This has been in use for a while, combining the multiple outputs of the Beacon Blaster and WSPRSONDE onto one SMA jack, allowing the use of a single antenna. The results have been excellent, so this box is now on the Turn Island Systems website, available for purchase:
Applications for the Filter-Combiner are not limited to the WSPRSONDE. Some have used this to combine the outputs of other QRP (1W or less) transmitters. One person is using the Filter-Combiner in reverse as a general preselector, sending the output of a single multiband antenna to several narrow-band SDR receivers (reducing overload from out-of-band signals).
What about eight bands? I glad you asked that question! Fitting additional bands into the combiner has proven to be a major challenge. A 160 meter port can’t be implemented using available (inexpensive) components — too much inductor loss. Squeezing the 17 and 12 meter bands into the gaps between 20, 15, and 10 meters also requires inductor tolerance and loss well beyond that of readily-available parts. However, if there is demand for it a future combiner could include a 6-meter port.
But single-channel filters can be provided for those “oddball” frequencies.
Rob Robinett and I will be co-presenting at the upcoming HamSci Workshop (https://hamsci.org/hamsci2024), our topic being High Resolution WSPR Transmissions for Ionospheric Research.
We will also have a hands-on demonstration of the hardware and software used, including the new WSPRSONDE-8.
So what is a BeaconBlaster-6??? It’s a six-channel transmitter, putting out one Watt FSK on up to six channels — simultaneously! The BB6 supports all ham channels from 160 meters to six meters, with extremely precise frequency, FSK shift. and channel timing when provided with an external 10 MHz reference clock.
The initial release of the BB6 generates FST4W-120 signals, but WSPR and other FST4W rates will be supported very soon.
The BB6 was developed to meet the needs of the HamSci community (see https://hamsci.org/ and http://www.wsprdaemon.org/ for more information), and is particularly useful in the study of the ionosphere. Of course the BB6 is also a great solution for general beacon activity.
The BB6 is available as individual components, or assembled and housed in a 19″ rack-unit enclosure, 1RU in height (1.75″ high, 19″ wide, 9.5″ deep). We’re still working out the mechanical details, but here is a mock-up of the faceplate:
Like most things out of Turn Island Systems, the BB6 evolved from designs initially developed for our own use. Here are the pieces of the BeaconBlaster-6:
BB6 Control / Clock Generator
This unit is an offshoot of our TIS-5351 ClockBox, which was developed to provide precise digital clocks, and is based on the ubiquitous Si5351 clock generator. Turning this into the BB6 CCG involved adding a second Si5351 (this required multiplexing the I2C control bus), and adding a GPS module to the board. The board also includes a GPS antenna splitter, allowing a single active antenna to be shared with both the BB6 and an external GPSDO. The SMA connectors shown here are for stand-alone operation, when incorporated in the complete BB6 these connections will be made using the tiny “U.FL” connectors
Outputs: Six transmitter-drivers (3.3V logic-level), GPS antenna splitter
The USB port is used to configure and monitor the BB6 operation, but is not required for regular stand-alone operation.
Digital One-Watt Amplifier
The DOW accepts a 3.3V logic-level signal from 1 to 30 MHz and generates a 1W square-wave. It requires a +5V and draws approximately 350mA when transmitting. This is a broadband Class-D amplifier, and will require an external filter before connecting to an antenna.
The DOW is the latest of several QRP amplifiers we have designed. Some of these were optimized for efficiency — these were single-band Class-D or Class-E designs. For the multiband frequency-flexible BB6 system it makes more sense to have frequency-flexible power stages and use external filters.
This amplifier is designed for a 50 Ohm load, and if connected to a load less than 25 Ohms will get quite hot. To avoid damage to the amplifier, a current-limited power source is recommended. The BB6 system includes such a limiter.
The BB6 includes six of these amplifiers.
Six-Channel Foldback Current-Limiter
This board provides overload protection for the Digital One-Watt Amplifiers.
Four-Band Power Combiner
With up to six outputs from the BB6, the 4BC will accept 1W inputs at 80, 40, 20, and 10-meters and combine them onto a single output, allowing use of a multi-band antenna. The 4BC insertion loss is <1dB and provides filtering which reduces the harmonic content to less than -40dBc.
Single-Channel Filter
The Single-Channel Filter is available for any ham band between 80 and 10 meters. This design provides a out-of-band high-impedance load, which optimizes amplifier efficiency, and reduces harmonic content to better than -40dBc.
Price and Availability
The complete and assembled BeaconBlaster-6 will cost approximately $700 (plus shipping), and should be available early August 2023.
The assembled Four-Band Power Combiner will cost about $70, and be available early August 2023.
Individual board price and availability are TBD. All prices are subject to change .
The new Clock Distribution Buffer is now available to order. I use this to send a 10 MHz reference clock to my various pieces of test equipment, such as the frequency counters, spectrum analyzers, and several signal and waveform generators. The Clock Distribution Buffer also sends the reference clock to my QDX transceiver, modified with the QDX External Reference Interface.
This unit accepts any input frequency between 100 Hz and 100 MHz, -10dBm to +20dBm, and sends the digitally regenerated clock to five output jacks.
