how many watts are used in simplex or repeater input on vhf
- Thread starter bailly2
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Most radios have the ability to select a high or low power setting. Normally, you set the power level to what ever works. (Or, in other cases, as cmdrwill points out, whatever the license allows).
High power radios (like the Motorola PM-1500) are unusual. The ~20-50 Watt range is typical for mobile radios.
High power radios (like the Motorola PM-1500) are unusual. The ~20-50 Watt range is typical for mobile radios.
They are often set to lower power except where needed. Typically, system subscribers are programmed to the lowest power setting that guarantees good access to the system, whatever type system that might be.
WA0CBW
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Another power limitation would be the maximum RF exposure limits set by the FCC.
BB
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Hooligan
Member
If a VHF radio is installed in a typical federal law enforcement unmarked vehicle, it's usually hooked up to a disguised or hidden antenna which is very inefficient. Thus, the land mobile radio techs program the radio for the highest transmit power output setting. On VHF that's often 90 to 110 watts transmitter output.
ecps92
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But since this is the Federal Forum, it's the NTIA not the FCC, until they start programming in the Part 90 Frequencies for Interop
This is from Chap. 8 of the NTIA Manual of Regulations and Procedures for Federal Radio Frequency Management:
8.2.19 Limitation of Radiated Power
Federal radio stations shall radiate only as much power as is necessary to ensure a satisfactory service.
8.2.19 Limitation of Radiated Power
Federal radio stations shall radiate only as much power as is necessary to ensure a satisfactory service.
ecps92
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The manner of how radios are programmed varies by agency. I worked for the U.S. Forest Service and National Park Service from 1974 to 1999. We used Bendix-King handhelds that had a maximum output of 5 watts, but all of them had a lower power setting that lowered the output by a half. Our mobiles and handhelds did not have different settings for simplex and repeater operations. We needed as much power as was possible to hit distant repeaters in rugged topography and we needed as much power as possible to speak to someone directly on simplex We rarely used the lower power setting on our handhelds even though we had a very handy toggle switch on top of the radio.
I always carried backup batteries, one rechargeable that I rotated with another so that each battery was used every other day and an alkaline battery clamshell inside my fireline pack along with 9 more AA batteries to fill the clamshell one more time. The fireline pack stayed in the toolbox of my truck at all times year round. The mobile in my truck had no means of varying the transmit power and the model radio I had was not capable of being programmed to have different transmit powers for each channel.
Some wilderness rangers, who used the alkaline clamshells only, used the lower power level if they could reach a repeater or could speak to the nearest wilderness ranger on simplex with it. Doing so as much as possible meant fewer batteries had to be packed in, either by horseback or muleback, or on their own backs when they came out of the wilderness after a ten day tour. At one time the Inyo placed some temporary repeater extenders to cover large blind spot areas. Often times the frequency was used on other tones for simplex and thus the wilderness rangers had their own private channel.
I always carried backup batteries, one rechargeable that I rotated with another so that each battery was used every other day and an alkaline battery clamshell inside my fireline pack along with 9 more AA batteries to fill the clamshell one more time. The fireline pack stayed in the toolbox of my truck at all times year round. The mobile in my truck had no means of varying the transmit power and the model radio I had was not capable of being programmed to have different transmit powers for each channel.
Some wilderness rangers, who used the alkaline clamshells only, used the lower power level if they could reach a repeater or could speak to the nearest wilderness ranger on simplex with it. Doing so as much as possible meant fewer batteries had to be packed in, either by horseback or muleback, or on their own backs when they came out of the wilderness after a ten day tour. At one time the Inyo placed some temporary repeater extenders to cover large blind spot areas. Often times the frequency was used on other tones for simplex and thus the wilderness rangers had their own private channel.
I just looked up a new model of Bendix-King that the Forest Service is now using. I believe the model was the P-150. It has an output of 6 watts. I didn't notice that it comes with a lower power setting. In the Forest Service the lower power setting was important for people working 10 day tours (ten days on, four days off} in the backcountry and for people assigned to a fire in the backcountry for several days. If a wilderness ranger could reach a repeater on a lower setting it saved batteries. If that same ranger could reach other rangers on tactical frequencies on lower power it saved batteries.
As for the fire folks, the average fire in a wilderness area is smaller than those in the frontcountry, so the lower power setting was usually quite adequate for them as well and batteries were saved. Often times fire management personnel had less access to fresh batteries than the wilderness rangers who usually had a good supply of them in their base camp or patrol cabin cache.
As for the fire folks, the average fire in a wilderness area is smaller than those in the frontcountry, so the lower power setting was usually quite adequate for them as well and batteries were saved. Often times fire management personnel had less access to fresh batteries than the wilderness rangers who usually had a good supply of them in their base camp or patrol cabin cache.
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