Category Archives: FST4W

BeaconBlaster, FST4W, Uncategorized, WSPR, WSPRSONDE

Nine-Band Filter-Combiner

I’ve been trying to avoid this one because winding and adjusting all those toroids is tedious and time-consuming, but this thing just makes so much sense that I had to do it. The Nine-Band Filter-Combiner (9BFC) is yet another filter-combiner for use with the WSPRSONDE and other QRP transmitters, and it allows a single multi-band antenna to be driven by multiple transmitters. It combines inputs on 80, 40, 30, 20, 17, 15, 12, 10, and 6 meter ham bands. You don’t have to use all the inputs; leaving any unused ones unconnected is just fine.

The 9BFC design is quite a bit more critical than the previous 6-band combiner, as the added 17 and 12 meter bands are extremely close to the 20, 15, and 10 meter bands. This tight spacing requires rather narrow filter passbands, and there is always a tradeoff between filter bandwidth, inductor “Q”, and filter loss. In order to keep the 9BFC loss to a reasonable level, commercially-available surface-mount inductors as used in the 6BFC are not adequate for these five closely-spaced bands. Instead, I am using iron-powder toroids (T50-6 variety) for those frequencies. The 80, 40, 30, and 6 meter filters do use surface-mount inductors.

Not only are these toroids tedious to wind, but the inductance of each of the ten toroids must be carefully adjusted to provide the proper filter shape and impedance match. Adjustment is done by spreading or compressing the windings while observing the filter response with a Vector Network Analyzer — this process requires some iteration since each channel has two toroids and they do interact. Once adjustments are complete the windings are secured with fingernail polish.

Of course, your antenna has to support the bands in use. When using the eight-output WSPRSONDE and the EFHW-8010 (end-fed half wave, 80-10 meters, from myantennas.com) I am using all the 9BFC inputs but the 6 meter port. It works quite well (my two WSPRSONDE locations are shown here, Friday Harbor WA, and Occidental CA). I have a separate 6-meter antenna for the Occidental site.

BeaconBlaster, FST4W, New Stuff, WSPR, WSPRSONDE

The WSPRSONDE v2 is here!

It’s alive!!! The new WSPRSONDE v2 WSPR/FST4W multichannel transmitters are rolling off the Turn Island Systems assembly line:

There are a few changes from the previous batch of WSPRSONDEs:

  • Smaller chassis, customized for Turn Island Systems.
  • Software control of output power: 1W or 250mW

There are a few other minor changes on the circuit board — things like Board Revision ID, allowing for future forward and backward compatibility.

But the WS-v2 is otherwise identical to the units that have been deployed on at least 2-1/2 continents. It continues to generate the clean, precise, and stable signals so necessary for accurate measurement of ionospheric propagation effects.

Along with this new hardware release comes updated WS firmware, with new features and options.

This has been in the works for a while now, and I am very pleased with the finished product!

If you are interested in some details of the WS-v2 assembly process, here is a short video of the Turn Island Systems CNC mill preparing a blank aluminum faceplate for the WS.

BeaconBlaster, FST4W, SDR, WSPR, WSPRSONDE

TIS-126 Clock Distribution Buffer

While there are different ways to distribute high-quality reference-clocks to multiple receivers and transmitters, or to general lab equipment, perhaps the best and easiest is with a Clock Distribution Buffer. The TIS-126 has been designed for this job:

This image has an empty alt attribute; its file name is back-1024x440.jpg

This unit can send a square-wave clock to six output ports. Input and output are 50 Ohm impedance, and the frequency range is from 100 KHz to 100 MHz (and down to under 1 Hz in many cases). The input level can range from -20 dBm to +20 dBm.

For details, see the product link: TIS-126

BeaconBlaster, FST4W, WSPR

BB-6 T/R Switch Interface

If the Beacon Blaster 6 is to be used with a receiver on a shared antenna, an external Transmit/Receive switch will be required. Some T/R switches provide automatic sensing that switches modes when the transmitter starts. This can work well, especially given the relatively low-power output of the BB-6.

But there are advantages to an externally-controlled switch, usually driven by the “PTT” output of the transmitter (this is often an “RCA” or phono jack.) This output is generally a contact-closure (relay or transistor) to ground, which connects during transmit.

The BB-6 T/R Switch Interface provides this control signal. Installation will require that a 10mm (or 3/8”) hole be drilled in the BB-6 rear panel, and the attached control wires be plugged onto an existing header on the BB-6 control board.

BB-6 firmware version 2.4.0 or later is required.

The T/R Switch Interface is offered free of charge to all owners of the BB-6, so please let me know if you want one.

More details here:

https://turnislandsystems.com/wp-content/uploads/2024/01/BB6-TRS.pdf

(the image above shows a 1/4W resistor where a small surface-mount resistor should be. Turns out I didn’t have the proper value on-hand when building the test unit.)

BeaconBlaster, FST4W, WSPR, WSPRSONDE

WSPRSONDE-8

Announcing the next stage in Beacon Blaster evolution: The WSPRSONDE 8!

