Tuesday, August 24, 2021

Is a "Poor Man's 705" possible?

While I am proud owner of multiple radios from Icom over the decades (and still own all of them) I am having a hard time cost-justifying an expensive and new shiny Icom IC-705 as part of my QRP kit, like Steve K2GOG already jumped in on. 

My Yaesu FT-817 has served me well the past twenty years which includes many ARRL Field Day's and HOPE conferences and with the 705 coming in at ~US$600 over the cost of a Yaesu FT-818ND, ~US$400 over a Elecraft KX-2, and even US$750 over a used Yaesu FT-817ND, what the premium that the IC-705 delivers is really just the same core capability as all these other fine radios, but with some fancy user interface (UI) and an improved overall user experience (UX)

The Shiny

The top three attributes often discussed about the Icom IC-705 are:

  • Color touchscreen display
  • Bluetooth and Wi-Fi connectivity
  • Compact size

To make my FT-817 or a new FT-818ND "shinier", I could buy a CAT-to-Bluetooth Adapter (US$20), use a Amazon Fire HD10 Tablet (US$15) as a touchscreen display running the 817 Companion app (Free.) This approach would allow for control of the radio, but not much else like how the Icom IC-705 integrates Wi-Fi to also offer full remote access which is very different compared to the basic bluetooth connectivity also present.

But the article is about a "Poor Mans 705." A FT-817/8 approach is still too much for your blood at ~US$700 to US$820.  We need to go much lowah ..... lowwwwaaahhhhh!

Cheap(er) Building Blocks

I recently completed building a uBitX. A QRP project with a sublime simple design blending analog and microprocessor technology. 

It is designed with experimentation in mind which can also combine a touchscreen display just like the one found on the expensive Icom radio. I figure this display upgrade would be a good start for a Poor Mans 705.

uBitx Architecture Model

The Block Model above is the uBitx with touchscreen modification. It is broken down into Analog, Digital, and Human Interface layers. 

It is important to note that the uBitx is a software-controlled radio as opposed to a software defined radio. 

In software-controlled, a microcontroller is used to control analog stages of the transceiver and interact with the user interface that makes and display changes/status. 

A software-defined radio (SDR) takes the  analog signals, converts them to the digital domain where the power of math (and coding) let us manipulate the signals to the desired analog output whether transmit or receive. The 705 is a SDR which also has software control, the best of both and you pay the price for it! 

With Arduino Nano as the microcontroller and all the uBitx code open sourced, this should help with the software learning curve.

User Interface and Experience

For those new to touchscreen projects, the Nextion HMI Display will expand your horizons when it comes to building/designing the user interface experience.  Many radio amateurs became familiar with these displays either through a uBitx project or something involving an MMDM digital hotspot

The Nextion has its own processor and memory that is programmed with its own editor software for developing the GUI you interact with. 

Nextion Editor with uBitx Main screen loaded

A web search will yield libraries of Amateur Radio screens made for the Nextion. The development experience is analogous (no pun intended) to front-end web development with your radio being the back-end infrastructure.  A robust community of users exists via various Facebook and Groups.io pages too.

It should be noted the Nextion does heavy processing and may introduce radio frequency interference (RFI) that may disagree with some less thoughtful HF QRP project designs. 

There are other TFTs to go with out there but few are simpler to program and addressing the RFI through the Nextion being in its own metal sub-enclosure will often suffice.

Wireless Connectivity

Anyone who has had a long history with digital modes commonly used on amateur HF spectrum is no stranger to the nest of wires and peripherals that would be built between their radio and a PC. In essence there are two services you are trying to make wireless; audio connectivity and control connectivity. 

Adding Bluetooth audio to a transceiver is a well trodden path of simple solutions  as long as you choose VOX over PTT. 

The same can be said for Bluetooth Serial device adapters that can plug into serial ports of common radio manufacturers. 

The Bluetooth serial connection is transparent to the radio control software and manufacturer protocols running across it. 

But many QRP builds do not include a serial connection nor a protocol to be used across one. The few that do like the QRPver Minion have standard on Yaesu FT-817 CAT Library.

One approach is for connectivity to be its own subsystem at the digital layer built with an ESP32. ESP32 have WiFi and Bluetooth built-in. 

Code would be built for the ESP32 to run network services (Bluetooth and WiFi) that understand various vendor protocols and give commands to the Arduino via I2C for control changes.

A Poor Mans Approach

Poor Mans Architecture

Based on what has been covered so far targeting the top three attributes of a 705, I come up with the above architecture. 

As of this publishing, I have yet to find a better source for the analog foundation than a uBitx kit which includes the microcontroller. 

For connectivity the Bluetooth Audio module and ESP32 can be readily sourced from Amazon. For the touchscreen I will go with a Nextion 4.3 inch - the same real estate as the 705.

Going larger than the available 3.5 inch touchscreen upgrade for the uBitx is going to require learning UX design with the Nextion Editor Software and the nuances of the controller running on the Nextion.

Once that is successful, adding connectivity require writing code on an ESP 32 and a routine added to the Arduino to look for I2C messages from the ESP32.

You would be correct in thinking I am planning to turn this into a fall/winter project.

 Be sure to keep an eye on the HVDN Github repo as ideation develops into design and prototype.

Any Pi?

At the Four Days in May (FDIM) 2021 annual QRP conference, the creator of the uBitx Ashhar VU2ESE announced work on the sBitx - an Open SDR using a Raspberry Pi. A PDF was published providing in-depth technical detail (that included code snippets) on their approach as well as a repo shared of code developed to date. 

Just like many of us saw with the expensive RS-BA1 remote control software that Icom sold, but has since been phased out due to competing lower cost (and better) options by the community itself, only time will tell if a combination of the sBitx and people like me will create a competitor via an open source low cost "poor man's 705".

Will be tracking this closely.


- Joe, NE2Z

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