A little rant

[TRDdave]

Ok so the other night my friend and I had nothing better to do so we went to the local car wash. Now on the way, I wanted to show him how much better of a detector $50 can buy you. He has a Cobra XRS9430, and I have the V940. We plugged them in both at the same time..(yes I know there would be some interference, thats what I was testing for) and to my surprise, the cobra was picking up 3 bars of K. I wasnt picking up anything. Needless to say, we unplugged the cobra and used mine. Saved our butts on the way home from base by an unmarked car hiding on the side of a dark side street. But I thought it was odd that I didnt pick up any of the infamous ka leakage that plauge cobras...

[ELVATO]

It could have very well been picking it up, just not reporting it. It was probably still affecting the 940's ability to pick up legit radar.

I think there was a video on here or something of someone having a cheap detector plugged next to a high end (something tells me STI), and the high end missing some alerts.

Or maybe I dreamed that up..

[MEM-TEK]

Well, this is exactly what I discovered and observed. A Cobra RD being operated at the same time as a Belscort RD model will kill K band performance on a Belscort RD model, and probably any other competing RD model too. A rough guess is that a Cobra RD in very near proximity slaughters Belscort RD K band performance by at least 10dBm if not more. On the other hand, a Belscort RD only seems to falsely alert to a Cobra if you are trailing a car with a Cobra, rather than approaching a car headed towards you with a Cobra RD. So the Belcort filtering is, overall, very effective against Cobra RDs, yet has its radar detection capabilities significantly lowered if a Cobra RD is on operation anywhere closely nearby.

Thus the Belscort Cobra RD filtering is quite good (preventing false Ka alerts). Yet on the other hand Belscort's filtering seems to assume that any detected Cobra RD is approaching you and will pass by you quickly. The result is that false Cobra alerts are suppressed. The one failure of the Belscort Cobra RD filter occurs, as mentioned, when trailing a car with a Cobra RD. In this case you can get false K or Ka band alerts. Yet it seems that Belscort rightly considers this to be a far less annoying scenario compared to multiple encounters with approaching Cobra RDs.

[focalcivic]

Well, this is exactly what I discovered and observed. A Cobra RD being operated at the same time as a Belscort RD model will kill K band performance on a Belscort RD model, and probably any other competing RD model too. A rough guess is that a Cobra RD in very near proximity slaughters Belscort RD K band performance by at least 10dBm if not more. On the other hand, a Belscort RD only seems to falsely alert to a Cobra if you are trailing a car with a Cobra, rather than approaching a car headed towards you with a Cobra RD. So the Belcort filtering is, overall, very effective against Cobra RDs, yet has its radar detection capabilities significantly lowered if a Cobra RD is on operation anywhere closely nearby.

Thus the Belscort Cobra RD filtering is quite good (preventing false Ka alerts). Yet on the other hand Belscort's filtering seems to assume that any detected Cobra RD is approaching you and will pass by you quickly. The result is that false Cobra alerts are suppressed. The one failure of the Belscort Cobra RD filter occurs, as mentioned, when trailing a car with a Cobra RD. In this case you can get false K or Ka band alerts. Yet it seems that Belscort rightly considers this to be a far less annoying scenario compared to multiple encounters with approaching Cobra RDs.

Cobras all false my Bel on K. Im sure the Cobra so close to your Bel messed up Your ability to pick up K as MEM said.

[dpatel01]

My own experience when having a 9-band Cobra user follow me has shown my RD get killed on K-band detection. C/O K-band range was drastically reduced, perhaps by around 80% with the Crapra causing only 2 short Ka falses on my RD (POP off) over a 50 mile trip.

[MEM-TEK]

While everyone hates Cobras because they cause Ka falsing on virtually every other RD, it is becoming obvious that everyone should hate Cobras because a Cobra in the near vicinity of any other brand or RD seems to slaughter the other RD's K band sensitivity. Yeah, those genius overseas Cobra engineers really did a great job of interfering with every other brand of RD. Personally, I think that their efforts are deliberate.

[KaPro]

Yea, they figure if theres don't work, why should anybody elses.

[Lucky225]

yea, it's never a good idea to run 2 RDs so close to each other, a better experiment would have been to plug one in, hit the tripometer reset when you pick up a stationary k band such as a speed sign and record how far away it detected, then return to the same spot and plug the cobra in and show the difference that way.

[dpatel01]

While everyone hates Cobras because they cause Ka falsing on virtually every other RD, it is becoming obvious that everyone should hate Cobras because a Cobra in the near vicinity of any other brand or RD seems to slaughter the other RD's K band sensitivity. Yeah, those genius overseas Cobra engineers really did a great job of interfering with every other brand of RD. Personally, I think that their efforts are deliberate.

I had 3 extremely short Ka alerts (2 seconds warning before visual) on the interstate today over the course of 100 miles or so while a Scion xB is following me. I let him pass as I move into the right lane to get my exit and what do I find on the toasters windshield? A $%^&n Cobra. It may not just be K-band that we're getting killed on, add Ka as well. I stared at it for a few seconds, It looked short front-to-back unlike their 9/10/11/12/thousand band units. Im convinced this was one of the 6-banders.

[jdong]

Most high-end detectors (the 940's platform I would think qualifies) use the scanning of lower harmonics to filter out Cobras. For example, if it sees a 33.8Ghz signal, it would FIRST wait for 500ms or so before alerting, in the meantime scanning 1/3 of that, 11.27GHz or so, for a principal frequency that would correspond to the 33.8 alert. If a match is found, the alert is assumed to be triggered by a detector. The Valentine One is unique in that even AFTER sounding an alert, it continues to scan for harmonics, even after the alert has terminated for a second or two too. During this time if it makes a match, it pulls back the alert and displays the infamous J. Now this poses two challenges for us:

(1) You better have good sensitivity in the 10-12Ghz range otherwise you first detect the Ka signal BEFORE being able to see the lower culprit. With detectors seeming to favor Ka sensitivity over other bands these days, it's a problem...

(2) If another detector happens to park in the 10-12GHz area at just the right spot, it can cause your detector to lock out an area of K band (times 2) or Ka band (times 3), ruining your detection. It also means someone really sinister can probably design a radar gun that also emits this lower frequency and your detector wouldn't alert at all



Now, cheaper detectors don't have the sensitivity or processing power to scan for this many signals at a time. So, the cheaper method of filtering? Well, most of these junk detectors simply park for 50ms up to 200ms on these culprit frequencies. If you reject all signals that don't last for 300 or 500ms, that filters them out. This has disadvantages too:

(1) You are more likely to reject short-duration signals, leading to a LEO technique called quick-triggering, where the officer simply blasts IO for half a second, and I've heard this gets around all Escort detectors.

(2) 50ms is awfully close to valid POP, so detectors using this method lose their Cobra immunity when POP is enabled, hence leading to the infamous level of POP falsing.