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[K1KIM]

According to ARRL the minimum safe distance from a 5 dBi gain antenna radiating 80 W at 146 MHz is 12 feet.

Is it safe to assume that this measurement is if you are standing along side the mobile antenna and not in the passenger compartment directly 6" below the antenna mount?

I've already lost enough hair, and the Covid-19 vaccine has already rearranged my RNA. HiHi.

[K1VSK]

what does it say about your cell phone 2 mm from brain tissue?

[W4MDP]

There are many factors to consider when concerned about RF exposure.  For example: is it a rooftop antenna or trunk mounted or possibly window mounted antenna.  For roof mounted, inside the car you are pretty much isolated from RF because of the metal roof.  In addition the amount of rf radiated down from the end of a vertical is also minimal.  There is another key piece of information which is the continuous exposure time.  RF exposure is not considered to be cumulative.  It is a heating effect.  a normal PTT use of a microphone will only exposure your for the few seconds you are talking  so keep it brief.  The sensitivity of the human body to RF is, unfortunately, in the VHF band.

The FCC has a publication available in very plain language.  It is call An elected Official's Guide to RF Exposure.  I teach classes on this topic to lots of government types.  One of my illustrations has a police officer leaning on the roof of his car while calling in.  All of the criical distances are shown as is the amount of exposure he is getting at both VHF an UHF frequencies.

73
Mark

[G4AON]

Another factor to consider is the potential to interfere with the vehicle electronics (and an insurance issue in the case of an accident).

With increasing sophistication and greater use of plastic, modern vehicles are at risk of malfunctioning in the presence of strong RF fields.

I used to work in the mobile radio industry and in the UK there were strict guidelines on the safe installation of radio equipment and post installation testing. In the case of police vehicle installations, there were vehicle specific instructions detailing antenna locations and cable routing that had been tested for that model of vehicle. I have encountered vehicles where the engine cut out when you transmit, although modern vehicles appear to be more immune to RF than some older models, probably due to more thorough EMI testing and hoped for sales to emergency services and taxi fleet operators.

Note also that some vehicle manufacturers specifically state the maximum power levels for a mobile radio installation. In the case of Seat (a VW group manufacturer), the level is only 10 Watts at the aerial base, although it does state in the handbook that an official Seat service workshop will be able to advise on the use of higher transmitting power.

73 Dave

[K1KIM]

Another factor to consider is the potential to interfere with the vehicle electronics (and an insurance issue in the case of an accident).

With increasing sophistication and greater use of plastic, modern vehicles are at risk of malfunctioning in the presence of strong RF fields.

I used to work in the mobile radio industry and in the UK there were strict guidelines on the safe installation of radio equipment and post installation testing. In the case of police vehicle installations, there were vehicle specific instructions detailing antenna locations and cable routing that had been tested for that model of vehicle. I have encountered vehicles where the engine cut out when you transmit, although modern vehicles appear to be more immune to RF than some older models, probably due to more thorough EMI testing and hoped for sales to emergency services and taxi fleet operators.

Note also that some vehicle manufacturers specifically state the maximum power levels for a mobile radio installation. In the case of Seat (a VW group manufacturer), the level is only 10 Watts at the aerial base, although it does state in the handbook that an official Seat service workshop will be able to advise on the use of higher transmitting power.

73 Dave

It's in an older truck with very little if any computerized ECU etc. The effect to the vehicle is none.

The intent is to mount the antenna, as mentioned, directly above my head on the roof. As expected, the radiation off the ends (or base in this case) is minimal.

I'll test it with my RF meter inside the cab after I install it completely.

[K6CPO]

According to ARRL the minimum safe distance from a 5 dBi gain antenna radiating 80 W at 146 MHz is 12 feet.

Is it safe to assume that this measurement is if you are standing along side the mobile antenna and not in the passenger compartment directly 6" below the antenna mount?

I've already lost enough hair, and the Covid-19 vaccine has already rearranged my RNA. HiHi.

Plugging those figures into the exposure calculator on the ARRL website gives exposure limits of 6.8 feet in a controlled environment and 9.6 feet in an uncontrolled environment. And it's even less if ground reflections are not considered.

