wattage

[Guest skipper]

Just wondering.....Been reading about the GMRS stuff.  I seem to understand that there is a 5 watt maximum power output for radios.  If so then why do I see a lot of GMRS radios(midland....etc..) have wattages like 30, 40 and 50 watts?

 

Tata...........Skipper

[dugcyn]

licensed GMRS is allowed up to 50 watts. most normally run just enough power to get point a to point b. it is considered courtesy.

[Guest skipper]

I see....Thanks dugcyn for the info and your time.

 

[OffRoaderX]

53 minutes ago, dugcyn said:

most normally run just enough power to get point a to point b. 

This is an assumption or opinion.

Around here we go full-blast all the time.

[BoxCar]

1 hour ago, dugcyn said:

licensed GMRS is allowed up to 50 watts. most normally run just enough power to get point a to point b. it is considered courtesy.

35 minutes ago, OffRoaderX said:

This is an assumption or opinion.

Around here we go full-blast all the time.

And good practice is to only use the amount of power needed to reach the destination. But then, why would you care?

[OffRoaderX]

I understand the reasoning, but this is GMRS - a huge percentage of GMRS users just turn on their radio and start talking with their group - they aren't thinking about power levels or anything else, other than "can my friend hear me" ...

[WRYZ926]

1 hour ago, Guest skipper said:

Just wondering.....Been reading about the GMRS stuff.  I seem to understand that there is a 5 watt maximum power output for radios.  If so then why do I see a lot of GMRS radios(midland....etc..) have wattages like 30, 40 and 50 watts?

To answer your question some more.

Hand held GMRS radios are limited to 5 watts maximum. Mobile GMRS radios are allowed to be up to 50 watts maximum.

[nokones]

The 5 watt limit rule is for the 462 MHz Interstitial channels and the .5 watt applies to the 467 MHz Interstitial channels. The 50 watt limit rule applies to all 462 and 467 MHz main channels and that is 50 watts out of the radio not the ERP from the antenna.

[SteveShannon]

2 hours ago, WRYZ926 said:

To answer your question some more.

Hand held GMRS radios are limited to 5 watts maximum. Mobile GMRS radios are allowed to be up to 50 watts maximum.

No, not by regulation on the main channels. Most handhelds are limited to that but as a practical matter rather than regulations. Kenny is absolutely correct in his post below:

17 minutes ago, nokones said:

The 5 watt limit rule is for the 462 MHz Interstitial channels and the .5 watt applies to the 467 MHz Interstitial channels. The 50 watt limit rule applies to all 462 and 467 MHz main channels and that is 50 watts out of the radio not the ERP from the antenna.

Except for the weird case of Fixed Stations, which are fixed in location and may only communicate to other Fixed Stations - they are limited to 15 watts. 

[WRKC935]

3 minutes ago, nokones said:

The 5 watt limit rule is for the 462 MHz Interstitial channels and the .5 watt applies to the 467 MHz Interstitial channels. The 50 watt limit rule applies to all 462 and 467 MHz main channels and that is 50 watts out of the radio not the ERP from the antenna.

A sort of limited explanation of ERP vs power. 

Where the power or watts measured from a power meter, which is where the 50 watts thing comes in.  There is something called ERP or effective radiated power.  This has to do with antenna gain. 

Gain is typically figured off of an Isotropic radiator, which is really a theoretical antenna that radiates power in all directions evenly.  All directions meaning up, down and every degree of a circle around the radiator at all angles evenly.  It's not an antenna that really exists except on paper as a reference.  To achieve gain in an antenna, the elements are configured in such a way that the power that is radiated up and down is redirected more toward a flat plane horizontal to the center of the vertical radiator (vertical antenna).  Since even basic quarter wave antenna's have some amount of gain over the reference, it's better to consider those as a reference point when trying to figure out performance gain.  But it works like this.  3dB of gain, either from some type of amplifier or an antenna is going to effectively be a doubling of power.  If you consider the 3 dB of gain against the reference antenna, the antenna in question will perform at a level as if the reference antenna had double the power feeding it.  So an antenna with 0dB of gain will talk as far with 100 watts as an antenna with 3dB of gain will talk with 50 watts, as long as you are considering the antenna radiation pattern.  Meaning since the antenna is taking radiation away from the higher and lower angles off the horizontal plane across the center of the antenna, it will talk farther across that plane, but you LOOSE coverage in the higher and lower angles of radiation. 

Yes, this is a difficult topic to really understand.  And not having radiation pattern diagrams posted here make sit harder to see. 

 

All that being said. There is no 'limit' to antenna gain in GMRS.  Part 90 licenses do have a maximum TX power and a maximum ERP.  We luckily are not saddled with a max ERP.  So we can run right up to the 50 watts of maximum power, and if we so desire to get totally crazy, we can legally put up a 20 foot dish and feed that dish with 30 dB of gain with our 50 watts of limited power and have 5000 watts of ERP.  Now there are some safety issues that need addressed with that sort of ERP, and of course, a dish is gonna be pretty tight with the radiation pattern, but it's still technically legal to do it.

As a side note to that.  We are NOT allowed to operate with those antenna gain levels on the 467 interstitial frequencies and I don't believe we can do it on the 462 ones either.  So bear that in mind when getting crazy with an antenna system.

 

[WRYZ926]

14 minutes ago, Sshannon said:

Except for the weird case of Fixed Stations, which are fixed in location and may only communicate to other Fixed Stations - they are limited to 15 watts. 

I forget about the fixed station power restrictions.