Japan Military News, Reports, Data, etc.


gelgoog

Brigadier
Registered Member
no, see radar horizon.
...
Flying at 1 km height (which is still relatively high), the maximum possible detection range by a 20 m tall radar source is 143 km due to the curvature of the earth.
Some of these marine radars have over the horizon (OTH) capability and I doubt this one is any different.

These are basically huge mobile air defense platforms to replace AEGIS Ashore I guess. Since you can actually position them they should be more operationally useful.
 

FairAndUnbiased

Colonel
Registered Member
Some of these marine radars have over the horizon (OTH) capability and I doubt this one is any different.

These are basically huge mobile air defense platforms to replace AEGIS Ashore I guess. Since you can actually position them they should be more operationally useful.
OTH RF emitters has 2 different mechanisms that I'm aware of: ionosphere reflection and surface wave.

ionosphere reflection where you bounce a beam from the ionosphere can only be done with a specific frequency in ~MHz range.

surface wave diffracts along the surface of the earth, and requires even lower frequencies.

Typically GaN radars are ~GHz range emitters.
 

CMP

Junior Member
Registered Member
You guys are really impressive in knowledge of technical details, but can you possibly include what are the consequences and implications for those looking to overcome Japanese military/naval forces?
 

Stealthflanker

Junior Member
Registered Member
29dB is almost 1,000 times more powerful than the SPY-1 radar. That’s 10 times the range against an equivalent target.

The SPY-1D(V) “can track golf ball-sized targets at ranges in excess of 165 kilometers.” A golf ball-size (1.68 inches diameter) metallic sphere corresponds to radar cross section of about 0.0025 m2 at 3.3 GHz. This is most likely for short dwells on target in volume search. Longer dwells can significantly increase radar range.

Therefore, I suspect the SPY-7 radar’s range against a 0,005m2 target would be at least on the order of 2,000km. Possibly more if using longer dwells.

No. When you see that value they are talking about LOOP GAIN. Which does not translates into range. You cannot just translate that 29 dB directly into the range without a context.

This is a bit of writing of mine about the term :

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Zichan

Junior Member
Registered Member
No. When you see that value they are talking about LOOP GAIN. Which does not translates into range. You cannot just translate that 29 dB directly into the range without a context.

This is a bit of writing of mine about the term :

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OK. What is your source for +29dB “loop gain”? I haven’t come across this term before.

SPY-6 was declared to have a +20dB (100x) advantage over SPY-1 in “sensitivity”. That translates to a range advantage of 3.2x if the radars are operated in an equivalent way:

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Other sources claimed that compared to SPY-1, SPY-6 can track a target half the size at twice the range.
 

Stealthflanker

Junior Member
Registered Member
OK. What is your source for +29dB “loop gain”? I haven’t come across this term before.

SPY-6 was declared to have a +20dB (100x) advantage over SPY-1 in “sensitivity”. That translates to a range advantage of 3.2x if the radars are operated in an equivalent way:

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Other sources claimed that compared to SPY-1, SPY-6 can track a target half the size at twice the range.

Have you even bother opening the link i provided ? Because i provided the source material and calculation methods too.

Oh My God seems i need to repeat it here. First the sources for the term :

"Andy Harrison's "Introduction to Radar using Python and MATLAB" 2019 edition."
 

Zichan

Junior Member
Registered Member
Have you even bother opening the link i provided ? Because i provided the source material and calculation methods too.

Oh My God seems i need to repeat it here. First the sources for the term :

"Andy Harrison's "Introduction to Radar using Python and MATLAB" 2019 edition."
No, the source for “+29dB loop gain” improvement for SPY-7.

All I found in your link is that Andy Harrison introduced the term “loop gain”, but not that either Raytheon, Lockheed Martin or the USN use it as such.

From the link I provided, it is clear that the the +20 dB improvement in sensitivity for the 37 RMA SPY-6 is a dimensionless quantity, therefore not the “loop gain”.
 

Stealthflanker

Junior Member
Registered Member
No, the source for “+29dB loop gain” improvement for SPY-7.

All I found in your link is that Andy Harrison introduced the term “loop gain”, but not that either Raytheon, Lockheed Martin or the USN use it as such.

From the link I provided, it is clear that the the +20 dB improvement in sensitivity for the 37 RMA SPY-6 is a dimensionless quantity, therefore not the “loop gain”.

I cannot blame you because the term is indeed very obscure. But that doesnt mean it not exist or unused. you only need to search for the term in relevant website and boom..

LoopGain Measure.png

IF you download the paper you will see it is used by kind of many US testing ranges.

USN.png

Surely Atlantic Fleet Weapons Training Facility, NAWC, NUWC, Pacific Missile Range is related to USN.

and if you do Practice the methods.. You will find they are correlated. Like this. The 29dB improvements is from calculations using the methods in the book. The real loop gain of the radar in dB is some hundreds of it. This is the Full table i calculated for the AMDR and become the baseline for the SPY-7.

LoopGain2.png

You see, the Baseline Aegis SPY-1 have loop gain of 239 dB.. and the estimated SPY-7 (AMDR with 82 RMA) which i consider it equivalent has Loop Gain of 268 dB.

Simple math : 268-239 = 29 dB of improvement.

Or do you really need me to go step by step ?

So you cannot really say it's dimensionless. It has a dimension, it is a legit merit.

Otherwise i wonder how do you make your conclusion about "100 times more sensitive" ?

Like if you see Radar Range Equation there is part of MDS or "Minimum Detectable Signal" That is your sensitivity and the value is a big NEGATIVE e.g -95 dB or -122 dB. How do you get positive number from there ?
 

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