RADAR dead zones - anyone seeing this?

Sgian Dubh · 04-03-07, 09:36 AM

Hi all,

Two things I have been noticing about surface RADAR, one which is really good and one which is puzzling me.

1) I have noticed that islands will block RADAR contact if the island is between you and the target. This is great. I have not bee able to conclusively determine is a target will be masked by a large island behind it. Unfortunately, since land does not show up as a RADAR return, it makes it more tricky to tell what is going on.

2) I have been noticing that there seems to be a dead zone for RADAR directly off the bow +/- 15 degrees. That seems odd. I could see a blind spot to the rear or perhaps to one side if there was an obstruction on the the sub that blocked the emissions.
I've seen it a number of times recently. I have a radar target. I turn directly toward it, and it vanishes. If I turn about 15-20 degrees to either side, it re-appears and remains stable.

Seadogs · 04-03-07, 10:23 AM

Sounds like a cut out zone due to the stucture of the ship, but I agree something seems fishy with the exact positioning of it.

SimJack · 04-03-07, 11:16 AM

Radar definitely has dead zones. Contacts are there, you turn, they are gone.

E.Hartmann · 04-03-07, 11:42 AM

yep typically dead ahead for me. If you run a zig zag suddenly all kinds of targetrs will show up. The 360 degree sweep does not work and has some errors in it.

Marcos Ramius · 04-06-07, 08:30 AM

From my testing the dead zone is any time your bow is pointing South of due East or West. No matter where the contact is in relation to your boat.

It seems the radar only works when your bow is pointing North of due East or West.

I just looked on the bugzillia thing and dont see this listed ......... is it just me or has anyone else noticed this.

CobraCommander · 04-06-07, 12:49 PM

Confirmed!
I noticed this one in the agent mission at the coast of china.
Fair to get in, extremly difficult to get out.

Reason:
On the way in the radar works, on the way out the air raids are only noticed by spotting.

tycho102 · 04-06-07, 02:01 PM

Quote:

Originally Posted by Sgian Dubh

1) I have noticed that islands will block RADAR contact if the island is between you and the target. This is great. I have not bee able to conclusively determine is a target will be masked by a large island behind it. Unfortunately, since land does not show up as a RADAR return, it makes it more tricky to tell what is going on.

2) I have been noticing that there seems to be a dead zone for RADAR directly off the bow +/- 15 degrees. That seems odd. I could see a blind spot to the rear or perhaps to one side if there was an obstruction on the the sub that blocked the emissions.
I've seen it a number of times recently. I have a radar target. I turn directly toward it, and it vanishes. If I turn about 15-20 degrees to either side, it re-appears and remains stable.

Seen both those. I agree the land should be reflecting. The blind spots I'm not real sure about -- based on the rotating antenna, I shouldn't be able to see anything aft of the boat, much less have those little open areas off the bow.

kakemann · 04-06-07, 02:07 PM

I've seen it, but I thought it was a realistic touch to the game

nattydread · 04-06-07, 02:38 PM

my understanding is that the real radar had dead zones. I read something about lobes and their being something like 4 small slivers that were "dead"

That actual live area was shaped like a four leaf clover

tommyk · 04-06-07, 02:50 PM

same here. hmm, maybe there is no real 360 sweep radar since sh3 never had one?

Sailor Steve · 04-06-07, 04:09 PM

SH1 did.

Marcos Ramius · 04-06-07, 04:53 PM

Im sure the radars should not have a perfect 360 degree circle of coverage but I really sort of doubt that every time a skipper steered a southerly course he ordered the radar turned OFF.

This needs a name like the North/South Radar Bug!!

If your seeing this also I posted it at the bugzilla, its bug #145, please go give it a vote.

www.sh4bugs.com

shawnyp420 · 04-06-07, 05:09 PM

Hi folks.

I used to be a radar tech in the navy. I MAY be able to shed some light on this. Depending on where the radar is located on the hull, the transmitter will "blank" (a real term) out the signal so that it does not radiate sailors. I was a technician on the P3 Orion. P3's have fore and aft radar dishes. On the fore dish the radar would not transmit to the rear and vise versa for the aft dish.

I'm not sure if this was implemented on purpose or if its a bug or just accidental.

