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Nextel interfering with Radar unit

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chiefhal3
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Nextel interfering with Radar unit

Postby chiefhal3 » Thu Feb 03, 2005 6:59 am

Hey, I know this is website is supposed to be about Motorola radios but I have a crazy situation regarding my Motorola i305 Nextel phone. Many times my radar unit will show "rfi" radio frequency interference and I have basically narrowed it down to my nextel. Is this comon, anyone else heard of it? Is there anything that can be done to prevent it other than not using nextel?
"Once man has hunted armed man and liked it there is no other hunt like it."

Microwave Mike
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RFI

Postby Microwave Mike » Thu Feb 03, 2005 8:24 am

Most modern Radar units will display the RFI error message when near any RF source. The reason for this is to prevent False readings during the usage of the radar. It should mute the function of the radar during the time the unit is exposed to external RF energy. Mine will display RFI with the use of a UHF hand held inside the car. It will also display RFI when I
get close to the Antenna Farm at Cedar Hill in the DFW area.

mm

VE3TUH
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rfi

Postby VE3TUH » Thu Feb 03, 2005 8:57 am

You didnt specify what freq band this phone is on, or what type of service, analogue, digital, etc. However, if you are using the handset in the vehicle without an external antenna, it might be worth considering a car kit with an external antenna, to get the rf away from your equipment.

Randy

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Re: rfi

Postby 1 Adam 12 » Thu Feb 03, 2005 9:55 am

VE3TUH wrote:You didnt specify what freq band this phone is on, or what type of service, analogue, digital, etc. However, if you are using the handset in the vehicle without an external antenna, it might be worth considering a car kit with an external antenna, to get the rf away from your equipment.

Randy

Well since he mention Nextel twice, once in the title and in his post and he is using a I ( as in IDEN) 305 Nextel, so I am going to go out on a limb :roll: and say its digital and 800-900MHZ range.... but as to the second part of the post I agree you very well may have to do a car kit or external antenna arrangement. The degree of effect they have varies on different electronic devices... One vehicle we have has a radio shack scanner to follow the 800MHZ traffic on the local systems and the Nextel just creamed it, another one has a BCT-8 and it has no effect. As mentioned either a car kit or RF adapter (if available) with outside antenna may resolve this.

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Postby chiefhal3 » Thu Feb 03, 2005 10:06 am

Thanks guys,

Yes being Nextel I to assume it is 800 mhz especially since when I get incoming calls my speaker on my astro spectra radio cracks and pops. I think it has to do with how close the two units are as I normally keep the Nextel in the cup holder of the equipment console. It stops when I pick it up.

The radar unit is a Custom Signals, I guess I could check on a car kit for the nextel but I get in and out of the car a bunch and I keep the unit in a holder with a swivel clip for my belt. I was hoping maybe there was some way to ground or sheild the radar antenna to prevent this.
"Once man has hunted armed man and liked it there is no other hunt like it."

VE3TUH
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rfi

Postby VE3TUH » Thu Feb 03, 2005 11:55 am

Sorry adam 12, I do not know nextel, or their freq allocations, or type of service, as you seem to. Thanks for pointing that out. Regardless, it is usually good advice to try and seperate rf sources, especially when having problems.

Randy

RKG
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Postby RKG » Thu Feb 03, 2005 12:42 pm

The Nextel is doubtless receiving on 851-869 and xmitting on 806-824. The radar unit is most likely a Class A Field Disturbance Device, operating on 10.525 GHz. However, because it uses Dopler shift to derive target speed, it is sensitive to RF of any frequency. Both units are working as intended; the Nextel should be "off" when the radar is actually clocking speeders.

Dan562
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Postby Dan562 » Thu Feb 03, 2005 12:45 pm

Hi Randy!

