AWG9 over land question

[Banzaiib]

I consistently cannot pick up bandits below 2000 ft over land... it's like there's nothing there, unless I'm below them.

 

TAW has a test mission where there are like 20 helicopters flying around at 1500 ft, and i can't see them at all until I get below them at any range. Not in TWS, RWS, or pulse scan... they don't show on the DDD until i'm below 1500 ft. The f-15s and F-18's see them fine in high prf...

 

I can post a track later tonight so you can see, or you can just go on the PG shooting range TAW server and find them yourself.

 

TL;DR the HB F-14B radar feels like total crap for anything below 3000 ft over land.

[Harlikwin]

True that...

 

I think the quotes are mostly being taken out of context, one which I can't find. I.e. comapring a F15C radar to the AWG-9 or much later radars. Which of course makes sense, since they were better.

 

As for the iranian thing, of course, different tactics, and who knows on RWR, I certainly wouldn't want to be driving a mig-21 with SPO-10 against an AWG-9.

[Harlikwin]

I consistently cannot pick up bandits below 2000 ft over land... it's like there's nothing there, unless I'm below them.

 

TAW has a test mission where there are like 20 helicopters flying around at 1500 ft, and i can't see them at all until I get below them at any range. Not in TWS, RWS, or pulse scan... they don't show on the DDD until i'm below 1500 ft. The f-15s and F-18's see them fine in high prf...

 

I can post a track later tonight so you can see, or you can just go on the PG shooting range TAW server and find them yourself.

 

TL;DR the HB F-14B radar feels like total crap for anything below 3000 ft over land.

 

Well, I was mostly asking about the real thing. But this is an interesting data point, were you flying as the RIO?

[near_blind]

Apg-63 had mprf/ hprf from the start, I’m no expert on why the awg-9 couldn’t do MPRF, but considering they never upgraded the AWG-9 to do that over its 40 years of use, and its a fairly significant limfac, it was probly not possible without completely rebuilding the radar (like they did with the APG-71)..

 

As far as I know MRPF wasn't a thing when the AWG-9 was designed, or at the total utility of MRPF wasn't fully understood. HRPF PD was used because the specification for long range look down / shoot down necessitated it. The large notch and susceptibility to terrain and maneuver understood, and LPRF pulse was chosen as the means to plug that capability gap.

 

Why? If I had to guess it had to do with budget and time constraints of modifying the AN/ASG-7 into the AWG-9. There was already a large unknown quantity in computer driven airborne multitarget tracking. For "the other stuff" pulse was a known, capable quantity and offered performance greater than Eastern contemporaries and probably on par with anything likely to be fielded into the 70s.

 

The APG-63 program had a different requirement specification, and chose a different, ultimately more successful path. As for why the AWG-9 itself was never physically upgraded, I would assume that has to do with the analogue nature of the set (hence the digital -71).

[Banzaiib]

Well, I was mostly asking about the real thing. But this is an interesting data point, were you flying as the RIO?

 

yep! And i feel totally blind below 5000 ft most of the time...

[Xenovia]

I consistently cannot pick up bandits below 2000 ft over land... it's like there's nothing there, unless I'm below them.

 

TAW has a test mission where there are like 20 helicopters flying around at 1500 ft, and i can't see them at all until I get below them at any range. Not in TWS, RWS, or pulse scan... they don't show on the DDD until i'm below 1500 ft. The f-15s and F-18's see them fine in high prf...

 

I can post a track later tonight so you can see, or you can just go on the PG shooting range TAW server and find them yourself.

 

TL;DR the HB F-14B radar feels like total crap for anything below 3000 ft over land.

 

Interesting, I've been able to pick up radar contacts that were pretty much in the weeds flying very close to the ground in the northern mountainous terrain on the Caucasus map, so long as I fly up high enough to where hiding in the terrain becomes less effective for them, and I point my radar downwards. By doing this I've picked up aircraft that I usually wouldn't even know were there in the first place, aircraft such as A-10's, and Harrier's, on the rare occasion I've found Huey's.