I suspect that big chunk of sheet metal between the antenna and the occupants of the vehicle will have an effect on how much RF is present in the vehicle. 

I'm going to have to run some tests on the pattern of my own mobile installation.

[WA2EIO]

So, basically, any mobile operation from a conventional car/SUV will now be problematic unless operating QRPp!

[K1KIM]

According to ARRL the minimum safe distance from a 5 dBi gain antenna radiating 80 W at 146 MHz is 12 feet.

Is it safe to assume that this measurement is if you are standing along side the mobile antenna and not in the passenger compartment directly 6" below the antenna mount?

I've already lost enough hair, and the Covid-19 vaccine has already rearranged my RNA. HiHi.

Plugging those figures into the exposure calculator on the ARRL website gives exposure limits of 6.8 feet in a controlled environment and 9.6 feet in an uncontrolled environment. And it's even less if ground reflections are not considered.

I suspect that big chunk of sheet metal between the antenna and the occupants of the vehicle will have an effect on how much RF is present in the vehicle. 

I'm going to have to run some tests on the pattern of my own mobile installation.

Uncontrolled is 12.16 feet. It's a 5 dBi antenna

[K6CPO]

According to ARRL the minimum safe distance from a 5 dBi gain antenna radiating 80 W at 146 MHz is 12 feet.

Is it safe to assume that this measurement is if you are standing along side the mobile antenna and not in the passenger compartment directly 6" below the antenna mount?

I've already lost enough hair, and the Covid-19 vaccine has already rearranged my RNA. HiHi.

Plugging those figures into the exposure calculator on the ARRL website gives exposure limits of 6.8 feet in a controlled environment and 9.6 feet in an uncontrolled environment. And it's even less if ground reflections are not considered.

I suspect that big chunk of sheet metal between the antenna and the occupants of the vehicle will have an effect on how much RF is present in the vehicle. 

I'm going to have to run some tests on the pattern of my own mobile installation.

Uncontrolled is 12.16 feet. It's a 5 dBi antenna

Obviously, you're using different parameters than I am.  This is what I used.

Power at antenna: 80W
Mode Duty Cycle: FM (duty cycle=100%)
Transmit Duty Cycle: transmit for 5 minutes then receive for 10 minutes
Antenna gain:5 dBi
Operating Frequency(MHz): 146

Including effects for ground reflections (unchecking this parameter will reduce the minimum safe distance.)

It still comes out to 6.7991 feet in a controlled environment and 9.6154 feet in a non-controlled environment.

What parameters did you use that are different?

[N8AUC]

I suspect that big chunk of sheet metal between the antenna and the occupants of the vehicle will have an effect on how much RF is present in the vehicle. 

Intuitively, I'd suspect this is probably an important consideration.

Assuming the antenna is on a metal vehicle roof, and you're inside the vehicle, it seems to me that you're not
very likely to see much exposure, because you're not within the radiation pattern of the antenna.
Consider a 1/4 wave antenna over a solid metal ground plane, and you're beneath the ground plane.

Now if that antenna is on the trunk lid, or on the side of the vehicle hood, and there's nothing but glass between
you and the radiating element, I would expect much greater exposure in that case. Because in that scenario,
you're directly in the radiation pattern of the antenna.

The calculator is great, but at some point you'd hope some common sense comes into play.

[K1KIM]

According to ARRL the minimum safe distance from a 5 dBi gain antenna radiating 80 W at 146 MHz is 12 feet.

Is it safe to assume that this measurement is if you are standing along side the mobile antenna and not in the passenger compartment directly 6" below the antenna mount?

I've already lost enough hair, and the Covid-19 vaccine has already rearranged my RNA. HiHi.

Plugging those figures into the exposure calculator on the ARRL website gives exposure limits of 6.8 feet in a controlled environment and 9.6 feet in an uncontrolled environment. And it's even less if ground reflections are not considered.

I suspect that big chunk of sheet metal between the antenna and the occupants of the vehicle will have an effect on how much RF is present in the vehicle. 

I'm going to have to run some tests on the pattern of my own mobile installation.

