Grumman F-14 Avionics

overscan (PaulMM)

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AWG-9 Radar

While I prepare this post, check out this video of the AWG-9 display

http://www.secretprojects.co.uk/secret/AWG-9.avi

Source
  • Great Planes: F-14 Tomcat Discovery Wings 1988
 

Ronny

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AWG-9 Radar

While I prepare this post, check out this video of the AWG-9 display


Source
  • Great Planes: F-14 Tomcat Discovery Wings 1988
Do you have any data about AWG-9 and APG-71 detection range? I tried to find myself and ask in several forums but get very conflicting information

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overscan (PaulMM)

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It's not secret, but radar range is a very complex subject.

Radar range varies with the mode used, the engagement geometry (above or below, approaching or receding) and target radar cross section. Often the range is quoted for a 50% chance of detection and a specific target RCS and geometry, but another radar's range figure might be for a 90% chance of detection resulting in a shorter quoted range.

The AWG-9 is a hybrid digital/analog high PRF pulse-dopple radar. It can theoretically detect a fighter-sized target (typically 5 sq m) at up to about 200km in PDS (Pulse Doppler Search) mode, but this gives no target range information, just velocity and azimuth, and was rarely useful in practice.

RWS (Range-While-Search) mode can detect a closing fighter-sized target in clear space at a maximum distance of about 170km, as can TWS (Track-While-Scan), but TWS can only cover the rapid +-40 deg 2 bar scan or +-20 deg 4 bar scan patterns (2 second cycle), while RWS can scan +-65 degrees in an 8 bar scan. Big difference, because the RWS scan takes 13 seconds and that's too long between target updates for tracking targets.

Detection range of both modes will be reduced in less favourable engagement geometries - HPRF pulse-doppler lookdown really only works well with closing targets. The AWG-9 retained low PRF pulse modes to use when lookdown wasn't needed, to improve detection range against non-closing targets.

AWG-71 was fully digital and added medium PRF modes for improved lookdown performance in all engagement geometries.
 

stealthflanker

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In the bottom line.

There is no real "right" or "wrong" Just condition of engagement/environment and the respective modes used by the radar.

As long as the figure is accompanied by the conditions where and how the measurement is taken, you can go with that. Should none available (e.g just "250 miles") You yourself may have to do research and provide some explanation on the figure.
 

GARGEAN

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It can theoretically detect a fighter-sized target (typically 5 sq m) at up to about 200km
You sure about fighter-sized? IIRC ranges for both AWG-9 and AIM-54 seeker were stated for bomber-sized target.
 

GARGEAN

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Hmmm... Isn't 200km was instrumental range for whole AWG-9?
 

overscan (PaulMM)

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Maximum range is achieved in PDS (Velocity Search) mode which doesn't show range, only velocity and azimuth. The AWG-9 isn't instrumented in km at all, it'd be nm (nautical miles).
 
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overscan (PaulMM)

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Range While Search is the basic Pulse Doppler search mode with range information, Track While Scan mode is a PD multiple target tracking mode, there's also Pulse Doppler Single Target Track.

PDS was supposed to be used when you know there's a bunch of Backfires headed your way and you need to detect them as far away as possible in order to head in the correct direction. Like all Velocity Search modes, it was of limited use generally.
 

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Maximum range is achieved in PDS (Velocity Search) mode which doesn't show range, only velocity and azimuth. The AWG-9 isn't instrumented in km at all, it'd be nm (nautical miles).
How much better APG-71 range compared to AWG-9?
Some source says APG-71 has twice the range of AWG-9 while some say it has 40% more range.
If APG-71 got twice the range of AWG-9 that put it in Irbis-e territory,
 

GARGEAN

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I'll be honest: I have some healthy scepticism about those numbers, including 200km range for fighter-sized target. This would put it quite ahead of N007, which is doubtful for me considering power comparison and tech level difference between two.
 

