Does having my radar transmitting make me more visible to others with radar?

[Wotname]

Originally Posted by a64pilot

.............


Just me but I don't think any of the radar reflectors we use on our little boats is as effective as we would hope. But they are better than nothing

Not just you, here is a good analysis of "little boat" radar reflectors.
http://keyassets.timeincuk.net/inspi...ce_ym_june.pdf

Originally Posted by a64pilot

.....
However I believe that radar transponders exist for boats, that would give you a very large radar signal.
......

Yes there is (or was?) and yes they are very effective. They work on a similar principle as your aircraft radar transponder (or IFF etc). I have seen any around for awhile but then I haven't been looking for such.

[deblen]

Are you saying RACON,s have been shut down?

https://en.wikipedia.org/wiki/Radar_beacon_(racon)

Radar reflectors are needed in poor vis. situations.
http://keyassets.timeincuk.net/inspi...ce_ym_june.pdf

/ Len

[Wotname]

^^ No, AFAIK RACONs are alive and well.

[thomm225]

Originally Posted by a64pilot

Your transmitting radar has no effect on a ships receiving radar.
However I believe that radar transponders exist for boats, that would give you a very large radar signal.
In WWII transponders were developed for military aircraft so that friendly radar installations could see them a long ways off and positively identify them as friendly, a transponder of course is a transmitter that transmits a signal that the other radar will see so to speak.


Just me but I don't think any of the radar reflectors we use on our little boats is as effective as we would hope. But they are better than nothing

The transponder is a whole separate system as you know with it's own transmitter and receiver not to be confused with raw radar data (targets, echos) and it gives much more data as in altitude, plane number, possible hijack code, comm failure code, etc.

The transponder video (IFF) is actually called secondary video. (Mode 1, 2, 3, and C for altitude)


AIS is similar I would guess .........

[El Pinguino]

It appears that in some places in Oz they are being replaced by AIS 'beacons'... I would have though that 'racon supplemented by AIS' would have been a better way to go... its all same same as the AMSA idea of turning off or downgrading a lot of the lighthouses because 'everyone has GPS' and the 'lets make an entire continent 'GMDSS Area 3' cos its cheaper' idea...

[hsi88]

My question would be how does two radars broadcasting on the same frequency know their own returning signals. Are they coded in some way with some sort of identity key? Or I would think broadcasting radar would indeed show up on the other guy's radar (if not filtered in some way). Isn't that the way active radar reflectors like "See-Me" work?

[captmikem]

Your radar pulses are seen by other radars, however circuitry exists in radar receivers to hide these pulses.

For instance, from A Furuno manual:

Limiter
The limiter protects the receiver circuits from damage
in the event own ship’s Radar receives radio pulses
from another ship’s Radar. When this occurs, the
limiter attenuates them to protect the next stage MIC
(Microwave Integrated Circuit).

And most radars have a manual control over seeing this on your screen, this called IR. Again from a Furuno manual:

Interference Rejection: This control reduces or
eliminates interference received from another ship’s
Radar. Turn it off when no Radar interference exists.


M

[a64pilot]

Originally Posted by thomm225

The transponder is a whole separate system as you know with it's own transmitter and receiver not to be confused with raw radar data (targets, echos) and it gives much more data as in altitude, plane number, possible hijack code, comm failure code, etc.

The transponder video (IFF) is actually called secondary video. (Mode 1, 2, 3, and C for altitude)


AIS is similar I would guess .........

Yes, mode 4 is IFF, identify friend or foe of course.
And the upcoming ADSB mandate is nothing more than AIS really, just mandated and way more expensive.

[crazyoldboatguy]

I have read several accounts of US WW2 submarines using radar to communicate with each other while on patrol in the Pacific theater. Since Japan didn't have widespread decent radar, the US subs would turn the radar transmitter on and off to send Morse code signals out. A nearby US sub would perceive intermittent interference on their radar screen that could be decided. I would assume since the radars were operating on the same frequency band this would work. I would guess modern radar wouldn't work the same way.

[thomm225]

Originally Posted by hsi88

My question would be how does two radars broadcasting on the same frequency know their own returning signals. Are they coded in some way with some sort of identity key? Or I would think broadcasting radar would indeed show up on the other guy's radar (if not filtered in some way). Isn't that the way active radar reflectors like "See-Me" work?

An example of a radar pulse width (PW) is 833 microseconds (or 833 millionth's of a second). This radar had a 40 mile range

A radar nautical mile is 12.36 microseconds. It would take 123.60 microseconds for the echo to travel back from 10 miles out. so for 40 miles that would be 494.4 microseconds

A receiver will only be able to "look" for these echos during certain portions of the PW time when the transmitter isn't on etc.

It would be quite hard for another radar to sync up with your radar and actually receive the echos during it's exact pulse width period.

And then there's the rotation............

[thomm225]

Originally Posted by a64pilot

Yes, mode 4 is IFF, identify friend or foe of course.
And the upcoming ADSB mandate is nothing more than AIS really, just mandated and way more expensive.

Mode 1, 2, 3a, and C are all IFF Modes. A quick search says Mode 4 and 5 are NATO IFF.

In aviation, many controllers I'm thinking use the IFF Display more than the actual radar echo.

We had the interrogators on the ground transmitting to and receiving from you folks' transponders in the air

[Suddy]

I was the radar operator on a submarine maneuvering into Norfolk one morning (about 44 years ago). I picked up some signals during the radar sweep that looked like multiple contacts at various ranges. They all lined up on a single bearing on the PPI display. When the Lookouts checked on that bearing, they saw a second submarine bearing down on us. (Same class, used the same radar as we did.) We were transmitting 600 PPS in the 88 GHz range (not too certain about the later). I don't remember what the pulse width was, but it was short enough that we could "see" a contact 400 yards distant.
If you are using a "pulse" type radar (typical surface search) with the same frequency, they will pick you up. It won't interfere with the operation of the other ship's radar, but it can confuse the display.

[a64pilot]

Its the mode 4 that changes daily, and it's mode 4 that air defense artillery and the Air Force will use to identify you, if you you have the wrong mode 4 or are using yesterday's mode 4 you may be a victim of friendly fire.
The mode 4 switch on the transponder has an a and b position to enable you to fly during the time the code changes, when that time comes, you select B mode hopefully

https://en.m.wikipedia.org/wiki/1994...tdown_incident

[1Sunseeker]

Another point...many years ago while I was taking classes to get my 6 pack license, the instructor emphatically tried to beat into our little gin soaked brains the importance of having your radar on at all times. He stressed that if you are involved in a collision at sea with another boat/ship the judge would ask if your radar was on. If you had radar on board but it was not turned on the fault of the collision could be judged as yours. Even on a blue bird day, his words. Maybe changed by now but that was what he was trying to stress.

[Cottontop]

Originally Posted by 1Sunseeker

Another point...many years ago while I was taking classes to get my 6 pack license, the instructor emphatically tried to beat into our little gin soaked brains the importance of having your radar on at all times. He stressed that if you are involved in a collision at sea with another boat/ship the judge would ask if your radar was on. If you had radar on board but it was not turned on the fault of the collision could be judged as yours. Even on a blue bird day, his words. Maybe changed by now but that was what he was trying to stress.

The Colregs (7b) say:

Proper use shall be made of radar equipment if fitted and operational, including long-range scanning to obtain early warning of risk of collision and radar plotting or equivalent systematic observation of detected objects.

Whether this language requires radar to be turned on has been debated, I believe, in this very forum. Surprisingly, no consensus was achieved.