This article details the development of a GPS module based on a U-BLOX NEO-XXX series GPS receiver. Two main applications were envisioned during the design process. The first is to integrate it with a GPS antenna inside a small waterproof casing, delivering RS232 and 1PPS time mark signals via a simple cable to the GPSDO frequency standard discussed in the previous article. The second, more general application is as a plug-in board for other designs, providing access to all available ports of the GPS receiver (RS232, 1PPS, SPI, and I2C) with the option to program the GPS chip externally.
It's frustrating when a whole row of RF measuring instruments in the shack - signal generators, frequency counters, spectrum analyzers - deliver readings that differ from each other. A receiver tuned to WWV can serve as a referee, but it's still annoying to have to account for discrepancies between all these devices. As is usually the case, my instruments also have an external 10MHz reference input, and it has long been my wish to use a single accurate frequency source as the central reference. Now, for a reasonable price, you can buy plenty of ready-made equipment, but often it comes with a separate distribution amplifier, unclear specifications, and a design I don't particularly like. So, I preferred to build something myself.
This topic is about building that device.
This design is about a clone of a clone. Following the footsteps of the WellBrook and the WellGood in this article, here's my version: 'The WellFlex Magnetic Loop Amp'!
Read more: Wellbrook ALA1530 alike Magnetic Antenna Loop Amp
In my article about the design of an RF RX front-end for the Yaesu FT-221 R, I had promised to revisit the extender I had created for it. In this article, I will provide some further information on that
Read more: Extender / Riser for the Yaesu FT-221 RD FT-225 D FT-301 D FT-625 R/RD and others
After I obtained my amateur radio C-license in 1977, I naturally had to get a transceiver right away. It became the Yaesu FT-221 R, a 2-meter all-mode transceiver that I thought was far superior to everything else available at the time due to its specifications, mechanical construction, and modular design. A beautiful device. Yet, I had to part with it rather quickly. Since my true passion lay in the shortwave bands, I immediately began working on Morse code to obtain my A-license. A Kenwood TS-430 S came along, and the FT-221 R was sacrificed for it.
But as it goes with true love, the regret lingered.
Read more: PA3AJR - RX RF Board for the Yaesu FT-221 R / FT-225 RD
Traditionally, modules such as GPS and AIS communicate with a serial protocol such as RS232 or RS422, whether or not packaged in a virtual COM port over USB or Bluetooth. That principle, of one producer supplying "hard-wired" data to one consumer, has its limitations. This becomes immediately clear when several customers have to be served or sensors of completely different nature have to work together. And, finally, it lacks a constact factor around which things can be organized in time. A marketplace where supply and demand of data come together, enrich each other, and remain available. An MQTT broker acts as a spider in the web and takes care of this. How to get from AIS via NMEA -> JSON -> Wi FI -> MQTT -> Node-Red -> both in every corner of the hobby space and in the wide world? That's what this story is about.
The AIS receiver described in this article is an update to an earlier version that revealed some issues in the print layout. Since I had to place an order for some other PCB projects anyway, I let this corrected version run along and also took the opportunity to add an extra Si4362 (or Si4463) to the design for dual channel simultaneous AIS-receipt.
Read more: AIS-receiver with two Silabs Si4362 | Si4463 chips and STM32 processer
About seven years ago I designed an information system for law enforcement along Europe's waterways and seaports: AQUATRACK. I then equipped the remote receiving stations with a AIS receiver OEM module from SRT Marine Systems. An excellent product. The phenomenon of AIS fascinated me so much that I was curious if I could make a building block as a hobby project for a fraction of the cost. A search on the internet led me to a nice initiative, the dAISy project which turned out to be based on an EZRadioPRO ISM Band receiver chip: the Si4362 from Silicon Labs and a simple 8-bit MSP430 processor from Texas Instruments. Because I am a little more comfortable on ARM processors and also have the development tools for it, I'd rewrote the source code for a Cortex M0 chip, the STM32F042K6 from STMicroelectronics to be precise. I also made some print circuit board designs for this.
Read more: AIS-receiver with Silabs Si4362 | Si4463 radio chip and STM32 processor
It must have been in the early '70s that I became interested in data transmission over radio. My school for Electrial Engineering in Amsterdam (the ETS, a great school) supported my enthusiastic and gave me two Siemens T37 telex machines. Those things weighed a ton, and it was a hell of a job to get them going again, but after a lot of fiddling with audio filters and discriminators, I finally knew the converting alternating tones on the shortwaveinto legible writing. And vice versa! "RYRYRYRYRYRYRY CQ CQ CQ de PE1BOS" A little later I got access to a beautiful sky-blue Siemens T100S Telex, complete with punched tape writer/reader. After that it became a green teletype video display unit and a IBM EBCDIC keyboard that I converted to ASCII and - later still - the Apple II+ with its plug-in cards and various TNCs for AMTOR, FEQ and AX25.
Silicon Labs provides a range of attractive receiver and transceiver chips in a QFN20 package for telemetry applications in the sub-GHz range with its EZRadioPro series. Additionally, complete modules equipped with this IC can be found for a low cost, notably on platforms like AliExpress. In the latter case, these modules typically feature the Si4463 or the somewhat outdated Si4432. For home automation applications operating at 433 or 866 MHz, I usually opt for the comparable RFM69 from HopeRF. However, what sets the Si4463 apart is its vast continuous frequency range (142-1050 MHz), including coverage of the VHF band, and the fact that it includes the maritime AIS channels (161.975 and 162.025 MHz).
Read more: An alternative matching network for the SI4362 | Si446x LC-Balun at AIS frequencies.