Is it possible to order a triplet that is adjusted to three arbitrary UHF channels?
The simple answer is no.
A triplet (3 channel equaliser), contrary to what one may expect, is not a three UHF channel amplifier.
In fact, it is an amplifier with a bandwidth of seven channels.
Three of the channels are adjusted and the others inbetween are used as guard channels (two channels between the selected three).
Therefore, the channels to be amplified must be within a bandwidth of seven channels.