Uncontrolled is 12.16 feet. It's a 5 dBi antenna

Obviously, you're using different parameters than I am.  This is what I used.

Power at antenna: 80W
Mode Duty Cycle: FM (duty cycle=100%)
Transmit Duty Cycle: transmit for 5 minutes then receive for 10 minutes
Antenna gain:5 dBi
Operating Frequency(MHz): 146

Including effects for ground reflections (unchecking this parameter will reduce the minimum safe distance.)

It still comes out to 6.7991 feet in a controlled environment and 9.6154 feet in a non-controlled environment.

What parameters did you use that are different?

I'm not that long winded.  I used 2 min/ 2 min. 

[K6CPO]

According to ARRL the minimum safe distance from a 5 dBi gain antenna radiating 80 W at 146 MHz is 12 feet.

Is it safe to assume that this measurement is if you are standing along side the mobile antenna and not in the passenger compartment directly 6" below the antenna mount?

I've already lost enough hair, and the Covid-19 vaccine has already rearranged my RNA. HiHi.

Plugging those figures into the exposure calculator on the ARRL website gives exposure limits of 6.8 feet in a controlled environment and 9.6 feet in an uncontrolled environment. And it's even less if ground reflections are not considered.

I suspect that big chunk of sheet metal between the antenna and the occupants of the vehicle will have an effect on how much RF is present in the vehicle. 

I'm going to have to run some tests on the pattern of my own mobile installation.

Uncontrolled is 12.16 feet. It's a 5 dBi antenna

Obviously, you're using different parameters than I am.  This is what I used.

Power at antenna: 80W
Mode Duty Cycle: FM (duty cycle=100%)
Transmit Duty Cycle: transmit for 5 minutes then receive for 10 minutes
Antenna gain:5 dBi
Operating Frequency(MHz): 146

Including effects for ground reflections (unchecking this parameter will reduce the minimum safe distance.)

It still comes out to 6.7991 feet in a controlled environment and 9.6154 feet in a non-controlled environment.

What parameters did you use that are different?

I'm not that long winded.  I used 2 min/ 2 min. 

OK... That matches with the results you reported in your post.  Again, being inside the vehicle is going to have a major effect on the exposure.  I have a simple field strength meter and I plan on making some comparison tests between the inside and outside of my truck. My truck is also an older one (23 year old Dodge) and the antenna is mounted very close to the center of the cab roof.  My radio is only 50 watts, however.

[W9FIB]

I suspect that big chunk of sheet metal between the antenna and the occupants of the vehicle will have an effect on how much RF is present in the vehicle. 

The calculator is great, but at some point you'd hope some common sense comes into play.

Common sense got pushed aside by apps. Unless an app says its ok, you shouldn't do it. And to think the human race survived so many years without apps. Astonishing!

[K1KIM]

OK... That matches with the results you reported in your post.  Again, being inside the vehicle is going to have a major effect on the exposure.  I have a simple field strength meter and I plan on making some comparison tests between the inside and outside of my truck. My truck is also an older one (23 year old Dodge) and the antenna is mounted very close to the center of the cab roof.  My radio is only 50 watts, however.

Please let us know.

Funny.....the truck I am referring to is my 23 year old 1998 1/2  Dodge Ram 2500 5.9 Cummins.
It's in Mint condition with only 77k miles.

[K6CPO]

OK... That matches with the results you reported in your post.  Again, being inside the vehicle is going to have a major effect on the exposure.  I have a simple field strength meter and I plan on making some comparison tests between the inside and outside of my truck. My truck is also an older one (23 year old Dodge) and the antenna is mounted very close to the center of the cab roof.  My radio is only 50 watts, however.

Please let us know.

Funny.....the truck I am referring to is my 23 year old 1998 1/2  Dodge Ram 2500 5.9 Cummins.
It's in Mint condition with only 77k miles.

Mine is a 1998 Dakota Sport.  It's got about 158K on it, which is pretty low for its age.  It looks like crap as the clear coat is gone but it still runs well with minimal maintenance.  It has the 318 V8 engine, which I've heard are pretty bulletproof.