Short range low power radar?

[Martin_J]

I was about to say the same thing about the detection/ranging capabilities that cars appear to have these days..

I also thought back to my university and dinghy sailing days from nearly forty years ago..

I recall at the time understanding the capabilities of military radar and how far away they could [potentially] detect a bumble bee from. At the time I imagined that one day we'd have radar capable of detecting the movement of all the fine particles/dust that already exists in the air and thus be able to display for us a chart of wind showing all the gusts and wind shifts as they happen live.

I also thought that by using the distorted reception of any other radio transmissions in range, that you could use the variation/variability in their reception to determine what was disrupting their signals (a bit like a radar but without having to transmit oneself)..

All pie in the sky maybe...

 

[AntarcticPilot]

I was about to say the same thing about the detection/ranging capabilities that cars appear to have these days..

I also thought back to my university and dinghy sailing days from nearly forty years ago..

I recall at the time understanding the capabilities of military radar and how far away they could [potentially] detect a bumble bee from. At the time I imagined that one day we'd have radar capable of detecting the movement of all the fine particles/dust that already exists in the air and thus be able to display for us a chart of wind showing all the gusts and wind shifts as they happen live.

I also thought that by using the distorted reception of any other radio transmissions in range, that you could use the variation/variability in their reception to determine what was disrupting their signals (a bit like a radar but without having to transmit oneself)..

All pie in the sky maybe...

Bistatic radar was actually the first kind demonstrated before WW2, by Watson-Watt I think. They used BBC transmissions and detected reflections from a test aircraft.

It's all about wavelength and permitted band use. Cars use very short wavelengths with limited range - my car detects vehicles in front when they're a hundred metres (or maybe less) or so away. Further, they don't have to look at the full circle round the car.

 

[st599]

Bistatic radar was actually the first kind demonstrated before WW2, by Watson-Watt I think. They used BBC transmissions and detected reflections from a test aircraft.

Second, the first in 1904 used two parabolic antennas on a rotating platform.

 

[AntarcticPilot]

Second, the first in 1904 used two parabolic antennas on a rotating platform.

I tend to discount the pre-1930s work a) because none of it was followed up and b) because there was little practical application. Watson-Watt et al only seem to have had the vaguest knowledge of it, though it may have been behind the German work.

Can you give a reference for the use of parabolic antennae in 1904? I would have thought the wavelengths in use at that time would have made directional antennae impractical.

 

[st599]

I tend to discount the pre-1930s work a) because none of it was followed up and b) because there was little practical application. Watson-Watt et al only seem to have had the vaguest knowledge of it, though it may have been behind the German work.

Can you give a reference for the use of parabolic antennae in 1904? I would have thought the wavelengths in use at that time would have made directional antennae impractical.

It's on the IEEE plaque on the bridge across the Rhine in Köln.

Einfache parabolantennen = simple parabolic antennas

https://mecorad.com/wp-content/uploads/2024/05/image-of-the-ieee-plaque.webp

Plus you can see a parabolic antenna in the patent diagrams in the supporting evidence https://ieee-aess.org/files/ieeeaess/2022-08/Huelsmeyer - Spring2019.pdf

 

[AntarcticPilot]

It's on the IEEE plaque on the bridge across the Rhine in Köln.

Einfache parabolantennen = simple parabolic antennas

https://mecorad.com/wp-content/uploads/2024/05/image-of-the-ieee-plaque.webp

Plus you can see a parabolic antenna in the patent diagrams in the supporting evidence https://ieee-aess.org/files/ieeeaess/2022-08/Huelsmeyer - Spring2019.pdf

Thanks. I knew about Huelsmeyer's work; I hadn't realized he used directional antennae, though at 50cm wavelength the antennae must have been enormous. I note that his system did not measure range.

 

[ylop]

As I was motoring through the Helsinki archipelago today in thick fog, I got to thinking.

, but the boats I'm worried about mostly don't have receiving AIS, so it doesn't help in this case.

Do the boats you are worried about typically go out in fog? Obviously it’s possible to get caught out (we did this year - and I had to get the fog horn out; interestingly I never heard any replies but the only vessel I made visual contact with changed course as soon as I blasted the horn; neither of us were transmitting AIS). Won’t help with moored boats or mooring bouys etc.

 

[Bitter-End]

Seems this discussion overlooks the radars fitted to cars for almost a decade now

Those parking sensors?

Yeah, those ultra short range radars will do a lot of good on boats.
Not to mention no display, range and bearing, etc.

 

[Bitter-End]

Do the boats you are worried about typically go out in fog? Obviously it’s possible to get caught out (we did this year - and I had to get the fog horn out; interestingly I never heard any replies but the only vessel I made visual contact with changed course as soon as I blasted the horn; neither of us were transmitting AIS). Won’t help with moored boats or mooring bouys etc.

I personally intend to go a bit further out with my new boat, and yes, I'd like to be prepared for low visibility situation. I need to cross 2 rather busy traffic seperation schemes.

