May AI6YM Project Updates

Well, I found what’s wrong with the FoxSniffer units that failed testing. It’s not fixable and all the units I’ve shipped will all fail too.

Read on for details but the tl;dr is this: I’ll be sending a replacement to anyone that has a FoxSniffer already and the next batch is pushed back a few weeks. I had to cancel fabrication that had already started.

I’ll be at FDIM and Hamvention this weekend. Looking forward to seeing a lot of you there!

FoxSniffer Details

The root cause of the issue is fairly simple. I did not add DC blocking capacitors around RF switches. The specific switches I used claim that no DC blocking capacitors are required (if no DC is applied) but that’s not entirely true - DC blocking is required when switches are connected to each other (e.g. switching an attenuator in / out of circuit).

Fresh boards seem to behave just fine but over time something happens with the switches. Insertion loss and capacitance go up leading to very low sensitivity. After a few switches fail the receiver goes deaf.

The fix is easy - add DC blocking capacitors into and out of each switch - that’s just not something that can be done without making new boards.

This was a hard update to write. These setbacks are incredibly frustrating but I’ll get it done, the FoxSniffer will ship and it will meet my standards (hopefully yours too).

Your patience and the community Ham Radio has given me are greatly appreciated.

73, AI6YM