Part 2 Of A Digital VFO For The G6LBQ Irwell HF Transceiver

For part 1 of the Digital VFO click here.

Digital VFO & RF Oscillator Module

"For The G6LBQ Irwell HF Transceiver"

Welcome to part 2 of my blog post series in which I present further details of my Digital VFO and RF oscillator module for the “Irwell HF Transceiver" project. This is a significant building block and is solely responsible for frequency generation and the control of other modules in the project.

Since I posted part 1 on the blog, I have made good progress with the software changes that I outlined. I have added additional commands to JA2GQP’s source code for the I2C Multiplexer and I am now at the stage where I can communicate with two SI5351 devices to produce two chip independent clock signals. In order to achieve this, I have had to make changes to both the main code as well as the SI5351 library file.

For now, I only need to generate two clock signals for my transceiver, one for the VFO and the other for the BFO. This will permit the radio to run as a single conversion superhet in its current state. Once further modules are developed, the receiver will be upgraded to a dual conversion superhet, this will require a third clock signal  for the requisite conversion oscillator.

The additional software code required to support a third SI5351 is going to be a bit more difficult for me to implement. I hope to replicate JA2GQP’s BFO oscillator code for this as it includes a routine for calibrating the BFO frequency and saving it to memory. If I can do this, it should also pave the way for implementing an IF shift control.

Part 1 Of A Digital VFO For The G6LBQ Irwell HF Transceiver

 Digital VFO & RF Oscillator Module

"For the G6LBQ Irwell HF Transceiver"

In this blog post, I present my digital VFO and RF Oscillator module for the Irwell HF Transceiver project, which is based on the Silicon Labs CMOS SI5351 Clock Generator.

Before we begin, I would like to pay homage to an era in my life which has flourished and brought great happiness, prosperity and achievement. 

I make the aforementioned statement with a sense of humbleness and I also feel privileged to have experienced great wealth in the recent flourishing times. 

If all this has got you thinking, I have won the national lottery or been a beneficiary to a nice windfall you are excused and forgiven :)  The truth is I have only ever been good at making other people wealthy and said people choose to forget what the catalyst was for their wealth status. Those people know who they are, shame on you!

I digress a little as I sailed off course for a moment there but suffice to say I am very happy with my modest lifestyle.

A HF Receive RF Pre-Amplifier For The G6LBQ Irwell HF Transceiver

 

HF Transceiver - Receive Pre-Amplifier Module

"A look At RF Preamplifiers For The G6LBQ Irwell HF Transceiver"

In this blog post I take a look at RF Preamplifiers and build a suitable module for my Irwell HF Transceiver project.

The RF preamplifier is one of the most important stages in a receiver and it has to meet certain criteria in order to cope with the vast range of signals available at its input. A poorly designed RF Preamplifier can destroy a receiver's overall performance so care must be given to the implementation of this stage.

A High Performance RF Mixer For The G6LBQ Irwell HF Transceiver

HF Transceiver H-Mode Mixer Module

In this blog post, I present details of  my high performance H-Mode RF Mixer stage. The H-Mode RF Mixer is a high performance circuit and a module for my homebrew ham radio transceiver that I call the "Irwell".

The H-Mode mixer was designed by Colin Horrabin G3SBI with subsequent revisions published by Giancarlo Moda I7SWX and Martein Bakker PA3AKE. Full credit is acknowledged to Colin, Giancarlo & Martein for their extensive work and research on the H-Mode mixer.

The H-Mode mixer gets its name from the letter "H" depicted in the transformer configuration, which resembles an "H".

During my research of the H-Mode mixer, I came across an interesting article by Bob Burns G3OOU, who used three individual NC7SZ04 TinyLogic high-speed inverters in the squarer, noting that the devices improved the VHF response and reduced power consumption above 50MHz

Cascode IF Amplifier With AGC For The G6LBQ Irwell HF Transceiver

 

HF Transceiver IF Amplifier Module

"Cascode IF Amplifier & AGC for the G6LBQ Irwell HF Transceiver Project"

In this blog post, I present details of  my Cascode IF amplifier with AGC function. The IF amplifier constitutes as a practical module for my HF multi-mode radio transceiver, which I call the "Irwell HF Transceiver".