Decided to go with AIS rather than radar. Small boats without AIS aren't all that easy to spot on radar anyway.

 

[davidaprice]

Do the boats you are worried about typically go out in fog? Obviously it’s possible to get caught out (we did this year - and I had to get the fog horn out; interestingly I never heard any replies but the only vessel I made visual contact with changed course as soon as I blasted the horn; neither of us were transmitting AIS). Won’t help with moored boats or mooring bouys etc.

There were a few small motorboats (perhaps taking people to their cottages on nearby islands), a few cruising yachts and a couple of large, fast motorboats. The large, fast motorboats rarely transmit on AIS, and some of them don't slow down for fog. I try stay to the side of the marked channel on my chartplotter, this once saved us from being run down by a large motorboat going through thick fog on the plane and clearly following the channel through the islands on their chartplotter.

 

[ylop]

There were a few small motorboats (perhaps taking people to their cottages on nearby islands), a few cruising yachts and a couple of large, fast motorboats. The large, fast motorboats rarely transmit on AIS, and some of them don't slow down for fog. I try stay to the side of the marked channel on my chartplotter, this once saved us from being run down by a large motorboat going through thick fog on the plane and clearly following the channel through the islands on their chartplotter.

Ah in that case, I’m not sure radar with range on 1 mile as per the OP is going to be that useful?

Let’s assume they are doing 25kts (could be more). Let’s assume you are doing 5 kts - which conveniently gives a closing speed of 30 kts. That gives a time of 2 minutes from very first sign on radar to collision. Obviously with an attentive, experienced radar operator and skipper that is enough time to spot the target, asses it’s collision risk, make a significant course change, reassess the target but it’s not a lot of time especially if the radar is low resolution, not overlayed with plotters and ais so you have to mentally match targets to islands and vessels. When the alternative for a conscientious skipper who expects to find himself in this situation often is a radar with much greater range, and quite sophisticated integration and automation tools the market for close proximity radar seems tiny. Radar is not cheap, but in boat terms it’s not actually crazy money. I have no radar, but for me to buy a short range radar it would either need to be amazing (finding pot bouys) or really cheap.

 

[AntarcticPilot]

Those parking sensors?

Yeah, those ultra short range radars will do a lot of good on boats.
Not to mention no display, range and bearing, etc.

There are longer range ones to do Adaptive Cruise Control, but a) I think they're Lidar rather than radar and b) still only ranges around 100m. Not sure if they work in poor visibility; if they are lidar then maybe not. They do range, and coarse direction (they can detect that a vehicle is in the lane next to you).

 

[Bitter-End]

There are longer range ones to do Adaptive Cruise Control, but a) I think they're Lidar rather than radar and b) still only ranges around 100m. Not sure if they work in poor visibility; if they are lidar then maybe not. They do range, and coarse direction (they can detect that a vehicle is in the lane next to you).

What meant is that you need to change the system so you can hook it up to a display. (assuming those parking sensors were meant, which are pretty much just a proximity sensor)

And yes, lidar will struggle in fog, and rain.

Anyway, I fail to see the point in wanting to replace radar in the first place. Decent radar systems can be had for dirt cheap, well, relatively speaking.
That wasn't your suggestion, I know.

I do see some merit in a cheaper, compact, short range radar or alternative, for smaller boats that want to be prepared for bad vis problems and don't quite need the range or resolution, or all the possibilities of a radar, but can't justify 2000-3000 for those rare occasions.

 

[seeSimon]

... The large, fast motorboats rarely transmit on AIS, and some of them don't slow down for fog. ... large motorboat going through thick fog on the plane and clearly following the channel through the islands on their chartplotter.

Yes, this REALLY scares me. My recent experiences too, off S Cornwall.

It seems many don't realise/care that not ALL hazards will appear on their chart plotter?
Viewing passage rather like a video game?

CORRECTION.
I've since bought a largish Echomax radar REFLECTOR (not transponder...my error, sorry) as a result...but not sure that really will really add much in this case?

Baulking at the £900 odd for an AIS transponder, so far...but again, I've little confidence this will protect me from idiots in MoBos/large RHIBS?
They Probably won't hear my sound signals either...due to enclosed wheel house/being on their phone/engine noise/ music on their "ghetto blasters".

Radar? Probably not much point if I'm running single/v short handed in near coastal traffic?

Consequently, I never plan passages in fog, but have been caught out unexpectedly several times.

 

[st599]

I've since bought a largish Echomax radar transponder as a result...but not sure that really will really add much in this case?

Baulking at the £900 odd for an AIS transponder, so far...but again, I've little confidence this will protect me from idiots in MoBos/large RHIBS?

The Echomax dual band transponder is about equal in price to an AIS Transceiver - what made you go for that as RHIBS are less likely to have Radar.

 

[seeSimon]

The Echomax dual band transponder is about equal in price to an AIS Transceiver - what made you go for that as RHIBS are less likely to have Radar.

The echo max is an inflatable , temporarily hoisted reflector. Appx £125.

Sorry...my typo in my post above. Corrected.