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Few words about AWG-9 range & some speculations:

Long time ago, I found in Flight International 1976/January(pages 17, 18) statement that F-15 radar has range less about 15% than AWG-9 rated on 115nm.
Both radars were produced by Hughes, share the same antenna (diameter 0.9m ?).
Comparing transmitter power -see post above (10.2kW vs 5.2kW) - this statement seems to be correct: (5.2/10.2)^0.25 = 0.845
On the other hand, Russian estimated range of APG-63 on 100km, and stated the same requirements for radar of Su-27.
So 118km or 115nm (213km)?
Both ranges might be correct.
Let's count down, using only radar equation: x^(1/4) - where ^ means power
-> 115nm is ~213 km.
1. Above is in PDS or velocity search. For range search (RWS) target have to be "scanned" triple : one for basic signal - to get doppler frequency, two times with signal linearly modulated (http://twanclik.free.fr/electricity/electronic/pdfdone8/Introduction_to_Airborne_Radar.pdf see chapter 14 FM ranging). Thus in RWS energy emitted is 3 times lower*, thus
213 * (1/3)^1/4 =213 * 0.76 = 161km
* in reality in VS - accumulated energy is not 3 times more , as period of coherent integration does not extend 3 times, rather - there are 3 coherent integrations averaged or summarize otherwise. (Postcoherent integration gives at least than N^(1/2) gain, or better so (1/3^0.5)^0.25 *213 =185km.)
Anyway it is stated that detection range in VS is 25% -30% more than in RWS. Taking 25% - gives exactly 170km (0.8*213=170.4) - as mentioned by Overscan


2. above range is for 5m2 target, for 3m2 this is : 170km* 3/5^(1/4) = 150km

3. This point is my speculation**, but I assume that waveform used in AWG-9 was almost 50% duty ratio, and AN/APG-63 use let say 25% duty ratio.
50% duty ratio means that radar emits signal about 50% of time, the rest time listen echoes. Actually this may give more range (up to 15-19%), but only for situation that target echo is not eclipsed by emitting pulse. There is chance for that about let say 20-30% . In other cases part of target echo is not visible what gives shorter range, or even not visible at all. In average, expected detection range will be less, but actual ranges will vary more = comparing to lower duty factor.

Lower duty factor gives shorter range "on paper" but with higher probability (let say chance is 60-70% of being not eclipsed at all)
Of course there may be some scenarios when high duty ratio has advantage: for example bomber 100m^2 , PDS detection range about 400km (vs 336); with low closure speed (let say 900km/h each, 250m/s), with 14s refresh ratio - scans are refreshed every 7km what, may give faster detection even if single detection probability is low.
But in case of many small targets with high closure speed, RWS , pilot probably want more confident detection.

Anyway, assuming 25% duty factor comparing to 50% is another 15% less range ((25/50)^0.25=0.84) that gives : 150 * 0.84 =126 km

4. Finally if we take difference in transmitter power between AN/APG and AWG-9 : (5.2/10.2)^0.25 = 106 km what is quite close to the Russian estimate

Anyway, using similar measure, one can say that that AWG-9 has average range about 126km for 3m2 target in RWS mode.

**My assumptions are made on basis of radar generation. Pulse doppler radars before AWG-9 , for example on USN Phantoms, uses such 50% duty ratio as this was simpler (simple filter can be used) also some later radars (like Fox hunter AI 24 on Tornado ADF- "interrupted continues wave"). In later design there was tendency to decrease duty rate, what decrease power but also decrease eclipsing. This requires more advance processing including digital filters, but also multiplies number of necessary doppler filters - as there is not single range bin for example 2 or more (if you include pulse compression). For example radar from Mig-29 has duty ratio 25% and two doppler "channels". I assume similar approach in APG-63. But this is my speculation, and actual in AWG this might be more complicated, and manually tuned by RIO.(reference in above post suggest many pulse width, and average power in doppler mode : 7kW vs 10kW peak power what suggest duty factor more than 50%)
 
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overscan (PaulMM)

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@GARGEAN your scepticism is irrelevant, the AWG-9 range figures given were published long ago by the US Navy and Hughes and broadly confirmed by former F-14 pilots.

