Window Size in Safari

The problem I'm having is that on my iMac, Safari seems to go through periods where no matter what I do, it ALWAYS opens new windows in a very annoying "letterbox" size. Quitting and rebooting don't seem to help. It'll do this for weeks, and then eventually at random it will go back to opening new windows in the size I want. There ought to be some place in the preferences where you can manually set the desired window size and have it stay that way.

BTW I'm currently running OS X El Capitan, and Safari 10.1.1 -- but this problem has been going on for the past several versions of both Safari and the OS.

Resize a window. That becomes the default size.

Hi...

You can resize the window by dragging out the bottom right corner. Next time you open Safari it should be the same window size.

Some sites use JavaScript to set the window size. All you can do about that is to disable JavaScript when visiting the site. There are Safari extensions, such as JavaScript Blacklist, that can do it automatically.

I was here earlier and didn't "like" or "grok" any of the answers but, later, grey matter synapses kicked in and I remembered how. [Am I having increasing senior moments?] The whole thing is better understood if you remember that your cursor, when placed on a window border, becomes like and acts like a needle-nosed plier with which you can pinch, grab and pull that side like a window shade to whatever position you want. So, up and down, side to side, you can literally fit it your needs of the moment and change it at any time.

Try right clicking (control click) on the radio link and choose to open it in a new window. That should leave your prefered sized window open and maintain it as the default.