Lights Out...

petenice

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I'm posting this as a caution to anyone driving with a radar detector and VHF/UHF radio. As you can see in the videos (which I shot to replicate a real-world event that I didn't capture at the time), RF from a handheld VHF/UHF radio can seriously interfere with the operation of the detector, potentially rendering it completely unconscious. If this happened while traveling and it wasn't immediately noticed, you'd be unaware of a threat until it was way too late.

In this case, the radio is a 2M/440 handheld Baofeng UV-5RA set at 5W transmit power and tuned in the 440MHz range. When I inadvertently keyed the remote mic trying to grab it for use, the brief burst of RF delivered an instant knockout blow to the R3. It didn't help that the antenna was in contact with the detector's power cord at the time. Even with the radio just in close proximity to the Uniden, the effect was the same.

I blame myself for sloppy operating and not paying attention to the potential for RFI from a familiar device. Nevertheless, it was a lesson learned that I wanted to share with the community that might save someone some grief.

As a side note, I also did some testing with the same radio in the 144MHz range, and while it didn't power off the RD, it repeatedly induced X-band falses. I also tried the same experiments with a GMRS handheld at work. That radio (at around 440MHz and 4W) put the R3 right to bed as well.

If I had a CB to work with I'd test that, too, but maybe someone else can look into it.

Finally, I'd note that prior to shooting the videos with the ham radio, I selected an unoccupied simplex frequency, transmitted my call sign and stated I was testing. I cleared the channel upon completion of filming.

https://youtu.be/3jqmU8-zS6M

https://youtu.be/vdwwNvXsJzU
 

a5owner

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So finally I see why all these HAM guys get very angry about using 'shitty leaky out of tune beofeng's' this must cause the same sort of havoc on their radios....
 

petenice

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So finally I see why all these HAM guys get very angry about using '$#@!ty leaky out of tune beofeng's' this must cause the same sort of havoc on their radios....
Ha! I've heard the same, but the radio is actually pretty decent for the money and the fault was all mine for not operating properly.
 

a5owner

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I still cant believe it shut the thing down! Set off a false alert or cause some weird interference i could see but.... this must be some sort of protection in the power circuit if it gets too much interference and dirty power maybe?
 

petenice

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I still cant believe it shut the thing down! Set off a false alert or cause some weird interference i could see but.... this must be some sort of protection in the power circuit if it gets too much interference and dirty power maybe?
That's what I was thinking, but it may also have been an EMP-like effect that triggered what looked to the circuit like a power switch input. Either way, it's not designed to be exposed to that kind of RF energy and I should have been more careful.
 

RobK

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Wow thanks! I'll have to try this with my Yaesu as well. I keep saying shielding.

This has a similar theme to the range reduction thread with cell phones.

This makes me wonder where the RF is leaking in. Power cord or directly into the circuit.

So I wonder if it is still interfered with if my antenna is outside the vehicle considering the vehicle is the ground plane.

'73
 
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5port

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Wrap power cord around a torroid choke. I get about 3 turns on the choke before the connector will not go thru. I do this with my LRD-950.
Now that I've seen this I will deff continue wih the choke when I get my R3. Thanks.
 
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Token

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So finally I see why all these HAM guys get very angry about using '$#@!ty leaky out of tune beofeng's' this must cause the same sort of havoc on their radios....
I am not a fan of the cheap Chinese radios (I am not claiming they don't work, in general I just don't like them, but there is no denying their value), however there is a very good possibility that this has nothing to do with the brand of radio or how leaky they might be.

The fact is many types of electronics will respond to high level RF fields. Often they just are not designed for you to key up a 5 Watt transmitter a few inches away, or even in contact with, them or any device attached to them.

Lets assume that handheld is 5 Watts, and the antenna gain is 0 dBi, or unity gain. At 6 inches the power density on the radar detector is about 17.1 Watts per square meter (roughly, since this is still near field it is hard to do an accurate calculation). At 2 feet it is down to about 1 Watt per square meter. You see that the power density falls off very quickly, and the maker probably never measured the response of the detector or designed it for operation in such a high level field.

There are many different ways that electronics responds to high EM fields, so the exact mechanism happening here would be hard to pin down. At the most simple level it might just be that all that RF raises the data line that controls the power on/off above its trigger threshold. And if something like that is involved then the brand of the transmitter, or its build quality, just does not matter.

By the way, just to put things in perspective, that roughly 17.1 Watts per square meter number from the 5 Watt handheld at 6 inches? That is roughly the same power level you get from a 50,000 Watt transmitter with a unity gain antenna at 50 feet. Most people would not hang out 50 feet from a 50 kW broadcast antenna, think about that the next time you key up your 5 Watt handheld 6 inches from your brain.

