Homebrew 500 watt HF power amplifier

Jeff (K6JCA) has written a series of posts describing his homebrew project 500 watt HF power amplifier:

I started this project back in 2016 — I had finished my Automatic Antenna Tuner (seen in the upper-left of the picture, above) and a PA project that would integrate into my FPGA-SDR and ATU system seemed like the ideal next step.
While researching RF amplifiers, I discovered a Microsemi App Note, “A 700W Broadband Amplifier using VRF2944”. I decided to use its design as the basis of my PA and began gathering parts.

See the full post on K6JCA blog.

How to make analog sensor readings with digital I/O pins

Edward Mallon wrote an article describing a technique he used to make analog sensor readings with digital I/O pins:

Will this method replace our pin-toggled oversampling? Perhaps not for something as simple as a thermistor since that method has already proven itself in the real world, and I don’t really have anything better to do with A6 & A7. And oversampling still has the advantage of being simultaneously available on all the analog inputs, while the ICU is a limited resource. Given the high resolution that’s potentially available with the Timer1/ICU combination, I might save this method for sensors with less dynamic range. I already have some ideas there and, of course, lots more testing to do before I figure out if there are other problems related to this new method. I still haven’t determined what the long-term drift is with our Pro Mini clones, and the WDT experiment taught me to be cautious about counting those chickens.

See the full post at thecavepearlproject.org.

Teardown of an Amrel PPS 35-2 programmable power supply

Kerry D. Wong did teardown on a single-channel Amrel PPS 35-2 programmable power supply:

A while back, I did a teardown on a dual-channel Amrel PPS-2322 programmable power supply, and was quite impressed by its solid construction. Recently, I found another Amrel power supply on eBay and this time it is a single channel version (PPS 35-2). Let’s take a look inside this signal channel version and see how much in common it has compared to the dual channel 2322.
The single channel version of the Amrel programmable power supply has front panel sensing terminals making it handy for remote sensing applications. Although the dual channel version has remote sensing capability as well it is only available through wiring at the rear terminal block so it is less convenient.

More details on Kerry D. Wong blog. You can see the teardown of an PPS 2322 dual channel power supply here.

Check out the video after the break.

Bus Pirate “Ultra”: using ADS7042 12bit Analog to Digital Converter from the FPGA

ADS7042 pins. Source: ADS7042 datasheet page 6.

Beginning with Bus Pirate “Ultra” prototype v1d, all analog measurements are handled by the FPGA using an external serial Analog to Digital Converter chip. This lets us pipeline ADC measurements into the command queue so that bus interactions can be done with very precise timing.

We’ll be using Texas Instruments’ series of tiny ADCs with a max speed of 1MSPS: the ADS7041 (10bit) and ADS7042 (12bit). For the prototype we went with the 12bit version, but availability and final BOM price will dictate what goes into the final design.

ADS7042 sampling interface timing. Source: ADS7042 datasheet page 10.

The ADC uses a dead simple three wire interface that resembles SPI without a Master Out Slave In connection. CS falls, the first two clock ticks are 0, then the next 12 bits are the analog voltage measurement. We stripped down a copy of our Verilog SPI peripheral to drive the chip, the current source is here.

ADS7042 calibration interface timing. Source: ADS7042 datasheet page 24.

There are two methods of calibrating the ADC. Offset calibration can be done immediately after power up by sending 16 clock ticks, however it’s risky to depend on the ADC being in the reset state. Calibration can also be done at any time by sending 32 clock ticks, which is the method we used.

Bus Pirate “d” command retrieves the ADC value through the FPGA

This is a very basic test that retrieves the raw ADC value from the FPGA while measuring the programmable output power supply voltage.

In the final revision, absolutely every aspect of the Bus Pirate hardware front end will be controlled from the FPGA:

  • IO pins (added in v1a)
  • Logic analyzer and SRAMs (added in v1a)
  • Analog voltage measurement (added in v1d)
  • Pull-up resistors (added in v1d)
  • Programmable output power supply (to be completed in v1e)

It’s possible we might use a 3.0volt reference for the analog section on the next revision. Currently we can measure 0-6.6volts with a divide-by-two resistor divider and a 3.3volt referent. A 3.0volt reference gives a 0-6volt measurement range, which increases the resolution over our target range of 0-5ish volts and might mean we can use a cheaper, lower resolution ADC. The Digital to Analog Converter used in the power supply has almost no noise rejection, so a dedicated reference voltage would help ensure clean DAC output as well.

App note: Keys to high flexibility

Ever wonder why some wires used on moving attachments last long? Cicoil who innovate the flat ribbon cable has done a lot since early computers on hi-flex wires. Link here

Most industrial wire is made up of multiple wire strands, called ‘base strands’, rather than being made of a solid piece of metal. Multiple strands make the wire more flexible, allowing it to bend and flex more easily than solid metal.

App note: Insulating and Jacketing Materials

Different application calls for different insulations, heres a great info on different insulation and jacketing materials from Calmont wire & cable Inc. Link here

Today’s wire user has a wide range of plastic insulating materials to choose from, and yet the selection of a particular dielectric for a specific application frequently is a trade-off in properties. Each plastic has both desirable characteristics and practical limitations, and the user must decide what can be sacrificed to assure overall satisfactory service.

Custom NES cartridge – Harambe’s revenge

Troy Denton and Brad Taylor made a USB reprogrammable NES cartridge:

Initially, Brad and I wanted to make a PCB that could do some very ambitious things, requiring either a very capable processor, or an FPGA device. We began down this path, but soon realized that we were biting off much more than we could chew for something we had never done before. So, we decided to take a step back, and make a smaller project to verify the foundations of our design. Our final design goals were:
*Be programmable via USB
*Be able to play NROM format games
*Feature nonvolatile storage (no battery required)
*Be as cheap and easy to manufacture as possible

Check out the video after the break.

Project info at troydenton.ca.

Monitoring GNSS constellations with Galmon using the LimeNET Micro Ublox-M8 module

Luigi Freitas (PU2SPY) writes:

In this blog post, I will explain how I managed to get a GNSS multi-constellation monitor called Galmon working on my LimeNET Micro. The Galmon project is a crowdsourcing tool developed by @PowerDNS_Bert to monitor the health status of GNSS constellations including the GPS, GLONASS, BeiDou and more notably Galileo. The project relies on volunteers to set up inexpensive stations based on the Ublox-M8 module to receive GNSS packets and send diagnostic data back to an aggregator.

More details at luigifreitas.me.