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.

 

[Blaise]

4 hours ago, WRKC935 said:

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. 

I'm still not following.   I don't see how representation changes anything.  Just representing field strength in an exponential way doesn't change the power at distance x.  If I decrease your salary by only one order of magnitude, using the number 1 looks a lot smaller than saying I've taken 90% of your pay, but did I take any less?   

If a signal is still "lost in the noise" after a power increase, it would be *less* lost in the noise by the root of the increase in power, meaning the range still increased, you were just still too far away, right?

[BoxCar]

While there is truth to the argument that increased power increases range, I have found that to not always be true in the real world. The range is governed by the antenna height because of the distance to the horizon. UHF doesn't follow the terrain so increased power nets out as increased coverage within the effective coverage area determined by the antenna type and height.

[Blaise]

Oh absolutely, that's fair, stuff gets in the way.  To antennae 6 feet off the ground, the horizon is roughly 3.1 miles away, so the maximum possible range the two of them can communicate at LOS is just over 6 miles, and obstacles between normally make it much less. But the argument rarely comes from that perspective, or at least not until someone pushes back on the "all things being equal" phrase that accompanies the original statement. 

I don't know, it just seems unnecessarily aggressive and not really accurate as generally presented...

 

[SteveShannon]

1 hour ago, Blaise said:

Oh absolutely, that's fair, stuff gets in the way.  To antennae 6 feet off the ground, the horizon is roughly 3.1 miles away, so the maximum possible range the two of them can communicate at LOS is just over 6 miles, and obstacles between normally make it much less. But the argument rarely comes from that perspective, or at least not until someone pushes back on the "all things being equal" phrase that accompanies the original statement. 

I don't know, it just seems unnecessarily aggressive and not really accurate as generally presented...

 

Certainly an increase in transmission power can increase range.  Just listen to the difference between a ham using QRP versus one with a 1500 watt linear amplifier. But it’s usually the least effective and the most expensive thing to try.

On GMRS Few of us ever transmit farther than the range that our power theoretically provides.  Our range is limited (either transmitting or receiving) due to absorption of RF by green plants and metal in everything else, natural blockages due to terrain, or interference from every form of emf that surrounds us.  In a perfect world, transmission power might make a huge difference, but a better receiver, better cabling, and better antenna and antenna placement can have a much greater effect.  

The most important thing is to consider all the components as part of a system.

[WROZ250]

.

[SteveShannon]

2 hours ago, Blaise said:

unnecessarily aggressive

You nailed it. 

[KAF6045]

One other limit on going to high-power on an HT...

HEAT!

Most output transistors emit half the power has heat. A 5W HT battery is maybe supplying 10W during transmit. Jumping to a 10W HT would require a battery pack capable of 20W during transmit -- 10 of which need to go through a heat sink to cool the rest of the circuits. Look at a small mobile rig (15-20W) -- practically the entire housing is a heat sink, and they also often have muffin fans to draw air through the housing.

Do you really want to be holding the equivalent of a 10W incandescent night light while transmitting?

[SteveShannon]

On 11/23/2022 at 3:58 PM, Coffeemaker said:

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

So is going from 25,000 watts to 50,000 watts.

[MichaelLAX]

12 hours ago, Sshannon said:

So is going from 25,000 watts to 50,000 watts.

I have friends that live around the corner from this 50,000 watt AM radio antenna system and have been none to happy about the possible affects on their children's brains!

[SteveShannon]

3 minutes ago, MichaelLAX said:

I have friends that live around the corner from this 50,000 watt AM radio antenna system and have been none to happy about the possible affects on their children's brains!

I can understand their concern.  Is that a phased array?

[MichaelLAX]

20 minutes ago, Sshannon said:

I can understand their concern.  Is that a phased array?

That question is beyond my pay-grade, but historically it was great fun to listen to with a cat's whisker home brew crystal radio (similar to this one):

 

 

 

In my days as a teenager it was KMPC, 710 AM, owned by the legendary Cowboy Singer, Gene Autry.  Now it is an ESPN affiliate, KSPN.

