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GMRS / FRS - Discussions related to GMRS (General Mobile Radio Service) and FRS (Family Radio Service) communications

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  #21 (permalink)  
Old 09-29-2013, 8:30 PM
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Originally Posted by dksac2 View Post
If you just use the top 7 Interstitial GMRS channels at a home station, are you considered a small GMRS station restricted to 15 watts erp or can you use up to 50 watts and if so, what are the antenna restrictions. The small station limits you to a 20' antenna or 20' above a tree, but not your home.
The interstitial channels shared by FRS & GMRS are channels 1 through 7. Power is limited to 500 mw in FRS, or 5 w in GMRS. I believe 15 w ERP is not allowed in those channels, you'd have to tune to channels 15 to 22 for that amount of ERP power. Actually, you could ratchet it up to 50 w for a base station and 15 w for a mobile station.
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Old 10-01-2013, 4:21 PM
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Thanks, channels 15 to 22 is what I'm referring to. It would only be if things went south and then I'd be on a 2 meter controlled ARES/RACES net, but it is always a good idea to monitor all frequencies and be able to reach others who may be in trouble who are not amateurs. There is a big GMRS EMCOMM group where I live.

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Old 10-04-2013, 8:37 AM
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On channels 1-7, the radio you are using will determine what rules you must follow. IIRC, some of the hybrid radios were capable of more than 0.5 watts (500 milliwatts) on those seven channels. If so, then you must follow the GMRS rules, even if you use the low power option, as an FRS radio cannot be capable of greater than 500 milliwatts ERP. (Also, although I'm unaware of any bubblepack radios with a detachable antenna, if the antenna is capable of detaching from the radio, you must follow the GMRS rules, as FRS radios are prohibited from having a detachable antenna.)

And I'd like to know where people keep getting this 15 watt ERP limit from? FRS radios have a 0.5 watt (500 milliwatt) ERP limit on all 14 FRS channels. GMRS radios have a 5 watt ERP limit when using channels 1-7, regardless if it's a handheld, mobile, or small base station. On channels 15-22 (462.550, .575, .600, etc) you can use up to 50 watts transmitted power output, whatever your radio make & model is capable of, with no ERP limit.
Edit: Are you referring to the archaic Fixed Stations? They had some severe restrictions imposed upon them. They were prohibited from being located within any large urban area; they were restricted to using a directional antenna with a minimum 15 decibel front-to-back ratio; were limited to 15 watts TPO; and lastly, were only allowed to communicate with another fixed station.
What were fixed stations used for? Base stations were not allowed to talk to each other. If you had a need to talk house-to-house across town, (assuming your town wasn't a part of a large urban area as defined by the FCC in Appendix B) you had to license them as fixed stations. (If you go back about 15 years, you'll see them referred to at 95.21(b), 95.29(g), 95.47, 95.49 and 95.61.)
Bottom line, don't worry about fixed stations, or the 15 watt ERP limit. It will not affect you.

Last edited by KB7MIB; 10-04-2013 at 9:47 AM..
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Old 10-04-2013, 9:03 AM
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Quote:
Originally Posted by KB7MIB View Post
[SIZE=1]And I'd like to know where people keep getting this 15 watt ERP limit from? FRS radios have a 0.5 watt (500 milliwatt) ERP limit on all 14 FRS channels. GMRS radios have a 5 watt ERP limit when using channels 1-7, regardless if it's a handheld, mobile, or small base station. On channels 15-22 (462.550, .575, .600, etc) you can use up to 50 watts transmitted power output, whatever your radio make & model is capable of, with no ERP limit.
95.135 sub d contains the power limit of 15 watts for a fixed station:

95.135 Maximum authorized transmitting power.
(a) No station may transmit with more than 50 watts output power.
(b) [Reserved]
(c) A small control station at a point north of Line A or east of Line C must transmit with no more than 5 watts ERP.
(d) A fixed station must transmit with no more than 15 watts output power.
(e) A small base station must transmit with no more than 5 watts ERP.
[48 FR 35237, Aug. 3, 1983, as amended at 53
FR 47717, Nov. 25, 1988; 63 FR 68975, Dec. 14, 1998]


The only definition of a fixed station that I can find in Part 95 is in 95.29 sub g where it refers to GMRS stations licensed before March 18, 1968. It appears to have no bearing on current GMRS rules at all.

The 15 watt rule for "fixed stations" is clearly in there, but no where that I can find do they tie the rule to any type of installation, be it base, mobile, or portable. Essentially, I don't see a definition of a "fixed station" that would apply to any current licensee.

So there is a 15 watt rule, but I don't see that it applies to any of us today. I suspect this is where the confusion arises.
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Old 10-04-2013, 9:39 AM
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I edited my comment above to include a synopsis of the circa January 1st, 1989 rules that referenced fixed stations. They are an archaic class of station, no longer referenced to for the most part, except in Subpart E, and no longer licensed.
I have a hardcopy of the 1989 rules, courtesy of my former subscription to the Personal Radio Steering Group (PRSG). When the goverment shutdown is ended, I really should print out a copy of the current rules.

Last edited by KB7MIB; 10-04-2013 at 9:42 AM..
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Old 10-04-2013, 9:44 AM
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[SIZE=1]I have a hardcopy of the 1989 rules, courtesy of my former subscription to the Personal Radio Steering Group (PRSG). When the goverment shutdown is ended, I really should print out a copy of the current rules.
The 1998 rules are available even with the shutdown at the gpo website:
http://www.gpo.gov/fdsys/pkg/CFR-200...ol5-part95.pdf
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Old 10-04-2013, 9:48 AM
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Ok, I can't reference them via my phone, since it won't do .pdf's. That's why I want a hardcopy that I can reference, since I don't have a computer to do so with.
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Old 10-04-2013, 10:04 AM
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It would actually depend on how the radio was type accepted. AFAIK, all 22-channel combo units are going to be type accepted for GMRS operation on 1-7, 15-22 and FRS operation on 8-14 (that is the case on all Uniden units). If you operate on 1-7, 15-22 a license is technically required, even if you are operating under .5W (since regulatory-wise the radio itself is not considered to be a "FRS" radio except on 8-14).

