M4 off Axis

[BlinderGuy]

I was just curiouse about something. I know that the M4 platform from Beltronics is not supposed to be good at off axis detection but was wanting to clear up exactly what is off axis. I have been using my new GX65 for about a week and love it...Last night I pulled onto a road and was heading north...Soon as I pulled on the road northbound I started getting a KA alert that kept getting stronger...I reached a intersection approximatly a mile away and sittin 4 or 5 cars back heading east was a Leo with constant on KA band. I picked him up pointing in a different direction from a mile away..Is this considered a good off axis detection? I know it was that leo because the alert never faded till I crossed through the intersection past him then it went away.

Just to clarify...I was heading north he was heading east and was a mile away at a intersection.

[BlinderGuy]

Does the question make since our do I need to explain better?

[YTCD]

Off-axis detection is when your vehicle/detector is facing lets say south and your detector goes off and up the road he is sitting southeastish from your original alert. Or your approaching a stop light and your detector goes off and at the stop light the cop is perpendicular to you, thats off axis. Really anything that is about 20+ degree's off of your line of sight.

And yes from my understanding that was off axis. If he was waiting a the stoplight, perpindicular to you (90 degree's) then that is great off axis. Especially if it was 35.5

[CJR238]

I actually tried to redefine off axis for the M4 design, i think off axis is misunderstood.

Off axis is more than 30 degrees off to the right or left of your RD, usually in sight to your immediate right or left.
If you pick up radar around a turn, 1/4mi or more ahead of you and the LEO is 35 degrees off axis, that far ahead isn't off axis because he's ahead of you.

Off axis close to you isn't off axis when your far away.

Hers an excerpt from my 9500 sticky:

The one big addition that i beleve Escort did to inhance the above is the horn on the 9500I is designed to help filter out those useless off axis falses “Detection range” verses “Sensitivity”. The 9500I has very good sensitivity but on signals passed 35 degrees the sensitivity starts to decrease(detection range is not affected and that’s also why “H” mode is still quiet). The horn actually takes into account for “Cosine error/effect” any radar more than 40 degrees off axis will show less than 80% of your speed so this is considered a low threat. For example if you are going 70 in a 55 zone and the LEO’s radar is 40 degrees off axis, his radar will show only 56mph. This dramatically reduces the falses from automatic doors without sacrificing real threat detection range.
I figured the angle of the walls on the horn at 15 degrees would equate to the off axis decrease. Because 15 degrees times 2 (each side at 15 degrees) plus add the antenna width so the total equals 35 degrees and that’s where the off axis starts to decrease (all horns seem to be similar).

For example:
Signals from motion sensors are, in most cases off axis from the side of the road, not sitting in the middle of the road facing you or very strong. So by just shaving a little off axis you maintain detection range with creating less falses.
Most falses will alert your RD for a couple hundred feet when you are near them because they are usually over 40 degrees shooting across the road. Now if theirs a LEO off axis down the road you will pick up his signal much, much farther. Even if he’s 40 degrees off axis he’s so far down the road when you receive his signal he's essentially only 10 degrees off axis. Because of this, detection range would be maintaned for around-the-curve or over-the-hill encounters.

A discussion of the M4 horn: K band door openers...Opinions please

[MEM-TEK]

Any radar source which isn't located directly ahead of where your radar detector is pointing is an off-axis radar source. Common examples are microwave door openers which are set back from the road on either side of a straight road which you are traveling on, or when encountering radar while you are rounding a curve.

[DeadReb245]

I picked him up pointing in a different direction from a mile away..Is this considered a good off axis detection? I know it was that leo because the alert never faded till I crossed through the intersection past him then it went away.

Just to clarify...I was heading north he was heading east and was a mile away at a intersection.

I think it's important to point out that just because the LEO's vehicle was FACING east does NOT mean that the radar antenna is also facing east. LEO's can sit in the U-turn spots on the freeways with their vehicles completely perpendicular to either direction of traffic (picture this |--|, with the two hyphens being the LEO's vehicle) and swivel the radar antenna to point to their left or right. I'm not sure what different models offer this or if it's a standard feature, but I have seen LEO's with their antennas on the front windshield and pointing to their left or right, as opposed to aiming straight at oncoming cars or cars going away.

[jdong]

Classic off-axis example:

180-degree circular highway ramp, speed sign 1/10 of a mile ahead on the entry lane of the highway. When does your detector pick it up?


On K-band signs like this in my area, the V1 will start blaring to it before I even get onto the ramp and it quickly pegs as I round out the final turn.

My XTR-690 will start alerting when I enter the ramp, lose it, then start picking it up about 20 degrees before getting out of the ramp.

My X50 won't start alerting to it until I come out of the turn, at which time it gives a 1-1-9-9-9-9 ramp-up.


I think this is mostly due to the pulse guard duration... the X50 probably sees the signal much more than the XTR-690 would, but the signal doesn't hold still long enough to get past the filter.

These kinds of scenarios make me a bit worried, and at times concerned that Escort may have been too aggressive in filtering -- had there actually been a cop at that location I think the XTR-690 would've BARELY provided me with the warning needed to avert disaster, the V1 would've saved me, and the X50 would've been too late.

[Silverstreak98]

Classic off-axis example:

180-degree circular highway ramp, speed sign 1/10 of a mile ahead on the entry lane of the highway. When does your detector pick it up?


On K-band signs like this in my area, the V1 will start blaring to it before I even get onto the ramp and it quickly pegs as I round out the final turn.

My XTR-690 will start alerting when I enter the ramp, lose it, then start picking it up about 20 degrees before getting out of the ramp.

My X50 won't start alerting to it until I come out of the turn, at which time it gives a 1-1-9-9-9-9 ramp-up.


I think this is mostly due to the pulse guard duration... the X50 probably sees the signal much more than the XTR-690 would, but the signal doesn't hold still long enough to get past the filter.

These kinds of scenarios make me a bit worried, and at times concerned that Escort may have been too aggressive in filtering -- had there actually been a cop at that location I think the XTR-690 would've BARELY provided me with the warning needed to avert disaster, the V1 would've saved me, and the X50 would've been too late.

WOW....I have had the exact same experience with my XTR-690 and X50, Escort definitely filters a lot more aggressively than Whistler.

I have noticed that my XTR-690 responds quicker to IO as well.

[MEM-TEK]

I don't think that Escort filters more aggressively. Instead I think that Mike B's unique patent for sniffing out radar comes into play even though Whistler's RDs have a bit less raw sensitivity. This is why I have tried to explain that raw sensitivity, although an important baseline measurement, isn't everything in terms of real world performance under certain conditions.

[jdong]

MEM-TEK, you have radar transmitters so you can verify this:

I have a strong suspicion that there is as much as a 1 second delay between the onset of a signal and the sounding of an alert on the X50... If that is the case, it can easily explain this perceived "more aggressive filtering" in real world cases.