In article ,
Boeland wrote:

Knowing nothing about radars and transponders could you tell us what
brands are there and how they function. Do they need to be attached to
a radar or standalone and do they respond only to Search and Rescue
radar signals?
Thanks

There is no such thing as a "Search and Rescue Radar" in the Maritime
Mobile Radio Service. There are three common Frequency Bands that
Marine Radars operate in.

S Band 2.4 - 3.1 Ghz
X Band 9.3 - 9.5 Ghz
Ku Band 14.0 - 14.05 Ghz

S Band is used on Large Ships for Long Distances and Weather/Storm
Watches.

X Band is the most common, and 95% of Marine Radars, as well as 99%
of non-commercial Marine Radars use this band. Good out to a Max Range
of 100 Miles, or so.

Ku Band Never actually seen a Ku Band Marine Radar in 40 years in
the Marine Electronics Biz, but there is a Ku Band Allocation. It
would have significantly better close-in resolution, but Max Range
over water would be the 10's of miles.

There is also a Marine Radar Frequency Allocation in the 5.46 - 5.56 Ghz
Band, and I have never seen a Marine Radar on this Band, either, however
this band is shared with the Aviation Radio Service, and there are
Aircraft Radars that do use this Frequency.

Radar Transponders in the Maritime Mobile Radio Service are licensed
under CFR47Part80, and the technical details for them can be found at
80.375 (d), and (e). They receive Radar emissions from Marine Radars,
and then add a predetermined Delay, and then Transmit a very large
Return Signal back, which shows up on the interrogating Radar Screen
as a VERY BIG TARGET. Radar Transponders are a separate device, and
are not part a Marine Radar, fitted on a vessel. They are REQUIRED
to be fitted to most classes of SOLAS REQUIRED Vessels. They also are
not cheap. Last time I looked, the cheapest one I saw was $1400US, and
that was some years back.

--
Bruce in alaska
add path after fast to reply