From my Twitter feed: SDR, SWL, kits

sdrsharp's avatarsdrsharp @sdrsharp
You want more and better rtl-sdr tools? Consider helping this initiative from Kyle Keen indiegogo.com/projects/a-mon…

 

UlisK3LU's avatarUlis K3LU @UlisK3LU
Western radio broadcasters tuning out (excellent article on the demise of #shortwave broadcasters) via Straits Times shar.es/LgFv9

 

wa1gov's avatar#hamradiopic.twitter.com/oaBaj00Ady

From my Twitter feed: SDR, KX3 news, IoT

SWLingDotCom's avatarSWLing @SWLingDotCom
Designing a truly portable SDR goo.gl/fb/zCsyPI #shortwave #swl #dx

 

QRZnow's avatarQRZ Now @QRZnow
Elecraft Says It’s 2 Weeks Away! #hamradio fb.me/3xncqJtBg

 

iot4all's avatarInternet of Things @iot4all
Pinoccio: Mesh All The (Internet Of) Things hackaday.com/2014/07/15/pin… via @hackaday #IoT #IoE

From the trade magazines: free design tools, DSP, education

Top Free DIY Tools Ever Engineer Needs. We’re seeing a relative explosion in free tools for engineering electronics. Some of those online tools prove to be worthless, and it’s back to blind searching or some paid tool. To help sort out the nonsense from the useful online tools, check out this list.

What Do You Know About DSP? Louis Frenzel, who is a ham by the way, reminisces about his experience with digital signal processing (DSP) and recommends a new book for those just learning about DSP.

Outrageous! Experience is no qualification to teach EEs. This is another column by Louis Frenzel. He writes:

It is obvious that the colleges do not value industry experience when it comes to hiring professors….It seems to me that professors with real world experience could teach the fundamentals in context and to explain what is really important and what is simply nice to know. Experienced teachers would be able to teach students things they ordinarily do not teach in school. They could tell their design war stories and explain that troubleshooting is just as important to know as design. I think that an MSEE with ten good years of experience is more qualified to teach than a no-experience PhD.

From my Twitter feed: wire splicing, SDR, BCB loop

kd0bik's avatarJerry Taylor @kd0bik
How-To: Splice Wire to NASA Standards fb.me/3BMl1CsL0

 

rtlsdrblog's avatar<b”>rtl-sdr.com @rtlsdrblog
Using and RTL-SDR and RTL_433 to Decode Various Devices rtl-sdr.com/using-rtl-sdr-…

 

ke9v's avatarJeff Davis @ke9v
@AA7EE goes mad scientist with his Tuned Loop for BCB –> aa7ee.wordpress.com/2013/11/17/a-t…

From my Twitter feed: new EchoLink for Mac, SDR

dusty_s's avatardusty_s @dusty_s
EchoHam (formerly EchoMac) update in Mac App Store” <- glad to see an update! feedly.com/e/G5x1odQW

 

dangerousproto's avatarDangerous Prototypes @dangerousproto
OHM2013: Hacking the radio spectrum with GNURadio goo.gl/krngx7

 

VA3BCO's avatarBrian (VA3BCO) @VA3BCO
Are we Getting Closer to a Touchscreen SDR HT? >#hamr #hamradio wp.me/p4GMgg-28

2215 problem found

A couple of days ago I reported that I’d let the magic smoke out of my Tek 2215 oscilloscope. I was playing around with it last Friday evening, heard some arcing, and then saw a puff of smoke exit the back of the instrument. Oddly enough, the scope still seemed to work, though.

To get some help, I joined the TekScopes Yahoo Group and described my problem. Almost immediately, I got a couple of responses. One guy suggested:

I would take a look at surge suppressor VR901 and line to neutral capacitor C901 at the AC input before the preregulator. Either could have failed without significantly affecting operation of the oscilloscope.

Another said:

I’ll wager that your Tek 2215 has a failing AC-inlet filter. Visit the following site: http://www.vintage-radio.net/forum/showthread.php?t=88137, which discusses failures of Schaffner AC-inlet EMI filters due to a certain type of capacitor manufactured by Rifa…http://www.vintage-radio.net/forum/showthread.php?t=69128

One commentator mentions incompatible rates of expansion between the epoxy encapsulant and the capacitor innards. Another explanation (which I like better) is that microcracks in the encapsulant allow moisture to get into the metallized paper that forms the capacitor’s innards. The innards expand, which applies stress and makes more cracks, and the deposited metallization corrodes and forms conductive compounds with the moisture. Before long…pffffft!

Neither was completely correct, but they both were close. See the photo and schematic below:

2215-problem

2215-problem-schematic

It looks like the problem is indeed a capacitor in the filter section, but my scope does not have a Schaffner AC filter, like they used on some of the earlier (and more expensive) scopes. Instead, this filter is right on the main board. I’m guessing that the 0.068 uF cap shorted out,which led to the resistor burning out.

