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Dual FRS/GMRS radio wattages?

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cpsTN

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Before anyone goes kaboom on me, let me tell you that I know that you need a license to operate legally on the GMRS freqs and of the 22 channels of these little radios, only channels 8-14 are FRS ONLY; that channels 15-22 are GMRS ONLY and channels 1-7 can be shared if the GMRS has the 500mw output only.

This is my question: According to the rules, you can use GMRS on channels 1-7 if they output 500mw or less, as do the FRS channels 8-14. The manual says nothing about the output of the radio, but by deduction can I assume that the GMRS ONLY channels of 15-22 have an output of 5w (5 watts, not milliwatts), which I hear is fairly standard for common GMRS radios (but can legally output up to 50w! Is my assumption here true or are all of the 22 channels outputting only 500mw, do you think? The radios are Uniden model GMR638-2CK. Thank You for you time.
 

SkipSanders

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The typical bubblepack FRS/GMRS radios have actual ERP's of no more than 2 watts, in general.

Often as little a 1 watt, or 1.5 watts.

A 5 watt unit would drain the battery in 3 hours or less.
 

slicerwizard

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by deduction can I assume that the GMRS ONLY channels of 15-22 have an output of 5w (5 watts, not milliwatts)
The radios run on 4 AAA batteries. Let's assume that for 5 watts of RF, you'd need 7 to 10 watts of DC power in. That's a 1500 to 2100 milliamp draw out of 700mAh cells. So 10 or 15 minutes of talk time? Maybe less. And how does all that heat get out with that cheap plastic case? Where's the metal heatsink to free air interface?

That's how you deduce... :)
 
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N_Jay

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If they don't say, they may be the same power on all channels.
 

cpsTN

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The radios run on 4 AAA batteries. Let's assume that for 5 watts of RF, you'd need 7 to 10 watts of DC power in. That's a 1500 to 2100 milliamp draw out of 700mAh cells. So 10 or 15 minutes of talk time? Maybe less. And how does all that heat get out with that cheap plastic case? Where's the metal heatsink to free air interface?

That's how you deduce... :)
I hadn't considered the power versus heat situation. It's one of those "V8 moments"! I really need to start thinking. a 4.8v, 700ma battery pack is not going to do a lot for transmission, it is? :)
 
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cpsTN

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If they don't say, they may be the same power on all channels.
I was thinking that also, because why would they give me more channels if I am not supposed to be using all of them. If they kept the wattage down on the other channels, using them would be no big deal. It can't really be marketing. It's not like I am going to run out and pay more for the same radios if they have 8 more channels on them. What made me wonder in the first place, when I am not on the FRS ONLY channels, the icon shows a solid radio with more radio "waves" emminating from the icon than are present with one the FRS ONLY channels, which shows a hollow radio.
 

hertzian

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If you have the FCC ID of the product, you might be able to search it, and look at the technical specs:

OET -- FCC ID Search

You might find that your radio is under .5 watts no matter what. Or you may find it above .5 watts on the gmrs channels meaning that you must get a license to operate at that power level on CH 1-7. CH 15-22 are gmrs-license mandatory.

Regardless of power output, you must be licensed for GMRS to use ch 15-22. Thing is, you run the risk of being clobbered by a repeater output if you are running simplex talkaround on those channels anyway.

I guess the marketing is that these radios are being sold to two types of users - unlicensed FRS, and licensed GMRS users that may want something simple / disposable at the lake. Nothing like dropping one of your Moto Sabers overboard. I might jump. For an frs/gmrs bubblepack overboard, I'd watch it sink. :)

Seriously, the link above will help you determine the level if it isn't stated, and keep you legal.
 

gewecke

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The only channels that are limited to 500mw. are 8-14 or the 467 mhz. channels,regardless of the manufacturer.
n9zas
 

UPMan

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If you have the FCC ID number for any particular radio, you can read the full RF emissions report on the FCC's web site (https://fjallfoss.fcc.gov/oetcf/eas/reports/GenericSearch.cfm).

As has been said, 8-14 are no more than .5W ERP (usually a tad less) and the other channels are typically 2W ERP or less (some manufacturers claim 5W, but that is conductive power...or power being pulled from the batteries; actual emitted power is less than 2W even on those).

Another consideration for high current draw from AAA batteries (besides heat and battery life) is that the internal resistance of the cells would result in a very large voltage drop during transmit, which would likely prevent good modulation control (and could show immediate low voltage even on a new pack).
 

hertzian

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Ah, so perhaps AA non-rechargeable lithiums might be the way to go in this application, unless there are safety / and or manufacturer warnings against it?
 

hertzian

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Thing is, isn't the ERP the REAL limitation for FRS, and not the power of the amplifier itself ?

(Although the real way to do it is not to raise power, but to find a better location / hot spot for what you already have! Higher power is just a battery-eater for the most part)

I believe that if you operate the typical bubblepack with hi power and a non-removable inefficient rubber duck on CH 1-7, you are going to be under the ERP limit anyway - especially so with a half-dead battery pack!

I read the the old PRSG comments and the FCC NPRM from way back (I think we've all read it at one point or another) and I had forgotten about erp.

FRS Rules

Basically stating that Motorola wanted stricter tech standards such as narrowband, limited modulation, non-removable antennas and power measured in ERP and not at the antenna itself. *THIS* was where the FCC decided how it was going to administer / enforce rules - by tech standards mainly - but that's another discussion.

I take it to mean in this case, ERP refers to the measurement of 500 milliwatts applied to a half-wave dipole.

Had this NOT been specified as ERP, I think manufacturers would have jumped all over putting out 1/2 watt units attached to very high-gain non-removable antennas. You can imagine the chaos of having a 10db-gain "non-removable" antenna attached to an FRS radio.

Maybe this was actually a good thing to specify ERP!
 
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