions with DVB-T dongles that use the RTL chips. One recent article compares SDR using the RTL dongles and the FunCube Pro dongle.

From my Twitter feed: Whitebox, four-layer PCBs, propagation service

HamBeat1
Combining Software Defined Radios and Smart Phones: http://t.co/reduPzk6Qn#hamradio #hamr

This is a very interesting project, and I hope that it gains some traction.

mikelectricstuf
How 4 layer PCBs are made http://t.co/R4VNy2yloj

DH1TW
Radio Propagation as a service http://t.co/siVQ8tEDsQ #hamr @k6tu

30 bucks seems reasonable for this service.

From the trade magazines: capacitors, inductors, radio architectures

Temperature and voltage variation of ceramic capacitors. Read the data sheet! This tutorial explains how ceramic capacitor type designations, such as X7R and Y5V, imply nothing about voltage coefficients. You must check the data sheet to really know, how a specific capacitor will perform under temperature and voltage.

Circuit measures capacitance or inductance. You don’t need a fancy LC meter to measure capacitance or inductance. This short article show you how to do it with a function generator, multimeter, frequency counter, and an oscilloscope. Hmmmmm. By the time you get that all lashed up, it might have been quicker to just buy one of these LC meters from China.

Understand Radio Architectures. This is the first in a series of excerpts from the book RF Circuit Design, 2e by Christopher Bowick. Even though this appears in an engineering trade magazine, some of this is pretty basic stuff. You even get a schematic for a crystal radio!

Yet another Heathkit?

heathkit-screenshot-20130521

 

Twitter is abuzz with news that someone is trying once again to revive Heathkit. The image above was taken right off the Heathkit home page.

Even more amusing is the online customer survery. It’s quite an extensive survey and very heavy on the amateur radio questions. GB Hoyt (KB4GVL, @kb4gvl on Twitter) has an interesting take on what it will take for them to succeed on his blog.

Take the survey and tell me what you think. Can Heathkit be resurrected?

 

 

From my Twitter feed: future of SDR, Dayton review, fritzing

K9ZW
The Future of SDR – Fat-Pipe vs. Thin-Pipehttp://t.co/u6WpGGv6ML

 

ke9v
Dayton in the Rearview Mirror | Smoke Curlshttp://t.co/PI25XUisGR #hamr

 

g6avk
This looks like an interesting and easy to use PCB package - http://t.co/xsL7rY2t7n

Amateur Radio Tip of the Day: Keep your soldering iron tip clean

To make good solder joints, you need to keep the tip of your soldering iron clean from any oxides and dust or dirt. A clean, well-tinned tip will transfer heat properly and help you avoid cold solder joints. Many solderers use wet sponges to clean soldering iron tips, and many solder stations have troughs to hold these sponges.

soldering_iron_tip_cleaner

An alternate method is to use a wire cleaning pad like the one shown above. You stick the iron into the pad and then draw it back out. The wire scrapes the oxides and dirt from the tip as you do this. Proponents of this method claim that this method increases the life of the tip as it avoids the rapid temperature changes that using a wet sponge cause.

73!

Dan

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Solder: 60/40 or 63/37?

File this under  “You learn something new every day.”

A 1-lb. roll of Kester 44 solder with a 63/37 tin-lead formulation is $22.96 from AllSpec Industries. Kester 44 with a 60/40 formulation costs only $21.06.

A 1-lb. roll of Kester 44 solder with a 63/37 tin-lead formulation is $22.96 from AllSpec Industries. Kester 44 with a 60/40 formulation costs only $21.06.

A couple of days ago, someone on the HamRadioHelpGroup mailing list asked, “So I’m about to put up my first antenna and I need to solder the connectors to the coax. I know learned this in the book but I can not find it, so what kind of solder should I be using?”

