Archive for December, 2008

Podcast: Linux in the Ham Shack

Over the past few years, I have developed the habit of listening to podcasts on my iPod as an alternative to broadcast radio. (See my post from April 2006: Competing for Ears.) Of course, some of my favorite podcasts are on the topic of amateur radio. I’ve noticed that some of them have come and gone, and my interest in them varies over time.

Recently, I just came across a new podcast called Linux in the Ham Shack, by Richard KB5JBV and Russ K5TUX. Richard also does the Resonant Frequency podcast. Both of these podcasts are available via iTunes and probably a whole bunch of other feeds. For you Linux enthusiasts, Russ’s call sign is a vanity call chosen for its Linux significance.

Most of my PCs run some version of Windows, but lately I have gotten more interested in what Linux can do for me. Earlier this year, I took one of my old PCs running Win98 and gave it some new Linux brains (Ubuntu). I have to admit that I have just been running non-ham radio apps such as OpenOffice and Firefox on that machine. I’d like to turn on PSK31, APRS, WinLink and other digital modes so this new podcast sounds like a great resource.

The first few episodes of Linux in the Ham Shack were interesting and helpful, with a nice interplay between Russ and Richard. Keep up the good work, guys!

73, Bob K0NR

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Managing Twitter Overload

Twitter is The Next Big Thing on the web…sometimes referred to as microblogging.  (For some background on Twitter, see my earlier post: Twitter: Yet Another Web Thing.)  Several of the ham radio bloggers have tried Twitter and have gotten frustrated with it. Steve K9ZW says that

Basically the few unique bits of information passed are overwhelmed by endless droning Tweets about microcosms of banality trying to add value to the mundane.

I think NØHR captured the issue succinctly by describing Twitter as having a poor Signal-to-Noise Ratio.

I suppose this is what you get from a free, web-based communication service that asks you “What Are You Doing?” and gives you 140 characters to form the answer.

My view is that we are living in a world where the barriers to communication have been dramatically lowered, meaning that there is more information flying in our direction than ever before. Twitter is just the latest example of this. If you “follow” a hundred or so people all tweeting away with their What Are You Doing? stream of consciousness,  you are going to end up with a Pile-O-Stuff of questionable value. To make this useful, you must be careful about who and how many people you follow or apply some kind of filtering/sorting mechanism to keep it under control. I noticed that WA4D expressed a similar view.

This is really no different from when we subscribe to other forms of electronic distribution, such as email lists (e.g., Yahoo groups) and RSS feeds. The reality is that you can easily get overloaded by all of the content out there….more than any human has time or energy to read. So be selective…it is the only way to survive the Information Diarrhea Age.

73, Bob K0NR

Followup on 30 Dec:

I guess I should have specifically stated: I am finding value in Twitter….usually in the form of a pointer to an interesting web page or an insightful observation by one of the people I am following. Your Mileage May Vary.


Favorite Radio Videos

As we head for the end of 2008, I am resisting the urge to do some kind of year-end retrospective. Instead, I’ll pull out some of the best amateur radio and technology-related videos on the web. OK, some of these were completed in earlier years, but this collection represents my favorite video finds on the internet.

Old Goat Field Day

Steve NØTU has captured a number of videos about his hiking / ham radio adventures with his two goats. This one is from Field Day 2008, operating from one of my favorite mountains: Mount Herman. If you like this one, check out Steve’s blog for other videos.

Digital Television Transition

This is a funny video about the transition to Digital TV (fasten your seat belts for that event, coming up in February 2009). It might be poking fun at the elderly, but it is also poking fun at the mess the FCC has created concerning this transition. Why can’t television be simple?

Mountain Dew Commercial with Ham Radio

This is a short Mountain Dew commercial with a reference to vintage ham radio in it.

“Radio Hams” Film

This Pete Smith movie is an oldie but goodie about ham radio….a trip back in time.