Edited November 21, 2019 by Xenovia

[Banzaiib]

Interesting, I've been able to pick up radar contacts that were pretty much in the weeds flying very close to the ground in the northern mountainous terrain on the Caucasus map, so long as I fly up high enough to where hiding in the terrain becomes less effective for them, and I point my radar downwards. By doing this I've picked up aircraft that I usually wouldn't even know were there in the first place, aircraft such as A-10's, and Harrier's, on the rare occasion I've found Huey's.

 

hmm.... that is interesting. I've had no such luck... i'll snag some tracks tonight if i can (unless the wife has a list :) )... but i don't know what good that will do, as tracks are kind of messed up right now... but i'll try. I'll record it in OBS and post a video, at the very least.

 

Xeno, is that in SP or MP? (i play exclusively in MP)

[Banzaiib]

Here's a video:

 

you can see a bunch of helos at 1600 ft, and i never get them on radar, despite closing speed being much greater than 200 kts

[IronMike]

Here's a video:

 

you can see a bunch of helos at 1600 ft, and i never get them on radar, despite closing speed being much greater than 200 kts

 

 

 

 

Yes, but they are notching you partly on the gimbals when you are maneuvering, plus being smaller targets against the ground. In general you are doing everything you can to make it as hard as possible on the awg9 in this situation. This would make it hard for newer radars as well. You are also using RWS with a wider scan (less focused radar energy on the targets), etc... instead a 20° tws scan with maybe 4 or even 2 bars instead of 8 etc etc...

 

Here's a little anecdote of how one of our slovenian pilatus shot down a US F-16 in an exercise, because the pilatus kept notching low against the forest and the F16 could just not find him and lock him up. [that was the story, haha.]

 

In such a case, if you have knowledge of the approximate location, you need to change aspect to head on or use pulse, ideally getting them above the nose. Either you do that by switching back to the back seat (I am pretty sure you would spot them on the DDD), or you use PAL for example, which will lock them up automatically for you.

 

The radar is often as strong as our understanding of its functionality and how to make it work in our favor. I'll see if I can recreate the mission and upload you an example.

Edited November 22, 2019 by IronMike

[IronMike]

Here you go:

 

 

 

Hope that helps!

[Banzaiib]

Yes, but they are notching you partly on the gimbals when you are maneuvering, plus being smaller targets against the ground. In general you are doing everything you can to make it as hard as possible on the awg9 in this situation. This would make it hard for newer radars as well. You are also using RWS with a wider scan (less focused radar energy on the targets), etc... instead a 20° tws scan with maybe 4 or even 2 bars instead of 8 etc etc...

 

Here's a little anecdote of how one of our slovenian pilatus shot down a US F-16 in an exercise, because the pilatus kept notching low against the forest and the F16 could just not find him and lock him up. [that was the story, haha.]

 

In such a case, if you have knowledge of the approximate location, you need to change aspect to head on or use pulse, ideally getting them above the nose. Either you do that by switching back to the back seat (I am pretty sure you would spot them on the DDD), or you use PAL for example, which will lock them up automatically for you.

 

The radar is often as strong as our understanding of its functionality and how to make it work in our favor. I'll see if I can recreate the mission and upload you an example.

 

I'd love to be able to tell jester the beam width and scan bars... ;) (my video was done on MP server, so i have to rely on tracks showing up on the TID) I've tried this in TWS too, and never get tracks no matter my approach angle... i'll test some more tonight as a RIO.

 

So... how big is the notch angle / filter? Because those helis' flight path couldn't have been more than 60-70 degrees off mine, and there were 16 of them spread across the horizon (meaning their relative aspect angles varied greatly) and not one showed as a track at any point in time... and an MI-8 is not a small aircraft (they should reflect tons of radar energy)

 

pls nerf stealth helicopters, kthx :P j/k

Edited November 22, 2019 by Banzaiib

[KlarSnow]

Notch filter is relative closure, not angles... angles reduce the relative closure, but helicopters already have such a low speed that they could be flying straight at you and still be in the Doppler notch for the tomcat.

