In the January 21, 2019 technical net (hosted by Aaren VA7AEJ) the topic was: transmission lines.
Mike VE7KPZ raised a question about whether there were ideal lengths of coax to use.
Aaren referenced an old document that had been given to him by Garry VE7EIY when Aaren was first setting up his shack.
That document is attached here for your reference.
Garry indicates that this is an excerpt from the ARRL Handbook. Please consider purchasing this book.
FYI,
Mike VE7KPZ