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Add an external antenna to the Radio Shack 12-469 by winding a half dozen or so turns on the empty end of the rod antenna. Ground the end farthest away from original antenna coil. The other end can be attached to a jack or binding post, you want to make it so it doesn't put any stress on the antenna rod. These boards are delicate, so you have to work with care, try to move the antenna rod as little as possible.

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My Notes

How to use the Radio Shack 12-469 for a box, instead of the hack. The processor board is removed per the following diagram, and an external sweep, or VT is used. I use an LM317L to provide the 3 volts from the main 12 supply of the seep board.

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I tried over the last couple years to change the system to single supply, a single 12 volt battery, or AC supply. This actually introduces too many problems with the op amp circuits, especially the Random Voltage Generator. This is the latest schematic for dual supply operation, I think it has some advantages over the single supply version, one is that the DC levels can be adjusted to zero volts, important in home made radios. As usual, always check the manufacturer data sheet for errors in my schematics. In one version I showed the outputs of the low pass filters in the RVG going to ground--no worky!
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The latest attempt at using the LA1816 Radio chip. The chip works, it's the antenna that is very critical. The antenna has to resonate across the AM band by adjusting the number of turns in the coil and the coil position on the ferrite rod. Because the system is voltage tuned, you can't just buy a pre-made AM antenna coil, the coil has to match the tuning capacitors.
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Another simple radio, the MK484 TRF chip. It is surprisingly sensitive, and reasonably selective as it's swept across the AM band. Combined with linear sweep, and the usual audio amplifiers, it makes a usable box in a small space. You can buy kits for this radio, and just replace the mechanical tuning capacitor with the varactors. Piece o' cake!
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Built on a small Radio Shack proto board, just because I had it in the junk box, but it made of a small main board, and I had only to add a small daughter board for the monitor amplifier. Not shown is another small board that holds the ferrite rod antenna. on the left side.

So far, this simple radio beats all others I've tried before, such as the RS 12-469. There is a replacement for the MK484, it is the TA7642. I just ordered some from electronics123.com

07/04/09 The next step is to see how this chip performs with random sweep, just out of curiosity. I was building the circuit last night, and forgot I was using a single ended supply. I did not put in the divider resistors to apply the 1/2 Vcc to the + input of the op amp, according to the data sheet for the LM324--and the damn thing works more better! Could it be the data sheet incorrect? I was having trouble getting random to work with a single supple, for one thing, the low pass filters, as shown in the data sheet don't work, but--if built as if using a dual supply-it works. I think to save money they just copy old data sheets and change the part number on it.