Q: How to compute signal range

[WRKI280]

Hi

I am kicking around setting up an antenna for a 50w repeater . In my case I maybe able to place the antenna  on  a building 70` in the air.

 

What is the formula to compute signal range?

 

I found this formula at https://electronics.stackexchange.com/questions/17454/how-do-i-estimate-the-transmission-distance-of-a-50-watt-2m-radio but it doesnt include the radio wattage.

 

I know signal power has to be in the equation somewhere.

 

Providing that the ground between transmitter and receiver is flat the following formula gives the distance to the horizon:

D=distance

H=height
D=1.2√H
D=1.2√70=10mi
Double this to get 20 miles.

Thank you

 

 

D=1.2H−−√

[BoxCar]

Output power isn't the biggest factor in calculating range, It's antenna height and obstructions. Power does play a good part but it's all about location, location, location. Granted 45W will transmit further than 5W but not that much more than 25W through the same antenna.

[gortex2]

There are some online programs to show you range. As said above height and antenna gain is everything. You can put 50 watts out on your garage roof and not talk as far as 5 watts on a 2500' mountain top.

[Lscott]

There are some online programs to show you range. As said above height and antenna gain is everything. You can put 50 watts out on your garage roof and not talk as far as 5 watts on a 2500' mountain top.

I agree. I have a Ham Radio buddy that got permission, yes it's possible, several times to use his HT on a commercial jet flight. There was a bit of a pile up when you're talking 500 to 1000 miles radius from 30,000 feet on FM.

[WRAK968]

Hi

I am kicking around setting up an antenna for a 50w repeater . In my case I maybe able to place the antenna  on  a building 70` in the air.

 

What is the formula to compute signal range?

 

I found this formula at https://electronics.stackexchange.com/questions/17454/how-do-i-estimate-the-transmission-distance-of-a-50-watt-2m-radio but it doesnt include the radio wattage.

 

I know signal power has to be in the equation somewhere.

 

Providing that the ground between transmitter and receiver is flat the following formula gives the distance to the horizon:

D=distance

H=height

D=1.2√H

D=1.2√70=10mi

Double this to get 20 miles.

 

Thank you

 

 

 

D=1.2H−−√

Also note that this is theoretical. I have a repeater mounted about 30' up. Going north, it loses signal about 3 miles out due to a large hill in that direction. To the south I easily get 8-10 miles reliably, and I've had reports of people reaching the repeater nearly 45 miles away from me, though only in particular spots. 

 

Terrain isn't the only issue that reduces range. Large buildings, high voltage transmission lines, and high RF environments tend to further diminish signals unless professional grade stuff is used. One thing I will say is if you get a flat pack duplexer, be sure to upgrade that first before switching to larger antennas. I found that each repeater I set up that started with flat pack duplexers, even the high quality ones like Celwave, often saw a 20-40% increase in range. I also found that by using 25W instead of 40W that the repeater seems to get the same range while being able to detect weaker signals from portables at longer distances.

 

 

[DONE]

If you are wanting to create a map, go find a piece of software called radiomobile and work out how to use it.

[berkinet]

Since UHF is essentially line-of-sight, you will often find you run into obstacles well before power becomes an issue.

 

BTW, if you really want a 50 watt transmitter be prepared to pay for it.. There is a huge difference between a 50 watt mobile and a repeater with the same power rating. The difference is duty cycle.  Your mobile will probably run around 0% much of the time, and then maybe 50% if you are in a conversation with one other station. However, the repeater can run at 100% duty cycle for long periods.  Try that with your mobile and you will fry/melt the finals.

[n4gix]

Hi

I am kicking around setting up an antenna for a 50w repeater . In my case I maybe able to place the antenna  on  a building 70` in the air.

 

Here is where you can generate "maps" of your expected coverage based on the data you enter. This program will also consider topographic data. The 'green' areas are predicted HT @ 70% reliability, the 'yellow' areas are mobile coverage @ 70% reliability.

 

This was for a proposed repeater to be located near Schaumburg, IL. Unfortunately, after a detailed site survey we determined that there would be to much potential for conflict with all of the other repeaters on the 150' tower.

 

https://www.ve2dbe.com/rmonline_s.asp

 

 

[WRKI280]

WQWU626

This is exactly what I need.

I ran a rough estimate, and I will cover most of the county in all directions using a 40' antenna.

 

Thank you