Regs don't list an actual power limit for HTs on the 462/467 main channels

[Photoman5k]

While it limits the TX power on the interstitial channels it does not specifically list HT portables in the 50w limit on the 462 and 467 main channels or specify a limit on the main channels for HTs at all.

So that being the case, why can't a manufacturer make an HT that is capable of transmitting more then 5w on 15-22 and the repeater inputs?

Thoughts?

Quote

§ 95.1767 GMRS transmitting power limits.

This section contains transmitting power limits for GMRS stations. The maximum transmitting power depends on which channels are being used and the type of station.

(a) 462/467 MHz main channels. The limits in this paragraph apply to stations transmitting on any of the 462 MHz main channels or any of the 467 MHz main channels. Each GMRS transmitter type must be capable of operating within the allowable power range. GMRS licensees are responsible for ensuring that their GMRS stations operate in compliance with these limits.

(1) The transmitter output power of mobile, repeater and base stations must not exceed 50 Watts.

(2) The transmitter output power of fixed stations must not exceed 15 Watts.

(b) 462 MHz interstitial channels. The effective radiated power (ERP) of mobile, hand-held portable and base stations transmitting on the 462 MHz interstitial channels must not exceed 5 Watts.

(c) 467 MHz interstitial channels. The effective radiated power (ERP) of hand-held portable units transmitting on the 467 MHz interstitial channels must not exceed 0.5 Watt. Each GMRS transmitter type capable of transmitting on these channels must be designed such that the ERP does not exceed 0.5 Watt.

 

[WRUU653]

8 hours ago, WROZ250 said:

You don't have to like it (or even understand it), it just is. RF engineering 'theory' ratification across decades of radio communications bears that out. 

People didn't just pull this stuff out of their proverbial behinds or, to look 'intelligent'!

Quite frankly, and on a personal note, willful ignorance and, the dismissing people that try to explain it, as being 'a know it all' or, a local favorite here, a 'Sad Ham' is pathetic!

Do yourself a favor and stop listening to the clown who tells you what you want to hear, who plays to your lack of knowledge, and you might just learn something,

Well you seem like a fun guy. Who knew learning could be so fun. "I wouldn't get too excited" only talking about increases of power in watts. If there was somthing good in there I couldn't hear it over the static. I'll take willful ignorance and an 8 watt hand warmer for two hundred Alex. 

[Sshannon]

I suspect a calculation of exposure limits would result in a practical limit, but I don’t know what that would be.  Such calculations are required by the regs.

[MichaelLAX]

You want to transmit 50 watts adjacent to your brain?!?

[WRUU653]

5 hours ago, MichaelLAX said:

You want to transmit 50 watts adjacent to your brain?!?

No.
But his observation does raise an interesting question. I see amateur HT radios at 8 watts. Why not that? I certainly don’t profess to know how much is too much or how that is decided or even if there is a correlation between frequency and acceptable wattage next to one’s melon. 

[WRUU653]

6 hours ago, Sshannon said:

I suspect a calculation of exposure limits would result in a practical limit, but I don’t know what that would be.  Such calculations are required by the regs.

I suspect you are correct here. A little dive into RF exposure evaluation and I have concluded…

 

26 minutes ago, WRUU653 said:

I certainly don’t profess to know how much is too much or how that is decided or even if there is a correlation between frequency and acceptable wattage next to one’s melon. 

These are things I’m okay not understanding.  

[Radioguy7268]

Practicality is the most simple answer. SAR is the more complicated answer.

Battery size and battery life are the limiting factors regarding transmit power. Sure, you can jack  your small hand held portable up to 8 or 10 watts, but how long will your battery last? Does a 10 watt transmitter become a feature or a liability when your battery life is measured in single digit minutes? Nothing holds anyone back from putting a 50 watt mobile into a backpack and strapping it to a 12volt battery, but at that point, you're losing some of the portability. Plus, where are you going to find a ground plane for your 5dB mag mount antenna??

The SAR (Specific Absorption Rate) is more complicated, but basically it's a measure of the amount of Electromagnetic radiation that's being transmitted (and absorbed) near a human body.

