Modem adjectives are listed in this post. Each word below can often be found in front of the noun modem in the same sentence. This reference page can help answer the question what are some adjectives commonly used for describing MODEM.
broadband, dialup
external, internal
more, most
up, wireless
Hope this word list had the adjective used with modem you were looking for. Additional describing words / adjectives that describe / adjectives of various nouns can be found in the other pages on this website.
Please add more adjectives to make this list more complete: