Weird Frequency?

RadarScout

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Friday I got a 23.9xx K band signal from a local LEO. It was about half a mile through some heavy vegetation, so no over driving of the detector. This is the second time in the past month I've seen this. If the radar gun is that far out of tune, is it even considered legitimate as for writing a ticket? Sounds like the local police aren't keeping their equipment tuned.
 

KASHER1979

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Friday I got a 23.9xx K band signal from a local LEO. It was about half a mile through some heavy vegetation, so no over driving of the detector. This is the second time in the past month I've seen this. If the radar gun is that far out of tune, is it even considered legitimate as for writing a ticket? Sounds like the local police aren't keeping their equipment tuned.
I think you can fight the ticket if it's not tuned up and maybe win. That is bad out of tune. lol
 

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If a gun that's running in the 23.9s leads to the LEO taking an interest in you and you not being aware; fighting against an out of tune gun just adds hassle to your life.

Better to be able to detect it, avoid the hassle altogether, and focus on other concerns.

This is similar in a way to the 24.200± guns I've been seeing. There's too many for it to be happenstance. I believe they are being tuned intentionally high or low.
 

V1Jake

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That is way too low for legit K band. Yikes.

I know the Stalker Patrols are 24.0XX range but in the 900's that's bananas
 

Deacon

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There's too many for it to be happenstance. I believe they are being tuned intentionally high or low.
I think Occam’s razor applies here. It seems far more likely their units are simply out of adjustment, but since they’re still working fine they have no idea. Hopefully soon enough Theia will make the whole thing a non issue either way.
 

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I will preface with, I don't know squat about the law concerning police radar usage, I have never been an LEO or in the police radar business, so below is all a guess.

I believe an officer in the field just performs a tuning fork test, logs the results, and that is the daily, or watch to watch, check for operation. If you go to court and anyone challenges the findings the police produce three documents, the log of daily, or watch to watch, checks done with the tuning forks, the documentation of the last time the radar gun was certified by an external lab or facility, and the officers certification / training to operate the radar. There is probably not a certification that the gun is on or off freq, just that it performed speed measurement as required.

But lets look at the technical end of what happens when a gun shifts frequency and the officer uses tuning forks to check it.

Assuming the gun was originally on 24.150 GHz. The gun is internally configured so that Doppler rates match speeds at 24.150 GHz. For example, 55 MPH is 3958 Hz (rounding tones off to the closest full Hz here) of shift and 30 MPH is 2159 Hz of shift. It shipped with two tuning forks, maybe 55 MPH and 30 MPH. The 55 MPH fork would be cut to produce a tone of 3958 Hz, the 30 MPH fork would produce a tone of 2159 Hz.

Now, if the gun is on 23.950 GHz the internal Doppler rate curve is still probably set for 24.150 GHz. 3958 Hz of shift will still show as 55 MPH on the gun, and 30 Hz of shift will still show as 30 MPH on the gun. Using the original tuning forks all will show good. However, it is no longer accurate. Because at 23.950 GHz 55 MPH would be 3926 Hz of shift, and 30 MPH would be 2141 Hz of shift. So the "real" speeds of the original tuning forks at the new frequency are 30.25 MPH for the 30 MPH fork, and 55.45 MPH for the 55 MPH fork.

Very small errors, and shifted up in speed, meaning the error is in your (the speeders) favor.

Technically it can easily be argued that the gun is still plenty accurate for the task. My biggest question would be the "certification" of the gun from the lab / technical facility that last certified it.

If the OEM specifications for the gun have a tuning range (example 24.150 GHz +/-200 MHz) or the service manual used in its certification has such a range, and the current frequency is within that range, there really is no argument.

The FCC has a specific allowable tuning range for each frequency, but this may, or may not, be the same as the technical specifications in the service manual or as designed. The users manual may have an allowable tuning range also (typically the same as the FCC allowable range), but again, this may, or may not, be the same as the service manual or the design specifications.

The FCC allowable range is, per 47 CFR Part 90.103, 24.050 to 24.250 GHz. While I would assume that is the designed performance range of the radar, that is an assumption. If that is what is in the service manual then it could be argued that the radar is no longer certified, it no longer meets the documented performance requirements.

The 2nd question to me would be authority to operate, as much as certification or accuracy.

The FCC authorizes operation based on frequency and other technical requirements, police use / service is no different. As long as you meet those requirements you have authority to operate. When you no longer meet those requirements you no longer have authority to operate.

A radar operating in the 23.9XX range would not be in the authorized 24.050 - 24.250 GHz range, and would have no authority to operate under Part 90. It may have authority under other Parts, I do not know, but its Part 90 authorization is void. For many guns I am not aware of any other Part that allows this kind of radiolocation operation by the Police.

Part 15 may allow operation outside the Part 90 authorized range, I mean below 24.050 GHz, but most police guns I have seen are Part 90 certificated, and the low power guns and unattended highway K band buzzers are Part 15.

If the gun or model number carries a Part 90 certification and is on 23.9XX GHz I would say it is probably not authorized for use under FCC regulations. On the other hand, the mentioned 24.200 GHz guns should still be legal.

So the impact is two fold, is it still meeting its performance requirements, operating within its certified frequency range of operation? Possibly not, I would say probably not, but without documentation you can't be sure. Is it still authorized for operation under FCC regulations? Probably not, but can be confirmed by the model number and required FCC certification sticker or FCC ID number.

T!
 
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RadarScout

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I will preface with, I don't know squat about the law concerning police radar usage, I have never been an LEO or in the police radar business, so below is all a guess.

I believe an officer in the field just performs a tuning fork test, logs the results, and that is the daily, or watch to watch, check for operation. If you go to court and anyone challenges the findings the police produce three documents, the log of daily, or watch to watch, checks done with the tuning forks, the documentation of the last time the radar gun was certified by an external lab or facility, and the officers certification / training to operate the radar. There is probably not a certification that the gun is on or off freq, just that it performed speed measurement as required.

But lets look at the technical end of what happens when a gun shifts frequency and the officer uses tuning forks to check it.

Assuming the gun was originally on 24.150 GHz. The gun is internally configured so that Doppler rates match speeds at 24.150 GHz. For example, 55 MPH is 3958 Hz (rounding tones off to the closest full Hz here) of shift and 30 MPH is 2159 Hz of shift. It shipped with two tuning forks, maybe 55 MPH and 30 MPH. The 55 MPH fork would be cut to produce a tone of 3958 Hz, the 30 MPH fork would produce a tone of 2159 Hz.

Now, if the gun is on 23.950 GHz the internal Doppler rate curve is still probably set for 24.150 GHz. 3958 Hz of shift will still show as 55 MPH on the gun, and 30 Hz of shift will still show as 30 MPH on the gun. Using the original tuning forks all will show good. However, it is no longer accurate. Because at 23.950 GHz 55 MPH would be 3926 Hz of shift, and 30 MPH would be 2141 Hz of shift. So the "real" speeds of the original tuning forks at the new frequency are 30.25 MPH for the 30 MPH fork, and 55.45 MPH for the 55 MPH fork.

Very small errors, and shifted up in speed, meaning the error is in your (the speeders) favor.

Technically it can easily be argued that the gun is still plenty accurate for the task. My biggest question would be the "certification" of the gun from the lab / technical facility that last certified it.

If the OEM specifications for the gun have a tuning range (example 24.150 GHz +/-200 MHz) or the service manual used in its certification has such a range, and the current frequency is within that range, there really is no argument.

The FCC has a specific allowable tuning range for each frequency, but this may, or may not, be the same as the technical specifications in the service manual or as designed. The users manual may have an allowable tuning range also (typically the same as the FCC allowable range), but again, this may, or may not, be the same as the service manual or the design specifications.

The FCC allowable range is, per 47 CFR Part 90.103, 24.050 to 24.250 GHz. While I would assume that is the designed performance range of the radar, that is an assumption. If that is what is in the service manual then it could be argued that the radar is no longer certified, it no longer meets the documented performance requirements.

The 2nd question to me would be authority to operate, as much as certification or accuracy.

The FCC authorizes operation based on frequency and other technical requirements, police use / service is no different. As long as you meet those requirements you have authority to operate. When you no longer meet those requirements you no longer have authority to operate.

A radar operating in the 23.9XX range would not be in the authorized 24.050 - 24.250 GHz range, and would have no authority to operate under Part 90. It may have authority under other Parts, I do not know, but its Part 90 authorization is void. For many guns I am not aware of any other Part that allows this kind of radiolocation operation by the Police.