Supplemental: Also, radar is NOT over the horizon. It will also not work very well in inclement weather (old radars anyway.) Newer radar recievers are able to gain up or tune out erronious returns using a feature called FTC (f*&ck the clouds) and AGC (automatic gain control).

mjrhealth · 04-06-07, 05:26 PM

Radar does not have a dead zone unless it has a structure blocking the signal in that direction. As for sidelobes etc they are problems caused by antenna design in general and are basically lower power signals sent either side of the main lobe at the same time and can cause false echoes, but antenna design ( side lobe supression ) reduces this issue somewhat. LAnd in the old days would always show up as would wave reflections as they didnt have the wonderfull computer power we have these days to reduce clutter. It sounds to me as though they have used the sonar programe as the radar programme as well, that would explain the dead zone at the stern. Someone obviously has little understanding of radar. As for land on a radar if an oblect is blocking the signal you would normally see the object with a nice clear area behind it. Hope this clears some issues. As for shawny he is right, some radars do have blanking zones but generally because radar is placed high it isnt an issue, and radar is restricted by frequecy and power to range. Modern OTHR have high power and very low frequency with slow rotaton times to see further, but these are effected by earth curvature, ie the will bend a little to follow the earth but eventually shoot off into space. The radar taht the subs use would only place them in the navigation area considering there size, frequency and power so wont see far.

-Pv- · 04-06-07, 08:53 PM

I have confirmed the NS radar bug. It only takes one degree S of the E-W line with the sub heading ON or BELOW the E-W line in either direction for contacts to immediately dissapear and remain so until the sub heading change back N of the line. It doesn't matter WHERE the contacts are- S or N of you. This is consistant and repeatable.

I now find myself doing lazy Ivans when scanning for contacts.
-Pv-

04-03-07, 11:16 AM	#3
SimJack Watch Join Date: Sep 2006 Location: Chattanooga, Tennessee Posts: 27 Downloads: 847 Uploads: 0	Radar definitely has dead zones. Contacts are there, you turn, they are gone. __________________ "Peace Through Strength"

04-06-07, 02:50 PM	#10
tommyk Watch Officer Join Date: Apr 2005 Location: Near U-995 (Kiel, Germany) Posts: 337 Downloads: 5 Uploads: 0	same here. hmm, maybe there is no real 360 sweep radar since sh3 never had one? __________________ Gute Jagd und fette Beute!

04-06-07, 04:09 PM	#11
Sailor Steve Eternal Patrol Join Date: Nov 2002 Location: High in the mountains of Utah Posts: 50,369 Downloads: 745 Uploads: 249	SH1 did. __________________ “Never do anything you can't take back.” —Rocky Russo

04-06-07, 05:09 PM	#13
shawnyp420 A-ganger Join Date: Mar 2005 Posts: 78 Downloads: 38 Uploads: 0	A real navy radar tech here Hi folks. I used to be a radar tech in the navy. I MAY be able to shed some light on this. Depending on where the radar is located on the hull, the transmitter will "blank" (a real term) out the signal so that it does not radiate sailors. I was a technician on the P3 Orion. P3's have fore and aft radar dishes. On the fore dish the radar would not transmit to the rear and vise versa for the aft dish. I'm not sure if this was implemented on purpose or if its a bug or just accidental. Supplemental: Also, radar is NOT over the horizon. It will also not work very well in inclement weather (old radars anyway.) Newer radar recievers are able to gain up or tune out erronious returns using a feature called FTC (f*&ck the clouds) and AGC (automatic gain control).

04-06-07, 08:53 PM	#15
-Pv- The Old Man Join Date: Apr 2006 Posts: 1,434 Downloads: 5 Uploads: 0	I have confirmed the NS radar bug. It only takes one degree S of the E-W line with the sub heading ON or BELOW the E-W line in either direction for contacts to immediately dissapear and remain so until the sub heading change back N of the line. It doesn't matter WHERE the contacts are- S or N of you. This is consistant and repeatable. I now find myself doing lazy Ivans when scanning for contacts. -Pv- Last edited by -Pv-; 04-07-07 at 01:13 AM.