Possibly you do know of MOTOROLA iDEN Products or NexTel or clearNET Systems. One of these must jog your memory slightly ... they're all the same product operating on the 800/900 MHz Band Plans. iDEN Products are a Digital Trunking TDMA Format set up in the same configuration as Cellular sites. They provide Direct Connect (the equivalent of PTT two-way radio) and a form of Interconnect "if" the network system is correctly set up, the human ear will not be able to detect the Subscriber unit switching between Tx and Rx audio, it's done so quickly to simulate full duplex operation. :D

Dan

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Postby chiefhal3 » Thu Feb 03, 2005 12:51 pm

RKG your statement of "Both units are working as intended; the Nextel should be "off" when the radar is actually clocking speeders" is interesting. I bet 75% of the officers I know use nextel or southern link which are both iden products.

I don't think we are all going to turn off our nextels or what ever while we run radar. I wonder if anyone has ever gotten out of a ticket in court because of something like that?

I am looking over the net to see if I can find any published data about this.
"Once man has hunted armed man and liked it there is no other hunt like it."

CTAMontrose
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Postby CTAMontrose » Thu Feb 03, 2005 12:55 pm

Dan562 wrote:Hi Randy!

Possibly you do know of MOTOROLA iDEN Products or NexTel or clearNET Systems. One of these must jog your memory slightly
Dan


dan,

take it easy, the guy is in canada, they dont have Nextel there, i think their version is called "Mike". No need to bash the guy because he hasnt heard of something that isnt where he lives.
Last edited by CTAMontrose on Thu Feb 03, 2005 3:40 pm, edited 1 time in total.

VE3TUH
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rfi

Postby VE3TUH » Thu Feb 03, 2005 1:52 pm

Thanks, Grem, that was kind of my thought on the first reply. However, I have heard of Clearnet, and yes, they operated in the 800 mhz band. My intention was to politely point out, that when asking for advice, it is usually good to provide as much detail as possible, as I for one have no idea about Motorola's iden products, etc. Here in Ontario, for instance, the Cellular provider could be either 800 mhz or 1.9 ghz, with a mix of analogue, or several different digital schemes. It could be relevent to specify which when having problems. Sometimes though it is just not worth it to open your mouth here.

Randy

chiefhal3
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Kustom Signals

Postby chiefhal3 » Thu Feb 03, 2005 2:01 pm

I mentioned this to Kuston Signals. They told me there was an rf antenna in the power cord to sense radio frequency interference. Furthermore, it was suggested that I could disconnect this antenna from the CPU board. Apparently this in not a necessary item for the unit to work properly, it just identifies when the unit is near an rf source. While I am rather tinkerous, I don't think I will try this myself, perhaps the guys at the radio shop can do this for me. But I wanted to share with all what I found out. Thanks for the help.
"Once man has hunted armed man and liked it there is no other hunt like it."

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Postby RadioSouth » Thu Feb 03, 2005 2:54 pm

I dunno Chief. As Microwave Mike points out it's a safety device to prevent erroneous reading due to RF, let's face it the radar unit transmits and receives RF and measures the doppler shift RF can alter the reading. To eliminate such a 'safety' device reduces the scientific reliability of the unit. I'm sure if a traffic judge was aware of this removal the result would be 'not guilty' verdicts and perhaps a few choice words.
I recall radar units where I was from needed annual calibration/certification. I don't know if the RF detect is part of this process
but if so the unit would not pass. Sounds like a PIA with the Nextel situation but what the Kustoms Rep. suggested is just irresponsible.

Dan562
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Postby Dan562 » Thu Feb 03, 2005 3:01 pm

Grem467,

I was not bashing Randy, (moderated)

"the guy is in Canada, they dont have Nextel there, i think their version is called "Mike".
(mod).. "clearNET" .... that is the NexTel system in Canada. I know without a shadow of a doubt because I helped implement part of that system working directly for MOTOROLA's iDEN Infrastructures Division out of Schaumburg as an iDEN System Engineer in June, 1998. The RF Cell Sites were up in Canada in 1997 being back fed by the U.S. NexTel Mobile Switching Offices along our mutual border. Canada's clearNET system presently has all of their own MSO's feeding their RF sites. The MiKE system provides Canada's Cellular & PCS services so they're two independent systems.

