Sunday, March 27, 2011

Where's Eric?

I recently investigated CB radios for use on an upcoming Jeep Jamboree. On the forums I saw some folks also using ham radios. This looked interesting, so I studied for and obtained an amateur radio license, and got a Yaesu VX-8GR 144/430 MHz handheld. This handheld also has a GPS, and supports APRS (Automatic Packet Reporting System). With APRS enabled the radio will regularly broadcast its current position and status to nearby APRS enabled receivers.

My last reported position and status is available mapped at

While the web display is similar to position displays enabled via smart phones, it differs in fundamental ways. APRS is peer-to-peer over radio, so each station is communicating directly with other nearby stations. Each handheld is able to directly generate and display the list of nearby stations, without using internet connectivity. This means a group of APRS users outside cell range can operate independently.


Paul Hubbard said...

Nice! I had gotten my tech-class as well, but hadn't bought the handset yet. Do you have a source with good prices?

Eric Rollins said...

I got mine at Ham Radio Outlet in Sunnyvale (they also have web sales). I didn't do a lot of price shopping, but their price looks comparable to some other web sites and the VX-8GR and some other Yaesu gear is on sale. I was also concerned about possible shortages -- Yaesu's Fukushima factory is closed right now.

The VX-8GR was only introduced a year ago, but appears to already be discontinued. Don't know why. It is accessory (battery packs, etc.) compatible with the other VX-8 models. I chose this one because the VX-8DR has an extra $$$ external GPS that looks awkward and possible to break off (unless I want to look like a cop with a separate mic). For the built-in GPS I did trade-off reduced send and receive bands and am only waterproof versus submersible (though the external GPS may not be submersible either).

I like the VX-8GR so far, though the menu system is ridiculous. Instead of shared ok and cancel buttons, every one of the 100+ menus has its own randomly chosen buttons for manipulation. It looks like each function was delegated to a separate programmer, with no overall coordination.

Gemfinder said...

This is super cool. Are these ever used for marine applications? If I ever do the Oxnard to Anacapa kayak run, it would be nice to have something with better than VHF range.

Eric Rollins said...

The submersible model (with bluetooth headset) is probably for kayakers. APRS is on a VHF frequency (144.390 MHz), and the other supported band is UHF (430 MHz). Both VHF and UHF are line-of-sight. On my hike up windy hill I turned on APRS in the parking lot just off Portola Road, and did a manual broadcast, but wasn't picked up until I reached 686 feet altitude. OTOH, at 1759 feet at Skyline I was heard by stations in Berkeley (37 miles) and further.

Most handhelds rely on repeaters for distance. HF goes much further (via erratic ionosphere bounce), but the backpacking models often involve tossing wires into trees since low frequencies (long wavelengths) require big antennas. I'm studying for my general class (HF) license now.

CB is (barely) HF (27 MHz) and actually does better at bouncing around line-of-sight obstructions. It is legally restricted to 4 watts, similar to the 5 watts found in most ham handhelds like mine. Mobile (auto) VHF/UHF ham radios are 50 watts (HF 100 watts), while HF base stations go up to 1500 watts.

Wikipedia says sea-level line-of-sight to the horizon is 3 miles. You get more distance if your target antenna is tall and on a hill. Looking at the map near Oxnard I see someone doing an APRS run to Anacapa Island right now.

Eric Rollins said...

The Oxnard -> Anacapa Island traveler is using a Byonics MicroTrack, "self-contained, water resistant APRS transmitter/GPS receiver designed for portable use".