All my RX path questions

[GTR8000]

There are many factors to take into account, it's too general of a question to give a definitive answer to.

What is the gain of the Yagi? What elevation is the Yagi at in relation to the surrounding terrain and transmitter sites you're asking about? Is there a clear line of sight between the Yagi and the transmitters you're trying to receive? Are those transmitters relatively high power and at a good elevation, in other words, is a good signal making it to the location of the Yagi before taking any gain or directionality into account?

Most Yagis have decent gain off the side lobes, it's the back of the antenna where things start to really drop off. However if you can receive good signal from those other transmitters with an omni antenna in the same spot as the Yagi, then it'll probably receive the signals decently.

 

[Bonkk083]

There are many factors to take into account, it's too general of a question to give a definitive answer to.

What is the gain of the Yagi? What elevation is the Yagi at in relation to the surrounding terrain and transmitter sites you're asking about? Is there a clear line of sight between the Yagi and the transmitters you're trying to receive? Are those transmitters relatively high power and at a good elevation, in other words, is a good signal making it to the location of the Yagi before taking any gain or directionality into account?

Most Yagis have decent gain off the side lobes, it's the back of the antenna where things start to really drop off. However if you can receive good signal from those other transmitters with an omni antenna in the same spot as the Yagi, then it'll probably receive the signals decently.

One the sites is 36 miles and the line of sight is maybe the elevation is over 800' I'm not sure about the power, I haven't gotten a antenna yet not sure what to get a yagi or omni

 

[Bonkk083]

I checked the transmitter power it's 250-400 ERP - 100 output power

 

[buddrousa]

We have ask what is the ground elevation of the site and what is the antenna height of the site and what is your ground elevation and antenna height at your house. What is the elevation line of site between you and this site. Is this site a 700 trunking site. Put your scanner in your car drive toward the site how far away from the site are you when you start decoding traffic without missing any traffic are you.

 

[Bonkk083]

We have ask what is the ground elevation of the site and what is the antenna height of the site and what is your ground elevation and antenna height at your house. What is the elevation line of site between you and this site. Is this site a 700 trunking site. Put your scanner in your car drive toward the site how far away from the site are you when you start decoding traffic without missing any traffic are you.

The sites elevation is 260m = 853' and antenna height is 91.4m = 300' my location elevation is 672' my antenna height is 20'

 

[buddrousa]

This site will give a ruff free idea. Drag the 2 dots 1 to your site and the other to the tower site

RF Line of Sight - SCADACore

RF Line-of-Sight provides radio path information for mapping long distance SCADA radio communications by using antenna height and topography.

www.scadacore.com

 

[Bonkk083]

This site will give a ruff free idea. Drag the 2 dots 1 to your site and the other to the tower site

RF Line of Sight - SCADACore

RF Line-of-Sight provides radio path information for mapping long distance SCADA radio communications by using antenna height and topography.

www.scadacore.com

I did another site and the light of sight is good

 

[Bonkk083]

This site will give a ruff free idea. Drag the 2 dots 1 to your site and the other to the tower site

RF Line of Sight - SCADACore

RF Line-of-Sight provides radio path information for mapping long distance SCADA radio communications by using antenna height and topography.

www.scadacore.com

Do I add the height in meters also

 

[Ubbe]

A direction pattern for a yagi can look something like this:

It will change with frequency and model of antenna so it will be impossible to know until tested.

/Ubbe

 

[paulears]

With those graphs, the terrain is well below your beam so looks good to me.

 

[Bonkk083]

Do I need to use a yagi or omni for 800 mhz

 

[jwt873]

For commercial LMR stations in the 30 - 40 mile range, I can't see why you'd need a Yagi. A vertical should do just fine. (If you want gain, you can buy verticals with gain).

For what it's worth, I have a 12 foot long 45 element Yagi for 1296 MHz. It's extremely sharp. (16 degree horizontal beamwidth). I was just listening to a repeater on 1285 MHz that's 30 miles away. Despite being very sharp, I can swing the beam 360 degrees and always hear the repeater.

I use mine for SSB and digital modes where I use tropo to go beyond line of sight. I've managed 2 way contacts of up to 300 miles. But.. For local scanning of commercial LMR stations, I'd use a vertical.