Long range High PRF Pulse-Doppler detection is achieved first using high power output and a high duty cycle, but the other vital technologies are the antenna and the receiver, the sensitiivity of the receiver, the antenna gain. I can have more power in radar A, but if the receiver is less sensitive, then the range at which you can detect a target can be lower than radar B, which has a lower power output.

In terms of development timing, AWG-9 was a little earlier than Zaslon, but given the relative lag in electronics and radar, not enough to expect Zaslon to be 'better' overall.

AWG-9 peak power of 10kW, assuming a typical early High PRF duty cycle around 50%, means that the average power transmitted would be 5kW.

Zaslon average power transmitted is 2.5kW, so assuming a High PRF 50% duty cycle, gives a peak power of 5kW. Half the AWG-9 power. Even if that is a 25% duty cycle, at best that is parity with AWG-9 peak power.

The one area Zaslon is operationally superior is the use of a phased array antenna, which means that the radar can quickly scan a much wider volume of space than the AWG-9, and its TWS mode isn't limited to a relatively narrow aperture like AWG-9. Arguably, this makes it better for its land based interception role than the AWG-9 would be - the range is good enough to support the maximum firing range of the R-33 AAM, and additional range capability would be unnecessary given reliance on ground based GCI. I don't have numbers, but it might be that the Zaslon's antenna gain is lower than the AWG-9's planar array antenna, and therefore some potential range capability was traded off for faster scanning. Certainly this was one of Ferranti's arguments against an RBE2 type antenna on CAPTOR.

Additionally the Argon-15 radar used by Zaslon isn't very advanced at all, which is probably why Zaslon only tracks 10 targets rather than 24 for AWG-9.
 

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Few words about AWG-9 range & some speculations:

Long time ago, I found in Flight International 1976/January(pages 17, 18) statement that F-15 radar has range less about 15% than AWG-9 rated on 115nm.
Both radars were produced by Hughes, share the same antenna (diameter 0.9m ?).
Comparing transmitter power -see post above (10.2kW vs 5.2kW) - this statement seems to be correct: (5.2/10.2)^0.25 = 0.845
On the other hand, Russian estimated range of APG-63 on 100km, and stated the same requirements for radar of Su-27.
So 118km or 115nm (213km)?
Both ranges might be correct.
Let's count down, using only radar equation: x^(1/4) - where ^ means power
-> 115nm is ~213 km.
1. Above is in PDS or velocity search. For range search (RWS) target have to be "scanned" triple : one for basic signal - to get doppler frequency, two times with signal linearly modulated (http://twanclik.free.fr/electricity/electronic/pdfdone8/Introduction_to_Airborne_Radar.pdf see chapter 14 FM ranging). Thus in RWS energy emitted is 3 times lower*, thus
213 * (1/3)^1/4 =213 * 0.76 = 161km
* in reality in VS - accumulated energy is not 3 times more , as period of coherent integration does not extend 3 times, rather - there are 3 coherent integrations averaged or summarize otherwise. (Postcoherent integration gives at least than N^(1/2) gain, or better so (1/3^0.5)^0.25 *213 =185km.)
Anyway it is stated that detection range in VS is 25% -30% more than in RWS. Taking 25% - gives exactly 170km (0.8*213=170.4) - as mentioned by Overscan


2. above range is for 5m2 target, for 3m2 this is : 170km* 3/5^(1/4) = 150km

3. This point is my speculation**, but I assume that waveform used in AWG-9 was almost 50% duty ratio, and AN/APG-63 use let say 25% duty ratio.
50% duty ratio means that radar emits signal about 50% of time, the rest time listen echoes. Actually this may give more range (up to 15-19%), but only for situation that target echo is not eclipsed by emitting pulse. There is chance for that about let say 20-30% . In other cases part of target echo is not visible what gives shorter range, or even not visible at all. In average, expected detection range will be less, but actual ranges will vary more = comparing to lower duty factor.

