APG-81 power output wattage

Cockpit, radar, helmet-mounted display, and other avionics
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tank-top

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Unread post06 Mar 2019, 06:02

I recently had the opportunity to speak with an F-35 pilot, while most of my questions got a smile and nod with a somewhat irrelevant answer he said something that peaked my curiosity and that was the APG-81 power. I’m not going to repeat the number he said as I’m unsure if he meant the power generated by the aircraft or the output wattage of the radar itself but it seemed a bit unbelievable. I know many people assume the APH-81 has jamming and hacking abilities of enemy radar, lets assume it has 100,000 watts of output power and 1,000 modules, if all pointed in the same direction what is the theoretical ionizing radiation at what distance? Not trying to wear a tinfoil hat here but it seems theoretical that with enough wattage it could be a defensive/offensive system, please correct me if I’m wrong. I know the radar is really designed to operate at very low wattage and blend in with background radiation but is an offensive capability that far fetched and if so is the theoretical ability not on my side of the assumption?
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SpudmanWP

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Unread post06 Mar 2019, 07:10

There were articles a while back that actually talked about the APG-81 being able to physically damage a system that it is jamming because of the power and "focusability" of the AESA antenna.
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Unread post06 Mar 2019, 08:24

WOW....very impressive!
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hornetfinn

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Unread post06 Mar 2019, 10:01

Getting any kind of real world damage from RF power alone is very unlikely except in very short ranges. This is because the radiation quickly gets spread out over very large area.

Even if AN/APG-81 had 100 kW of output power (not possible with current tech really) and very narrow beam of say 2.5 degrees (extremely high efficiency from the antenna), the power would be very small even at 1 km away. That 2.5 degrees beam would cover an area of approximately 2 000 square meters (or over 21 000 square feet). That would mean only 50 Watts of radiated power for each square meter. In real life it would be smaller due to energy absorption and dissipation in the atmosphere. That kind of radiation would not affect anything, especially not radiation hardened or shielded military electronics. Even human beings would need at least 20 times higher radiated power to have real health problems (1000 W/square meter is usually used here). And that would need to be average power, not peak power. Beyond couple of hundred meters/yards, you need very big radars (like ground radars or AWACS) to have any kind of radiation effects on anything. Even those huge radars would only be really dangerous to couple of kilometers at most.

AN/APG-81 probably has many ways of attacking electronics systems, but raw radiated power is not going to be one of them.
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Unread post06 Mar 2019, 18:49

Think of putting your cellphone in a microwave.

That is the damage I am talking about. Basically that RF energy being converted to electricity in the presence of an unshielded electronic piece of equipment.
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Unread post06 Mar 2019, 19:07

SpudmanWP wrote:Think of putting your cellphone in a microwave.

Prolonged exposure to 1,000W concentrated in a .15m^2 area? nearly 6,700W/m^2

That's the point hornetfinn was making. 50W/m^2 just isn't enough juice.
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tank-top

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Unread post06 Mar 2019, 19:17

well there goes that theory, thanks for the quick physics lesson.
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Unread post06 Mar 2019, 19:48

I found a reference:

Posted 05/30/05 15:24
By MICHAEL FABEY
DefenseNews.com


The radar mounted on the F/A-22 Raptor and F-35 Joint Strike Fighter (JSF) can be used to fry electronic parts of ground-based radars and disable airborne cruise missiles, program officials for the planes acknowledge.

U.S. Air Force officials and contractors have longed bragged about the active electronically scanned array (AESA) radar, citing its ability to track multiple targets, map terrain and protect planes from attack. And there have been hints of offensive capability, like a brief mention of "high power electronic attack" on one of the JSF’s glossy marketing brochures.

But contractors say they have not publicly talked about the capability — until now.

"It could cause actual physical damage to a system … providing it’s on the X-band," a common frequency for military radars, said Wayne Wilson, the director of fighter business development for Northrop Grumman Electronic Systems.


All I found so far was this quote but not the original article.
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Unread post06 Mar 2019, 20:07

AFRL regards 200 V/m (~ 100 Watts/m^2) or stronger as a threat to sensitive electronics.

GaA MESFETS and MMICs have very low damage thresholds.
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Unread post06 Mar 2019, 20:55

They say the 81 and 79 can radiate to cause physical damage. This was a 79 spec 15 years ago, but the 79 has gone black. I tried to find some recent info, but it isn't there. You have the dot&e saying there are issues, Dot&e is almost famous, for their reports are on the information that USN and Co. provide. They can an be wrong sometimes by there misinterpretation of the info provided. So the baby is thrown out with the bathwater on forums. The USN were running the block 2 as block 1 in mission planning. This fact was seen as not providing additional mission effectiveness by dot&e and is still on the rafale thread being talked about. Again I haven't seen the USN say a lot about the block 2s, in their own mission sets. I was aware that the RAAF was the first to use the 18f rear seat to its full effect. The RAAF say even less than USN and USN have really shut it down and only the f-35 is being promoted as a modern weapon system. It's annoying but I don't have a big barrow to push with the 18ef, as the RAAF are getting the superior f-35 and we probably won't be flying the 18f in 10 years

It's easy to become platform centric. Especially on a f-35 board. :mrgreen:
This also works the other way, word is on ships, new aesa systems are doing the same thing, only with a lot more power available. The e-7 and g550 can also do some tricky stuff.
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marsavian

