The mast mount for the Ham IV will match the Ham III, Ham II, and Ham-M! All the controls boxes work on everyone of them too! 73 Mike K0BUD -- FAQ on WWW: http://www.contesting.com/towertalkfaq.html Submissions: towertalk@contesting.com Administrative requests: towertalk-REQUEST@contesting.com Problems: owner-towertalk@contesting.com Search: http://www.contesting.com/km9p/search.htm