)Moderated, Will)

Dan

CTAMontrose
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Postby CTAMontrose » Thu Feb 03, 2005 3:27 pm

what part of "I THINK" didnt you understand << SELF MODERATED>>?

do i live in canada? im sorry im not a super expert on all things RF like you << SELF MODERATED >>.

your post to him came off like he was stupid, and he even posted that he read it the same way. See how stuff can happen? should i know what EVERY iden network around the world is called? hell i didnt even know that it WASNT called mike... why is that? because i dont live here.. hense the reason for the "I THINK".

geez

:roll:
Last edited by CTAMontrose on Thu Feb 03, 2005 3:38 pm, edited 1 time in total.

kmoose
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Postby kmoose » Thu Feb 03, 2005 3:37 pm

chiefhal3 wrote:I don't think we are all going to turn off our nextels or what ever while we run radar.



I have a better idea...............turn off the radar gun! ;)

OX
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Postby OX » Fri Feb 04, 2005 4:18 am

/RANT
It floors me that Public Safety is using the very thing that is causing RF Desense to their "safety net" radio systems. Let me put my own radio system up, desense the inputs to yours with it and then rent airtime to everyone including your own employees so they can communicate privately. While Nextel did not intentionally do this, the result is the same. I don't get it.
/rant

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Jay911
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Postby Jay911 » Fri Feb 04, 2005 4:35 am

Dan562 wrote:"clearNET" .... that is the NexTel system in Canada. I know without a shadow of a doubt


Sorry to cast shadows, Dan, but Clearnet hasn't existed here in Canada for years. They were bought out by Telus at least 4+ years ago, and Telus operates the MiKE system (basically rebranded Nextel).

Careful what you "know" for a fact. :)

The original sentiment still stands - giving the poster a hard time because he doesn't intuitively know about a system that doesn't exist in his country by that name is not helpful.

CTAMontrose
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Postby CTAMontrose » Fri Feb 04, 2005 5:02 am

guess i was right after all..

oh the irony

hahahahha

http://www.telusmobility.com/mb/mike/index.shtml

so much for me being made out ot be a fool eh?

VE3TUH
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clearnet

Postby VE3TUH » Fri Feb 04, 2005 5:28 am

Well, not only that, but when Clearnet started here around 15 years ago, they where using Johnson LTR radios, exclusively, I think. We sold and installed many. I think that they may have eventually loaded Motorola radios on their system too, but that was after I left Toronto, and I just didnt keep up with the latest and greatest happenings with Clearnet. I guess that as pointed out, they are now the MIKE system, but this system is not yet active in the area that I live, though I understand that they are in a continual expansion mode and I may see then here someday

Randy.

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Postby RKG » Fri Feb 04, 2005 5:36 am

Chiefhal3: I wouldn't modify the radar unit. You might be altering the unit to be outside of its type acceptance specs, but more importantly you would likely invalidate the radar unit's data for use in speeding infraction prosecutions.

By definition, if the radar detects a return from an object that is in motion, the frequency of the return signal will be different from the frequency of the sent signal. The unit extracts the difference (or beat frequency) and is calibrated to correlate the beat frequency to the speed (signed for moving toward or moving away) of the reflection target.

When last I knew anything about these units (which I admit was quite a while ago) there were two protective routines for eliminating spurious readouts triggered by non-related but detected RF. The first is in the software: if the calculated target speed is above a certain value (for instance, 150 mph), the unit assumes that the reading is invalid because no car is likely to be going that fast. (Also, if within a given time window the unit makes multiple but different calculations because of frequency shift in the return signal, such as might be caused by multipathing or multliple targets in the beamwidth, the unit reports a false.) The second is a broadband RF detector, which, if triggered by a signal high enough in detected field strength, could alter the response of the detector's primary receiver, and so the unit is programmed to display a "false" or "unreliable" indication. If you disable the latter and it comes out in court, the court will throw out the complaint.