SAR measurements for hand held devices (portable radios & cell phones) has been part of the Type Acceptance process with the FCC, but they've also recently taken a more active look at regulating amateur hand held devices:

SAR writeup in 2021 ARRL

Most newer commercial portable radios now carry a tag like this one, limiting the device to being used for "occupational use only" Not sure how long ago those started showing up, but it's only been in the last few years that I've noticed the labels.

[PACNWComms]

25 minutes ago, Radioguy7268 said:

Most newer commercial portable radios now carry a tag like this one, limiting the device to being used for "occupational use only" Not sure how long ago those started showing up, but it's only been in the last few years that I've noticed the labels.

Excellent point. This made me check some of my radio gear, with the XPR6550 radio label on the left and the newer XPR7550e label on the right. Occupational Use to Satisfy FCC RF Exposure Limits. The XPR6550 is considerably older than the XPR7550e in this case, but had the same type of label, whereas the older XTS1500 did not have a label like this. Not shown is also the APX4000 that does have the occupational use label, like the two Motorola Trbo radios, so it might have been ten years or so for this tag to be present (at least for Motorola manufactured radios, do not have any other brand next to me right now to verify). 

[wayoverthere]

5 hours ago, PACNWComms said:

do not have any other brand next to me right now to verify). 

My vertex standard handhelds all display a similar label as well, both the newer dot matrix and older segmented EVXs, the p25 824 and 829, and then straight analog 924.

 

[Sshannon]

So, what does the presence of that label mean to the average Joe Blow?  Does it mean we can be confident that exposure limits are not exceeded?

[PACNWComms]

Many of "my" portable radios used in the professional environment are issued with remote speaker mics, and belt hosters.....so the exposure of RF to the head is minimized, as the radio is further away from a user's head. To me, this means exposure levels for users that operate the radio for work and use it in that regard, police, firefighters, medics and similar users, do not get enough exposure to have FCC RF exposure limits exceeded. It is probably buried deep inside of this link's information somewhere.

https://www.fcc.gov/general/radio-frequency-safety-0

However, I do also often demonstrate that there is power in handheld radios by keying up 800 MHz P25 radios near bathroom paper towel dispensers, where they then dispense paper towels when I key the radio. For office workers using UHF Trbo based radios instead, many Plantronics headsets and earpieces go "off mute" when a Trbo UHF radio is keyed near them. The user may not get a headache, but I do not recommend keying the radio for long periods of time (the Timeout Timer is set to default of 60 seconds) and show that it is a good thing to use a remote speaker mic. They do transmit more than a cell phone, and some users are still scared of those in 2022. 

Occupational use to me means someone who is not using it for a hobby, on a workday basis of 5/5/90 model transmit/receive/standby, five days a week, and 8-12 hours per day. Where a hobbyist may be using it a lot more, or considerably less (depending on how much into the hobby the person is).....I know a lot of people that just listen, and never talk back or radio check anyone. Those types will not get as much exposure. then you have the "rag chewers"......on the other end of the spectrum. If anyone finds out what the FCC really means on this, it would be nice to know the details, I just do not have the patience for digging. 

[WROZ250]

9 hours ago, WRUU653 said:

No.
But his observation does raise an interesting question. I see amateur HT radios at 8 watts. Why not that? I certainly don’t profess to know how much is too much or how that is decided or even if there is a correlation between frequency and acceptable wattage next to one’s melon. 

I wouldn't get too excited when expressing increases of power in Watts. Going from 5 watts to 8 watts (if any of those 8W claims are even accurate), is a relatively small increase in transmitted signal. So when one factors in battery drain/life and heat generation, for example, it's not really a performance enhancement.

Typically, the single most detriment to the performance of any hand held radio, is the antenna.   The vast majority of 'duck' antennas have far more impact on radiated signal than any power out of the PA. Not to mention antenna system loss goes both ways (receive and transmit).  The ubiquitous 'rubber duck antenna on most HTs, is only moderately better a dummy load. Indeed, virtually all 'duck' antennas have losses on the order of several, even tens of dB, when referenced Isotropic dBi  (perfect radiator (theoretical) verse dBd (real dipole).

However, as others have pointed out, the effective radiated power out of any given HT is a balance between the convenience of operating portable and, meeting mandated exposure limits. The latter, in the case of GMRS (UHF) is quite relevant.

That said, were one to hook up an 8W verses a 5W HT to identical (external and proper) antenna systems, most would find very little difference in signal performance.  Again, all other things being equal.