Part 15 may allow operation outside the Part 90 authorized range, I mean below 24.050 GHz, but most police guns I have seen are Part 90 certificated, and the low power guns and unattended highway K band buzzers are Part 15.

If the gun or model number carries a Part 90 certification and is on 23.9XX GHz I would say it is probably not authorized for use under FCC regulations. On the other hand, the mentioned 24.200 GHz guns should still be legal.

So the impact is two fold, is it still meeting its performance requirements, operating within its certified frequency range of operation? Possibly not, I would say probably not, but without documentation you can't be sure. Is it still authorized for operation under FCC regulations? Probably not, but can be confirmed by the model number and required FCC certification sticker or FCC ID number.

T!
Believe it, or not, I was actually able to follow that.:golfclap:
Since I've lived here my entire life and have never seen the frequency that low, I think I can assume it's not that way by design, thus making it unlikely that the LEO has any special certification to be using the dash mount at that level.
Not too long ago, I remember seeing one in the 24.0xx range. I wonder if it's the same gun that's continuing to fade. Could it be a gun that's about to close its eyes for good?
 

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I think Occam’s razor applies here. It seems far more likely their units are simply out of adjustment, but since they’re still working fine they have no idea. Hopefully soon enough Theia will make the whole thing a non issue either way.
I've seen too many (mostly eastern TN) that are right in the 24.195 to 24.205 range. That's not likely just out of tune. The 23.9xx might be though.
 

Token

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I've seen too many (mostly eastern TN) that are right in the 24.195 to 24.205 range. That's not likely just out of tune. The 23.9xx might be though.
24.195 to 24.205 is still well within the authorized band.

I have not been paying attention to police radar frequencies in detail long enough to have seen, but like some vendors in Ka use specific frequencies, maybe some in K also do? The Ka vendors could all use anything from 33.4 to 36.0 Ghz, both the hardware (in most cases) and the law (all cases) would allow that. But we see some specific vendors on 33.8, some others on 34.7, and yet others on 35.5 GHz. This makes sense, you need to optimize your production and your QA / final alignments to some specific frequency, so whatever one you pick becomes "your" company freq.

The K band allows anything from 24.050 to 24.250 GHz. This is often stated as 24.150 +/- 100 MHz. But, there is no reason to stay in the center. You want to stay slightly away from the band edges so that as a radar heats and cools during the day it does not leave the authorized band, but 50 MHz should be more than enough for that, I would think roughly 25 MHz should be enough. A specific vendor could easily pick 24.200 GHz as their "center" freq for final QA / alignment.

Also, for front and rear antennas you should pick two different freqs. Here I see a lot of F/R spacing of 50 or 60 MHz. Even if you select 24.150 GHz as your normal center, the other center has to be something else, either 24.100 or 24.200 GHz would fit that very well.

T!
 

Yippeekyaa

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I will preface with, I don't know squat about the law concerning police radar usage, I have never been an LEO or in the police radar business, so below is all a guess.

I believe an officer in the field just performs a tuning fork test, logs the results, and that is the daily, or watch to watch, check for operation. If you go to court and anyone challenges the findings the police produce three documents, the log of daily, or watch to watch, checks done with the tuning forks, the documentation of the last time the radar gun was certified by an external lab or facility, and the officers certification / training to operate the radar. There is probably not a certification that the gun is on or off freq, just that it performed speed measurement as required.

But lets look at the technical end of what happens when a gun shifts frequency and the officer uses tuning forks to check it.

Assuming the gun was originally on 24.150 GHz. The gun is internally configured so that Doppler rates match speeds at 24.150 GHz. For example, 55 MPH is 3958 Hz (rounding tones off to the closest full Hz here) of shift and 30 MPH is 2159 Hz of shift. It shipped with two tuning forks, maybe 55 MPH and 30 MPH. The 55 MPH fork would be cut to produce a tone of 3958 Hz, the 30 MPH fork would produce a tone of 2159 Hz.

