Thursday, July 4, 2013

Why APRS is boring...and what can be done to fix it


As my friend Cory Sickles WA3UVV eluded to in his article in the June issue of Crosstalk (the newsletter of the Gloucester County Amateur Radio Club), APRS did indeed contribute to the demise of traditional packet radio (along with the advent of ubiquitous Internet e-mail). Like traditional packet radio, APRS is an underutilized yet very valuable ham radio tool that still has much useful life left in it.

While traditional packet radio and APRS are both built on the same underlying technology, they way they both operate and their use cases are very different. Traditional packet radio is connection based, to communicate with another station you must issue a connect command like [C]onnect WA3UVV. This establishes a virtual circuit between my station and Cory's, when my station sends a packet his station will [ACK]nowledge it. This back and forth continues while data is flowing between the two stations. When the session is complete I [D]isconnect from WA3UVV and both stations are available for use. This same paradigm works whether it's two user stations connecting or a user connecting to a digipeater or BBS. Unless specifically configured, the TNC will only support 1 connection or virtual circuit at a time. While in a connected state, the TNC will not show me any other traffic going on the frequency, unless I specifically send a command to enable that functionality.

Conversely, APRS is a connectionless (or broadcast) system. There are no ACK messages passing between two stations, all packets are a special type called UI (Unacknowledged Information) and simply launched into the ether. Since there are no virtual circuits or connections, all the information that needs to be sent must fit into one packet, making brevity the watchword for operation in APRS. Since there are no connections in the APRS flavor of packet radio, you see all the traffic going on around you, and that is by design. Bob Bruninga WB4APR, the creator of APRS, had the concept of a real time information exchange system; the free exchange of data throughout the system is the value proposition of this mode. Connected mode packet radio excels for message transmission, especially when the person you want to communicate with is not on the air (just leave the message on a BBS or personal mailbox). The meat and potatoes of APRS are things happening and people participating in realtime. Fortunately for anyone interested in either mode, you don't have to make a choice, the equipment for both is the same, just use different (free) software.

Cheap GPS receivers are the single greatest cause of the boredom of APRS. Bob Bruninga has ranted (for years) that APRS stands for Automatic PACKET Reporting System, not Automatic POSITION Reporting System. Users can participate fully in the system without a GPS, the introduction of cheap GPS receivers got everyone distracted with vehicle tracking and losing sight of all the other rich features available. Bob's design intent was for a system that hams could use to find out about whatever interesting things are going on in their area. Broadcasting about nets, meetings, text messages, weather and road traffic information, local voice repeater information, and points of interest locations are all examples of valuable ham radio situational awareness items. Are several hams at a diner for lunch and want to let other hams know to come on down? Put it on APRS! Having a tech session at the club house? Put it on APRS! Rag chew net coming up? Put it on APRS! Want to show people where the hamfest is? Put it on APRS! If you use Twitter, anything (ham radio related) that you might tweet about would work great on APRS. I could go on but I think you get the idea.

Here are some examples of behaviors I have seen, using APRS, that contribute to increasing the boredom factor:

Broadcast the position of your car, 24x7, especially if you are not in it. Really, I couldn't care less where your car is if you aren't in it.
Broadcast the position of your house, 24x7, especially if you're not home. Again, if you're not available to communicate what's the point? Though if your house starts to move you probably have larger issues to be concerned about.
Broadcast a message that says "station unattended". Stating the obvious is not a real effective way to win friends or influence people.

I don't mean to sound like the grumpy old man here, or the arbiter of all things APRS, but my simple rule is "if I'm available to communicate, the APRS is on, if I'm not, it's off".

APRS can be an exiting adjunct to other ham radio activities by letting other hams know you're doing something interesting, fun, or of service to the community. You can advertise what repeater you are listening to, have a text message chat with a friend, or let people know of a traffic jam on a busy road. The possibilities are limited only by your imagination. If you'd like to know more, e-mail k2za@arrl.net or send an APRS message to K2ZA-1.

