Airborne weather radar

[Let'sgoflying!]

Anyone have a copy of Dave Gwinn's cassette/book How Radar Works?
Is it worthwhile?

(Trade you Archie Trammell's vcr tape for a look-see at Gwinn's.)

Can't find any other sources of practical radar use online.

 

[W. Stewart]

If you succeed in obtaining one, Dave, I would like to read/watch it after you. I have radar in my 210, but I am not all that knowledgeable about it.

Wells

 

[DouglasBader]

I'm sure I've got one or the other at home somewhere, but it might be a stretch to get home, or find them. It seems that there are enough people who visit here who understand airborne weather radar enough the that a thread about it's use and function might be productive, though.

Do you have specific questions?

 

[Threefingeredjack]

Just remember that when you see those beautiful clear areas that magically appear in front of you in heavy weather........

 

[wabower]

Do any of the Vegas Casinos post odds on the length of time you can watch Archie's radar video without falling asleep?

 

[Captain]

This is going to be sorta 'inside baseball' and you may want to skip it...

My job in the Navy (91 to 98) was two fold. I was a technician and an operator. As a technician I performed preventive and corrective maintenance on the A/N SLQ-32 (V2). It's basically a big radar detector. As an operator my station was in CIC (Combat Information Center). That's the dark room in the middle of the ship where all the radars and fire control are located.

So, I would stand watch and pickup radars. The equipment broke the radar down to its fundamental elements and we would then identify what the radar was. If you know what the radar is you can know what the platform is. The more radars you pickup and can correlate to a contact the more precise your identification is. We could even Hull Tech many Russian radar signals right down to the specific boat...not just class of ship but actual hull number.

So our ship had radars, but unless they were friendly (had IFF (a transponder)) we would just get a primary contact. That doesn't tell you much about the contact. You can get bearing and range and over time course and speed...but WHAT the contact is you have no idea. That's where we came in. We would pick up the contacts radar. We had no idea what the range was as the signal just propagates through space forever. It does attenuate along the way, so you could guess on range based on the strength of the signal...but that is very crude at best.

But knowing the bearing we could then, over time, assign it to the contacts the radar operators had. ie, An unknown contact is at 335 and I have a radar at 335. 12 minutes later the contact is at 339 and my radar is at 339 as well. Pretty soon it's obvious the radar contact and my received radar are the same and I'd assign my identification to that unknown contact and that information would be presented to the decision makers.

So, radar identification. There are a few radar characteristics that we use to identify the radar:

Frequency: This is a huge indicator of what type of platform holds said radar. The size of a radar antenna is directly tied to the frequency of that radar. Lower frequencies have longer wave lengths and therefore require a larger antenna. You want the antenna to be half the size of the wave length. Wave length is measured in distance using the speed of light and how many cycles have to fit in one second. So 1 hertz would be the full distance light travels in a second and you would need an antenna 90,000 miles long.

Lower frequencies travel farther and tend to bend around the earth more. They are used for early detection and long range scanning. Ever see the radar at the airport? That big orange one? That's the size of an air search radar on a ship. BTW, that rectangle gate looking thing on top of the radar dish is transponder interrogator.

PRF Pulse Repetition Frequency. A radar works by sending out a stream of pulses and then shutting up and listening for echos from that stream. By measuring how many pulses go out per second you can further identify a radar. More or less pulses also function help the radar see the desired contact. For example, a PRF that is a multiple of 200 best displays returns of moisture. All aircraft weather radars had a PRF of 200 or 400 and a high frequency (only small antennas fit on planes (AWACS excluded) so the frequency had to be high).

PW Pulse Width. This is the width of individual pulses from the radar and is measured in time. Usually on the order of micro seconds...like .4 ms. The point of the pulse width is the wider the pulse the more time the radar has to get up to full power to send out energy. A radar you want to go way out there see what's going on is going to have a wider pulse width while a simple Nav Radar for maneuvering around the port with have a smaller one.

Scan Type and Time This is probably the most important feature to identify a radar. A circular scan is used primarily in search. The radar goes around and around. This is like the big orange radar at the airport. It's identified by even time measured between each 'chirp'. Scan time is simply measured from chirp to chirp. An early warning radar will have a slow scan time of around 8 seconds (go time the one at the airport sometime). This is because you want to give the signal time to go WAY out there...bounce of the contact and return. A nav radar, like what you see on small fishing boats (the spinning bar) will have a much faster scan time. This is because you don't care whats far away. You want as much information as you can about whats nearby so you don't hit it.

A sector scan is what airplanes have. It goes back and forth and is identified by two chirps close together with a pause. If you are centered on a sector scan it can sound like a circular scan. Exact timing can usually identify this. Timing is from the first chirp to the third chirp.

Fire Control scans use a neutator to spin the beam to form a cone. If the contact moves out of the center of the cone the radar gets more pulse on one side than the other and the radar is realigned to put the contact in the center. This is used to 'lock on' to targets. There is no timing but the sound is VERY distinctive.

A Raster scan looks like a search pattern. The beam is steered back and forth in rows. Missiles often have this type of radar for target acquisition. Timing this is tricky and often involves finding the strongest chirp and timing between strongest pulses.

I know this got long and sorry if it was boring. Thought I'd just share some info that is not likely to be anywhere else most pilots go.

