The W5GI is similar to the ZS6BKW. I trimmed my 450 ohm ladder line to give me the best possible SWR on 40m. It works great on 40. On 20 and the other bands I use my trusty Heath SA-2060. As others have posted, trim for the band of your choice and antenna tune the others. Do this, and you will be happy One other thing... Write down the length of your ladder line so that if you have to replace it, you won't have to play games when it comes to replacement.