[SteveShannon]

On 11/25/2022 at 7:54 AM, 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?

I am not the person to say you’re missing anything.  I agree that the inverse square law affects RF as you say, but that’s the best case scenario.  In a vacuum, each time you quadruple the power (6 dB gain), you reach twice the distance at the same signal strength. This is assuming that nothing else changes: antenna gain, cable losses, etc. But that’s the theoretical maximum. Practically speaking, by using a Radioddity DB20G that outputs 16 watts, instead of a handheld with a four watt output, you could potentially double the range, if you’re using the same antenna and cable.

I think that when people quickly retort that a 3 dB increase is nothing, they’re wrong, but in their defense, I think that what they’re really saying is the slight difference in range (no more than 41%) is not enough to them to justify doubling the power.

Quadruple it again (another 6dB) and you can now reach four times the original distance, with sixteen times (12 dB) the original power. So, if your power was originally 5 watts, your power is now 80 watts.

But that’s strictly signal strength.  At that greater distance what can happen to compromise the quality of the signal? In the real world, you end up with a lot of things affecting the actual signal quality, including man made interference, effects of multipath, moisture and dust in the air. So that 41% greater distance will always be something less. Each person must decide for themselves what their threshold is for cost/range.

 

[Blaise]

On 11/26/2022 at 11:30 AM, WROZ250 said:

Bottom line, one's inability to understand any of the above does not make it religious or even dogmatic ideology. 

Skirting for a moment that someone else already did the "I wrote twelve paragraphs to explain that if you convert to an exponential scale the numbers look smaller" explanation you just repeated, and I already responded about how it doesn't seem like converting your measurements to an exponential representation to make it look smaller doesn't change the laws of physics, I feel like this was exactly the sort of condescending, knee-jerk response that makes my point.
 

On 11/26/2022 at 11:30 AM, WROZ250 said:

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

I never said they did.  I questioned why they think that constantly regurgitating what appears to be an incorrect, or at least greatly exaggerated, statement is helping anyone, and why they were so aggressive about it.  Like you are, for example.

 

On 11/26/2022 at 11:30 AM, WROZ250 said:

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!

So let me get this straight. 

• I question a statement because a) it always seems to be delivered with an unthinking, nearly religious fervor, and b)it doesn't seem to jibe with the known laws of physics. 
• I then present those physics as I understand them and ask for someone to help explain to me how to square what I know with the statement it seems to contradict.
• You ignore my question almost completely and respond with paragraph after paragraph of dense jargon that seems to boil down to "Decibels are exponential, so the numbers looks smaller", which a) someone else already did without being disrespectful and b) I already responded to.
• You characterize my questioning as pathetic "willful ignorance and dismissing people that try to explain it", in shouty bold text, even though you've done nothing to actually help explain anything.

No, definitely nothing dogmatic or aggressive about that at all....

 

On 11/26/2022 at 11:30 AM, WROZ250 said:

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,

If by "the clown", you mean three different physics professors at a highly respected polytechnic institute who taught "Fields and Waves", "Fields and Waves II", and "Photonics", then I can assure you, my assignment lists alone would make it pretty clear that they very rarely told me anything I wanted to hear.  What is it you think I want to hear, anyway?  I'm really interested to know.  Because it sounds like whatever crazed little story you've made up in your head about it is almost certainly a) wrong, and b) stupid.

 

[Blaise]

1 hour ago, Sshannon said:

I am not the person to say you’re missing anything.  I agree that the inverse square law affects RF as you say, but that’s the best case scenario.  In a vacuum, each time you quadruple the power (6 dB gain), you reach twice the distance at the same signal strength. This is assuming that nothing else changes: antenna gain, cable losses, etc. But that’s the theoretical maximum. Practically speaking, by using a Radioddity DB20G that outputs 16 watts, instead of a handheld with a four watt output, you could potentially double the range, if you’re using the same antenna and cable.

I think that when people quickly retort that a 3 dB increase is nothing, they’re wrong, but in their defense, I think that what they’re really saying is the slight difference in range (no more than 41%) is not enough to them to justify doubling the power.

Quadruple it again (another 6dB) and you can now reach four times the original distance, with sixteen times (12 dB) the original power. So, if your power was originally 5 watts, your power is now 80 watts.

But that’s strictly signal strength.  At that greater distance what can happen to compromise the quality of the signal? In the real world, you end up with a lot of things affecting the actual signal quality, including man made interference, effects of multipath, moisture and dust in the air. So that 41% greater distance will always be something less. Each person must decide for themselves what their threshold is for cost/range.

 

Thank you for making a wonderfully concise, clear, and unnecessary-jargon-free response! 

Yes, I agree that we're talking about ideal case, not practicalities here.  I was just trying to ensure that I wasn't missing something about the actual physics, because this whole em transmission thing is so damned convoluted I rarely know what to expect. 

As far as how consequential a particular increase in range is, maybe I just see it differently.  To me, that "slight" 41% increase in range is pretty significant, especially if the cost of achieving it is paying an extra $12. 

Legal questions aside, managing almost a mile and a half in the woods rather than a mile would seem to be pretty good when you're out hunting or hiking with friends, for example.  Would you get better range by climbing a tree and hanging a $150 dipole antenna for your $40 5W unit, then retrieving it and repeating whenever you need to talk as opposed to just buying an 8W unit? Sure, but how practical a way is that to get better range?  Can you put a 15-plus inch antenna that costs $60 on your $40 HT and do better range-wise than paying $12 for an extra 3W? Sure, but again, between the cost and the inconvenience of trying to walk in dense brush with a 15 inch antenna, it's again not terribly practical. 

I'm not saying power is magic, I'm just questioning why there is such a borderline fanatical aversion to even discussing it...

[SteveShannon]

32 minutes ago, Blaise said:

Thank you for making a wonderfully concise, clear, and unnecessary-jargon-free response! 

Yes, I agree that we're talking about ideal case, not practicalities here.  I was just trying to ensure that I wasn't missing something about the actual physics, because this whole em transmission thing is so damned convoluted I rarely know what to expect. 

As far as how consequential a particular increase in range is, maybe I just see it differently.  To me, that "slight" 41% increase in range is pretty significant, especially if the cost of achieving it is paying an extra $12. 

Legal questions aside, managing almost a mile and a half in the woods rather than a mile would seem to be pretty good when you're out hunting or hiking with friends, for example.  Would you get better range by climbing a tree and hanging a $150 dipole antenna for your $40 5W unit, then retrieving it and repeating whenever you need to talk as opposed to just buying an 8W unit? Sure, but how practical a way is that to get better range?  Can you put a 15-plus inch antenna that costs $60 on your $40 HT and do better range-wise than paying $12 for an extra 3W? Sure, but again, between the cost and the inconvenience of trying to walk in dense brush with a 15 inch antenna, it's again not terribly practical. 

I'm not saying power is magic, I'm just questioning why there is such a borderline fanatical aversion to even discussing it...

Those are good questions that deserve to be tested in the real world.  I sincerely hope you’re a ham as well because to me, that’s where the joy of being a ham emerges. (I’m sorry, I don’t remember if you said you were).

I will say this.  When I mount the ~15” Faux Nagoya (Tidradio 771 that came “free” with a Baofeng UV5R several years ago) on my Alinco DMR radio, and look at the difference in signal report from the 70 cm DMR repeater that’s 16 miles away, the S meter goes up by two S units.  That’s 12 dB. I was completely surprised. Nothing else changed, but the antenna. I don’t have a 70 cm radio other than 5w handhelds to compare. But, using the longer antenna cost me nothing in terms of power usage.  I’m not certain about RF exposure.

And I agree about the bias against adding a few watts of power.  There are obviously those who say 3dB makes no difference, but many times those same people are very critical of others for choosing a coax cable that has 3dB of loss. 3dB is 3dB, regardless of the direction. 

I would never turn down an extra few watts, all other things being equal (features, quality, etc.) iff my power budget supported it, but I wouldn’t trade the features I want, or quality without weighing the benefits.

[SteveShannon]

15 hours ago, Blaise said:

Thank you for making a wonderfully concise, clear, and unnecessary-jargon-free response! 

