The answer is a bid different depending on the model and how they implemented the POP.
The Bel models false to certain radar detector models when in POP is ON
The Bel models will ignore some models when POP is ON but it has been known to POP alert to K band door openers.
The Bel units will not respond to triggered radar between 200 and 400ms.
It ignores them, thinking that it may be a radar detector
The Bel units offer a Ka narrow band where it only accepts Ka from the known radar guns. The idea that if it ignores some of the Ka coverage not needed, it will be less susceptible to falsing from other radar detectors. I did not find it to lessen the falsing during my tests. Certainly it may have less susceptibility to certain radar detectors, but it did not seem to make much difference in my 30 minute drive test.
The Cobra models work similar to the Bel in that it will not respond to radar between 200 and 400ms thinking it may be a radar detector.
Cobra is to blame for all of this.
Starting when they sold the 9 band series, Cobra did 2 very bad things.
1) Cobra operated in the VSAT band and caused the FCC to condemn everyone and now we have to be tested by a TCB lab
2) Cobra instituted a Sweep and Park method of operation for detection of radar and detection of radar detectors. They CW at 12.2 GHZ and 11.8 GHz. The 2nd harmonic of 12.2 is 24.4 and therefore at the edge of K band. The 3rd harmonic of the 11.8 is 35.5 and therefore in the Ka band
This method causes CW radar to be interoperated as K and Ka unless you take the time to see if it goes away.
Time is not a luxury when you are trying to determine if POP is used.
Therefore Cobra and Bel and Escort look to see if the CW is 67ms. If so, they indicate POP
If the CW is seen for greater than 67ms they choose to ignore the radar unless it is seen for at least 400ms.
This was they can attempt to avoid falsing to their own crappy Cobra units.
Cobra continues to operate a CW and swept frequency plan with the 10 and 11 band series but it is now at 11.350 GHz to 10.950 GHz with the 3rd harmonic of 11.350 at 34.050 in the Ka band area. When will they stop creating problems for everyone?
It’s like causing a plague and saying you have a cure. No kidding Sherlock! You created the problem to begin with.
PNI is the worst. They operate only 33% of the time in the POP OFF mode. You need to have CW X band for over 1/2 seconds before it will respond. K band also needs to be greater than ½ second to respond. Ka band requires 1 full second to respond otherwise it will ignore it. This is how they minimize falsing to radar detectors. In the POP ON, the unit had many falsed in a 30 minute drive. The unit was tested in my lab and found to only offer Ka band for the guns currently in use. THEY DO NOT OFFER FULL KA BAND!
I developed a circuit and applied for a patent that triple checks the signal in the required time to determine if it was CW vs. a swept source. It works quite well as it reduces the chance of falsing to a swept radar detector quite efficiently. As for the CW from the Cobra product, the circuit reduces the sensitivity to this by 10db for the first 67ms then the sensitivity is restored to full for the remainder of the signal to help reduce falsing to the Cobras.
The Cobra and Bel and Escort have also instituted a range of POP eligible areas in their sweep plan. That is, only 33.8 and K band are eligible for POP.
PNI only offers POP Ka and does not respond to POP K.
The Whistler has taken the lead to allow POP at X, K, and Ka band in the event future radar guns operate with POP type modes.
It will be difficult for Cobra, Escort, and Bel and PNI to accommodate other frequencies without incurring additional falsing issues.