My version of the Cascode IF amplifier is based on Wes Hayward's (W7ZOI) & Jeff Damm's (WA7MLH) as presented in QST magazine December 2007.

Multimode Audio Sub-System For The G6LBQ Irwell HF Transceiver

 

HF Transceiver Audio Amplifier Module

"A Multi-mode Audio Subsystem for the G6LBQ Irwell HF Transceiver Project"

As I mentioned in my previous blog post, I have been developing a high-performance HF multi-mode radio transceiver based on a series of modules that can be upgraded or improved over time.

For this blog post, I present my multi-mode audio amplifier subsystem, which handles the receive audio for the various modes of operation.

Noise Reduction for radio communications.

 DSP Audio Noise Reduction

"Noise Reduction for the G6LBQ Irwell HF Transceiver"

For some time now, I have been developing a high-performance HF multi-mode radio transceiver based on a series of modules that can be upgraded or improved over time. 

The modular approach has some great advantages and makes it easy to upgrade the transceiver or carry out repairs. There is, however, a negative effect of adopting this approach in that I find myself constantly changing things and wanting to try different ideas and ways of doing things.

Suffice to say my "Irwell HF Transceiver project" is very much a labour of love and a long-term project that is often sidelined while I moonlight on other projects.

I am for ever the optimist that my "Irwell HF Transceiver" will one day be finished so I will continue to add new additions and make improvements!

Allstar Link Node Build - Part 6

Welcome to part 6 of my Allstar Link node build. 

In this instalment the project finally comes together with the boxing up of all the various modules and parts that I covered in my previous blog posts.
 

Choice of enclosure

To enclose the project, I decided that I wanted to keep everything screened to minimize the possibility of unwanted interference in the shack. You may remember in part 4 of my build I commented that there's a reason computers are built into metal boxes!

I suspect that some readers of the blog maybe thinking but "my laptop case is plastic";  therefore my comment or argument is not a valid one! 

 

Well, having stripped down many laptops for repair, I can substantiate my point due to the fact that the internal electronics of a laptop are shielded either by tin sheeting or a screened coating on the inside of the plastic shell, the same can also be said for tablet computers and mobile phones.

Allstar Link Node Build - Part 5

Welcome to part 5 of my Allstar Link node build. 

If you read part four of my node build, you probably arrived here expecting to read a blog post covering the grand boxing up of the project!  Fear not, this is just a short interlude and the boxing up will now commence in part 6.

I need to vent a little about my concerns regarding the "Buck Converter Module" that is commonly used in node builds. The idea of using a buck converter to regulate a DC supply voltage is fine and I intend doing this myself but there is a caveat! 

If you are not aware of what a buck converter is, it is a type of switch mode Power Supply; they are highly efficient when compared to traditional linear voltage regulators.

The buck converter module that I will be referrincing is shown below and can be purchased from eBay, AliExpress and many other online sources for less than £2. 

These modules are sold as being equipped with a LM2596 switching regulator,  a device from the Texas Instruments portfolio of power management devices.

Allstar Link Node Build - Part 4

Welcome to part 4 of my Allstar Link node build. 

In this installment I will prepare some additional components in preparation for casing the project up.

Before I get started

In the last installment, I covered modifying the popular CM108 USB sound module for use with the Allstar Link Node and I remembered that I had used the CM108 in a digital mode interface that I designed and built back in 2018.  Below is a photo of the interface completed.

Click for a larger image

Allstar Link Node Build - Part 3

Welcome to part 3 of my Allstar Link node build. 

In this instalment I will start working on the CM108 USB sound modules and show you how to modify one for use with an Allstar Link node.  The module forms a link between the modified Baofeng radio transceiver and the Raspberry PI single board computer.

The CMedia CM108 is a highly popular single chip USB audio solution. All essential modules are embedded into an LQFP 48 pin package. The chip includes a dual DAC, earphone driver, ADC, microphone booster, PLL, voltage regulator and USB 2.0 compliant transceiver.

Shown enlarged, the actual IC is 7mm by 7mm

 

 

 

 

Allstar Link Node Build - Part 2

Welcome to part 2 of my Allstar Link project build. Before I continue, I would like to take the opportunity to wish everyone around the world a happy, healthy and prosperous 2021.