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Unread post06 Mar 2019, 21:25

optimist wrote:This also works the other way, word is on ships, new aesa systems are doing the same thing, only with a lot more power available


https://www.express.co.uk/news/world/10 ... ea-ukraine

Nov 26, 2018. This is the dramatic moment 17 Russian fighter jets swarmed around a Royal Navy warship in the Black Sea near Crimea. The remarkable footage shows HMS Duncan being ‘buzzed’ by the Russian jets as it led a NATO fleet through the disputed region earlier this year. The government labelled the incident, which happened in May, an act of “brazen hostility”. In the footage, which was filmed as part of a Channel 5 documentary, Russian jets can be seen circling around HMS Duncan and the NATO fleet.

The jets, which are a mix of fighters and bombers, are shown coming so close to HMS Duncan the crew is worried their high-powered radars might scramble the jets’ computer systems causing them to crash. Naval officers on the £1billion Type 45 Destroyer then issued a warning to the Russian pilots amid fears the planes might attack. One communications technician told the Russians: “We are operating high powered radars. Request you remain outside of two miles for your safety.”


https://en.m.wikipedia.org/wiki/Type_45_destroyer
https://en.m.wikipedia.org/wiki/SAMPSON

Type: Solid-state AESA radar
Frequency: 2–4 GHz (S band)
Range: 400 km
Power: 25 kW
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tank-top

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Unread post06 Mar 2019, 22:39

marsavian wrote:
optimist wrote:This also works the other way, word is on ships, new aesa systems are doing the same thing, only with a lot more power available


https://www.express.co.uk/news/world/10 ... ea-ukraine

Nov 26, 2018. This is the dramatic moment 17 Russian fighter jets swarmed around a Royal Navy warship in the Black Sea near Crimea. The remarkable footage shows HMS Duncan being ‘buzzed’ by the Russian jets as it led a NATO fleet through the disputed region earlier this year. The government labelled the incident, which happened in May, an act of “brazen hostility”. In the footage, which was filmed as part of a Channel 5 documentary, Russian jets can be seen circling around HMS Duncan and the NATO fleet.

The jets, which are a mix of fighters and bombers, are shown coming so close to HMS Duncan the crew is worried their high-powered radars might scramble the jets’ computer systems causing them to crash. Naval officers on the £1billion Type 45 Destroyer then issued a warning to the Russian pilots amid fears the planes might attack. One communications technician told the Russians: “We are operating high powered radars. Request you remain outside of two miles for your safety.”


https://en.m.wikipedia.org/wiki/Type_45_destroyer
https://en.m.wikipedia.org/wiki/SAMPSON

Type: Solid-state AESA radar
Frequency: 2–4 GHz (S band)
Range: 400 km
Power: 25 kW





I’ve heard stories of AEGIS popping seagulls, wonder if there’s a plan to do the same thing to a swarm of Iranian speed boats should the need ever arise? I’m sure at 500 yards with AEGIS pointed at you it would get warm very fast! :shock:
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Unread post06 Mar 2019, 22:56

Alaskan service members used to quickly step out in front of the large radar dishes to "warm up"...

Wonder how their kids turned out? :doh:

Imagine the power of this thing?

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Last edited by SpudmanWP on 07 Mar 2019, 08:00, edited 1 time in total.
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Unread post07 Mar 2019, 07:38

Didn't Viktor Belenko claim that MiG-25 pilots were instructed to switch off their radar while on the ground. It was apparently powerful.enough to.kill.a.rabbit at extended distances.
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Unread post07 Mar 2019, 10:38

SpudmanWP wrote:I found a reference:

Posted 05/30/05 15:24
By MICHAEL FABEY
DefenseNews.com


The radar mounted on the F/A-22 Raptor and F-35 Joint Strike Fighter (JSF) can be used to fry electronic parts of ground-based radars and disable airborne cruise missiles, program officials for the planes acknowledge.

U.S. Air Force officials and contractors have longed bragged about the active electronically scanned array (AESA) radar, citing its ability to track multiple targets, map terrain and protect planes from attack. And there have been hints of offensive capability, like a brief mention of "high power electronic attack" on one of the JSF’s glossy marketing brochures.

But contractors say they have not publicly talked about the capability — until now.

"It could cause actual physical damage to a system … providing it’s on the X-band," a common frequency for military radars, said Wayne Wilson, the director of fighter business development for Northrop Grumman Electronic Systems.


All I found so far was this quote but not the original article.


That makes some sense as directing powerful beam towards a radar can do some damage if the beam and radar operate in the same frequency band. This is because radar is designed to collect very low powered signals when it is receiving and putting a lot of RF power in the same frequency band is very likely going to damage the receiver or associated circuitry (mostly Low Noise Amplifier, LNA). All radar receivers are well protected when the radar is transmitting, but there is less protection when receiving (to keep the system as sensitive as possible). It depends on radar design how well protected the LNA and receiver are, but those can be protected pretty well with good design.

I think most likely effect would be blinding the radar temporarily when talking about modern military radars. Basically that would make the targeted radar receiver protection systems to kick in and make it unable to receive anything. Still the range would likely be relatively short, although it might be usabel even in real life.
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