As to maximum power level, the practical limit for a body-worn or handheld UHF is around 3W ERP. This is due to rules regarding Specific Absorption Rate (SAR), or how much of the radiated power is absorbed by your body tissue under normal operating conditions. Above 3W ERP for a body-worn UHF transceiver and you are going to run into SAR limit rules.

You will find some manufacturers claiming up to or even over 5W power. However, this power level is the conducted power (essentially, how much power is drawn from the batteries) and not the radiated power (the power that is actually effectively used for communications). If you look at the FCC test reports for these models, you'll find that they all fall in the 3W ERP range.
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Old 10-04-2013, 10:17 AM
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The current Part 95 in html format all on one page is located at eCFR — Code of Federal Regulations
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Old 10-04-2013, 10:29 AM
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Thank you. There are a lot of sections missing in the current rules vs. the 1989 rules.
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Old 10-04-2013, 4:12 PM
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Quote:
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Thank you. There are a lot of sections missing in the current rules vs. the 1989 rules.
I presume that means that those missing sections are not operative anymore.
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Old 10-04-2013, 5:02 PM
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I presume that means that those missing sections are not operative anymore.
That is correct. The 1998 version is much different from the '89 one. They dropped a whole bunch of stuff.
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Old 10-05-2013, 12:59 AM
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Quote:
Originally Posted by Rudester View Post
The interstitial channels shared by FRS & GMRS are channels 1 through 7. Power is limited to 500 mw in FRS, or 5 w in GMRS. I believe 15 w ERP is not allowed in those channels, you'd have to tune to channels 15 to 22 for that amount of ERP power. Actually, you could ratchet it up to 50 w for a base station and 15 w for a mobile station.
You can run 50 watts in a mobile not 15watts.
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Old 10-05-2013, 1:02 AM
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Quote:
Originally Posted by UPMan View Post
It would actually depend on how the radio was type accepted. AFAIK, all 22-channel combo units are going to be type accepted for GMRS operation on 1-7, 15-22 and FRS operation on 8-14 (that is the case on all Uniden units). If you operate on 1-7, 15-22 a license is technically required, even if you are operating under .5W (since regulatory-wise the radio itself is not considered to be a "FRS" radio except on 8-14).

As to maximum power level, the practical limit for a body-worn or handheld UHF is around 3W ERP. This is due to rules regarding Specific Absorption Rate (SAR), or how much of the radiated power is absorbed by your body tissue under normal operating conditions. Above 3W ERP for a body-worn UHF transceiver and you are going to run into SAR limit rules.

You will find some manufacturers claiming up to or even over 5W power. However, this power level is the conducted power (essentially, how much power is drawn from the batteries) and not the radiated power (the power that is actually effectively used for communications). If you look at the FCC test reports for these models, you'll find that they all fall in the 3W ERP range.
A license IS required not technically required.
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Old 12-04-2013, 7:49 AM
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Cool Re-hash

Although already stated where you want to operate, I'd like to share that my bubble packs automatically limit power on the FRS channels to .05watts. The other channels used at I guess the five watt limitation. Technically considered that these handi-talkies can go mobile, although they cannot operate at fifty watts.
We used to be restricted to the first seven channels, but now we're licensed.
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Last edited by MeddleMan; 12-04-2013 at 7:51 AM.. Reason: more info added
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Old 12-04-2013, 8:41 AM
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I think you'll find that the hand-held radios are limited to about 2W ERP (although they might claim higher power, that power rating is "conducted power" which is roughly equivalent to the power drawn from the batteries...ERP is "Effective Radiated Power" which is the power actually coming from the antenna).

The 2W ERP limit is imposed due to two factors:

1) SAR limits: Specific Absorption Rates...basically the amount of RF energy absorbed by the human body from the radio during normal operation. Even though the service allows 50W, SAR limits will reduce that to about 2W in a handheld/body-worn configuration radio.

2) Canada limits power to 2W ERP on the GMRS channels and manufacturers make a single model for both markets...in order to get IC approvals, they are going to be limited to this lower number.
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Old 04-23-2014, 12:28 PM
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So what happens if you get more than the legal absorbed limit. is it like Ionizing radiation where you have a cumulative exposure and then you have to stop the exposure?
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Old 04-23-2014, 12:36 PM
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You cook in your own juices. Well, maybe not that drastic at these power levels, but the RF is absorbed and converted into heat. It is not like ionizing radiation. More like microwave oven.
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Old 05-28-2014, 8:04 AM
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Cool reading lesson

As stated above (unless you are programming a commercial radio,) bubble pak radios automatically adjust power for the shared frequencies. No problem. However, you might find sorrow to program fifty watts on channel one.
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Old 07-13-2014, 3:34 PM
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Quote:
Originally Posted by MeddleMan View Post
As stated above (unless you are programming a commercial radio,) bubble pak radios automatically adjust power for the shared frequencies. No problem. However, you might find sorrow to program fifty watts on channel one.
How do they determine when to adjust power? Is there a way for them to detect in which mode the unit is being used, perhaps based on incoming signals? I have a Cobra CXT-88, but I can't find any reference to what power out it is using on Channels 1 - 7. I've sent an email to Cobra support asking specifically what it is and if there is a way to switch between the two power levels.
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