Archive for March, 2011
The National Institute of Standards and Technology (NIST) recently launched a survey of time/frequency users. See the ARRL announcement here. This is a pretty simple survey asking about how you use WWV, WWVH, time.gov, etc. If you use these services, you should probably fill out the survey.
Along the way, I realized that NIST offers a time widget that can be embedded into a web site. It looks to be very handy and well done, so here it is:
I don’t know if I’ll keep this around or not, but I wanted to see if it would work
- 73, Bob K0NR
As previously reported, I’ve been tuning up my APRS gear and have several stations (usually) on the air: K0NR home station, K0NR-1 Trout Creek Pass digi, K0NR-5 smartphone and K0NR-7 VX-8GR handheld.
Someone asked me “What’s the purpose of this APRS stuff, anyway?”
I wasn’t sure what to say, so I answered with…
The Universal Purpose of Amateur Radio:
To Have Fun Messing Around with Radios.
73, Bob K0NR
There was an interesting exchange on the AMSAT-BB email list last week. Dave KB5WIA noted a strange signal on the AO-51 satellite:
I just thought I'd relay a bit of QRM I observed on AO-51 on this morning's 3/16/2011 1322z pass. The bird was totally quiet (just a nice carrier) for the first 5 minutes of the pass, but then it sounded like a repeater was getting into the sat uplink: 3/16 1327z: "Connected, KD7xxx repeater." 3/16 1328z: "KD7xxx repeater disconnected." 3/16 1328z: "hey Stacy did I see you at the corner there by Wendys?" 3/16 1330z: "...repeater in Middleton, Idaho."
I obscured the KD7 call sign to protect the
guilty innocent. A little searching on the internet by some of the AMSAT folks revealed that there was an EchoLink station that matched the KD7 call sign.
Patrick WD9EWK/VA7EWK wrote (again, I obscured the call signs):
And there is an Echolink system (KD7xxx-R). What may be more interesting, after some Google searches, is a series of references I saw where the KC0xxx-L system had been linked to the KD7xxx-R system. On http://www.echolink.org/logins.jsp now (1839 UTC), I saw this for KC0xxx-L: KC0xxx-L Clay Cntr,KS 145.920 (1) ON 01:27 367513 In the station description, it shows 145.920 along with the QTH in Kansas. This may be the system that's causing the QRM on AO-51, and the other system is just linked to KC0xxx-L at that time.
So it turns out that the KD7 call sign heard was linked to the KC0 EchoLink station which was operating on the uplink frequency of AO-51. George, KA3HSW, sent the KC0 operator an email and reported back that the KC0 station “has graciously changed frequencies.”
What can we learn from this?
- Check the VHF band plans for your area before getting on the air. Be extra careful when setting up stations such as EchoLink or similar system that transmits frequently.
- Be aware that there are amateur radio modes that you can interfere with even though you don’t hear anything on frequency. In the case of the AO-51 interference, the satellite hears the uplink frequency over a wide geography but never transmits on that frequency. The downlink is on the 70 cm band.
- Note that the first call sign associated with the interference (KD7xxx) was not at fault. It would have been easy to jump on his case and chew him out for transmitting on the satellite uplink frequency. Showing good judgment, the satellite guys investigated further.
- The issue was resolved by a polite (I assume) email to the offending radio amateur and he agreed to change the frequency of the EchoLink station. Nicely done.
So check the band plan for your area and follow it. And proceed with caution when interference does occur. It was a rookie error to put an EchoLink station in the satellite sub band and it was quickly resolved.
For more information on 2 Meter band usage, see this Choose your 2 Meter Frequency Wisely.
- 73, Bob K0NR
The ARRL just filed a Petition for Rule Making with the FCC concerning a specific modulation format called TDMA (Time Division Multiple Access). This issue has been simmering in the community of repeater operators but I suspect that most hams have no idea what this is about. It so happens that the land mobile industry (most notably, Motorola) has developed a very efficient and cost-effective digital standard called DMR (Digital Mobile Radio). Motorola markets this technology under the name MOTOTRBO.
As often happens, some radio amateurs deployed this new Part 90 radio technology on the ham bands. Along the way, people started looking carefully at the emission designator that Motorola was using for MOTOTRBO and began to question whether it was allowed under Part 97. I won’t go into the gory details as it makes my head hurt :-). My brief look at this concluded that there is definitely an issue here but I am not completely convinced that DMR is illegal under Part 97. If you want to dig into this, read the petition in detail with a copy of Part 97 and a few aspirin in hand.
