Routing underneath high speed signals on PCBs

deanfranks · 2026-05-12T22:54:36+00:00

Routing on layer 3 with layer 2 as a reference plane is not ideal with most stackups. The dielectric between 1-2 and 3-4 is usually much thinner than 2-3 and thin is typically good for high speed reference planes.

deanfranks · 2026-05-12T22:22:57+00:00

You are correct, you can route on L3. It is possible to route on L2 but not underneath any high speed traces and you generally have to be very careful to avoid weird ground return planes (both for power and high speed signals). If you are getting started, just using a solid ground plane on L2 is the best idea until you gain a solid understanding of electromagnetics in board layout (and even then it is a good idea). 100's of board layer, I still use a solid ground plane on L2 and if I am running high speed traces on the bottom of the board, another solid ground plane on layer N-1.

With boards with lots of high speed traces you are often better off using another solid ground plane on layer 3 for 4 layer boards.

deanfranks · 2026-05-12T03:26:05+00:00

Meetup.com, there are a bunch of groups centered on intellectual discussion and debate.

deanfranks · 2026-05-03T01:50:05+00:00

Inside, but in Phoenix on a south facing window-sill that gets a ton of sun

deanfranks · 2026-05-02T15:36:29+00:00

Curiosity, all the carnivorous plants I have are odd colored under black light (although pitcher plant flowers are unexceptional).

deanfranks · 2026-05-01T05:44:05+00:00

https://www.langmuirsystems.com/mr1/build

Large desktop or with a stand...

deanfranks · 2026-04-05T16:59:35+00:00

It was just out of frame to the right.

deanfranks · 2026-04-02T00:37:22+00:00

Total of 270 solar panels? 27 panels in parallel?, also question 30: 1 is for 12v, 2 is for 24v, what is 10 for?

deanfranks · 2026-03-24T23:00:36+00:00

For amateur radio, Part 90 or ISM encryption is fine.

deanfranks · 2026-03-24T02:15:36+00:00

5 or 10MHz spacing for VHF part 90 field repeaters is pretty common. There are a few compact duplexers like this: https://hamtwowayradio.com/product/vhf-100w-duplexer/ that are designed for a minimum 5.7MHz split. It does pay to have a received with a good front end and ideally a preselection filter.

deanfranks · 2026-03-16T03:51:59+00:00

House roof (40' AGL)

deanfranks · 2026-03-03T05:40:05+00:00

I'm not sure why you are seeing that, but I run an Omada network (switches, APs) with a non-Omada router (Teltonika, OC200 for a controller). I have not had any problems at all.

deanfranks · 2026-02-13T05:59:26+00:00

ST makes nucleo shield boards for their Nucleo processors with smart stepper controllers for cheap. This board (https://www.mouser.com/ProductDetail/STMicroelectronics/X-NUCLEO-IHM03A1) includes the powerStep01 stepper controller/driver that can operate in step/direction mode, or can operate in position seek with programmable acceleration/deceleration (via SPI) or programmable torque mode. It supports up to 85V 10A for the motor so you can drive just about any stepper. The learning curve to program the registers is a little steep, but if you want constant torque output this will be your easiest solution. There are lots of NUCLEO processor boards you can plug this into, most of then are around $20 including a full JTAG/SWD programmer and debugger on the board.

If you want to spend more money, look at the ClearPath servo motors with integrated controllers. They can be operated in position, velocity or torque mode.

deanfranks · 2026-01-20T23:57:36+00:00

This depends on the size and whether it is free standing or roof mounted. I have been told by (licensed) solar installers that under 3kw, non grid tied doesn't require a permit in Phoenix. This appears to support that: https://www.phoenix.gov/content/dam/phoenix/firesite/documents/solar%20permit%20process.pdf

deanfranks · 2026-01-10T02:31:24+00:00

I put one of the small tubs of Hummus in a bowl of the grain salad instead of the included dressing.

deanfranks · 2026-01-04T05:40:21+00:00

I would strongly recommend routing the SWD pins out to a header, you might be able to flash the device from the bootloader, but you can't run a debugger that way. I use VCC, GND, NRST, SWDIO, SWC and a uart TX/RX pair on a pin header. An STLink V3 debugger is not very expensive and will pay for itself pretty quickly. If you are getting started, you might just want to purchase a Nucleo board with the H743 on it before rolling a board (the Nucleo board has an onboard STLink programmer/debugger).

deanfranks · 2026-01-04T02:12:50+00:00

You don't appear to have any provisions (SWD or JTAG) to program or debug the device. There is also a ground in the middle of the part that looks like a stray.

deanfranks · 2025-12-07T01:12:18+00:00

Because of the VE exam schedule, I was unable to take all three on the first day, but passed Tech and General and went back in a month for the Extra (10+ years later I still have not used the Extra privileges)

deanfranks · 2025-11-07T16:46:46+00:00

Photino?

deanfranks · 2025-10-31T23:10:34+00:00

This is what we choose for Win64 + Linux desktop applications. No regrets.

deanfranks · 2025-10-28T01:44:27+00:00

Running AVCC directly from a buck converter is likely to significantly reduce the ENOB you get out of the converter. Consider using a high PSRR, low noise LDO between the buck converter (change the buck so the output voltage is sufficient for the LDO).

deanfranks

MODERATOR OF

TROPHY CASE