Lower duty factor gives shorter range "on paper" but with higher probability (let say chance is 60-70% of being not eclipsed at all)
Of course there may be some scenarios when high duty ratio has advantage: for example bomber 100m^2 , PDS detection range about 400km (vs 336); with low closure speed (let say 900km/h each, 250m/s), with 14s refresh ratio - scans are refreshed every 7km what, may give faster detection even if single detection probability is low.
But in case of many small targets with high closure speed, RWS , pilot probably want more confident detection.

Anyway, assuming 25% duty factor comparing to 50% is another 15% less range ((25/50)^0.25=0.84) that gives : 150 * 0.84 =126 km

4. Finally if we take difference in transmitter power between AN/APG and AWG-9 : (5.2/10.2)^0.25 = 106 km what is quite close to the Russian estimate

Anyway, using similar measure, one can say that that AWG-9 has average range about 126km for 3m2 target in RWS mode.

**My assumptions are made on basis of radar generation. Pulse doppler radars before AWG-9 , for example on USN Phantoms, uses such 50% duty ratio as this was simpler (simple filter can be used) also some later radars (like Fox hunter AI 24 on Tornado ADF- "interrupted continues wave"). In later design there was tendency to decrease duty rate, what decrease power but also decrease eclipsing. This requires more advance processing including digital filters, but also multiplies number of necessary doppler filters - as there is not single range bin for example 2 or more (if you include pulse compression). For example radar from Mig-29 has duty ratio 25% and two doppler "channels". I assume similar approach in APG-63. But this is my speculation, and actual in AWG this might be more complicated, and manually tuned by RIO.(reference in above post suggest many pulse width, and average power in doppler mode : 7kW vs 10kW peak power what suggest duty factor more than 50%)
So AWG-9 is only approximately as powerful as APG-80?
Is APG-71 detection range supposed to be 40% better or 100% better than AWG-9?

1201eb7f-6ffd-465f-9c79-271c6ff86c47-png.625696
 
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GARGEAN

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@GARGEAN your scepticism is irrelevant, the AWG-9 range figures given were published long ago by the US Navy and Hughes and broadly confirmed by former F-14 pilots.


In terms of development timing, AWG-9 was a little earlier than Zaslon, but given the relative lag in electronics and radar, not enough to expect Zaslon to be 'better' overall.
Ugh... I kinda disagree that it's irrelevant. Cuz AWG-9 wasn't just "little" earlier than N007 and tech difference between two is quite substantial, in processing power too.
Argon-15 bashing is something out of here. Tracking limits were more established by memory usage and doctrinal shaping (why have more than 4 firing channels when you have 4 LRAAMs).
 

overscan (PaulMM)

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More usefully - here's the complete picture on ranges and modes, from James P. Stevenson's Aero Series Grumman F-14:
 

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overscan (PaulMM)

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@GARGEAN your scepticism is irrelevant, the AWG-9 range figures given were published long ago by the US Navy and Hughes and broadly confirmed by former F-14 pilots.


In terms of development timing, AWG-9 was a little earlier than Zaslon, but given the relative lag in electronics and radar, not enough to expect Zaslon to be 'better' overall.
Ugh... I kinda disagree that it's irrelevant. Cuz AWG-9 wasn't just "little" earlier than N007 and tech difference between two is quite substantial, in processing power too.
Argon-15 bashing is something out of here. Tracking limits were more established by memory usage and doctrinal shaping (why have more than 4 firing channels when you have 4 LRAAMs).

So what aspect of Zaslon's design implies it should have longer detection range than AWG-9?

NIIP have given range figures which are shorter than those known for AWG-9, and I see no reason to doubt them. You can believe Zaslon is superior operationally to AWG-9, but it's strange to argue it must have longer range because its newer.