Now, if the gun is on 23.950 GHz the internal Doppler rate curve is still probably set for 24.150 GHz. 3958 Hz of shift will still show as 55 MPH on the gun, and 30 Hz of shift will still show as 30 MPH on the gun. Using the original tuning forks all will show good. However, it is no longer accurate. Because at 23.950 GHz 55 MPH would be 3926 Hz of shift, and 30 MPH would be 2141 Hz of shift. So the "real" speeds of the original tuning forks at the new frequency are 30.25 MPH for the 30 MPH fork, and 55.45 MPH for the 55 MPH fork.

Very small errors, and shifted up in speed, meaning the error is in your (the speeders) favor.

Technically it can easily be argued that the gun is still plenty accurate for the task. My biggest question would be the "certification" of the gun from the lab / technical facility that last certified it.

If the OEM specifications for the gun have a tuning range (example 24.150 GHz +/-200 MHz) or the service manual used in its certification has such a range, and the current frequency is within that range, there really is no argument.

The FCC has a specific allowable tuning range for each frequency, but this may, or may not, be the same as the technical specifications in the service manual or as designed. The users manual may have an allowable tuning range also (typically the same as the FCC allowable range), but again, this may, or may not, be the same as the service manual or the design specifications.

The FCC allowable range is, per 47 CFR Part 90.103, 24.050 to 24.250 GHz. While I would assume that is the designed performance range of the radar, that is an assumption. If that is what is in the service manual then it could be argued that the radar is no longer certified, it no longer meets the documented performance requirements.

The 2nd question to me would be authority to operate, as much as certification or accuracy.

The FCC authorizes operation based on frequency and other technical requirements, police use / service is no different. As long as you meet those requirements you have authority to operate. When you no longer meet those requirements you no longer have authority to operate.

A radar operating in the 23.9XX range would not be in the authorized 24.050 - 24.250 GHz range, and would have no authority to operate under Part 90. It may have authority under other Parts, I do not know, but its Part 90 authorization is void. For many guns I am not aware of any other Part that allows this kind of radiolocation operation by the Police.

Part 15 may allow operation outside the Part 90 authorized range, I mean below 24.050 GHz, but most police guns I have seen are Part 90 certificated, and the low power guns and unattended highway K band buzzers are Part 15.

If the gun or model number carries a Part 90 certification and is on 23.9XX GHz I would say it is probably not authorized for use under FCC regulations. On the other hand, the mentioned 24.200 GHz guns should still be legal.

So the impact is two fold, is it still meeting its performance requirements, operating within its certified frequency range of operation? Possibly not, I would say probably not, but without documentation you can't be sure. Is it still authorized for operation under FCC regulations? Probably not, but can be confirmed by the model number and required FCC certification sticker or FCC ID number.

T!
Had to read this twice in my Saturday afternoon inebriated state of omg it is effing too hot outside to do anything......sorry...train ran off topic.....can easily see your explanation parlaying into a dismissal via a well educated argument with documentation.
 

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24.195 to 24.205 is still well within the authorized band.
Agreed.
A little background real quick on this subject because this is a slightly different point than what it sounds like you might have been thinking I was talking about. :)

A couple of years ago I noticed an increase in K-band usage in some of my travels and a portion of those guns were right in the 24.200± range instead of the typical 24.150 (or 24.125) that I had been seeing prior.

I started reporting these occurrances and it came as a pretty big surprise to many.
Since it started, I've seen even more of them all in the same areas as the first.
I've suggested that these group of K-band guns are being tuned higher than normal either by the manufacturer or the neighboring counties that are using them.

Related to that observation for which nothing else is currently known; I'm suggesting that there might be a "trick" employed by some LEOs in which the guns are being tuned to known weak spots in some detectors. That's all. :)
 

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Related to that observation for which nothing else is currently known; I'm suggesting that there might be a "trick" employed by some LEOs in which the guns are being tuned to known weak spots in some detectors. That's all. :)
You think the donut snacking crowd is going to put that much work into revenue enhancement? :happyanim:
 

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I'm the areas I'm seeing the majority of 24.200± I'm also seeing a lot of sneaky parking/hunting spots, totally unmarked cars, heavy presence, and a wholesale switch from Ka back to K.
I think it's likely.

BTW, as a fellow Accord driver you might appreciate that I now have 114,xxx on my 2018 that I bought 6/29/18. Just changed out the chrome grill piece for a JDM style black grill last Saturday. :)
 
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