Sunday, September 16, 2012

Ham Radio on the Batona Trail

This is Scout and he was becoming a pest, as he does when he needs some exercise. I decided we both needed a nice long hike on the Batona Trail in Wharton State Forest. Since all my antennas are down at home, and most of my gear is over at the new place, taking the first module of my go-kit would give me the chance to do some field operating.





We stopped after a few miles and took a break. Here is the first module of my modular go-kit perched on a log. The radio is a Yaesu FT-817ND with a Miracle Ducker TL antenna and 33' counterpoise attached to the radio ground stud. It was getting late so I only had about half an hour of radio time available, so I was unsuccessful making any contacts. This was my first long hike with the Maxpedition Sitka pack, it was pretty heavily loaded at 18 lbs, but remained very comfortable for the whole hike (about 6 miles). Next hike will have to happen earlier in the day so I have more time to stop and operate.





Here is some video of some attempted contacts on 20 CW (my favorite mode).

For more information on my modular go-kit click on these links:













Saturday, September 15, 2012

A bittersweet day...

video

The realtor said to me "John, if you really want to sell your house, all this ham radio... err... stuff has to disappear". My wife and I are going to purchase my mother's house and I don't fancy becoming an absentee landlord so I have been dismantling the radio shack, the basement, the antennas, and my antenna tower. My Dad helped me install the tower in December of 1987 and has been up until today; for the first time in 25 years I'm completely off the air at my house. That's the bitter part, the sweet is the 50' Glen Martin aluminum tower at the new house. The new install needs some service work, new cables, and lightning protection but it will be a huge upgrade when completed. Watch the video above to see the tower being lowered and loaded onto a trailer to it's happy new home.

Thursday, April 12, 2012

Finished!

Well, I'm about 4 months late but here is the finished Red Hot Norcal 20. Purchased in 1999 and completed in 2012. The rig spent several months on the shelf because I got very frustrated chasing down a problem with the mute circuit which was absolutely vexing. When I had cooled off enough to think rationally, I posted a help request to the QRP-TECH group on Yahoo. Steve "Snort Rosin" Smith pointed me in the right direction (thanks for the e-mail!). I also downloaded the Spring 1999 issue of Norcal's QRPp journal (which they have thoughtfully posted on their website) that has the theory of operation of the rig. Ultimately I had a bad 2N3906 transistor on the TX +12 circuit along with the wrong resistor at location R99. R98 and R99 make a voltage divider that biases the base of transistor Q21 so that the +5 VDC from pin 5 of the TiCK keyer chip (U9) will turn off Q21. When Q21 turns off, it removes power from certain parts of the receiver circuit thereby muting it so the transmitter doesn't overload the receiver when in transmit mode. The bad 2N3906 (Q20) revealed itself when I was probing it's collector and found that the voltage went negative during transmit rather than going to +12 VDC.

Several more evening sessions had the radio completed but now I had a new problem, the receiver was deaf as a post! It turns out that when I was winding and installing T2, I got the primary / secondary leads mixed up so the signals were not getting out of the bandpass filter. That was very easy to correct but I took the opportunity to rewind both T1 and T2 to make a neater job of it.

Overall, it was a really fun radio to build, aside from the rework I had to do (which was my own fault). Hopefully one day very soon 20 meters will be open when I'm home to operate and I can get that first contact with the Red Hot Norcal 20 in my logbook.



Norcal QRP Club

Sunday, December 18, 2011

Red Hot 20 Update

With the cooler weather finally upon us I've had time to turn my attention to the Red Hot 20 project. I'm coming up on the 50% completion point and am currently working on the receiver section. The VFO, Audio Frequency Annunciator (AFA), and keyer have been assembled and function tested; happily the magic smoke stayed in all the components on power up.

