Outdoor Antenna for PiAware ADS-B Receiver

About 3 years ago I built a PiAware ADS-B receiver with a Raspberry Pi 3B+ computer and a FlightAware Pro Stick Plus ADS-B USB Receiver with Built-in Filter. For the antenna, I used an inexpensive 1090-MHz indoor antenna mounted in the windowsill. This is a very easy, inexpensive, and fun radio project with a Raspberry Pi, and I would encourage anyone interested in radio and/or aviation to build one. The FlightAware website includes parts lists and detailed instructions for building an ADS-B receiver with a Raspberry Pi computer. You can also build an ADS-B receiver with a Raspberry Pi computer and hardware from AirNav.

Automatic dependent surveillance–broadcast (ADS–B) is a surveillance technology in which an aircraft determines its position via satellite navigation and periodically broadcasts it, enabling it to be tracked.

This setup worked fairly well, and I was able to receive position and heading information for several aircraft within a range of approximately 50 nautical miles, and sometimes a bit farther depending upon the altitude of the aircraft. An indoor antenna is a compromise solution and will generally limit the range from which ADS-B signals can be received.

This morning I replaced the indoor antenna with a FlightAware 1090 MHz ADS-B Antenna mounted outdoors on a 12-foot fiberglass push-up mast. I used 50 feet of LMR-400 coax cable terminated with N male connectors outside, and a short adapter cable with N male and SMA male for the connection to the FlightAware receiver. The antenna is compact and very light, so the installation was very easy.

After installing and attaching the outdoor antenna, there was a dramatic difference in the number of signals received, as well as the distance. The PiAware will now receive signals for almost every aircraft flying inside of 1oo nautical mile radius, and is receiving some as far away as 200 miles!

New DXCC on 20 Meters – Hong Kong

I haven’t been on the radio much over the past week, but this morning I had some time and found that 20 and 30 meters were open to the Far East. It took a bunch of tries, but I was able to complete a FT8 QSO on 20 meters with VR2XRW in Hong Kong. That’s a new DXCC entity for me, and he confirmed the QSO on Logbook of the World in just a few minutes! The new DXCC entities are becoming fewer and further between, and it’s always special to work a new one!

A few good FT8 and FT4 QSOs on 20 and 30 meters
VR2XRW confirmed our QSO on Logtbook of the World within minutes!
N1ADM’s DXCC Account Status as of August 15th, 2020

Accurate Time for Digital Modes by GPS

Accurate computer time is absolutely essential for successful QSOs using digital modes such as FT8, FT4 and JS8. While millisecond accuracy is not necessary, if the computer clock is off by more than a second, you are likely to experience problems. It is very easy to check the accuracy of your computer’s clock by using the website time.is.

A check of my computer’s clock on time.is showed that it was 0.3 seconds behind. This is well within specs for digital modes.

Recent versions of Windows will frequently update the clock through time servers, but the updates are not usually as frequent or accurate as I would like. There are also several applications that will connect to Internet time servers to periodically update the computer clock. Some examples are Meinburg NTP, BktimeSynch, Dimension 4, and NetTime. I have Dimension 4 loaded on my shack computer.

Dimension 4 periodically updates the computer clock using a low level internet protocol, called SNTP, to connect with special purpose Internet Time Servers.

But what if you don’t have Internet access, due to an outage or working in the field? Fortunately, there are computer applications that will synchronize your clock using GPS signals. To do this, you need the software and a GPS receiver for the computer.

For my computer, I use a GlobalSat BU-353-S4 USB GPS Receiver and NMEATime2 software for GPS-PC time synchronization. The GPS receiver cost me $34, and it also cost me $20 to register the software.

The GPS receiver connects to a USB port on the computer as a serial device. I have the receiver in a windowsill near the computer.

On my computer, the GPS receiver is the Prolific USB-to-Serial Comm Port (COM4).

After the GPS receiver, I installed the NMEATime2 software. It was very easy to set up the software to work with the GPS receiver. Once installed, the software runs in the background to keep the computer clock updated. There is an icon in the system tray that shows the current status.

The green satellite icon in the system tray indicates that NMEATime2 has a good GPS signal lock and the application is disciplining the computer clock.

A right click on the tray icon and selecting “Show Panel” will bring up the software control panel with menus for settings and four tabs: Status, GPS Status, Loop Status, and NMEA Output. For my purposes, the Status panel and GPS Status panel contain the most important information.

The Status panel shows the current time and overall quality of the GPS satellite signals.
The GPS Status panel shows which GPS satellite signals are being received, and the signal quality for each, as well as location information.
The Loop Status tab displays the status of digital filters that filter out any spikes or outliers before sending the filtered signal to the application’s control algorithm.
The NMEA Output tab displays the NMEA data strings as they are received from the satellites.
While running NMEATime2, my computer time is usually exact or very close.