And that last point brings us to another good reason to at least loosely adhere to Part 97.313(a) "An amateur station must use the minimum transmitter power necessary to carry out the desired communications".

T!
 
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mikeoxlong

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The Baofeng radios are notorious for spurious emissions. Basically you get what you pay for.

However, exposing a radar detector or any other electronic device to a high amount of rf from any transmitter will likely cause the effects shown.

I've even seen a 6 GHz microwave radio get confused with an old tdma cellphone operating near by.
 

RobK

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So I tested this at home with my Beofeng UV-5RE connected to my Alinco power supply. It seems the RF comes in through the radar horn. Holding the coiled cord to the antenna has no effect but when the 5RE antenna is in front, right on top or below, it does power off but it has to be really close.

Sent from my LG-H831 using Tapatalk
 

wirelessandy

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Not surprised. After all, the Uniden was designed to DETECT faint signals.
 

5port

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Starting to wonder if the shutdown is a design feature to protect the front end in the presence of strong RF fields.
 

FWGuy

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Guys -

Stop doing this to your RD's! You could be damaging them...maybe not totally killing them but weakening them.

I don't know the mechanism but because detector's are designed to work in automobiles, they've got some protection circuitry on the power input lines. An Automotive environment is very noisy and the designers (hopefully) put protection circuitry on the 12v line powering the detector.

I did see the post above where someone got his detector to shut off by keying the radio near the horn and not near the power cord. I was going to guess that some RF energy was conducted in through the power cable and maybe activated some over-voltage protection. I'm less inclined to suggest this after seeing the post from the user who had to key the radio near his horn to trigger a shutdown.

But stop doing this to your RD's!!

Dan
 

RobK

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Guys -

Stop doing this to your RD's! You could be damaging them...maybe not totally killing them but weakening them.

I don't know the mechanism but because detector's are designed to work in automobiles, they've got some protection circuitry on the power input lines. An Automotive environment is very noisy and the designers (hopefully) put protection circuitry on the 12v line powering the detector.

I did see the post above where someone got his detector to shut off by keying the radio near the horn and not near the power cord. I was going to guess that some RF energy was conducted in through the power cable and maybe activated some over-voltage protection. I'm less inclined to suggest this after seeing the post from the user who had to key the radio near his horn to trigger a shutdown.

But stop doing this to your RD's!!

Dan
Thank you. However, this would be no different than with a fender mount dual band antenna and the detector on the driver side visor running 5 to 50 watts either on 144 or 440 MHz. I agree this is an extreme test and can confirm at 5 watts you need to be close to the horn, top or bottom as the display side doesn't work but with a 5db gain 1/4 wave antenna running at 50 watts, it would be no different.

The question is, is the Uniden shutting down due to being over driven or is it shutting down to voltage induction on the power off circuit.

Not sure how many Ham guys are on here but the antenna mount and detector placement scenario above is quite common.

And yes, on Ham transmitters the finals can be blown from overdriving and is no different in the detectors receive circuitry.

Max caution here!

Sent from my LG-H831 using Tapatalk
 

petenice

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Thank you. However, this would be no different than with a fender mount dual band antenna and the detector on the driver side visor running 5 to 50 watts either on 144 or 440 MHz. I agree this is an extreme test and can confirm at 5 watts you need to be close to the horn, top or bottom as the display side doesn't work but with a 5db gain 1/4 wave antenna running at 50 watts, it would be no different.

The question is, is the Uniden shutting down due to being over driven or is it shutting down to voltage induction on the power off circuit.

Not sure how many Ham guys are on here but the antenna mount and detector placement scenario above is quite common.

And yes, on Ham transmitters the finals can be blown from overdriving and is no different in the detectors receive circuitry.

Max caution here!

Sent from my LG-H831 using Tapatalk
Agreed. And FWIW, I induced shut downs on my detector with the rubber duck just over the top of the R3, closer to the display than the horn. I think the induction theory is a good possibility.

Posted from my Pixel using the RDF Mobile App!
 

Doppler

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R1/R3 also have reports of reduced range because people dashmount their cell phones. V1 and the original Redlines had magnesium cases for a reason, Uniden saved some money going with plastic case and riveting the horn instead of using screws; the plastic case seems to have the draw back of being extremely susceptible to RF. I can have a center mounted V1 and put out 50 watts on VHF and UHF ~6 ft directly behind the RD and not have an issue and only a pane of glass between the two. Inverse square law, and all but 10x the starting power and some gain off the antenna (~3.5 and ~5.something dBi respectively). I seriously do wonder if a simple tin foil wrap might make a difference, just as a simple faraday cage for the RD. That power cord running right near the antenna isn't helping and can pickup the signal and dump it into the RD as well.