For all those who may not be familiar with the dark arts as relates to electronics, all these devices run on magic smoke and when you do something to cause the release of said magic smoke the device will no longer function. ;-)

One of the really nice things about this kit is the way the designer, Dave Fifield AD6A, thought about the builder. The radio goes together in stages with power-up and performance checks along the way so there are no surprises when the rig is finished, you know it will work. I had a small solder bridge on the pads of the switch that controls the keyer which caused it to stay in command mode and I was easily able to find the problem and fix it because there were so few components on the board, it made troubleshooting a breeze.

When I get to the receiver alignment portion of assembly, I intend to produce a YouTube video of the procedure to aid others who might be building this rig or happened to acquire an already built one. I'm going to use an audio spectrum analyser program on my Mac to set the BFO sideband and check the filter shape. I learned this technique building several Elecraft K2s and once you understand the concept it works very, very well. Unfortunately I don't currently own a calibrated signal generator, it would be nice to check to see if the Minimum Discernable Signal (MDS) in my built unit is as good as the radio's specification (-135 dbm which puts this rig's receiver in the same class as an Elecraft K2).

One great piece of news, Doug Hendricks KI6DS, proprietor of Hendricks QRP Kits has purchased the assets of Red Hot Radio:

     December 1, 2011 I am pleased to announce that Hendricks QRPKits has purchased Red Hot Radio       Company, owned by David Fifield, AD6A. With this purchase, I now have the exclusive rights to produce and sell all of the Red Hot Radio Kits, including the Red Hot 40, the Red Hot 20, and the SMK-1. Red Hot Radio produced some of the highest quality kits for several years, but was closed due to Dave not having the time to run the company because of his day job. Now, those kits will again be available. The first kit that I will bring back online is the Red Hot 40, and it is available for shipping now. There are 35 kits in the first run, all on 40 meters. The next kit will be the SMK-1 which will be available in about a month. I encourage you to go to the website, www.qrpkits.com and check out the manual for the Red Hot 40. The kit will sell for $250 plus shipping and handling. And the kit is in stock and available for immediate shipping. 

If I can manage my time well, there is a possibility that the Red Hot 20 will be completed in time for the G-QRP club's "Winter Sports" activity. It's a non-contest that runs from Christmas to New Years to encourage QRP ops to get on the air; with the current level of sunspot activity working Europe on 20 meters QRP should be easily achievable.

Hendricks QRP Kits

G-QRP Club

Thursday, November 3, 2011

Aboard the USS Acokeek, 1947

Radioman 1st Class Jack Zaruba in the radio shack aboard the USS Acokeek, circa 1947.

Saturday, August 13, 2011

AquaPac for the win!

I went kayaking yesterday with my friend Bill and decided to bring my Kenwood TH-D72 APRS radio along for the trip. My usual rule is never bring anything in the boat you can't afford to lose, but I was making an informed exception here. I really like the D72, it performs well, has a built in GPS receiver, and the user interface is very straight forward. Unlike the Yaesu VX-8DR, the Kenwood is not water-proof so I used an AquaPac vinyl bag made for marine handhelds to try and protect it. My inadequacies in kayak handling were revealed in stark relief once we got out of Corson's Inlet and out in the Atlantic Ocean. I flipped the borrowed sit-on-top kayak on multiple occasions when hit by 2-3 foot waves in the surf zone. The AquaPac has a lanyard attached to it which I clipped to the boat, and it did not let so much as a molecule of sea water touch the radio. Kayaking in the surf is pretty physically demanding, by the time I was done I felt like I went a couple of rounds with Mike Tyson. At one point my buddy Bill noted that I had been towing the floating D72 behind my boat "like a buoy" for about a half mile. I was that tired, only thinking about the next paddle stroke. Tiredness aside, it was an awesome day and I really want to do it again!

Here is the track recorded on APRS.fi, it doesn't look like much but it represents about 5 hours of paddling.











AquaPac

Kenwood TH-D72

Yaesu VX-8DR

APRS.fi