If you are using the long serial cable to connect to your iPaq you require a genderbender and a null-modem adapter, such that when the two are connected the male ends of each are exposed, to connect the iPaq and GPS cables.
If you are fortunate enough to own a 31/36/37xx series, you can get away with the short serial cable (part # 236251-B21) (
http://www.compaq.ca/english/busines...e_cpq=ppc_cont for canucks or
http://h20022.www2.hp.com/busprod/po...debarLayId=823 about half-way down otherwise) and the GPS cable, no adapters necessary.