This isn't helped by the hit or miss of the Baofeng, but until you test them, there's a few general assumptions on batch, to know if it's actually legal or not in controlling spurious emissions, but it really is case by case with them; and given the other interference the Unidens are having issues with, I'm not pinning this on the HT in this case. But the right harmonic or spurious emission could be what's getting just the right frequency to shut things down.
 

Token

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I can have a center mounted V1 and put out 50 watts on VHF and UHF ~6 ft directly behind the RD and not have an issue and only a pane of glass between the two. Inverse square law, and all but 10x the starting power and some gain off the antenna (~3.5 and ~5.something dBi respectively). I seriously do wonder if a simple tin foil wrap might make a difference, just as a simple faraday cage for the RD. That power cord running right near the antenna isn't helping and can pickup the signal and dump it into the RD as well.

This isn't helped by the hit or miss of the Baofeng, but until you test them, there's a few general assumptions on batch, to know if it's actually legal or not in controlling spurious emissions, but it really is case by case with them; and given the other interference the Unidens are having issues with, I'm not pinning this on the HT in this case. But the right harmonic or spurious emission could be what's getting just the right frequency to shut things down.
50 Watts with 5 dBi of antenna gain and 6 feet from the RD is less than 1/4 the power density at the RD as a 5 Watt HT with 0 dBi at 6 inches. The higher power and antenna gain don't make up for the path loss induced by being 12 times as far away. In your case it amounts to about 4.2 Watts per square meter on the RD, in the close HT case it is more like 17.1 W/m^2.

Certainly it could be shielding, no doubt, but also this case is very fringe, and I am absolutely sure the maker, probably any RD maker, did not design for such high power density levels as a specific design goal. If some are better than others at this power level it is likely a happy coincidence.

These devices are probably designed to function in the same environment the drivers of the car might experience, plus some overhead or engineering fudge factor. The MPE (Maximum Permissible Exposure) for the 2 meter frequency range is 1 mW/cm^2, or 10 W/m^2 for up to 6 minutes per hour. This close HT test is subjecting the RD to power densities of well over the maximum permissible human exposure levels. Why would you design a device that is going to set next to the drivers head that can take much more power than the driver safely can? This would drive production cost up for little real world reason, 99+% of the users would not have an issue with this.

T!

- - - Updated - - -

Thank you. However, this would be no different than with a fender mount dual band antenna and the detector on the driver side visor running 5 to 50 watts either on 144 or 440 MHz. I agree this is an extreme test and can confirm at 5 watts you need to be close to the horn, top or bottom as the display side doesn't work but with a 5db gain 1/4 wave antenna running at 50 watts, it would be no different.
No, this is very different than 50 Watts into a 5 dBi antenna 6 feet away, or even 4 feet away. The power density levels in this 6 inch test are several times as high as would be found in your example.

T!
 
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LeftLaneInPA

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I can't say I'm surprised. I too have a Baofeng UV-5R which I use, usually transmitting around 131.8 MHz. I've learned a long time ago not to do so in close proximity to other electronics. My computer monitor in particular throw a fit when I do so.
 
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petenice

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I can't say I'm surprised. I too have a Baofeng UV-5R which I use, usually transmitting around 131.8 MHz. I've learned a long time ago not to do so in close proximity to other electronics. My computer monitor in particular throw a fit when I do so.
Interesting. Are you using the radio for aircraft communications? Given what I learned from my recent experience with the Baofeng, I'd be especially careful about having one in a cockpit! Combined with the excellent analyses of the issue provided by the folks in this forum (especially Token's detailed breakdown) and some additional research on the Baofengs and spurious emissions, I'm retiring the radio to receive-only duties. I still own the fact that the whole thing started with my lid-like practices in that moment and have to credit the UV5 with lots of other trouble-free miles over the last few years.

If I run into a similar situation with the Yaesu FT-857D, I'll be sure to let everyone know what I find...
 

LeftLaneInPA

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Interesting. Are you using the radio for aircraft communications?
Okay, I had a total senior moment. That's what I get for posting in the middle of the night.

Amateur radio. Our local repeaters are in the 2M band, mostly around 144.920-146.865 MHz. I had "131.8" on the brain because I glanced down at the radio and that's what the PL tone was set as.
 

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