Also its fine for Zaslon to have 4 channels instead of 6, but it would surely (given its wide field of view in TWS mode) operationally important to track MORE targets than AWG-9, not less.
 

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So what aspect of Zaslon's design implies it should have longer detection range than AWG-9?

NIIP have given range figures which are shorter than those known for AWG-9, and I see no reason to doubt them. You can believe Zaslon is superior operationally to AWG-9, but it's strange to argue it must have longer range because its newer.
Range is different from range. That's why I tried to specify details for those numbers. As for what tech should've given it better detection range? It's ESA, thus have quite a bit narrower beams giving it better power to return ratio. It has quite healthy dig processing (despite your bashing of Argon-15A which I tbh not totally understand). It IS quite powerful (don't have specific tube info, but N011M have 8kw tube with ~5kw peak while having 1.2kw average, so it's not just ×2). BTW on N011 example - M has better range chars despite having less peak power than slotted 011. ESA matters.
 

overscan (PaulMM)

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N011M have 8kw tube with ~5kw peak while having 1.2kw average, so it's not just ×2)

If you don't know what a duty cycle is, then there's little point pursuing the conversation.

Early pulse-doppler radars typically used High PRF high duty cycle of about 50%, that is the transmitter is transmitting 50% of the time, receiving 50% of the time (hence average power is half maximum power).

Modern pulse-doppler radars typically use lower duty ratios and medium PRF (or mixture of high and medium) or example N001/N019 use 25% duty cycle (radar is transmitting 25% of the time, receiving 75% of the time) hence peak power is 4 times average power.

I don't have detailed information on Zaslon's waveforms. duty cycles etc. I know Zaslon development started well before N001/N019 (mid/late 1960s) and was optimised for long range bomber detection, so it is quite likely it is a High PRF radar.
 

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Regarding the Argon-15, while it seems to have been a successful computer design, it is based on the 133 IC element base, which is a Soviet clone of the Intel 7400 series of ICs from 1964. It is based on SSI (small scale integration ) and MSI (medium scale integration) IC technology. It's a reasonable 1960s technology level computer, and certainly saw a lot of use in various military systems. Incidentally, the larger Ts100/Ts101/Ts102 (POISK architecture) computers made it to LSI IC technology but weren't actually faster than Argon-15, just cheaper to build and smaller.
 

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If you don't know what a duty cycle is, then there's little point pursuing the conversation.
Mkay, if you REALLY feel the need to go that defensive - it's indeed pointless to continue. I personally tried to figure it out properly, not going into "hurr burr my toy is better than yours".
 

overscan (PaulMM)

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I have no idea why you imagine AWG-9 is 'my toy'. I'm not American, I've never flown an F-14. I spent many years compiling information on Russian avionics.

Its simply a documented fact than the AWG-9 has a longer maximum detection range than Zaslon. Doesn't mean its "better". If you want to argue with the facts, you should at least know some of the basics of how radar works. "It's ESA so its better" is not a technical argument.
 

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N011M have 8kw tube with ~5kw peak while having 1.2kw average, so it's not just ×2)

If you don't know what a duty cycle is, then there's little point pursuing the conversation.

Early pulse-doppler radars typically used High PRF high duty cycle of about 50%, that is the transmitter is transmitting 50% of the time, receiving 50% of the time (hence average power is half maximum power).

Modern pulse-doppler radars typically use lower duty ratios and medium PRF (or mixture of high and medium) or example N001/N019 use 25% duty cycle (radar is transmitting 25% of the time, receiving 75% of the time) hence peak power is 4 times average power.
To be fair though, why couldn't modern radar use higher PRF? Aren't they supposed to be changeable?. I know too high PRF could lead to range ambiguity, but if i recall correctly velocity search is still a function on most modern radar
 

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In this context - a thing I do not quite understand is the stated peak power of fighter radars.