04-03-07, 09:36 AM	#1
Sgian Dubh Officer Join Date: Sep 2002 Posts: 245 Downloads: 0 Uploads: 0	RADAR dead zones - anyone seeing this? Hi all, Two things I have been noticing about surface RADAR, one which is really good and one which is puzzling me. 1) I have noticed that islands will block RADAR contact if the island is between you and the target. This is great. I have not bee able to conclusively determine is a target will be masked by a large island behind it. Unfortunately, since land does not show up as a RADAR return, it makes it more tricky to tell what is going on. 2) I have been noticing that there seems to be a dead zone for RADAR directly off the bow +/- 15 degrees. That seems odd. I could see a blind spot to the rear or perhaps to one side if there was an obstruction on the the sub that blocked the emissions. I've seen it a number of times recently. I have a radar target. I turn directly toward it, and it vanishes. If I turn about 15-20 degrees to either side, it re-appears and remains stable. __________________ \"One ping to find them all, One ping to link them; One ping to promote them all, and in the darkness sink them.\" with apologies to J.R.R. Tolkien

04-03-07, 10:23 AM	#2
Seadogs Ensign Join Date: Mar 2007 Posts: 228 Downloads: 3 Uploads: 0	Sounds like a cut out zone due to the stucture of the ship, but I agree something seems fishy with the exact positioning of it.

04-03-07, 11:42 AM	#4
E.Hartmann Soundman Join Date: Mar 2007 Posts: 147 Downloads: 0 Uploads: 0	yep typically dead ahead for me. If you run a zig zag suddenly all kinds of targetrs will show up. The 360 degree sweep does not work and has some errors in it.

04-06-07, 08:30 AM	#5
Marcos Ramius Swabbie Join Date: Sep 2006 Posts: 10 Downloads: 11 Uploads: 0	From my testing the dead zone is any time your bow is pointing South of due East or West. No matter where the contact is in relation to your boat. It seems the radar only works when your bow is pointing North of due East or West. I just looked on the bugzillia thing and dont see this listed ......... is it just me or has anyone else noticed this.

04-06-07, 12:49 PM	#6
CobraCommander Watch Join Date: Jun 2005 Location: Wolfsburg, Germany Posts: 15 Downloads: 0 Uploads: 0	Confirmed! I noticed this one in the agent mission at the coast of china. Fair to get in, extremly difficult to get out. Reason: On the way in the radar works, on the way out the air raids are only noticed by spotting.

04-06-07, 02:07 PM	#8
kakemann Samurai Navy Join Date: Feb 2007 Location: Pretty close to the big german cruiser Blücher in Norway Posts: 568 Downloads: 29 Uploads: 0	I've seen it, but I thought it was a realistic touch to the game

04-06-07, 02:38 PM	#9
nattydread Captain Join Date: Jan 2004 Posts: 498 Downloads: 2 Uploads: 0	my understanding is that the real radar had dead zones. I read something about lobes and their being something like 4 small slivers that were "dead" That actual live area was shaped like a four leaf clover

04-06-07, 04:53 PM	#12
Marcos Ramius Swabbie Join Date: Sep 2006 Posts: 10 Downloads: 11 Uploads: 0	Im sure the radars should not have a perfect 360 degree circle of coverage but I really sort of doubt that every time a skipper steered a southerly course he ordered the radar turned OFF. This needs a name like the North/South Radar Bug!! If your seeing this also I posted it at the bugzilla, its bug #145, please go give it a vote. www.sh4bugs.com

04-06-07, 05:26 PM	#14
mjrhealth Swabbie Join Date: Apr 2007 Posts: 6 Downloads: 3 Uploads: 0	Radar does not have a dead zone unless it has a structure blocking the signal in that direction. As for sidelobes etc they are problems caused by antenna design in general and are basically lower power signals sent either side of the main lobe at the same time and can cause false echoes, but antenna design ( side lobe supression ) reduces this issue somewhat. LAnd in the old days would always show up as would wave reflections as they didnt have the wonderfull computer power we have these days to reduce clutter. It sounds to me as though they have used the sonar programe as the radar programme as well, that would explain the dead zone at the stern. Someone obviously has little understanding of radar. As for land on a radar if an oblect is blocking the signal you would normally see the object with a nice clear area behind it. Hope this clears some issues. As for shawny he is right, some radars do have blanking zones but generally because radar is placed high it isnt an issue, and radar is restricted by frequecy and power to range. Modern OTHR have high power and very low frequency with slow rotaton times to see further, but these are effected by earth curvature, ie the will bend a little to follow the earth but eventually shoot off into space. The radar taht the subs use would only place them in the navigation area considering there size, frequency and power so wont see far.