 

[wayoverthere]

1 hour ago, Sshannon said:

So, what does the presence of that label mean to the average Joe Blow?  Does it mean we can be confident that exposure limits are not exceeded?

I had a longer post I'll rewrite later on a computer. In short, i take it as needing to be aware of exposure requirements.

[Coffeemaker]

Increasing 5 watts to 10 watts is +3 dB.  Is that worth it? 

[WRUU653]

38 minutes ago, WROZ250 said:

I wouldn't get too excited when expressing increases of power in Watts. Going from 5 watts to 8 watts (if any of those 8W claims are even accurate), is a relatively small increase in transmitted signal. So when one factors in battery drain/life and heat generation, for example, it's not really a performance enhancement.

Typically, the single most detriment to the performance of any hand held radio, is the antenna.   The vast majority of 'duck' antennas have far more impact on radiated signal than any power out of the PA. Not to mention antenna system loss goes both ways (receive and transmit).  The ubiquitous 'rubber duck antenna on most HTs, is only moderately better a dummy load. Indeed, virtually all 'duck' antennas have losses on the order of several, even tens of dB, when referenced Isotropic dBi  (perfect radiator (theoretical) verse dBd (real dipole).

However, as others have pointed out, the effective radiated power out of any given HT is a balance between the convenience of operating portable and, meeting mandated exposure limits. The latter, in the case of GMRS (UHF) is quite relevant.

That said, were one to hook up an 8W verses a 5W HT to identical (external and proper) antenna systems, most would find very little difference in signal performance.  Again, all other things being equal.


 

I wouldn’t say I was excited about this, it was just a more realistic idea of an increase in wattage than MichaelLAX comment of 50

 

14 hours ago, MichaelLAX said:

You want to transmit 50 watts adjacent to your brain?!?

Granted I get that was a joke.

I agree from 5 to 8 is likely not significant and I agree with all you are saying here. That said people always will be willing to pay for more (because more) I guess if more is allowed than how much more? I’m not saying it should or shouldn’t. I just thought the lack of a stated max presented the idea there could be more and the fact that there are non GMRS HT’s out there that are more, well it would not surprise me to see it at some point in GMRS. Of course there could be factors at play that could prevent it or make it less feasible.  I’m no expert on this, I did stay at a Holiday Inn once. 

[MichaelLAX]

3 hours ago, PACNWComms said:

Many of "my" portable radios used in the professional environment are issued with remote speaker mics, and belt hosters.....

Are you beyond  your child bearing years?

[MichaelLAX]

3 hours ago, WRUU653 said:

Granted I get that was a joke.

Having been a lifelong radio geek, when I leave a joke here, which is quite often, I always put a "" after it, for those of us without any sense of humor! 

After all, he did not seem to limit the suggestion below the 50 watt limit; hence my comments!

I still wouldn't put one of the 10 watt HTs next to my brain or my aging family jewels either (you never know when you might get pressed into action again! )

[wayoverthere]

20 hours ago, wayoverthere said:

I had a longer post I'll rewrite later on a computer. In short, i take it as needing to be aware of exposure requirements.

So...I had a longer post put together on mobile browser, all typed up, used ARRL's RF Exposure calculator, had a screenshot...and the forum said "NOPE!" and deleted the whole thing.

The shorter version is that running the calculation using 5 watts, 33% duty cycle (5 min tx, 10 min rx), at 462.550mhz and 2.1dbi, it spit out a safe distance of just shy of a foot for controlled space (informed operator), and not quite 1.5 ft for uncontrolled (uninformed bystanders), though perhaps 2.1dbi is a little overestimating a rubber ducky. bumping up the power and/or duty cycle pushes the distance out further.  IIRC, when i ran my calculations for my "shack", it was something like 3 ft at 50 watts, controlled, and either 4.5 or 6 uncontrolled, for UHF, and a bit more for VHF.

Based on that, i read that "occupational use" disclaimer as the manufacturers' attempt (even if FCC forced) to ensure the operator is informed of the RF exposure involved, and can adjust their exposure accordingly, whether with less TX time, lower power, or moving the radio away via remote mics. i suspect many of the 5 watt limits came down to balancing allowable exposure with being able to keep a reasonable amount of talk time.

