I believe it is a PAL (75 Ohm) jack. When using the SAT 700
several years ago I noticed spurious FM and TV sounds breaking through
on certain SW bands. This was observed using the built in
telescoping antenna on two 700s . Prior to September
11,2001 electromagnetic emissions from the broadcasting
antennas,located atop of North tower must have been enormous- millions
of watts of RF. Sadly we do not have this condition any longer nor
do we have these interesting receivers anymore.
Having considered this an outside antenna cannot be used in a strong RF
environment ,may be a preselector can help . The audio is incredible-a
true Grundig sound . Enjoy.