One odd thing about troubleshooting this problem is that while it looks pretty obvious from the photo, it wasn’t that obvious right off the bat. As you can see from the schematic L925 is not on the board. Instead, it’s mounted in a little housing that sits right above these two components. I had to remove that housing before I could see them.

At any rate, now I just have to find a suitable replacement capacitor and solder it all back together.

Station Notes: June 6 – June 9, 2014

While going through some boxes last Friday, I came across a Heathkit IG-102 signal generator. It was in pretty good shape, so I thought I’d fire it up and see if it was still working. I fired up my Tek 2215 scope and connected to to the IG-102. Unfortunately, I wasn’t getting any output.

I pulled the cover off the signal generator, and was going to start poking around, when I heard some arcing, and then saw a puff of smoke come out the back of the scope. I quickly pulled the scope plug, but of course, the damage had probably already been done.

Today, I finally got around to getting the Torx screwdriver that I needed to take the covers off the Tek. After removing more than a half dozen screws, I was finally able to get the power supply shield off to look for damage. Oddly enough, I couldn’t find any obvious signs of arcing or burnt components, and the scope seems to power up and work.

Even so, I’m hesitant to just button it up and start using it again. There must be a problem in there that’s just waiting to happen. If you have any experience with Tek 2215s, I’d love to hear from you.

Museum ships ahoy!
On Saturday, I operated the Museum Ships Weekend special event. This was a lot of fun. In a couple of hours, I worked 15 of the museum stations, which qualifies me for some kind of certificate.

One of the more interesting contacts was with AC0TX, operating from the SS Grandcamp Memorial. This ship was the site of one of the worst industrial disasters in the U.S. The Grandcamp had docked in Texas City to pick up a load of ammonium nitrate fertilizer.

Just before the longshoremen finished loading the fertilizer, a fire broke out aboard ship. It eventually got so hot that the ammonium nitrate exploded. Hundreds of employees, pedestrians and bystanders were killed. This was truly a disaster.

Alabama QSO Party
Kind of surprisingly, I was the high scorer from Michigan in the 2013 Alabama QSO Party. I don’t think I’m going to repeat this year. Last year, I scored over 2,000 points. This year, I barely broke 200. I guess I spent too much time working the museum ships.

Press release: RF Test Blog

From time to time, I get press releases that might be of interest to radio amateurs. Here’s one.

Making RF measurements can be difficult, especially if you need to make high-precision measurements. Fortunately, most amateur radio operators don’t need to make such measurements, but you can always learn something by reading articles by those who do it for a living…Dan

Agilent Technologies Announces Availablity of RF Test Blog – A Resource for Making Better Measurements

The RF Test Blog is a resource for finding ways to make better RF measurements. With over 10,000 visits since 2013, this popular blog includes information on equipment and measurement techniques that improve accuracy, measurement speed, dynamic range, sensitivity, repeatability, and more. Ben Zarlingo, an applications specialist for Agilent Technologies, shares what he has learned through several decades of working as an electrical engineer in test and measurement.

From my inbox: 100 years of ham radio, spectrum analysis, mesh networks

Celebrating 100 years of ham radioThis month marks the centennial of the American Radio Relay League, the largest ham radio association in the United States. That means it will be a special year for the hundreds who converge annually on W1AW, a small station known as “the mecca of ham radio” in Newington, Conn., to broadcast radio signals across the globe.

Spectrum Analysis Basics - Application Note 150Spectrum Analysis Basics – A Resource Toolkit. Learn about the fundamentals with Agilent’s most popular and recently updated application note, Spectrum Analysis Basics – Application Note 150, which is now paired with a toolkit of app notes, demo videos, web/mobile apps, and related material.

When the Internet Dies, Meet the Meshnet That Survives. The art and technology nonprofit center Eyebeam recently staged a small-scale scenario that mimicked the outage that affected New York after Superstorm Sandy hit in 2012. As part of the drill in Manhattan, a group of New Yorkers scrambled to set up a local network and get vital information as the situation unfolded.

My Dayton purchases

I didn’t buy a lot at Dayton this year, but I did pick up a couple of cool things:

I'm not sure if this cap will actually help me sell more study guides, but it looks cool.

I’m not sure if this cap will actually help me sell more study guides, but it looks cool.

scope-cart

I bought this Tek Model 3 scope cart from a guy in the far reaches of the flea market. Then, I had to roll it through the crumbling asphalt of of the Hara Arena parking lot to get it to my car. As you can see, it was made for a bigger scope, but my 2225 fits nicely on the top shelf, while my bench DMM fits nicely on the shelf that was made to house the plugins. The drawer down below is plenty big for all the DMM and scope probes and accessories that I have. A bonus is a four-outlet power strip on the back of the cart.