Pat, K7KBN, replied, “Rosin core, 60/40 lead/tin (63/37 is better).  Don’t use any acid core or acid flux solder, and avoid the no-lead junk.  The diameter of the solder depends on your taste and experience.  Connector work requires more solder than circuit board work in most cases. And for connectors you need an iron with a massive tip that won’t cool off when you touch the body of the connector like a typical gun tip will.”

So, of course, I had to ask, “Why is 63/37 better?”

The answer? “The 63% tin/37% lead solder alloy is “eutectic” (Google it).  Basically it has NO ‘plastic range.’ It changes instantly from liquid to solid.”

Mark, K5LXP, ever the practical ham, added, “For anything hams solder you would be hard pressed to discern the flow, hardness or durability difference between any of these lead alloys. Hams being hams, 60/40 is usually the cheapest. That makes it ‘better’ right there!”

From the trade magazines, impedance matching, EMI basics, open-source hardware

elelctronic-design-logoBack to Basics: Impedance Matching. electronic design editor (and amateur radio operator) Louis Frenzel is the author of this short e-book on impedance matching. Note: this e-book was intended for engineers and does use a fair amount of math, but nothing you can’t figure out if you work at it.

EMI Basics. This article  comes from the book Signal Integrity Issues and Printed Circuit Board Design by Douglas Brooks. I like the discussion of how twisted pair wire helps prevent radiation.

Interview With SparkFun’s Director Of Engineering. Peter Dokter is director of engineering for SparkFun, one of the major suppliers of open source hardware. SparkFun designs and sells things useful and interesting to the aspiring electronics tinkerer, including microcontroller boards, Bluetooth, GPS, Wi-Fi, LCD displays, e-textiles components, robots and robotic parts, motors, motor drivers, buttons and switches, tools, and books.

From my Twitter feed: kits, cool transmitter, new CW book

MW0IAN
Tim Walford G3PCJ does a nice bunch of radio kits and accessories http://t.co/ZgIdxUc2aj

 

This brings new meaning to “having a cool one.”

kc5fm
“A new “Cool Transmitter” from W5IG.”http://t.co/vtxAwfsWar #ARRL #hamradio

 

The ARRL stole my idea! (just kidding)

ke9v
NEW book from the @ARRL – Morse Code Operating for Amateur Radio ~ Don’t Just Learn Morse Code, Master It!http://t.co/kzlgAQJSUN #hamr

 

From my inbox: 1, 2, 3-tube radios, cheap cap tester, cheap frequency synthesizer

  • Build a radio with three tubes or less. This article lists radios that you can build with three tubes or fewer. In general, this is a very cool website. (Thanks to Brad, AA1IP, and the Glowbugs mailing list.)
  • Cheap capacitance tester. The Glowbugs mailing list also recently had a discussion of cheap capacitance testers. I just bought a fancy, new Keithley DMM  that measures capacitance, but some of the instruments mentioned in this thread also measure inductance. The consensus seems to be that while they’re not as accurate as a “real” test instrument, for $20 or so, how can you go wrong?Brad, AA1IP mentions the article, “A Low Cost Automatic Impedance Bridge” by Dr. George Steber, WB9LIV, that appeared in the October 2005 QST. Brad says, “This arrangement uses a PC’s sound ports, a dual-section op amp, a few components and some software to deliver reasonably precise RLC measurements along with a graphic screen display.”
These frequency-synthesizer boards use the AD9850, and can be purchased on eBay for as little as $5 each.

These frequency-synthesizer boards use the AD9850, and can be purchased on eBay for as little as $5 each.

 

  • Cheap AD9850 boards. The AMRAD mailing list has a thread on these inexpensive signal-generator modules. One of the AMRAD guys has been experimenting with using them with an Arduino to make frequency control easier. They’re only $5 each and generate 0 – 40 MHz.On the Glowbugs list, they talked a little bit about these boards, too. One guy gave a link to the article, “An Improved VFO Driver Amp for Tube Rigs.” This article describes a circuit that allows you to easily use the AD9850 boards (or any other digital synthesizer, for that matter) as the VFO for a tube rig.