[How] To Kill a WINDOM / OCF
IT IS VERY EASY TO KILL A WINDOM:
RUN IT ON A BAND IT WAS NOT DESIGNED FOR BY USING A MATCHBOX.
The BALUN is typically wound on a Ferrite Toroid.
If you try to run too much power through any toroid, it will heat up, saturate, and eventually burn up.
Each Ferrite Toroid is rated for a maximum power, which depends on its size and the compound of its material. The power rating is based on usage in a well matched condition. In other words, a 4:1 balun with 50 Ohms on one side is expecting 200 Ohms on the other side. If the impedance is different by a significant amount, the Toroid will heat up much faster.
Loading the Windom on a band it was not designed for, especially in the worst case of 15m with a classical Windom (or OCF), the SWR can be very high - 10:1 or higher. Running power through it with this mismatch can result in high voltage arcing inside the balun.
THE PROBLEM GETS WORSE:
In some of the multi-band Windoms I describe on my web, there is a lot of inhernet Common Mode Current (CMC), due to the very lopsided feedpoint I have chosen. In order to cope with the high level of CMC, I have built a balun using #43 ferrite rather than #61. Although #43 impedes CMC better than #61, it saturates at a MUCH lower temperature. When running this type of balun, even 5:1 might be too great of a mismatch to match with a matchbox.
The matchbox is matching a bad impedance to the transceiver. In doing that, it protects the transceiver from damage due to high SWR, BUT IT DOES NOT PROTECT THE BALUN.