Japan Military News, Reports, Data, etc.

Zichan said:

There’s more parameters than just power. I pointed out earlier that your aperture size for SPY-1 was wrong, hence also the antenna gain. Furthermore, we don’t know the system noise temperature and line losses for SPY-6.

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You know.. there is more than antenna aperture for gain. You might also want to consider beamwidth too because that's what i use to calculate gain. The equation would be G=30000/Beamwidth in degrees^2. Squared if the antenna is symmetrical. Why i am using beamwitdh ? because there is thing called Antenna weighting pattern. This changes your antenna radiation distribution pattern. Commonly used was Taylor-40 dB This give you.. antenna efficiency of 76%.

That's my friend is more useful than having to blindly estimates using antenna area.

Zichan said:

My argument: even without knowing SPY-1s loop gain, the fact that the 37 RMA SPY-6 is +20dB (100x) more sensitive (loop gain) allows us to determine the range at which it can track the golf ball at the same (uknown) SNR.

r_spy6= 100^(1/4) * 165 = 759km.

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Your argument keep changing all over the place. First you debate if Loop gain exist or not, Then you go on range, and now power. The last one which you yourself does not even sure if the figure given was correct or not.

Regarding your calculation.. You cannot just plug anything to the inverse square law and expect it to work. I suggest you do a reading on George M Siouris book titled "Radar System Performance Modelling" 2nd Edition particularly page



You need to know the SNR Value.. You cant just plug any random factor and expect it to work. Now i ask you what is your source for directly plugging in that 100 into 4th root law ?

In the other hand if you KNOW the amount of Loop gain.. not just the differences then you can use it to find the "excess" SNR which then you can plug in the 4th root law to find the range.

I'll be honest you're more in position of infuriating than helping at this point.

Stealthflanker said:

You know.. there is more than antenna aperture for gain. You might also want to consider beamwidth too because that's what i use to calculate gain. The equation would be G=30000/Beamwidth in degrees^2. Squared if the antenna is symmetrical. Why i am using beamwitdh ? because there is thing called Antenna weighting pattern. This changes your antenna radiation distribution pattern. Commonly used was Taylor-40 dB This give you.. antenna efficiency of 76%.

That's my friend is more useful than having to blindly estimates using antenna area.

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Sure, but that assumes that you know what the beam width is to begin with. If you don't know it, then you have to work with antenna aperture, TRM count and some reasonable guess for antenna efficiency. Now, Friedman reports both: 1.7deg beam width and 42dB gain. But the two figures don't mutually check out. So which one is it? Neither? I hope you are starting to appreciate the futility of your approach.

Stealthflanker said:

Regarding your calculation.. You cannot just plug anything to the inverse square law and expect it to work. I suggest you do a reading on George M Siouris book titled "Radar System Performance Modelling" 2nd Edition particularly page

You need to know the SNR Value.. You cant just plug any random factor and expect it to work. Now i ask you what is your source for directly plugging in that 100 into 4th root law ?

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It's elementary math based on the definition you pasted in the secretprojectsforum:

Let C1 and C2 denote loop gain for SPY-6 and SPY-1, respectively. Let r1 and r2 be reference ranges for SPY-6 and SPY-1 radars. Given that SPY-6 is 20db more sensitive than SPY-1, and assuming(!) that this relates to loop gain, then we can write C1/C2 = 100. Let reference SNR and radar cross section be the same for C1 and C2, then these cancel out and we are left with the ratio of r1^4/r2^4 = 100. Which gives you the result I derived when you plug in the value for r2.

Zichan said:

Sure, but that assumes that you know what the beam width is to begin with. If you don't know it, then you have to work with antenna aperture, TRM count and some reasonable guess for antenna efficiency. Now, Friedman reports both: 1.7deg beam width and 42dB gain. But the two figures don't mutually check out. So which one is it? Neither? I hope you are starting to appreciate the futility of your approach.

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Well then knowing the antenna diameter helps. You know to estimate beamwidth you do :

K*Lambda/D where D denotes width or diameter Where K is the beamwidth factor which 1.25 for Taylor -40 dB or 0.886 for Unweighted radiator. If the antenna is not equal in the dimension then you do the calculations twice to find Horizontal and Vertical beamwidth

The TRM number can then be worked out with methods you can find in "Methods for Array Antenna".

and i hope you understand that finding consistency is already difficult in the first place. and you seem on the attitude that "there has to be something wrong" but you cannot provide even proper comparable methods. That is my friend not a good way to build discussion.

Zichan said:

Let C1 and C2 denote loop gain for SPY-6 and SPY-1, respectively. Let r1 and r2 be reference ranges for SPY-6 and SPY-1 radars. Given that SPY-6 is 20db more sensitive than SPY-1, and assuming(!)

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you still can't accept they were talking about Loop gain eh ? Now i am still wondering how you define or what is your source for sensitivity ?

Stealthflanker said:

you still can't accept they were talking about Loop gain eh ? Now i am still wondering how you define or what is your source for sensitivity ?

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I acknowledge it as one possible explanation.

However, depending on how they define “sensitivity “ it can mean different things. Perhaps they take into account realistic conditions with weather effects or they take into account performance under adversarial jamming, performance under heavy clutter or some other complex measure of merit that takes all of that plus additional factors like the number of tracked targets, angular resolution, discrimination capability, etc.

SPY-6 is advertised as a fully digital AESA radar, which comes with significant improvements to operational parameters like jamming resistance, target discrimination, clutter removal and target search performance thanks to digital beamforming.

My money is on the digital techniques accounting for a fair share of the 100x fold improvement over SPY-1.

This animation showcases some of the advantages of digital radar:

So....what does all this mean for Japan's capability of defeating J20s/H20s?

I found this. It seems Japanese officers are complaining about li-ion only submarines, namely the Soryu Mk2 and Taigei. I remember reading a similar thing too. As far as I remember the sharp decrease in underwater endurance at normal patrol speeds wasn't liked.

BoraTas said:

As far as I remember the sharp decrease in underwater endurance at normal patrol speeds wasn't liked.

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interesting. i'm curious on how fast they patrol. In normal condition.

I mean the record for staying the longest underwater by a conventional submarine was done by the small German U212A with its innovative fuel cells powered AIP. Batteries give you the option to dash if necessary but nothing beats the endurance of a modern AIP system.

anzha said:

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Uhhhhh, looks like an ugly LPD


Edit: my mistake, the picture depicts an american design.