My models used bare wire. If using insulated, all dimensions will get about 2% shorter. It requires an adjustable L-C matching network right at the base of the vertical section to make the antenna usable at various frequencies in the 160m band. Unfortunately, that requires a large variable C and a variable L in a weatherproof enclosure, and you have to run outside to re-tune the network to a new frequency when you QSY. An expensive way is to add a remote automatic tuner like my MFJ-998RT. If you just prune the antenna so that its lowest Swr is at 1.85MHz, it should be usable without a tuner at either end of the coax at frequencies where the Swr is less than 3. Using a wide-range manual desktop tuner will extend the usable frequency range a bit, but likely not all the way to 2.0Mhz. Don't expect much out of an automatic tuner built-in to a transceiver.