Operating rover in a VHF contest is a fun activity, one that I have been known to do. It does take a bit of a warped mind to truly excel at this….as shown in this video.

The Ham Band

This is a music video by by OZ1XJ and friends, with a ham radio theme to it. You gotta love the guys singing while hanging from a tower!

The Neighbors Find Out About The Ham Radio

This is what happens when the neighbors suspect you of operating a ham radio set.

Amateur Radio Today

This ARRL video with Walter Cronkite narrating is one of my all time favorites as it does a good job of telling the ham radio public service story. It is special to me since it includes coverage of the Hayman Fire….the biggest wildfire in Colorado history, which happened about 15 miles from my home

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Investigating the D-STAR Modulation Format

The D-STAR buzz continues to build in Colorado with a few repeaters on the air and more to come. For an overview of D-STAR, take a look at the article I wrote for CQ VHF magazine. I decided to dig into the digital modulation format that is used in D-STAR so I could understand it better. (Moving Forward!) At first, I figured that this newfangled digital modulation had nothing to do with FM but later realized that this is not completely true. (No, FM and D-STAR do not interoperate.)

It turns out that D-STAR uses Gaussian Minimum Shift Keying (GMSK), the same modulation format that GSM mobile phones use. What is that, you say? Let’s start with Frequency Shift Keying (FSK)…when the digital signal is a logical one, a particular frequency is generated. When the digital signal changes to a logical zero, a different frequency is generated. On the receive end, we just keep an eye on the frequency and decode the digital signal accordingly. In concept, we could generate this FSK signal by hosing the digital signal into an FM modulator. Minimum Shift Keying is a special case of FSK where the frequency shift (and the phase changes) are carefully controlled (modulation index of 0.5) to keep the phase discontinuities low and the bandwidth minimal. Add a Gaussian filter on the front end of this and you have GMSK. (The gaussian filter smooths out the digital transitions and gives an even narrower bandwidth.) I found this GMSK tutorial to be very helpful.

On the air, a GMSK signal has a constant amplitude, just like FM. It will switch back and forth between two frequencies as the digital signal goes high and low. The digital signal can be recovered using an FM detector but the output of the detector is the digital format.

Of course, GMSK is only part of the D-STAR modulation system. The other key component is the vocoder, which is the AMBE-2020™ Vocoder from Digital Voice Systems, Inc (DVSI). This chip performs the magic of smooshing the digitized voice signal into a reasonable number of bits per second so that when they are turned into GMSK they fit within the rather narrow bandwidth (6 kHz nominal). Since this vocoder chip is proprietary, it has caused some hams to grumble about the lack of an “open” vocoder algorithm. I think they have a point but it does get overblown. I have heard statements that this proprietary algorithm adds $100s to $1000s of dollars to the price of a D-STAR radio. My sources tell me the chip sells for about $20, a very reasonable price for this functionality.

I’m in the process of turning this investigation into my FM column for the Winter issue of CQ VHF, so there will be more detail there. I hope this short note gets your brain thinking.

73, Bob K0NR


Digital TV Transition

The February 2009 shutdown of analog TV is approaching fast so I am actually starting to prepare for it. I previously wrote about this topic in Here Comes Digital TV. The FCC has asked the ARRL (really the amateur radio community) for help in getting the word out. This request emphasizes information sharing, not hands-on installation and troubleshooting of DTV systems. This is going to be interesting to watch….people that are served by cable or satellite are likely to be buffered from this change. The Over The Air User may have a different experience.

The FCC is pushing these settop converter boxes that allow people to convert their old analog TVs to digital. They will probably work fine for many people, especially if they have some technical knowledge. I really wonder about the less sophisticated consumers that are already struggling with their VCR and TV combo….now with a converter box in the middle of the system. “Let’s see, to record off the air I set the VCR to Channel 3 and the converter box to Channel 8 and then….” I am thinking there will be quite a few analog TVs headed to the trash heap. (Please recycle responsibly.)