 

[wsuffa]

So, radar identification. There are a few radar characteristics that we use to identify the radar:

There's actually more identification "stuff" that's "behind the curtain" in a Slick-32 and the future replacement. Those are some key elements, but there's a bunch more. :wink2:

 

[Captain]

There's actually more identification "stuff" that's "behind the curtain" in a Slick-32 and the future replacement. Those are some key elements, but there's a bunch more. :wink2:

What I described are the only the radar parameters that the SLQ-32 uses to analyze a radar. I didn't go into the libraries because that isn't relevant. I am quite certain Freq, PRF, PW, Scan Type and Scan Time are the only metrics the SLQ-32 can measure an intercepted radar.

I am curious about the successor to the SLQ-32 if you have any info on that...

 

[DouglasBader]

Do any of the Vegas Casinos post odds on the length of time you can watch Archie's radar video without falling asleep?

Marcus Jallalaboux holds the world record, set in 1992, of 2.5 minutes.

He did, however, slip into a coma shortly thereafter, from which he has never recovered.

 

[denverpilot]

I'm a microwave radio geek, so I appreciated the story, Cap.

The only part you left out is that most higher tech systems these days often try to emulate other systems to throw off the ELINT ops as to what type they really are.

The phased array antenna tech overall is also quite impressive engineering. Steering RF without moving the antenna was a huge jump technology-wise.

The giant 400MHz (approximately) ground-based phased-arrays are enormous and amazing at what they can "acquire", size-wise, with modern DSP post-processing.

Pave-Paws is what I'm referring to here. Monsters. Impressive.

http://en.m.wikipedia.org/wiki/PAVE_PAWS

Someone's gotta monitor space junk.

Dad was a Fire Control tech on Naval 10 GHz gear. Outdated today, he still thought it was cool when I was able to order up and easily operate on 10 GHz using a design that utilized a surplus Dish Network dish and a 2W commercially available transverter from Down East Microwave.

No harder putting that station together than setting up a typical CB radio back in the day when he first started playing with radio -- when 10 GHz was only available on his ship paid for handsomely by the U.S. taxpayer.

He did have a much bigger final amplifier though! Klystron tubes are still amazing tech, considering they were high-tech originally around 1940.

Fun stuff. I missed the big VHF and up contest this year to go to Gaston's. Dad joked that I was "fired". Another friend helped him operate from home this last weekend.

He jokes that I'm his radio "Elmer", since I was a Ham long before he had time for it. He is wrong though, he knew everything he needed to know decades after Navy radio tech school.

They knew how to make the information stick. Looks like your tech school did too.

Good stuff.

 

[Captain]

Phased array is very impressive. It too has a very distinctive sound. Sorta sounds like a cross between popcorn and sizzling bacon.

I was on a Arliegh Burke class Destroyer and I remember they used to do a monthly (I think) test where they went out on the flight deck and let loose a balloon with a steel ball about a foot in diameter. The test was satisfactory if they could track it over 300 nm!

 

[ARFlyer]

I'm a microwave radio geek, so I appreciated the story, Cap.

The only part you left out is that most higher tech systems these days often try to emulate other systems to throw off the ELINT ops as to what type they really are.

The phased array antenna tech overall is also quite impressive engineering. Steering RF without moving the antenna was a huge jump technology-wise.

The giant 400MHz (approximately) ground-based phased-arrays are enormous and amazing at what they can "acquire", size-wise, with modern DSP post-processing.

Pave-Paws is what I'm referring to here. Monsters. Impressive.

http://en.m.wikipedia.org/wiki/PAVE_PAWS

Someone's gotta monitor space junk.

Dad was a Fire Control tech on Naval 10 GHz gear. Outdated today, he still thought it was cool when I was able to order up and easily operate on 10 GHz using a design that utilized a surplus Dish Network dish and a 2W commercially available transverter from Down East Microwave.

No harder putting that station together than setting up a typical CB radio back in the day when he first started playing with radio -- when 10 GHz was only available on his ship paid for handsomely by the U.S. taxpayer.

He did have a much bigger final amplifier though! Klystron tubes are still amazing tech, considering they were high-tech originally around 1940.

Fun stuff. I missed the big VHF and up contest this year to go to Gaston's. Dad joked that I was "fired". Another friend helped him operate from home this last weekend.

He jokes that I'm his radio "Elmer", since I was a Ham long before he had time for it. He is wrong though, he knew everything he needed to know decades after Navy radio tech school.

They knew how to make the information stick. Looks like your tech school did too.

Good stuff.

What about Over-the-Horizon RADAR? You can't beat the Russian Woodpecker! It was the bane of HAMs worldwide during the 80s.

Just remember that when you see those beautiful clear areas that magically appear in front of you in heavy weather........

Is that related to how heavy precip will shadow the stronger echos directly behind that first return?

 

[denverpilot]

What about Over-the-Horizon RADAR? You can't beat the Russian Woodpecker! It was the bane of HAMs worldwide during the 80s.

Duga-3, NATO code word "Steel Yard", which is quite apt. 10 Hz requires a big huge freaking honking antenna... as Captain pointed out.

http://englishrussia.com/2008/04/28/duga-the-steel-giant-near-chernobyl/

http://www.artificialowl.net/2008/12/abandoned-giant-duga-3-system-antenna.html

http://en.wikipedia.org/wiki/Russian_Woodpecker

And of course, we have our own interesting toys...

http://en.wikipedia.org/wiki/High_Frequency_Active_Auroral_Research_Program

 

[wsuffa]

Phased array is very impressive. It too has a very distinctive sound. Sorta sounds like a cross between popcorn and sizzling bacon.

I was on a Arliegh Burke class Destroyer and I remember they used to do a monthly (I think) test where they went out on the flight deck and let loose a balloon with a steel ball about a foot in diameter. The test was satisfactory if they could track it over 300 nm!

Synthetic Aperture Radar is also very impressive....