There is no straightforward way to achieve what you want. The long winded way is to set two discounts for each satellite dish product that you have.
For instance, your product is priced $15 and your current discounts look like
10% for min. $10 order
20% for min. $20 order
30% for min. $30 order
Then, you can create following two discounts
100% for $15.00 order <--- so there is no shipping charged if only a dish is bought 10% for $15.01 order <-- to resume the prior discount
There are two issue in this scheme though.
1. If the total of your any other products is $15, then shipping would go 0. You can counter that by setting the price of your product to $15.01 or something so you can be sure that no other products together will form this total.
2. If buyer is purchasing two or more satellite dishes in one order, then this scheme will fail and shipping will be charged as usual.
