i got the gps reciever saturday, hooked it up and it`s 100%. i want to buy another one but the humminbird accessory book says it only fits 800 models on up. the part # i bought and hooked up is "as gr50 407480-1". the one i want to buy is part # " as gpr 408920-1". i read it will work with software ver. 6.30 on up. i have 7.13 in my 788 but the catalog said it only works with the 800`s and up. hoping it will work if i buy it ? i want the 2nd one for an ice fishing set up. i did look up the vhf antenna like you said and many nice low cost options, thanks again Greg.