Getting 50 watts actually out of repeater

[WRYD530]

So 50 watts is the maximum allowed to transmit on GMRS.  If i setup a repeater with 2 radios  a duplexer and separate antennas for each radio and the best cable i may still lose about 10-20 watts correct? So is there a way to boost the 50 watt radios to actually get the 50 watts out of the transmission?

[OffRoaderX]

not really.. you have to push all the power before the duplexer, and cheaper/smaller duplexers eat a huge %% of the power. So you will either need to push more power into the duplexer (if it can handle it), or get a better duplexer that doesnt eat so many RF electricities.

HOWEVER - the difference between ~20 watts and 50 watts is probably not going to be noticeable.. I have tested my base setup at 40 watts vs 110 watts, and people at the outskirts of my range (around 60 miles) can't even hear a difference between 40 and 110W ..

[Guest]

I agree with randy. you’re not going to notice much change.  Heck I get 200miles from a 20w base station and a good antenna.   The key is the antenna and height and line of site  more then the wattage. 

[WRWE456]

Heck the furthest report I have heard with a hand held GMRS radio was 127 miles. That was hill top to a repeater at 7500 feet line of sight. KG-935G with a Nagoya NA-771G 15"whip. 5.5 watts.

[BoxCar]

10 hours ago, WRYD530 said:

So 50 watts is the maximum allowed to transmit on GMRS.  If i setup a repeater with 2 radios  a duplexer and separate antennas for each radio and the best cable i may still lose about 10-20 watts correct? So is there a way to boost the 50 watt radios to actually get the 50 watts out of the transmission?

You can't boost the output of the radio to overcome losses downstream from the radio. The FCC limited the radio's output to 50 watts so you have to eat the losses.

[SteveShannon]

11 hours ago, WRYD530 said:

So 50 watts is the maximum allowed to transmit on GMRS.  If i setup a repeater with 2 radios  a duplexer and separate antennas for each radio and the best cable i may still lose about 10-20 watts correct? So is there a way to boost the 50 watt radios to actually get the 50 watts out of the transmission?

If you use a separate antenna for each radio you don’t need a duplexer. The reason for the duplexer is to allow you to simultaneously transmit and receive using a single antenna.
Using separate antennas can be done but requires enough separation between the antennas to achieve a level of RF isolation. That’s usually done by separating them vertically.  I’m not recommending that you do that, just explaining that it can be done. It is one way to overcome the losses incurred by using a duplexer.

But everything Randy (@offroaderx) said is correct.  Better quality duplexers result in less loss and chasing those last several watts makes very little difference. As someone else said in a similar thread recently, many repeater owners run their transmitter outputs at reduced output to ensure long life. 

[WRYZ926]

1 hour ago, Sshannon said:

But everything Randy (@offroaderx) said is correct.  Better quality duplexers result in less loss and chasing those last several watts makes very little difference. As someone else said in a similar thread recently, many repeater owners run their transmitter outputs at reduced output to ensure long life. 

That is how our club does it. We are using a Bridgecom repeater and running it at a lower power. We do the same with our 2m and 70cm repeaters. Running a busy repeater constantly at full power will shorten the life of the repeater. 

Another thing to look at is the duty cycle of the radios or repeaters. The higher the duty cycle is the better.

[WSEL330]

Sooo...jumping after reading. I understand that more Watts doesn't necessarily ,equate to more fars. I realize from here that my repeater pushing 24 Watts will work almost as well as 50 Watts. My question is about Watts vs fars and obstacles. Is Watts vs fars linear, geometric, exponential? For example: 5W output on the repeater vs. 24W output more drastic improvement than 24W to 50W. Second part is: does more Watts afford more 'muscle' to propagate through foliage? (understanding that height and antenna is king here. I can not get above canopy but can get to about 70')

[SteveShannon]

2 hours ago, WSEL330 said:

For example: 5W output on the repeater vs. 24W output more drastic improvement than 24W to 50W. Second part is: does more Watts afford more 'muscle' to propagate through foliage?

24 watts compared to 5 watts will get you a slightly better signal at greater distance than the 5 watts. The difference between 24 watts and 50 watts will be less noticeable.

Yes, more power goes through foliage and walls better.

But the real secret to getting farther range is to put a very good antenna up as high as you can.

[Blaise]

1 hour ago, SteveShannon said:

But the real secret to getting farther range is to put a very good antenna up as high as you can.

I climb the tallest tree around before attempting to use my radio...

[marcspaz]

 

Well, lets address these separately.

 

2 hours ago, WSEL330 said:

Is Watts vs fars linear, geometric, exponential? For example: 5W output on the repeater vs. 24W output more drastic improvement than 24W to 50W. 

 

The answer is "none of the above".  It's logarithmic.  Calculating range verses distance in free-space (not accounting for the curve of the Earth nor obstacles) involves a complex formula, based on things like the distance between the antennas, the frequency, the gain of both the transmitting antenna and the receiving antenna, and the attenuation value of the atmosphere.  

If we assume that neither antenna has gain, at 465MHz (about the center of the GMRS frequencies), 1 mile of free space has about 90dB of signal attenuation.  At 10 miles, there is 110dB of attenuation.  At 100 miles, there is 130dB of attenuation.

So, lets say you are transmitting a 1 watt signal to a station 1 mile away.  Your signal will be reduced to 1 nano-watt, or about 224 micro-volts.  This is just a little higher than the 60% mark of receive sensitivity for most retail OTC radios.  That station can receive your signal, but its about 60% audio and 40% static.  It's usable, but a lot of static.  If you want a station 10 miles away you hear you just as well, you need to increase your power to 100 watts.  If you want to have a station 100 miles away be able to receive your signal at the same levels, you would have to increase your power to 10,000 watts.

As you can see, trying to increase your range by increasing your power becomes very impractical.  Most of the time we look at things like using antennas with high gain or increasing receive sensitivity and selectivity.  For example, if you use that same 1 watt with a 14dB gain beam antenna on both ends of the communication path, that would be like increasing your power to 630 watts and both antennas having no gain. 

 

2 hours ago, WSEL330 said:

Second part is: does more Watts afford more 'muscle' to propagate through foliage? 

 

To make life easy for yourself, to figure out how much more power you need, just estimate foliage loss using the 15–20 dB rule of thumb.  Increasing power does help penetrate through trees and buildings.  It does help fill-in hole and dead spots a bit too... but like free-space attenuation... more power has massively diminishing returns.

If you want to "know" actual numbers to calculate the RF power needed to penetrate foliage, you need to determine the signal attenuation caused by the vegetation.  You need to use the frequency, vegetation depth you want to penetrate, the water content in the leaves and trees, and the path geometry. The angle the signal gets bent to as the signal passes through the foliage affects the amount of attenuation.  Vegetation type and density affects signal scattering and absorption, too.

And did I mention this changes seasonally?  And the more dramatic the season changes, the more dramatic the variations will be.

[LeoG]

The legal way to get 50 watts out of the duplexer is to buy an all in one repeater.  The duplexer is internal to the repeater unit and the output on the antenna connection can't be more than 50 watts.  In order to do that you have to put 60-70 watts into the duplexer which is fine as long as the output on the connector isn't above 50 watts.  I'm running such a repeater.

[nokones]

You can go with a high gain antenna. There is no rule on the ERP with the 462 MHz main channels, but that will change your effective radiation pattern.