The effectiveness of the built-in whip really depends on the construction of your house. Metal siding or brick will reduce the signal, for example. I would think your best bet is to clip a length of wire to the whip antenna using an alligator clip. Place no more than 30 feet of the wire outside your dwelling if you can. Generally with portables, any more than that would only increase the chances of signal overload and cause the receipt of spurious signals. I'm not familiar enough with the 7600 to know if it has an attenuator switch (like my Sony 2010). But if yours did, that would be helpful to reduce the overload. Another possible solution is the use of a band preselector. A model such as the MFJ-1046 would be one choice. I used to use a preselctor with my 2010 at one time, and that typically removed all phantom signals, and allowed me to use a random wire antenna mounted outside. I now use an Icom R-71A, so overload with an outdoor antenna is not an issue. Hope this helps.