Please reference HP App Note 95-1, available on the web.

There's only one in every half a million of radio amateurs who have a
copy of this document, or have ever heard of its existence, let alone
having any chance of finding a readable copy of it within the next
dozen years. By which time they will have changed their hobby to
keeping tropical fish or making Newtonian telescopes. Or just died.

In all likelihood they won't be able to make any sense out of it
anyway.

Cec, why do you bother to mention it? (smiley)
----
Reg.