[IronMike]

Notch filter is relative closure, not angles... angles reduce the relative closure, but helicopters already have such a low speed that they could be flying straight at you and still be in the Doppler notch for the tomcat.

 

 

 

 

Correct, the Tomcat's notch filter in PD iirc is +/-100 compared with the F-15's +/-20, that is 5 times as much. But you have pulse to counter it. If you have no option to switch to the RIO seat, PAL/VSL/PLM is preferable for choppers. it will find and lock them 10/10.

[Harlikwin]

Correct, the Tomcat's notch filter in PD iirc is +/-100 compared with the F-15's +/-20, that is 5 times as much. But you have pulse to counter it. If you have no option to switch to the RIO seat, PAL/VSL/PLM is preferable for choppers. it will find and lock them 10/10.

 

So Mike, since you probably know the most about the radar here. IRL what were the issues with over land performance? Clutter rejection? Big notch filter? Something else?

[Banzaiib]

Correct, the Tomcat's notch filter in PD iirc is +/-100 compared with the F-15's +/-20, that is 5 times as much. But you have pulse to counter it. If you have no option to switch to the RIO seat, PAL/VSL/PLM is preferable for choppers. it will find and lock them 10/10.

 

+/- 100? My Vc was around 350+ kts in my video... i think you may be confusing two different filters. Notch != Doppler filter... again, i'm no pilot, so i would love a better explanation if i'm totally wrong :)

Edited November 22, 2019 by Banzaiib

[toilet2000]

+/- 100? My Vc was around 350+ kts in my video... i think you may be confusing two different filters. Notch != Doppler filter... again, i'm no pilot, so i would love a better explanation if i'm totally wrong :)

 

 

The notch filter is about the speed difference from ground relative to you. Anything flying below 100 kts even going straight toward you is going to be filtered out.

 

The Notch filter is there to remove Doppler returns from the ground, whereas the Doppler "filter" (really not a filter) is just the absence of Doppler effect due to an object moving at your own speed.

 

Anything flying at +/- 100 kts relative to the speed of the ground for you (either via moving perpendicularly from your direction or by simply moving slowly in your direction relative to the ground) isn't going to appear on the F-14's radar (with the Notch filter on).

 

 

EDIT: Just to be more clear, you will never be able to see a heli flying less than 100 kts ground speed if your Notch filter is on, which is definitely something that will happen often for a heli (flying less than 100 kts GS).

Edited November 22, 2019 by toilet2000

[Banzaiib]

The notch filter is speed difference from ground relative to you. Anything flying below 100 kts even going straight toward you is going to be filtered out.

 

The Notch filter is there to remove Doppler returns from the ground, whereas the Doppler "filter" (really not a filter) is just the absence of Doppler effect due to an object moving at your own speed.

 

Anything flying at +/- 100 kts relative to the speed of the ground for you (either via moving perpendicularly from your direction or by simply moving slowly in your direction relative to the ground) isn't going to appear on the F-14's radar.

 

 

EDIT: Just to be more clear, you will never be able to see a heli flying less than 100 kts ground speed if your Notch filter is on, which is definitely something that will happen often for a heli (flying less than 100 kts GS).

 

Thanks for the explanation... i get it now :)

Edited November 22, 2019 by Banzaiib

[Banzaiib]

deleted

[captain_dalan]

Correct, the Tomcat's notch filter in PD iirc is +/-100 compared with the F-15's +/-20, that is 5 times as much. But you have pulse to counter it. If you have no option to switch to the RIO seat, PAL/VSL/PLM is preferable for choppers. it will find and lock them 10/10.

 

Within 20 NM this is what i usually do anyway. But above these ranges, is it possible to tell Jester to scan in pulse mode (i know he can lock in it):book:

[IronMike]

Within 20 NM this is what i usually do anyway. But above these ranges, is it possible to tell Jester to scan in pulse mode (i know he can lock in it):book:

 

 

Unfortunately no, we are not sure if we will implement that, or in other words, if it will be "easily" doable, but ofc it would be a nice thing to have, we agree in that.