[WRKC935]

On 11/23/2022 at 3:37 PM, Sshannon said:

So, what does the presence of that label mean to the average Joe Blow?  Does it mean we can be confident that exposure limits are not exceeded?

Purely a guess here.  But it would make sense that occupational use would be limited to work activity for 8 or less hours a day, with a small percentage of actual transmit time in that 8 hour period. 

The difference being with 'hobby use' is the guy that in 10 minutes will time out the repeater 2 times and will be well on his way to doing it a third time as the ten minute time passes.  You know, the gas bags that will get on the local ham repeater and seem to never shut up. 

And again, speculating, that the SAR numbers for the radio's rated wattage over time allows it to be used SPARINGLY throughout the work day, but being a gabtastic hammie would possibly exceed the SAR numbers for that power level and exceed the total exposure limit over time.  OF course the sticker is there same as the sticker on your lawn mower to NOT put your fingers under the deck while the mower is running.  And not to use a push mower as a hedge trimmer, and all the rest of the dumb stuff we have warning labels for.  To LIMIT liability.  And while the 'don't be a dumbass' stickers are not gonna keep you from getting sued, they do show some level of effort to inform the user that a danger COULD exist if the product is used in a way that doesn't conform with the design of the product. 

[Blaise]

On 11/23/2022 at 5:32 PM, WROZ250 said:

I wouldn't get too excited when expressing increases of power in Watts. Going from 5 watts to 8 watts (if any of those 8W claims are even accurate), is a relatively small increase in transmitted signal. .... were one to hook up an 8W verses a 5W HT to identical (external and proper) antenna systems, most would find very little difference in signal performance.  Again, all other things being equal.

I really don't understand that this keeps getting repeated over and over in GMRS-land.  I'm new, so maybe I need to be schooled, but I've been reading stacks of antenna resources, and I started out with an engineer's education in fields and waves theory, and I just don't get this point!

According to everything I understand, rf signal strength, all other things being equal, follows the same inverse square law that all electromagnetic fields do.  This means that the distance at which signal strength drops off to unreadable levels increases proportional to the square root of any increase in power.  So on a direct line between two antenna, assuming proportions of open air, obstructions, reflections, etc remain constant, doubling the power of a transmission provides more than 40% more range, quadrupling it provides twice the range, etc.

Now, I can certainly understand providing a caution to new users that range isn't proportional to radiated power, because that's an easy mistake to make that will confuse a lot of newbs, but saying things like "Going from 5 watts to 8 watts is a relatively small increase in transmitted signal" that produces "very little difference in signal performance, all things being equal" when in fact a 60% increase in transmitted power results in more than 25% increased range, all things being equal, seems at best sloppy and at worst disingenuous. 

And people repeating it constantly across an en entire community seems... well, I won't say religious, but at least dogmatically ideological, anyway...

What am I missing?

[Blaise]

On 11/23/2022 at 10:53 PM, MichaelLAX said:

I still wouldn't put one of the 10 watt HTs next to my brain or my aging family jewels

I don't see the problem.  Don't you want to keep them toasty warm?!?!?  I mean, it's not like it's ionizing radiation...

[Sshannon]

4 minutes ago, Blaise said:

I really don't understand that this keeps getting repeated over and over in GMRS-land.  I'm new, so maybe I need to be schooled, but I've been reading stacks of antenna resources, and I started out with an engineer's education in fields and waves theory, and I just don't get this point!

According to everything I understand, rf signal strength, all other things being equal, follows the same inverse square law that all electromagnetic fields do.  This means that the distance at which signal strength drops off to unreadable levels increases proportional to the square root of any increase in power.  So on a direct line between two antenna, assuming proportions of open air, obstructions, reflections, etc remain constant, doubling the power of a transmission provides more than 40% more range, quadrupling it provides twice the range, etc.

Now, I can certainly understand providing a caution to new users that range isn't proportional to radiated power, because that's an easy mistake to make that will confuse a lot of newbs, but saying things like "Going from 5 watts to 8 watts is a relatively small increase in transmitted signal" that produces "very little difference in signal performance, all things being equal" when in fact a 60% increase in transmitted power results in more than 25% increased range, all things being equal, seems at best sloppy and at worst disingenuous. 

And people repeating it constantly across an en entire community seems... well, I won't say religious, but at least dogmatically ideological, anyway...

