Has anyone had experience booting over USB?  I have had an interesting experience with it and I thought I would share.
I set up a Raspberry Pi OS system on a SSD drive and connected it to lower USB3.0 slot.  It started up initially just fine and was working fine but over a period of time (a few hours) it would start failing in strange ways. Mostly all the icons and task bar would go away, but the splash screen remained and mouse over Bluetooth continued to work.  I tried reloading os several times but same or similar issues occurred.  Now the interesting part, I plugged the SSD drive into the upper USB3.0 slot and booted up and has now been working normally for over 30 some hours no more failures.  I am hopeful this continues because performance is nice.

When I was at Purdue in the 70's we used Cat3 plain old 24ga telephone cable for hundreds of RS232 terminals on our Engineering Computer Network.

We found, experimentally, that we could run 1Kft at 9600 BPS on that cable.  So, we established a 500ft Engineering Max and never had any problems.

Each terminal/printer was supplied with 2 pairs.  One pair was ground and Transmit, the other was ground and Receive.
The grounds were broken out and grounded at the computer room wall.  That allowed us to use one pair for each port between the computer (typically VAX 11/780)
and the 66M1-50 blocks on the wall.  That also meant that we could use conventional bantam patch panels which provided access to 48 serial ports in 1U rack space.
Custom adapter boards between the ribbon cables from DH style serial boards and 25pr telco connectors meant NO D-connectors at the machine. Doors would close
and BA boxes would push in and pull out without breaking anything.  We typically put 96 ports on a Dual VAX 11/780

Wish I could find my old pictures, it was quite the setup in the day.

This was for runs from computer rooms to offices in the same building.

If we went between buildings we converted to RS422 4wire and added Telco standard 3 terminal gas tubes to both ends of the between building cable.
In the basement of the daughter building we converted back to RS232 and used our standard in house cable standard.

We also found that the speed/distance trade off was more or less linear.  In other words  250ft at 19200 and 1000ft at 4800.

T3

It actually works really well. I picked one up super early (before they sold out!) and have loved it ever since. I am still in the "testing" phase with my go-kit, but I do think it's going to replace my dedicated Pi (plus screen) in my box. It's really convenient, works well with wired and wireless mouse, and supports dual HDMI screens. Keyboard is great, well designed, spacious. Performance is as good as all other Pi4's with 4GB. Love it!

How is the performance of the Pi 400 with ham radio apps? It kind of looks like with a small HDMI touch screen it could work well for portable operation.

RS232 physical properties

The RS232 standard describes a communication method capable of communicating in different environments. This has had its impact on the maximum allowable voltages etc. on the pins. In the original definition, the technical possibilities of that time were taken into account. The maximum baud rate defined for example is 20 kbps. With current devices like the 16550A UART, maximum speeds of 1.5 Mbps are allowed.

Voltages

The signal level of the RS232 pins can have two states. A high bit, or mark state is identified by a negative voltage and a low bit or space state uses a positive value. This might be a bit confusing, because in normal circumstances, high logical values are defined by high voltages also. The voltage limits are shown below.

 

 

RS232 voltage values

Level	Transmitter capable (V)	Receiver capable (V)
Space state (0)	+5 … +15	+3 … +25
Mark state (1)	-5 … -15	-3 … -25
Undefined	–	-3 … +3

 

 

More information about the voltage levels of RS232 and other serial interfaces can be found in the interface comparison table.

The maximum voltage swing the computer can generate on its port can have influence on the maximum cable length and communication speed that is allowed. Also, if the voltage difference is small, data distortion will occur sooner. For example, my Toshiba laptop mark’s voltage is -9.3 V, compared to -11.5 V on my desktop computer. The laptop has difficulties to communicate with Mitsubishi PLCs in industrial environments with high noise levels where the desktop computer has no data errors at all using the same cable. Thus, even far beyond the minimum voltage levels, 2 volts extra can make a huge difference in communication quality.

Despite the high voltages present, it is not possible to destroy the serial port by short-circuiting. Only applying external voltages with high currents may eventually burn out the driver chips. Still then, the UART won’t be damaged in most cases.

Maximum cable lengths

Cable length is one of the most discussed items in RS232 world. The standard has a clear answer, the maximum cable length is 50 feet, or the cable length equal to a capacitance of 2500 pF. The latter rule is often forgotten. This means that using a cable with low capacitance allows you to span longer distances without going beyond the limitations of the standard. If for example UTP CAT-5 cable is used with a typical capacitance of 17 pF/ft, the maximum allowed cable length is 147 feet.

The cable length mentioned in the standard allows maximum communication speed to occur. If speed is reduced by a factor 2 or 4, the maximum length increases dramatically. Texas Instruments has done some practical experiments years ago at different baud rates to test the maximum allowed cable lengths. Keep in mind, that the RS232 standard was originally developed for 20 kbps. By halving the maximum communication speed, the allowed cable length increases a factor ten!

 

 

RS232 cable length according to Texas Instruments

Baud rate	Maximum cable length (ft)
19200	50
9600	500
4800	1000
2400	3000

Ref: RS232 Specifications and standard - Lammert Bies

I have no connection to Sparkfun. (I found my Pi 400 kit at CanaKits.) 73

Troy

Do a quick search on YouTube for "Fldigi field day" there's a couple of videos which may help if needed.

73 Glen

Hi Troy

I'm not saying it's the best, but Fldigi may be worth checking out if using data modes. I noticed in the Fldigi configuration there's options to setup a multi-op Field Day logging Server/Client.

73 Glen

What’s the best Pi logging SW to use for Winter Field Day? Thinking about doing Pi only ...

It's TERRIBLE advice to other users to "never ever" patch your computers.  If they are connected to a network that can reach the Internet, you're putting your system at risk as there are just too many ways that computers can be compromised these days (web browsing, looking at PDF files, etc).  The primary way to keep your risks low is to keep them patched and reboot when required.  A pain?  Absolutely.  Necessary evil?  Absolutely!

The back up of SD cards is a good idea.  This is also very important as SD cards just aren't intended for any heavy duty write operations.  If they are used this way, it's only a matter of time before your SD card fails.  Current image backups will make moving to a new SD card very simple and painless.

--David
KI6ZHD

Then Name the security updates.

Once your Pi is working never ever do an UPDATE, it makes no sense unless there is an absolute requirement by the developer of the application software. Create a backup image of your SD card once you are satisfied with operation.