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#1 RickW

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Posted 05 April 2019 - 08:21 PM

From time to time I check out YouTube videos that cover the use of GMRS, and services licensed by rule (CB, MURS, FRS) and also ham radio which often comes up as a comparison. I notice that it is common to have errors in the presentation, sometimes fairly serious errors. And the comments by others, which may even be rude and arrogant, can actually have even more errors in what they present. So I will make comments, hopefully in a respectful manner and point out some of the pros and cons of Part 95 and Part 97 services. 

 

Of course I want to be accurate and there are a few things that I would like to clarify:

 

1. Mobile, hand-held portable, repeater, base and fixed station can transmit on the main 462 MHz channels up to 50 watts output. And mobile, hand-held portable and base stations can transmit at a maximum of 5 watts ERP on the 462 interstitials. 

 

But, if you have a station running 5 watts with a gain antenna, (mobile or base) and not enough loss in the coax, then do you avoid using the 462 interstitials?

 

2.Only mobile, hand-held portables, control, and fixed stations can transmit on the 467 main channels. 

 

Does this really mean that I can not access a repeater from my home base station? There are times that we can access a repeater at some distance out and make it possible to communicate from mobile to base via the repeater. 

 

3. When I contacted B-Tech prior to buying a couple of their GMRS-V1 HT's, I questioned why the power output levels were reduced to only 2 watts instead of an earlier version that I had read were 5 watts. They indicated that they had to drop the power to 2 watts to be legal. The only reason that I could think of was that they only had two power levels in these modified Baofeng radios, and one had to be 0.5 watts for the 467 MHz interstitials, so perhaps the earlier models had too high an output for those frequencies? 

 

 

 

 



#2 marcspaz

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Posted 05 April 2019 - 09:08 PM

1.) ERP is defined as the product of the power supplied to the antenna and the antenna gain. While manufactures produce equipment designed to be approved/accepted by the FCC for certain use cases, it is ultimately up to the licensed responsible party to be sure they are in compliance with the rules and regulations.

I don't know anyone that is using a field strength meter to ensure they are legal on FRS/GMRS frequencies, especially if they are using type approved hardware. While I can't advocate intentionally breaking the law, to the best of my knowledge, the assumption is being made by many that if an operator is using type accepted hardware, they are good. Though, that may not actually be the case.

That said, if you are intentionally transmitting in a means or manner that is not compliant, then you are committing a crime. I would recommend avoiding the frequencies that would put you in jeopardy.

2.) I have no first-hand knowledge of what base station equipment is available. If you can not find a base that meets your requirements, I would buy a 14 volt power supply and simply run a mobile radio with appropriate performance for the desired mode of opperation.

3.) To the best of my knowledge, Baofeng has not had a 5 watt GMRS type approved radio. They made a 5 watt handheld Ham radio (UV-5R) that can be illegally programed for use on FRS and GMRS frequencies. They have replaced that model with an 8 watt version (current gen 3 is BF-F8HP), which is still made today.

Also, to the best of my knowledge, the new Baofeng GMRS 2 watt handheld is their first FCC Part 95 type approved handheld for sale in the US. As indicated by the name, the Baofeng GMRS-V1 is the first version (-V1 or Version 1) of their FCC compliant GMRS radios.


EDIT: On #1, you can figure out what your ERP is without a field strength meter. It will not be exact... but close enough to tell if you are compliant.

You measure your forward and reverse/reflected power at the radio. Subtract your reverse/reflected power from your forward power and that gives you your real output power. Subtract your line loss and add the DB gain of the antenna.

These are completely hypothetical numbers... just an example of what you could actually read.

Example: Assuming 1.5 DB of line loss and 6 DB of antenna gain. Take 37 watts forward power, minus 3 watts reflected = 34 actual output power. Subtract 1.5 DB of line loss and add 6 DB of antenna gain, you end up with 49.8 watts ERP.

Used this calculator... https://www.everythi...-radiated-power




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