August 9, 2026:

For these current tests, the transmit power will be either 20 mW or 500mW (using a modified $12 “2W” linear amplifier).  The transmit frequency will be changing from time to time, depending on propagation and which receive sites are capable of measuring Time of Arrival.  For more information on Time of Arrival measurements see:

• http://wb6cxc.com/?p=513 ,
• https://turnislandsystems.com/time-of-flight-presentation-hamsci-2026-workshop/
• https://turnislandsystems.com/product/tis-ts1-timesync/

The BPSK bit rate will be reverting back to 511.5 Hz, for a two-second repetition rate of the 1023-bit pattern.  This is because my simple modulator design can’t provide a < 2.8 kHz occupied bandwidth (new FCC limit) above the 15 meter band.  At the 511.5 Hz rate the occupied bandwidth on all HF bands is between 0.65 and 1.3 kHz — comfortably in spec.  I’m working on a  new modulator / amplifier design that will behave well over the entire HF bandplan.

As mentioned below, the bit pattern is the the GPS CA code #1.  See this for more information about the code:

https://natronics.github.io/blag/2014/gps-prn/

Here is the bit pattern, shown as a sequence of binary bytes:

August 2, 2026:

On the air with my timestamped transmitter:

3.595 MHz, 100mW (400mW peak)
Pattern: BPSK-modulated 1023-bit pattern: The GPS CA code #1, at a 1023 Hz bit (or chip) rate.  This pattern starts at the top of UTC minute, and repeats every second.  Morse ID every ten minutes (“timestamp test de wb6cxc.com”).

The pattern starts 6.6 us after the GPS pps (pulse per second).  BPSK transitions are envelope filtered for an occupied bandwidth of <1.5 kHz.

This will be on and off the air for Time of Flight testing.

May 18, 2026:

The transmitter has been off the air since Hamvention.  More tests to come, stay tuned!

May 7, 2026:

Back on the air, this time transmitting on 3.700 MHz, 10 milliwatts.

The signal is a BPSK-modulated 1023-bit pattern: The GPS CA code #1, at a 511.5 Hz bit (or chip) rate.  This pattern starts at the top of UTC minute, and repeats every two seconds.  For now this is carrying no data, but I am planning to include basic station information (as is carried in WSPR), plus timing and mode information.  Raised cosine envelope shaping is used to hold the occupied bandwidth to about 700 Hz:

Every ten minutes there is a one-minute pause for CW station ID.  The CW dots and dashes are also envelope-shaped to avoid key-clicks.

This signal is being received at the Pt. Reyes KPH receiver site (about 33 km distance as the RF flies), which is using the RX-888 SDR coupled with a Turn Island Systems TimeSync unit for precise Time of Arrival measurement.

I will be giving a talk on this and related developments at the 2026 Hamvention.  If you plan to attend Hamvention please drop in for the TAPR presentation or at least stop by the TAPR and HamSCI tables.

January 20, 2026:

In the latest test I am transmitting a signal using BPSK  carrier inversion driven by the one pulse-per-second output of a GPS receiver.  This highly accurate time-stamped signal is used in the analysis of ionospheric propagation.   Receivers having precise time resolution are used to measure time-of-flight of this and other time-stamped signals.

Here are the details:

• Power: 1W
• Frequency: 7.0399 MHz
• Modulation: BPSK, 1 Hz phase inversion
• ID modulation: 18 wpm morse, on/off keying
• Transmitter location: Friday Harbor, WA (48° 30′ N, 123° 1′ W)
• Transmit sequence:
  • Minute 0 – 3 : PPS BPSK
  • Minute 4: morse ID, followed by carrier off
  • repeats every five minutes