The ARRL probably did the right thing by requesting a very focused rule change which should remove any ambiguity from Part 97. (I know this will disappoint the arm-chair lawyers who make a so-called life out of debating these issues to death.) The ARRL also asked for an immediate temporary waiver from the FCC to allow for DMR operation while the rule making proceeds…another good move.
It is unfortunate that the FCC amateur rules were written in a way that (potentially) disallowed the use of the latest land mobile radio system. This is exactly what we don’t want to have happen in the Amateur Radio Service, as it should be a place for easy adoption of new technology. Future FCC rule making should keep this in mind, always erring on the side of flexibility.
- 73, Bob K0NR
Update on 25 Mar 2011:
Just this past week, I read the following exchange on one of the many ham radio email lists I subscribe to:
I have a rat shack universal DC adapter for my charger. It is rated at 12 volt 500 mA. On the bottom of the [radio brand] charger it specifies 450 mA. My question here, is will it be ok to use the RS adapter without causing damage to the [radio brand] charger cradle?
One person replied with this:
500 ma is the maximum the dc adapter will put out. 450 is the minimum that the charger wants to have available. 450<500. with 10% to spare.
Not to pick on you, [name], but is there any requirement these days to have a basic knowledge of electricity and/or radios to get a ham license?
The good news is that the second ham provided a helpful answer. The bad news is that he felt it necessary to slam the questioner due to his limited knowledge. (Actually, I didn’t think the question was that naive.) Fortunately, a large number of subscribers jumped in and assisted the questioner and chastised the grumpus.
The truth is that it doesn’t take that much effort and knowledge to get a ham radio Technician license. I think of it as a beginner’s permit. The license exam attempts to enforce a basic set of knowledge required to get on the air. After that, it is up to us to Elmer these newbies as they learn more. When someone asks a question, no matter how basic, that is a good thing — an opportunity for learning.
After all, I really like new ham radio operators —- I used to be one!
73, Bob K0NR
This week I attended the International Wireless Communications Expo, a wireless radio conference centered on land mobile radio (LMR). While not an amateur radio event, it was three fun days totally immersed in radio technology. Being a professional show, not a hobby event, the emphasis was on modern and emerging technology in the industry. No boat anchor radios here.
Amateur radio often adopts and adapts technology from the LMR industry, especially for mobile operating on frequencies above 50 MHz. I guess we could call VHF FM amateur land mobile.
A few highlights from the show:
- A large portion of LMR is Public Safety Radio: fire, police, ambulance, so emergency communications was inherent in many of the conference sessions.
- There was quite a bit of analog FM equipment on display but LMR is clearly shifting to digital, with formats like APCO Project 25 leading the way. The FCC requirement to go narrowband by January 1, 2013.
- Several vendors are familiar names in the amateur radio industry: Kenwood, Vertex (Yaesu), ICOM and Alinco. Of course, Motorola had a major presence at the show. I noticed that ICOM had a stack of amateur D-STAR equipment on display.
- Historically, LMR radios covered only one band (VHF low, VHF high, UHF, 800 MHz), which matched the tendency for each organization to deploy channels in only one band. With an emphasis on interoperability, more organizations are finding the need to operate on multiple bands and the manufacturers are responding with multiband radios (see Motorola APX™ 7000, for example).
- A number of radio manufacturers from China were present, generally with lower cost radios (Hytera, Kirisun).
- The FCC recently announced that the frequency range known as Block D (two sections: 758–763 MHz and 788–793 MHz), dedicated to public safety broadband use, will use the LTE air interface standard. LTE is the dominate 4G mobile phone standard, just starting to be deployed. The conference had many sessions on the challenges of getting funding and actually making this work.
- Since Block D will use LTE, it opens up the potential for public safety networks that also use commercial networks (e.g., Verizon) for extended coverage. These hybrid systems provide for tight control over the primary network while leveraging the infrastructure investments from commercial providers.
- Quite a few sessions on the integration of IP-based networks into radio systems. The general trend is that the local “air interface” may be a specific radio technology (P25, LTE, …) but the network is always IP-based.
I was struck by the forward march of technology in the LMR industry. In the ham radio world, we often see strong opposition to adopting anything new. And we’re supposed to be the experimenters!
- 73, Bob K0NR
STS-133 launched from the Kennedy Space Center on Feb24th. This is the 35th shuttle mission to the International Space Station and the last <sob> flight for Discovery.
A few people were fortunate enough to see the launch from a passing commercial airliner. How lucky is that!
- 73, Bob K0NR