I have a functional Pi 4 B that I want to swap for a Pi 4 B which has a modification to support an external WiFi antenna. Is it as simple as shutting down the old unit, moving the SD card to the new unit and power it up? In other words, is everything on the SD?
Believe you are correct.
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Yes, that won’t be an issue, when swapping different models you could run into different drivers due to hardware changes but that won’t be the case here.
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Yes it is.
However if you are using DHCP then just note that the ip address on your local network will change because of the MAC address being different on the 2 pi4s.
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Thanks, I am using a static IP
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@dosmond if you’re using Windows to SSH to remote in to your Pi4, then the certificates will be different - you might need to remove the old SHA key from the %USERPROFILE%\.ssh\known_hosts file before trying to connect, as it might perceived as an attempt to hijack the connection, so SSH will throw an error.
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@TonyLeverett Thanks I will keep that in mind. I am using Putty when to connect to check temps and WiFi signal strength.
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@dosmond if you’re keeping an eye on signal strength, might be worth installing Graphs-1090 - this will give you signal strength, noise, numbers of messages and cpu utilisation and more, all on a web page.
I installed it today. Will of course need it to run for a while for some data but I really like the layout. Nice job to @wiedehopf
I’d recommend trying adsb.im as a premade image.
But maybe you’re into the custom side of things vs running an appliance 
@wiedehopf This is what my graphs look like with my current setup of one antenna, one coax, then split to two dongles. I will add 2nd antenna and 2nd coax (LMR240) so should see improvement and less loss. I will use your graphs to show the results. One thing, do you have the ability to graph the WiFi signal level? I still have Pi 4 with onboard WiFi antenna and was looking at Pi 4 modified to support external WiFi next. Reason being my setup is in a steel weather proof box outside. Has temp controlled fans and such but quality=41/70 Signal level=-69 dBm and I would like to improve that.
no you can’t graph custom stuff.
Ok, I use putty to access the Pi and then run “iwlist wlan0 scan” and can get it. Just a thought. Thx
@wiedehopf What do you make of the noise in the graph from today? I do not have a filter on the 1090 but do on the 978.
Too much gain for my taste.
There is plenty of historic posts on the topic.
Nowadays i just refer to my readsb using --gain=auto
Good luck though with the manual gain fiddling if you want to go down the rabbit hole.
Also i already made a suggestion. Less gain.
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You can tell if the gain is too high by seeing if you have dropouts from planes that are very near your site. If you have a lot of dropouts, it’s an indication of receiver overload due to too high gain.