September AI6YM Project Updates

Hey folks,

September was a busy month! I have some major progress on the T42 Mini to share with you and some updates on FoxSniffer too.

Before we get to the technical updates I’ll give you the details I know you’ve been waiting for. The T42 Mini preorders will open in about three weeks. Ship date is May 2027 (in time for FDIM) - maybe sooner but I want to give myself some extra time for the inevitable complications

For you fine folks on my mailing list the price will be $399. For everyone else it’s going to be $449 - I did my best to keep the price down but I also want to build a great radio. Engineering is an infinite set of tradeoffs but I hope you’ll agree with the decisions I made.

My first batch will be 100 units Some of the parts are special order with six month lead times so batch two will take a little while but it’ll happen.

Let’s get in to it.

T42 Mini Development Update

The main board of the T42 Mini has been laid out and what I hope is a final prototype is in fabrication now. The major components of this board have all been prototyped in smaller modules already but it’s finally coming together in the final shape

At the core this is a T41 QSE and QSD circuit but a lot has changed. I hope you’ll agree that the mini isn’t just a smaller T41, it’s an improved T41 too. You can take a look at the render yourself but I’ll call out some of the important bits.

First let’s talk about power. We have an ATTiny based soft power circuit with reverse polarity protection. Not one or the other. Both. The circuit can also switch between external DC and an internal battery (coming as a future upgrade).

Outside the amplifier the radio runs entirely on 3.3V. For efficient battery operation a switching regulator is used but that regulator has been carefully engineered to prevent HF noise and the switching frequency can dynamically move to keep what little noise remains out of the receive band. Another regulator feeds the amplifier with an adjustable voltage. Power output stays consistent regardless of battery voltage and lower RF power output can be achieved very efficiently.

The QSD is now differential instead of single ended. That adds some BOM cost since now we need four low noise op-amps instead of two but the benefit is huge. Common mode noise is almost completely eliminated and we gain significant headroom.

The QSE and QSD are now independently clocked through a dual flip-flip arrangement. This makes for easier calibration but also significantly reduces phase noise - eliminating a lot of the need for calibration in the first place. As a free bonus 160M operation becomes incredibly easy - no more manual phase offset nonsense.

You probably noticed the bandpass filter array - four filter modules you select when you build the radio and can swap out any time. Careful filter design allows up to eight bands with those four modules - filters are available for 6M, 10 & 12M, 15 & 17M, 20M, 30 & 40M, 60 & 80M, and 160M.

The header supports an all-band upgrade that I may offer in the future, if enough people want such a thing.

A single PE4312 programmable attenuator supports both receive and transmit. The switched array can even loop the QSD and QSE through the attenuator for automatic calibration.

Many thanks to Jack, N6CH, for his contributions to the T42 Mini including the incredible renders. More updates coming soon. Let me know what you think.

FoxSniffer Update

Most of my FoxSniffers have been sold already! I have parts left to make about a dozen more - if you order now expect one to two weeks before your order ships.

Another batch is already in fabrication but these things take a few months. I’m expecting to start shipping that batch in December. It’s almost time to start another PicoFox batch too. You folks have been buying a lot of them!

That’s all for now folks.

73, AI6YM