The fact that you have to be careful with unrelated emissions while operating equipment that is sensitive to near field RF is not new. It is an issue with Lo-Jack and other beacon-based radiolocation devices. In some cases, officers OPs call for turning off the cruiser radio and/or his personal PD portable. An OP that calls for turning off a personal Nextel is not at all unreasonable.

chiefhal3
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Postby chiefhal3 » Fri Feb 04, 2005 5:53 am

Here is the email I got from Kuston Signals. I don't know what I am going to do yet but I would think that if doing this was a problem the tech at Kustom Signals wouldn't have suggested this. I am going to continue my research before doing anything.

Kustom Signals email -

The unit shows RFI because a Nextel is also a two way radio. You can remove the RFI antenna in the power cable from the CPU board in the eagle by opening the unit and cutting either the green or white wire coming from the power cable. The color depends on how old the unit is. If you have any questions please let me know either by e-mail or phone at 800-835-xxxx.

Regards,

Sxxxx Fxxxxxxxx
Support Specialist/RADAR
mailto:sfxxxxxxxx@kustomsignals.com

Want to be a PREFERRED KUSTOMER?
Visit our website at http://www.kustomsignals.com to sign up!
"Once man has hunted armed man and liked it there is no other hunt like it."

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Postby RKG » Fri Feb 04, 2005 9:06 am

Kustom doesn't have to get grilled on the witness stand.

I stand by my advice.

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Postby RadioSouth » Fri Feb 04, 2005 9:32 am

This Kustoms guy is bad news. Radar is only recognized as a scientifically reliable instrument because it had been demonstrated as such to the courts satisfaction. This RF detect feature was likely demonstrated as part of getting it's initial approval. Take this away and recognition of the technology could collapse as easy as it came about.
On a side note some jurisdications to this day still do not recognize the reliability of 'moving radar' (patrol vehicle in motion). Basically it really only requires one additional step to be reliable and that's comparing the patrols odometer to the patrol speed window on the radar panel just to be sure the patrol reading isn't being skewed by other influences which would alter the target reading as the patrol speed is automatically added to or subtracted from the target speed in moving mode. Moral of story is that radar isn't a given, it's a fragile acceptance and could easily be knocked down by such advise as given by that Kustoms E-Mail.

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Postby PETNRDX » Fri Feb 04, 2005 11:55 am

I assume that your radar units must be "calibrated" by a contractor, etc. periodically. We had to do ours monthly.
Making ANY change (even replacing the cig lighter plug end) can be construed to be "tampering".
Check with the contractor that does the calibrations.
I have found them to be VERY knowledgeable about the local laws and policies, as they are the ones that have to go on the witness stand regarding the units.
Think of it as being the same as the BAC Verifier DATAMASTER, you can't disable the RFI sensor on that or the old BAC.
You might have to use a car kit to get the RF away from the radar unit.
And I also have to kinda second the rant about Nextel and the 800 interference.
It is very ironic that Public Safety is relying so much on Nextel when it is also the cause of so much (unintentional) interference.
I guess its too bad that the Nextels are such a good product for that application.

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RADAR noise.

Postby Cowthief » Sat Feb 05, 2005 6:08 pm

Hello.

I have trouble with NextHell on my RADAR.
If I set the handset on top of the display I will see little track marks on the screen.
This in not mounted in a boat.
This is not mounted in a police car.
This is a military RADAR, mounted in a truck.
So, if the NextHell can give a military radio trouble, it can sure rip into a police doppler unit.
Most police RADAR now operate in the "K" or "Ka" band, and not the older "X" band.
The RF sens line is there due to the fact that doppler RADAR that makes use of gunn diodes has a VERY large bandspread.
I can set the pip rate of my RADAR to make ANY police RADAR read whatever speed I want,(gunn diode units).
Without the RF sense, there is no warning this is happening.
You can do nothing to stop this, and the range of this can be easily be miles.
Both the FCC in the US and IC in Canada are aware of this.

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muggsy09
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Postby muggsy09 » Sun Feb 20, 2005 3:19 am

I have had those types of interferance too. When I'm talking on my nextel and a call comes in over the 2-way mobile in my cruiser the radio speaker sounds like a helecopter is landing in the car I can't even hear dispatch. Damn nextel.


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