[captain_dalan]

Unfortunately no, we are not sure if we will implement that, or in other words, if it will be "easily" doable, but ofc it would be a nice thing to have, we agree in that.

 

Roger that! :thumbup:

[Beamscanner]

So, ive read various sources that say the AWG9 was bad over land. Can anyone specifically explain to me why this should be given that its a pulse doppler radar?

 

@beamscanner

 

FYI, I dont search for threads with "beamscanner" in it. So i just now saw this.

 

There's a bunch of stuff getting tossed around that isn't completely accurate to your question.

 

 

- The AWG-9 was an analog pulse doppler radar. No FFTs (or DFTs) were performed.

 

- Physical band pass filters were used for doppler binning. These were tuned circuits made of inductors and capacitors. A lot of these were needed to account for all closing velocity scenarios.

 

- Band reject filters were used for notching out zero doppler (altitude line) and the main beam clutter return (this likely would have been a voltage controlled tuned circuit so that the band reject could be moved in freq with the scan of the antenna)

 

- MPRF wasn't around with analog radar because of practical size limitations. MPRF uses range and doppler bins to filter for targets. usually returns are filtered in time(range) first. Then each range bin has the entire series of doppler bins within. Thus, if an analog radar was to filter 100 doppler bins and 100 range bins, it would actually need 10,000 doppler bins (100 doppler bins per range bin). Each of those 10,000 bins being a physical tuned circuit. MPRF only became practical with digital signal processing where ADCs took the place of range bins, and FFTs were used in place of doppler bins. ie everything was done in code.

 

- An analog pulse doppler radar, only using HPRF (like the AWG-9), will only use doppler bins. And thus, given the same example above, would only use 100 doppler bins (FYI the AWG-9 likely used many more than 100, but this is just to compare the number of bins required for HPRF vs MPRF). As no range binning took place. In RWS/TWS HPRF modes, range is resolved post detection via FMR (freq modulated ranging).

 

- The AWG-9's overland performance was probably more dependent on the skill of the RIO than anything. Modern digital radar receivers can employ DSP techniques to reject much of the ground clutter. But digital receivers usually add thresholds which prevent noise like sources from entering. This also means that weak returns would be filtered out by the digital receiver. That threshold doesn't exist in analog radar. Instead, the RIO has a gain control which lets them control how much noise comes in. Todays DSP have certainly beat out the best of AWG-9 RIOs, but when comparing a 1980s airborne radar, like the APG-63v0, I think an above average RIO would win.

 

EDIT: my source for all of this is George stemson's intro to airborne radar. Which was originally an internal Hughes aircraft company handbook handed out to company engineers. Thus, much of the material contained within uses company products (like the AWG-9) as examples. There's even a picture of the bandpass filters (ie doppler bins) used on the AWG-9. They were about the size of a quarter, each.

[Harlikwin]

Cool Thanks Beamscanner. I assumed at least some of that engineering based on my experiences with Hughes radio products from the same era.

 

[Victory205]

 

EDIT: my source for all of this is George stemson's intro to airborne radar. Which was originally an internal Hughes aircraft company handbook handed out to company engineers. Thus, much of the material contained within uses company products (like the AWG-9) as examples. There's even a picture of the bandpass filters (ie doppler bins) used on the AWG-9. They were about the size of a quarter, each.

 

Several of us purchased that book and used it as a sleep aid while on cruise. It's sitting on my shelf as we speak. It helped me understand radar, even later using the weather radar in the airliners. I used to paint other aircraft from time to time, which was fun to correlate against TCAS when that system came on line. ;)

 

A proficient RIO with good technique made it difficult to escape the AWG9, even overland. The aspect that no one considers is that ability to use manual inputs in the presence of jamming is what made the AWG9 effective in the realm for which it was designed, The Apocalypse of all out War between two super power nations.

 

If you only knew...

 

[Harlikwin]

 

 

If you only knew...

 

So tell us.

 

Also, I did order the book, looks like it should be a decent read.