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Power supply for repeater!

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I am looking to build a portable GMRS repeater station but I am having trouble with the power supply portion. I would like to know what is the amount of power drawn from a repeater setup or at least how to figure it out myself. Also if you could please give me some good ideas of what I could do to put together a rechargable battery pack that will power the repeater for a continuous 20 or more hours that will also fit in my car. Thanks for all your help.
 

SkipSanders

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The maximum allowed power for a GMRS repeater is 50 watts output. You won't be carrying around a car battery that will handle that for 20 hours unless it's in an RV, and consists of multiple batteries. However, it shouldn't be needed.

If you're creating a 'temporary repeater' in a vehicle (I would NOT operate in repeater mode while moving!) you're presumably intending to set up a repeater for use by handhelds in a park or the like, and they'll be limited to 5 watts. No reason for the repeater to use more than 10 watts output.

The antenna is limited to 6.1 meters (20 feet) above the ground, or the top of the structure or vehicle it's mounted on.
 
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I will be using it as a relay for my handhelds where My family and myself hunt. The terrain is very rough including hills, mountains, and dense forests. The reason for the repeater is so that we can reach persons on the opposite side of the mountain. I will be leaving it unattended for a good portion of the time. So it needs to be able to opearate on it's own for a very lengthy period of time.
 

Grog

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This could have been handled in your other thread about the repeater, not sure why a new one was needed. All that does is have people wonder what you are wanting to do in case they did not read your other thread.
 

n8emr

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Malicious-Intent said:
I am looking to build a portable GMRS repeater station but I am having trouble with the power supply portion. I would like to know what is the amount of power drawn from a repeater setup or at least how to figure it out myself. Also if you could please give me some good ideas of what I could do to put together a rechargable battery pack that will power the repeater for a continuous 20 or more hours that will also fit in my car. Thanks for all your help.
Without knowing your power output and the current output in receive mode you question cant be answered. How much power your need and how much current does the receiver draw?
Once we have that we can start working up a plan.

But to get you started.
Figure a modest 3 amp receive and controller power, thats 36w/hr
Figure 10watts RF output, crappy efficiency thats 20watts of power draw maybe
2hrs/day for 40watts/hrs. With losses stations accessories your looking at 100w/hr
or about 8AH
 

SkipSanders

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Forgot to mention, it's very unlikely any 'bubblepack' GMRS radios you already have will work through a repeater. They can receive repeaters, but not transmit through them.

Only a very, very few had the option to run duplex through a repeater, so you'll probably end up having to buy all new radios to use a repeater anyway.

This means something like $125 or so each for new radios such as the Icom IC21GM

Quality of the radios will be higher, though.
 

key2_altfire

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Figure a modest 3 amp receive and controller power, thats 36w/hr
Figure 10watts RF output, crappy efficiency thats 20watts of power draw maybe
10 watts RF output at 20 watts consumption, that's 50% efficiency, which is probably on the high side even for a class C amp!

Personally I would alot for 30% efficiency, so leave enough room in the stack for a larger battery.
 

n8emr

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10 watts RF output at 20 watts consumption, that's 50% efficiency, which is probably on the high side even for a class C amp!

Personally I would alot for 30% efficiency, so leave enough room in the stack for a larger battery.
Dont forget duplexer losses.
 

rescuecomm

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We used to do that when our comm group was working a triathlon in mountainous area not well covered by our amatuer repeaters. Between the hams, we had a 4 cavity duplexer and a Icom 220 repeater. It operated in a pickup truck parked on a high ridge overlooking the bicycle route. We used a Hustler G7-220 antenna on a mast in the bed which made it work very well. Most large car batteries will power a repeater for the period listed if the tramsmit usage is about 15%. If your GMRS repeater is to work well, you will need a decent base antenna on a mast bolted to your bumper/roof, etc. On a repeater, receive is everything, so go with the largest antenna you can manage without making a hazard of it.

Bob
 
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