An additional wrinkle that I just realized is that many of the VHF television stations are are moving to UHF for digital….but they will keep their existing channel designator. It turns out that the DTV system is defined such that the channel number that the user sees has nothing to do with the actual over-the-air channel that is used. For example, an analog TV station on VHF Channel 4 might move to UHF channel 35 for DTV but still be called “Channel 4″ on the DTV screen. This is supposed to keep things simple for the consumer. This will work out OK if the consumer has a TV antenna that handles both VHF and UHF. However, in some regions VHF is so dominant, people may not have bothered with a UHF-capable antenna. They will have to make an antenna change to receive the new DTV signals.

In Denver it is going to be even more interesting. Channels 7 and 9 are starting out on UHF for their digital broadcasts and then will move back to VHF after the analog signals go off the air. This leaves them on their original VHF channel after the dust settles. So a viewer watching digital Channel 7 needs to view them on UHF Channel 17 right now, but it will be referred to as Channel 7. Later, their DTV signal will move over to the “real” VHF Channel 7.

This is going to be interesting.

73, Bob K0NR

Update 22 Dec 2008:

Take a look at this humorous video about the Digital TV transition:



Moving Forward or Stuck in the Past?

Are you moving forward or stuck in the past? This all started with a blog posting by Dan KB6NU appropriately titled I’m Tired of Pessimism. Dan basically said he has grown weary of the folks that specialize in displaying a negative attitude in ham radio. Jeff KE9V responded with a post of his own, writing:

The final determination of whether amateur radio remains an avocation of any significance will be made by those who actually enjoy the hobby. My advice for them on that fast-paced journey is to trample the slow and hurdle the dead lest they become bogged down by the rotting corpses of the “old guard” who refused to change.

This reminded me of one of my postings from January, titled Paul Rinaldo’s Rule of Amateur Radio Progress, which related some words of wisdom (not mine):

Progress is made in Amateur Radio by letting energetic individuals move forward. Conversly, nothing in Amateur Radio is accomplished by complaining about other individual’s projects. Simple summary: If you don’t like their project, then go do or support your own choices. Get out of their way.

Note the common theme of lead, follow or get out of the way but don’t be the curmudgeon that spoils everyone’s fun. If you have spent much time with me, you would know that I can get as cynical as the next guy. I specialize in sarcasm and can derive great satisfaction from pointing out the errors in other people’s thinking and actions. The only problem with cynicism is that it doesn’t accomplish anything beyond generating that smug feeling of being right. It doesn’t move anything forward — it just complains loudly about the situation.

The older I get, the more I try to avoid the easy out of that soothing cynical attitude. For me the test is simple: does an attitude/statement/question/action move things forward or keep the situation stuck? Things that move forward have value; things that keep us stuck are worthless. See Paul Rinaldo’s comments.

Lately, I have been applying the Moving Forward / Stuck in the Past Test to ham radio activities. I flip through the ham magazines and I see quite a number of articles on vintage radios. Moving Forward? I don’t think so. How about AM operation? Stuck in the Past. Ham radio connected via the internet? Moving forward. Sound-card digital modes? Moving forward.  What about CW operation? (Be careful here.) I actually think this one is Moving Forward. Why? Because CW still represents an extremely efficient operating mode in terms of bandwidth usage, simplicity of equipment and versatility. I can do a lot with just a simple QRP rig and my brain on CW. (I know some of you will argue that it is Stuck in the Past and you might be right.) Radio amateurs that are helpful Elmers? Moving Forward. Grumpy old men that look down on newcomers: Stuck in the Past.

Now there is nothing wrong with Stuck in the Past activities….as long as they don’t get in the way of Moving Forward. I know some guys that get great pleasure out of running their old AM rigs on HF. I am glad they are having fun with it. But we don’t use up all of the 20 Meter phone band running such an inefficient mode….we keep it to a few frequencies.

So where are you: Moving Forward or Stuck in the Past?

73, Bob K0NR