The counterpoise is a ground plain the radials that you see under a vertical antenna. You must provide radials that will match the lowest band you wish to operate on in my case you are looking at 64' of radials. I used 1/2" copper water pipe for mine cut into 4' lenghths. These are mounted on a 18"  square piece of aluminum 3/8" thick  You might also want to seal the antenna in a piece of  2" pvc pipe to protect it from the weather and dirt this antenna is very sensitive to mosture and dirt lesson learned this winter . mount it in the center of the aluminum plate and set the counterpoise radials around the antenna at equal distances.  Also please note that a good  conductive silicone greese on the connectors will keep them easyly removable if you should want to do any maintanance to your antenna

Mike WD9GJK  

I am curently using the ATAS 120 as a base antenna. For me it works fine a little research on the net on conterpoise ground plain and I designed one that works fine. Have been getting fb reports as far away as the southern tip  of  Africa on the little antenna mounted 25 feet on my chimney 20 meters band .
I designed the counterpoise for 40 meters and added earth grounds 8' apart from the antenna and the mast  only problem I have run into is during real damp weather antenna SWR climbs to higher than normal 1.5.1 we live with it as for 2 - 440Meters I have a separate antenna system for them but 6-40 meters life is good.  I was impressed by my FT 847 and this antenna after being away from ham radio for 10 years and picking up wher I left off I am again hooked  antenna is worth the effort that you can design into it

Mike WD9GJK