What am I missing?

You make an interesting point.  Also, many of us who have said “That’s only a 3 dB gain! You probably won’t notice it,”  are the ones who get wound around the axle about a 3dB loss when someone picks a coax type and length with 3dB attenuation. And I’m sure I’ve done it myself.

[KAF6045]

5 minutes ago, Blaise said:

What am I missing?

VHF and UFH are primarily line-of-sight. The signal essentially propagates until it runs into something (trees, horizon, big warehouse).

People use <5W HTs to hit amateur satellites (70+ miles up), so distance isn't really a deterrent.

FCC regulations specify SAR values for RF exposure -- not raw ERP. The permitted SAR varies with frequency.

[WRKC935]

7 hours ago, Blaise said:

I really don't understand that this keeps getting repeated over and over in GMRS-land.  I'm new, so maybe I need to be schooled, but I've been reading stacks of antenna resources, and I started out with an engineer's education in fields and waves theory, and I just don't get this point!

According to everything I understand, rf signal strength, all other things being equal, follows the same inverse square law that all electromagnetic fields do.  This means that the distance at which signal strength drops off to unreadable levels increases proportional to the square root of any increase in power.  So on a direct line between two antenna, assuming proportions of open air, obstructions, reflections, etc remain constant, doubling the power of a transmission provides more than 40% more range, quadrupling it provides twice the range, etc.

Now, I can certainly understand providing a caution to new users that range isn't proportional to radiated power, because that's an easy mistake to make that will confuse a lot of newbs, but saying things like "Going from 5 watts to 8 watts is a relatively small increase in transmitted signal" that produces "very little difference in signal performance, all things being equal" when in fact a 60% increase in transmitted power results in more than 25% increased range, all things being equal, seems at best sloppy and at worst disingenuous. 

And people repeating it constantly across an en entire community seems... well, I won't say religious, but at least dogmatically ideological, anyway...

What am I missing?

It's all going to depend on how you are looking at it.  As you mentioned 5 watts to 8 watts seems like a big increase.  It is 30% more in fact. 

BUT, if you look at it in dBm or field strength at the receive site, then the story is told about how much it's NOT an increase.  Since dB is logarithmic, and that's the easiest way by far to do the actual math (you ever figure path loss from watts to microvolts?) or adding antenna gain and coax loss in volts, watts or whatever before converting to dBm.

And I know the 6dB rule for S-units.  Yes, I quote it since many GMRS guys are EX-CBer's.  But I also know what we use in the commercial field.  And that is dBm for 12dB Sinad measurements, desense testing, receiver full quieting testing and repeater drop out and squelch opening tests.  And the differences for those tests are all in either a dBm level, or a dB difference. 

Now that's established.  Lets discuss a new XPR 5700 repeater.  These are the current offering from Motorola for a midpower (50 watt) repeater.

The standard point in analog wide band squelch opening for these is about -122dBm.  Some are a bit hotter, but that's about the norm.  And that is JUST opening the squelch.  12dB Sinad, which is about a 70 percent signal to noise ratio.  Meaning a 1Kc tone imposed on the carrier with be 70% of the total received signal but STILL 30% noise, is going to occur at about -118dBm or so.  Full quieting isn't there (no noise) until -105 to -95dBm.  So the increase of LESS than 3dB is NOT going to improve a received signal to a great extent.  And even a 6dB increase will not take a signal that is in the noise and bring it to the point it has full capture of the receiver and is full quieting. 

Once you are applying dB and dBm as a specific power level, things come more into focus.  Especially when you are testing receiver performance. 

Oh, and so you have a reference 5 watts is equal to 36.9897dBm  And 8 watts is equal to 39.0309dBm.  And for further reference 50 watts is 46.9897dBm. 

[Sshannon]

Good post, except 8 watts is 60% more power than 5 watts. 
 

[Blaise]

> VHF and UFH are primarily line-of-sight. The signal essentially propagates until it runs into something (trees, horizon, big warehouse).

But the amount of those obstacles that you can propogate through or reflect around still increases with the root of the power increase, right?  I understand that completely blocking a signal is completely blocking a signal, of course, you can't go through mountains etc, but every attenuating material will still allow propogation to *some* depth, so if you increase power it will come out the other side of relatively more stuff than before, no?