input transformer to a transmatch= reason galvanic isolation

[redterrior]

i know its me , perhaps after X way too many years working with DC , i need to create a 1:1 transformer that is totaly isolated from its output
but will be seen as 50ohm _+ a tadd regardless of load which could well vary but with luck only at what i class as low power circa +1dbw

i know what i need just dont know how to create it!
yea it sucks your correct