Explain dual freq. FM pulse homing

"some military grade gear"? WTF is that supposed to refer to?

You're a dork. They use huge chassis full of SBCs and custom cards that perform custom functions. All the boards are like 12 x 12 inches and densely populated. There could be several dozen full on computers in ONE chassis, and that chassis will fit two in a rack!

Ever seen a data center? Most comm centers are stuffed full of redundant routers and hardware encryption devices you have never even seen before in your life. You couldn't be more wrong, boy!

encrypted analog? video,

That is NASA, idiot.

Military uses whatever design level they need to make whatever transducer they need and have it survive what environ it needs to survive.

You're a complete idiot.

No shit, idiot! That is what redundancy is, dumbfuck!

I made HV supplies for the NOAA in Bolder (NIST as well) for a certain type of weather balloon experiment that they send up every half decade or so..

We would make and send three identically configured supplies.

They beat the piss out of two of them to be sure they are compliant, and they REALLY beat the shit out of the third and actually cause it to fail. Then, they take the best of the two they beat up earlier, and run that on the balloon.

Jibbersih.

from the drones.

Whoopie doo. They did not secure one of their relays that carried non-critical unencrypted video streams. Big deal.

You're a goddamned retard when you spew biased horseshit.

I'll bet that my remark is more accurate than yours is.

I'd hazard a guess that FM pulse was a precursor to modern chirp or pseudo-random correlator designs in an attempt to separate out multiple targets. The conflict is always between the need to send enough power out to see a decent echo back and the pulse width being sent.

A lot of the open literature for radio astronomy aperture synthesis is pretty much identical to military radar and sonar beam steering technology with the detail of the power pulse transmitting step being entirely missing. Modern sonar imaging companies probably have the most accessible discussion of the technology with only minor omissions.

And to that end the pattern transmitted and any other beam steering that is done can be used to determine the best trajectory to follow. Unsurprisingly a naval ship that sees an active torpedo in the water will deploy counter measures intended to fox the more basic designs. It then becomes a game of cat and mouse until either the torpedo hits the target or something else that makes it explode.

A fairly nice article on modern imaging sonar using chirp techniques to maximise echo impulse response and minimise ambiguity is online at:

The OP might find it interesting although it deals with a slightly different (better) method of range disambiguation. Bats use chirp.

Regards, Martin Brown

"Martin Brown"

** You would hazard far too much.

While totally ignoring all facts.

** Irrelevant to a homing torpedo.

** Directly towards the target is the best one. ** Not even faintly possible in the OP's example.

Cos the torpedo he is on about is only intended to attack subs.

Try to pay attention.

And get your fist off it.

.... Phil

I'll say. Fuckhead.

I have nothing to refute this with. Cop doppler uses the chirp to detect speed, but I don't know if it resolves distance. It seems in my headbone that there'd be a confusion factor there, as in, how to distinguish return time from doppler frequency.

Maybe somebody around here actually knows the answer to this.

Thanks, Rich

Of course the speed of sound is the same for any frequency in a given medium - If I understand, the problem is how to distinguish the distance return from the doppler return. I'd think there's an answer, but I don't have that advanced of math, or know the formulas (formulae?)

Heck, for all I know, it could be as simple as linear algebra, or two equations in two unknowns?

Thanks, Rich

Boy, ain't this the truth! I once (while a tech in the USAF) ordered a 15A fuse, but made a mistake on the stock number, or some supply grunt couldn't read my chicken scratches, and they sent a 15A, 15,000V fuse. It had the same form factor as a 3AG, but magnified to about the size of a thermos bottle.

Cheers! Rich

Well, as someone who works for a company that sells to the military, let me tell you...

-- Our designs could be improved by a significant margain if we were building them in the quantities you have in the commercial world. Pretty much in all the areas of raw performance as well as power consumption and volume.

-- Our schedule times are longer than has been my experience in the non-military world. Much of this is taken up by additional testing and documentation.

A few, perhaps. Most of them... nah, they're (often) necessary and useful projects, but cutting-edge? No.