This is still in development, but the initial prototypes look very promising. Similar in many ways to the BB-6, this has the same type of frequency-flexible 1W Digital (square wave) outputs, the same GPS and 10 MHz clock reference inputs, 9-24VDC input, and USB configuration port. The WSPRSONDE-8 supports both WSPR and FST4W-120 modes.

But the WSPRSONDE-8 adds these new features:

  • Eight frequency-flexible outputs, 1W, 160-6 meters (requires external filtering)
  • Spurious output levels greatly reduced. The BB-6 was designed to meet a spurious output level of -40dBc or better. The WSPRSONDE-8 uses a different modulation technique to provide close-in spurs typically better than -90dBc
  • A single-board design that eliminates the many subassemblies and interconnections inside the BB-6. This is a rugged system.

The WSPRSOND-8 provides ultimate frequency accuracy and stability limited only by the external 10 MHz reference.

WSPRSONDE-8 shown with 6-band filter/combiner and Bodnar GPSDO
Close-in spurious typically better than -90dBc (20-meters shown here, spurs -96dBc)
Using the 6-band filter/combiner, the harmonic outputs are typically better than -60 dBc (20 meter output shown here)
BeaconBlaster, FST4W, WSPR

Beacon Blaster 6 Now Supports WSPR

I’ve been running this code (or the previous version) for a few weeks now, and it runs well. The latest version of wsprdaemon is able to calculate spectral spreading for WSPR as well as FST4W, so there’s little reason not to switch over to WSPR.

There are some upgrades to the configuration commands and I will be soon editing the user’s guide to show this, but the old commands still work: just add “MODE WSPR” to the start of your config.txt file. Then reload the file (or restart the BB-6) and you’re now running WSPR!

Get the new Version 2.3.1 upload here:

https://turnislandsystems.com/downloads/

BeaconBlaster, FST4W

Eclipse!

We’ve had at least five Beacon Blaster 6 boxes running during last week’s solar eclipse (plus another custom beacon design that used the BB-6 motherboard.) A lot of good propagation data was captured using these and other beacons.

I’ve got two BB-6 prototypes running, one in Friday Harbor Washington (WB6CXC, Grid CN88) and another in Occidental California (WB6CXC, Grid CM88). These were both transmitting on 80, 40, 30, 20, 15, and 10 meters, connected through a prototype Six-Band Filter/Combiner.

Here’s the setup in Occidental:

Prior to the eclipse, in order to verify the BB-6 “baseline” performance I set up a little monitoring system. This way we can confirm the validity of remote measurements of frequency, amplitude, or spread.

To do this I used a QRP-Labs “QDX” transceiver, running as a receiver on the 20 meter band. Some external shielding and cable-clamp chokes were needed to attenuate the strong local signal, as even with a dummy-load in the QDX antenna jack the receiver was initially overloading. The QDX was then connected to a computer running the wsjtx program to decode my FST4W-120 transmissions. wsjtx saves a log file showing the time-stamped parameters of every decoded transmission.

For additional monitoring the “-40 dB Tap” output of the Combiner was connected to a spectrum analyzer, which was also plugged into the computer. I first used a “SignalHound SA-44B” analyzer, but wanting to free up that device for other measurements I switched to the amazing “tinySA” (which also has an available computer interface program.)

The Bodnar GPSDO which provides the 10 MHz clock to both the BB-6 and the QDX has a monitoring program that displays internal PLL and GPS satellite status — this was also on the screen.

Finally, the BB-6 USB serial port was connected to the “Putty” terminal emulator. Here’s how it looked:

Here’s the tinySA in action:

The BB-6 performed flawlessly!

BeaconBlaster, FST4W

BB-6 goes to Antarctica!

The first build of the Beacon Blaster 6 transmitters is being deployed, and I am very excited to announce that one of these is on the way to the remote Neumayer Station III in Antarctica.

Some of the researchers there are radio amateurs and have been operating from this remote location using WSPR and other modes. The BB-6 will provide FST4W capability, and the frequency stability and “spreading” resolution of this mode (and this polar location) will greatly enhance the ability to study ionospheric propagation. Neumayer Station III operates under the callsign DP0GVN.

Neumayer Station III is operated by the Alfred Wegener institute, which is a center for polar and marine research, with particular focus on the cold and temperate regions of the world.

DE: Neumayer Station III in Polar Nacht. EN: Neumayer Station III in polar night.

The Alfred Wegener institute is not limited to this one Antarctic base — for more information please see:

https://www.awi.de/en/about-us.html

https://www.awi.de/en/expedition.html

https://www.awi.de/en/expedition/stations/neumayer-station-iii.html

Of particular amateur radio interest, the Alfred Wegener institute ship Polarstern was very recently operating in the vicinity of the North Pole, and has been transmitting WSPR, call sign DP0POL:

https://follow-polarstern.awi.de/?lang=en#main-menu