Yes, I agree that we're talking about ideal case, not practicalities here.  I was just trying to ensure that I wasn't missing something about the actual physics, because this whole em transmission thing is so damned convoluted I rarely know what to expect. 

As far as how consequential a particular increase in range is, maybe I just see it differently.  To me, that "slight" 41% increase in range is pretty significant, especially if the cost of achieving it is paying an extra $12. 

Legal questions aside, managing almost a mile and a half in the woods rather than a mile would seem to be pretty good when you're out hunting or hiking with friends, for example.  Would you get better range by climbing a tree and hanging a $150 dipole antenna for your $40 5W unit, then retrieving it and repeating whenever you need to talk as opposed to just buying an 8W unit? Sure, but how practical a way is that to get better range?  Can you put a 15-plus inch antenna that costs $60 on your $40 HT and do better range-wise than paying $12 for an extra 3W? Sure, but again, between the cost and the inconvenience of trying to walk in dense brush with a 15 inch antenna, it's again not terribly practical. 

I'm not saying power is magic, I'm just questioning why there is such a borderline fanatical aversion to even discussing it...

Here’s a video of a 25 watt hand-held:

 

[PACNWComms]

On 11/23/2022 at 5:27 PM, MichaelLAX said:

Are you beyond  your child bearing years?

That's funny. More like me thinking out loud. Even though I maintain a large radio network, I myself rarely even carry a radio unless I am troubleshooting. Many users are firefighters with speaker mics and holsters.....which would be radiating into the thigh or waistline, great joke. I do have some paranoid security workers too, former cops that had X-band radar on their lap in previous lives.....they think everything will make them sterile. 

[Lscott]

7 hours ago, Sshannon said:

Here’s a video of a 25 watt hand-held:

 

I looked at the video and I failed to notice an FCC ID number on the back. That should be a requirement to legally import the radio to the US. By any chance do you know if there is an FCC ID and what it is?

The reason for asking is the FCC grant will show what power level the radio was tested at and issued the grant for what service(s). I wanted to see if it actually tested at 25 watts (Chinese) and what that ends up in US watts.

[Blaise]

1 hour ago, Lscott said:

I wanted to see if it actually tested at 25 watts (Chinese) and what that ends up in US watts.

China has their own watts!?!?!?

[Lscott]

17 minutes ago, Blaise said:

China has their own watts!?!?!?

It seems that way. Look at a Baofeng that "claims" 18 watts of output. Skip to time mark 8:00 for the power test.

https://www.youtube.com/watch?v=LPM7PsO2McI

 

[SteveShannon]

It’s part 90 certified according to the Notarubicon video I linked and at 421 MHz it tested 24.5 watts. Lower everywhere else. 

[Lscott]

1 hour ago, Sshannon said:

It’s part 90 certified according to the video and at 421 MHz it tested 24.5 watts. Lower everywhere else. 

Time mark 8:17 shows the two test frequencies as 146.520MHz on VHF and 441.000MHz on UHF.

The highest power the guy measured was 4.5 watts on 441.000MHz at time mark 9:05.

I don't know where in that video you saw the test being done at 421MHz with a power output of 24.5 watts. 

[WRUU653]

 

24 minutes ago, Lscott said:

I don't know where in that video you saw the test being done at 421MHz with a power output of 24.5 watts. 

13:10 of notarubicon’s video I believe is what he’s referring too. Why everyone so angry all the time? It’s just radio’s. 

[Lscott]

9 minutes ago, WRUU653 said:

 

13:10 of notarubicon’s video I believe is what he’s referring too. Why everyone so angry all the time? It’s just radio’s. 

Not angry. It wasn't clear to me which video he was referencing. I went back and looked at the one I mentioned to see if I had somehow missed something.

[SteveShannon]

9 minutes ago, Lscott said:

Not angry. It wasn't clear to me which video he was referencing. I went back and looked at the one I mentioned to see if I had somehow missed something.

Sorry, I thought it would be obvious that I was referring to the video I linked rather than one posted by someone else. I’ve edited my post to make it clear.