Early AI Radars like the SCR 720 of the 1940s had a peak output of around 70kw and this number typically rised to 150kw - 250kw for fighter radars in the 1950s (example AN/APG-37 at 250 KW peak power for the F-86D). For later fighter radars the stated kw-output numbers were drastically reduced - for example 12kw peak power for the huge ASG-18 of the YF-12 or 10kw for the AWG-9 (as mentioned above).

Is this the result of a change in output measuring method?
 

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Many
In this context - a thing I do not quite understand is the stated peak power of fighter radars.

Early AI Radars like the SCR 720 of the 1940s had a peak output of around 70kw and this number typically rised to 150kw - 250kw for fighter radars in the 1950s (example AN/APG-37 at 250 KW peak power for the F-86D). For later fighter radars the stated kw-output numbers were drastically reduced - for example 12kw peak power for the huge ASG-18 of the YF-12 or 10kw for the AWG-9 (as mentioned above).

Is this the result of a change in output measuring method?
Many things included, but they mostly can be summed as better energy handling. Better antenna designs produce much narrower beams, thus needing less energy for same radiation density and return accumulation. Plus, as usual, measurement confusion: some state power as whole system consumption, some as specifically radiating element consumption, some as finalized power after all losses and so on.
 

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Peak power is not important.
The most important is energy received from target and possibility to gather that energy (sum, integrate and so on)
Energy has to be higher than energy of background noise significantly enough.
And in older pulse radar power was high but radar emits short pulses with low pulse repetition frequency (RPM). So having radar 100kW, pulse width 1us and RPM 1kHz this gives mean power:
1us/(1/RPM)*100kW
10^(-6)/ 10^(-3) *10^5= 100W
On the other hand pulse doppler radar may emits pulses with RPM about 200kHz
and with peak power 5kW have mean power 1kW
And also important is how long your beam is over target (dwel time). This gives energy. Also radar have to integrate that energy.
If you scan fast this shorter time but you can faster refresh data or scan more in time.
 

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In this context - a thing I do not quite understand is the stated peak power of fighter radars.

Early AI Radars like the SCR 720 of the 1940s had a peak output of around 70kw and this number typically rised to 150kw - 250kw for fighter radars in the 1950s (example AN/APG-37 at 250 KW peak power for the F-86D). For later fighter radars the stated kw-output numbers were drastically reduced - for example 12kw peak power for the huge ASG-18 of the YF-12 or 10kw for the AWG-9 (as mentioned above).

Is this the result of a change in output measuring method?

No. It's more like the move into Transmitting more pulses (a.k.a Higher PRF) which means shorter PRI.

So in radar we have 2 terms for power namely :

The Peak Power : This term is for the power of the emitted pulse, the maximum power of a pulse emitted by a radar.

Average Power : This term is a peak power but averaged in some point of "reference time". In pulse radar our transmitter does not continuously emitting in peak power, but there is a "dead time" in between pulses which referred as PRI Or "Pulse Repetition Interval". The average power is then calculated by dividing the time when the transmitter a single pulse which termed as "Pulsewidth" with the PRI. This yield the Duty Cycle.

This is how it's look like when depicted :

Peak vs Average.png

The early radar is characterized with very high peak power, very short pulse and rather long PRI. Thus relatively small average power.

Later in 1950-1960's People start to realize "Hey how about if we emit more pulses, we can get better average power and we can integrate the pulses for more range" And then a mode is born namely High PRF. This mode have high PRF, means they transmit more pulses compared to early radars, this in turn crank up the duty cycle.

Hopefully this make sense.

Anyway the image above is coming from this :

 

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LukaszK & stealthflanker,

thanks a lot, great explanation. I got it.
 

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Yes, exactly this. It's not hard to generate a high power output for a short duration with long gaps between for traditional pulse radar. Its just not possible to generate very high power output for a 50% duty cycle High PRF radar - the electrical power needed would be unfeasible for the aircraft.
 

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