Almost all modern radar units have a guard zone feature. This is a user setting
that sets off an alarm if a radar target enters the preset zone area. The radar
unit is programed to sleep for a preset time, wake up and transmit a few sweeps
and if no targets are found, go back to standby until the next wake time. This
"active" system is a good addition to the "passive" radar reflector up on the
mast.
I would not rely upon the larger ship watching out for you. There have
been too many reports of tankers making their destination with sailboat
rigging snared in their anchor.
andy shor wrote:
>
> Almost all modern radar units have a guard zone feature. This is a user
setting that sets off an alarm if a radar target enters the preset zone area.
The radar unit is programed to sleep for a preset time, wake up and transmit a
few sweeps and if no targets are found, go back to standby until the next wake
time. This "active" system is a good addition to the "passive" radar reflector
up on the mast.
>
> Regards:
> Andy
>
> "Gary W. Sims" <simsgw@c...> wrote:
> From: "
> Almost all modern radar units have a guard zone feature. This
> is a user setting that sets off an alarm if a radar target enters
> the preset zone area.
Yes, but this is installed on the radar on the big ship. Very few
single-hand cruisers carry radars.
I'm not a mariner but I wondered if a radar detector
might be a simpler thing to construct? I assume all
the targets are likely to be running radar of at least
one type, it's an issue of whether the watch is
effective?
Would a signal strength detector give enough
discrimination for target distance. Could check for a
rising trend in that.
If 'big boats' use multiple radar wavelengths (I don't
know why I think they do, but my memory of trips on
RoRo is that the have lots of rotating antennae) using
multiband reciver might give a vessel-type profile?
From: "Adrian" <adrian650@y...>
>
> I'm not a mariner but I wondered if a radar detector
> might be a simpler thing to construct? I assume all
> the targets are likely to be running radar of at least
> one type, it's an issue of whether the watch is
> effective?
>
Yes, I would say that's a good statement of the problem. It is much more
likely that the radar will be operating than that someone will be paying
attention.
And we obviously know that signal strength at the target is going to be
several orders of magnitude greater than it is at the antenna looking for
the return, so if it might well be practical to build an inexpensive
detector to show when you're being painted by someone's radar.
A little research should tell us what frequencies are used for shipboard
radars, and with luck it won't be the same as shore radars -- nor will it be
too many different frequencies. I know in general that radar bands are P, L,
S and so forth up through K or V or something, but I never had to pay
attention to licensing issues on the ones I used, so I have no idea which
bands are assigned to which civilian purposes. One of our hams will surely
know.
> Could check for a rising trend in that. [noparse][[/noparse]and]
> multiband reciver might give a vessel-type profile?
>
Quite possibly, especially if I can remember which bands are allocated to
the US/UK navies. Watchkeeping is more disciplined on those vessels, but
personally I'd still rather be alerted if a tin can is nearby. I can picture
a detector that we tune to different bands if that is reasonably cheap to
build, or possibly a set of detectors for the likely frequency bands. Then
the Stamp aggregates the positive responses it receives in a given time
interval and displays either the raw profile, or possibly a "likely source"
indication.
Gary
Whose cruising is limited to the dining room and the
Internet these days, but I still empathize with Stein
Archiver
Posts: 46,084
Comments
that sets off an alarm if a radar target enters the preset zone area. The radar
unit is programed to sleep for a preset time, wake up and transmit a few sweeps
and if no targets are found, go back to standby until the next wake time. This
"active" system is a good addition to the "passive" radar reflector up on the
mast.
Regards:
Andy
"Gary W. Sims" <simsgw@c...> wrote:
From: "
been too many reports of tankers making their destination with sailboat
rigging snared in their anchor.
andy shor wrote:
>
> Almost all modern radar units have a guard zone feature. This is a user
setting that sets off an alarm if a radar target enters the preset zone area.
The radar unit is programed to sleep for a preset time, wake up and transmit a
few sweeps and if no targets are found, go back to standby until the next wake
time. This "active" system is a good addition to the "passive" radar reflector
up on the mast.
>
> Regards:
> Andy
>
> "Gary W. Sims" <simsgw@c...> wrote:
> From: "
> Almost all modern radar units have a guard zone feature. This
> is a user setting that sets off an alarm if a radar target enters
> the preset zone area.
Yes, but this is installed on the radar on the big ship. Very few
single-hand cruisers carry radars.
Gary
wrote:
> From: "
I'm not a mariner but I wondered if a radar detector
might be a simpler thing to construct? I assume all
the targets are likely to be running radar of at least
one type, it's an issue of whether the watch is
effective?
Would a signal strength detector give enough
discrimination for target distance. Could check for a
rising trend in that.
If 'big boats' use multiple radar wavelengths (I don't
know why I think they do, but my memory of trips on
RoRo is that the have lots of rotating antennae) using
multiband reciver might give a vessel-type profile?
Adrian
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>
> I'm not a mariner but I wondered if a radar detector
> might be a simpler thing to construct? I assume all
> the targets are likely to be running radar of at least
> one type, it's an issue of whether the watch is
> effective?
>
Yes, I would say that's a good statement of the problem. It is much more
likely that the radar will be operating than that someone will be paying
attention.
And we obviously know that signal strength at the target is going to be
several orders of magnitude greater than it is at the antenna looking for
the return, so if it might well be practical to build an inexpensive
detector to show when you're being painted by someone's radar.
A little research should tell us what frequencies are used for shipboard
radars, and with luck it won't be the same as shore radars -- nor will it be
too many different frequencies. I know in general that radar bands are P, L,
S and so forth up through K or V or something, but I never had to pay
attention to licensing issues on the ones I used, so I have no idea which
bands are assigned to which civilian purposes. One of our hams will surely
know.
> Could check for a rising trend in that. [noparse][[/noparse]and]
> multiband reciver might give a vessel-type profile?
>
Quite possibly, especially if I can remember which bands are allocated to
the US/UK navies. Watchkeeping is more disciplined on those vessels, but
personally I'd still rather be alerted if a tin can is nearby. I can picture
a detector that we tune to different bands if that is reasonably cheap to
build, or possibly a set of detectors for the likely frequency bands. Then
the Stamp aggregates the positive responses it receives in a given time
interval and displays either the raw profile, or possibly a "likely source"
indication.
Gary
Whose cruising is limited to the dining room and the
Internet these days, but I still empathize with Stein