撒種的那一個
這一支就是核心畫面的字面版本，撒出去的東西是種子或肥料。
noun · C1
A machine, or a part fitted to one, that throws seed or fertiliser out over a wide strip of ground instead of dropping it into holes in a line.
撒播機（撒種子、肥料的機器）
核心畫面
One way to hold this word: picture someone walking across a field with a hand full of seed, swinging their arm so the seed lands spread out over a wide strip of ground. Nothing is aimed at one spot; everything is sent out broadly. That is the picture inside broad + cast, and it is still the picture when a voice or a programme goes out — one person speaks, and the sound lands across a whole country at once. A broadcaster, in every use, is whatever does that : a machine, a person, or a company.
可以想成一個人走過田地，手裡抓著一把種子，手臂一甩，種子就散落在一整片地上。沒有瞄準哪一個點。全部都是往外撒開。這就…更多收起
可以想成一個人走過田地，手裡抓著一把種子，手臂一甩，種子就散落在一整片地上。沒有瞄準哪一個點。全部都是往外撒開。這就是 broad（廣）加 cast（撒）裡面的畫面。聲音和節目播出去時，畫面其實一樣：一個人講話，聲音同時落在全國各地。所以 broadcaster 不管哪一個意思，都是「負責把東西撒開的那一個」——可能是機器，可能是人，也可能是公司。From the word’s history
Wiktionary derives broadcaster from broadcast plus the agent-noun ending -er, and its own first two senses of the word are agricultural: the machine that spreads seed, and (obsolete) the person who sows by scattering rather than by drilling.
Wiktionary 記錄 broadcaster 是 broadcast 加上表示「做這件事的人或東西」的 -er，而且它自己列出的前兩個意思都是農業的：撒種的機器，以及（已廢）用撒的方式播種的人。所以「撒種」不是我們硬套的比喻，而是這個字原本就有的用法。
Wiktionary entry for broadcaster (kaikki:3f6f69a190036ae4:983738194:29123): "From broadcast + -er (suffix forming agent nouns)"; senses 0-1 labelled (agriculture).
Two branches
把節目撒出去的那一個
同樣是撒，只是撒的東西換成聲音和畫面：一個人講話，全國同時聽到。
noun · B1
Someone whose work is speaking on radio or television programmes — reading the news, hosting a show, or presenting something like a documentary or a live match.
廣播／電視節目主持人