Perhaps you work at one of the companies that *is* designing the cutting-edge stuff...

Selective availability degrades the quality of the signal in the sense that the information embedded within it has purposely been made less accurate.

My wording there was perhaps a bit clumsy...

Have I mentiond how many things useful to the military don't have to be cutting-edge designs?

---Joel

n

nt

y d

g.

rd

he

n

ls

If you send out a chirped signal, the Doppler shift is indistinguishable from the reflection from a static object at a different distance. Changing the rate of the chirp lets you see a difference, and even two successive identical chirps will give you two different distances from which you can infer the rate of change from the source to reflector if you are prepared to assume a constant rate of change. Obviously, if the two idnetical chirps are too close together in time, the reflector won't have moved enough to give you an accurately measurable difference or velocity, so changing the rate of frequency change between successive chirps gives you more information.

-- Bill Sloman, Nijmegen

Where is IP encryption used? Mil networks. Beyond your grasp.

What is HAIPE? A mostly mil acronym beyond your grasp.

Where are all those consumer hard drive encryptors?

Oh... that's right, consumers do not have thousands of dollars for hardware level encryption and secure, logged access and EMI/Tempest hardened enclosure.

You could not be more clueless, and I don't care that you CLAIM to be a mil product maker.

I deal with millions of dollars worth of gear on a daily basis, both mil and commercial. ALL cutting edge.

Hell, one of my Gyros goes for $100k. Every vehicle in the field will have one, once BFT is fielded further.

You, idiot? Yes.

The military, absolute cutting edge? Yes.

Case closed.

analog? video,

from the drones.

Your vast ignorance is showing. The original Videochiper (I) with eencrypted audio and video was designed and built for the military 30 years ago. They didn't give a shit that someone might see a missle was a couple seconds from destroying them.

--
You can't fix stupid. You can't even put a Band-Aid? on it, because it's
Teflon coated.

If I were to design such a system, I would definitely want to find out to what extent that is true...

A linear chirp indeed yields ambiguous results if the target can move w.r.t. the observer. The obvious trick would be to chirp both up *and* down. A gaussian or sinc chirp would probably lead to some nice mathematical transform delivering both range and speed for many targets simultaneously.

Jeroen Belleman

Do you happen to know how sophisticated the radar systems found on small pleasure craft boats tend to be these days? Until recently I was thinking it was mostly still, "antenna rotates, you send out a pulse, just plot the returned signal strength as an intensity in the radial direction," but I'm starting to get the impression that even these relatively inexpensive commercial-grade radar units probably now have lots of DSP in them and can generate range and rate estimates, size/classification, etc.?

No, sorry, I don't know.

Jeroen Belleman

AFAIK, most of the commercial trackers depend on an alpha-beta (or alpha-beta-gamma) estimate of the motion of the centroid. There typically is a fair amount of DSP nowadays to replace the original analog FTC and STC, of course, as well as for automatic contact recognition and tracker assignment.

--
Rich Webb     Norfolk, VA

=46rom the title of your OP they are two separate frequencies, no?

The

return

Most older and some current Cop radar was/is FM-CW. This is also currently popular for vehicle detectors. If you bother to sort out the = FM and AM return components it gives you both speed and range at the same time. The newest Cop stuff is pulsed and chirped like old SPS-48 and SPS-51 (Koran war vintage) Navy 3D air search radars.

message=20

COTS

to

me=20

building=20

all=20

useful=20

Yep. GPS and MLC capacitors are two cases where Military was bit ahead. But they are the exception rather than the rule. Both over 30 years old now.

cutting-edge=20

that=20

accurate.

Umm, no. That is not what is going on. See:=20

Hmm, thanks for the link.

I was going off of my -- rather oversimplified -- knowledge that "selective availability makes fixes less accurate." (Similar to what Wikipedia says: GPS includes a (currently disabled) feature called Selective Availability (SA) that adds intentional, time varying errors of up to 100 meters (328 ft) to the publicly available navigation signals.)

---Joel