Edit.. And for reference, the repeater I was listening to is up 220 feet and is running 10 Watts.

 

[Bonkk083]

For commercial LMR stations in the 30 - 40 mile range, I can't see why you'd need a Yagi. A vertical should do just fine. (If you want gain, you can buy verticals with gain).

For what it's worth, I have a 12 foot long 45 element Yagi for 1296 MHz. It's extremely sharp. (16 degree horizontal beamwidth). I was just listening to a repeater on 1285 MHz that's 30 miles away. Despite being very sharp, I can swing the beam 360 degrees and always hear the repeater.

I use mine for SSB and digital modes where I use tropo to go beyond line of sight. I've managed 2 way contacts of up to 300 miles. But.. For local scanning of commercial LMR stations, I'd use a vertical.

How much gain would be good

 

[jwt873]

I live 35 miles from the downtown area of a larger city. I can hear the city bus service repeater at 412 MHz on my handheld sitting on my living room table.. It's on a 200 - 250 foot building in the city center. Commercial LMR sites generally try to cover as much area as they can.

There's a thread here talking about 900 MHz antennas... Base antenna for 700-800 MHz P25 trunking systems

 

[Bonkk083]

These are the antennas I'm looking at

FG8063 : 806-866 MHz, 3 dBd/ 5.15 dBi Outdoor Fiberglass Omni base Station Antenna with N-Female Connector

The FG8063 from Laird (formerly Antenex) is a heavy duty, omni-directional fiberglass base station antenna operating at 806-866 MHz, providing 3 dBd/ 5.15 dBi of linear gain.*Note: This antenna DOES NOT ship with mounting hardware. We recommend the ROSA-HDM1 mounting bracket*

www.arcantenna.com

Wilson Yagi Style Outdoor 50Ohm Cellular Antenna 700-900MHz (301111)

Call us now for the custom system design quote from our experts! Wilson Yagi Cellular Antennas are very effective in increasing your... Learn More!

www.solidsignal.com

FG8066 : 806-866 MHz, 6 dBd/ 8.15 dBi Outdoor Fiberglass Omni base Station Antenna with N-Female Connector

The FG8066 from Laird (formerly Antenex) is a heavy duty, omni-directional fiberglass base station antenna operating at 806-866 MHz, providing 6 dBd/ 8.15 dBi of linear gain.*Note: This antenna DOES NOT ship with mounting hardware. We recommend the ROSA-HDM1 mounting bracket*

www.arcantenna.com

800 MHz UHF Vertical Outdoor Base Antenna (851-869 MHz)

Specs Gain: 7 dBi SWR: 1.5:1 or Less on Center Pattern: Omni-directional Wavelength: Multiple 1/2 Tuned: 851-869 MHz Band: 800 MHz Safety Connector: N Female Cable: RG8X Cable Length: 24 Inches Height: 57" Width: 1 1/4" Weight: 2 lb Wind Area: 0.50 Sq Feet Features Ready Made...

dpdproductions.com

 

[Bonkk083]

Will a yagi with 13 dbi reach further than a omni 8 dbi @ 40 miles and I have line of sight

 

[MUTNAV]

This site will give a ruff free idea. Drag the 2 dots 1 to your site and the other to the tower site

RF Line of Sight - SCADACore

RF Line-of-Sight provides radio path information for mapping long distance SCADA radio communications by using antenna height and topography.

www.scadacore.com

One of the problems with this sites calculations is they don't do earth curvature at all. Try and put two sites 100 miles apart, on the ocean, with 1 meter high antennas, it shows no problem, with earth curvature, problem..



and I really like the site also..

Thanks
Joel

 

[Bonkk083]

One of the problems with this sites calculations is they don't do earth curvature at all. Try and put two sites 100 miles apart, on the ocean, with 1 meter high antennas, it shows no problem, with earth curvature, problem..



and I really like the site also..

Thanks
Joel

How much does the curvature effect a site 36-48 miles away

 

[Bonkk083]

I'm looking for a antenna to pick up frequencies in the 850's that is 36-48 miles away and I have line of sight by a graph that I used, is my best bet to go with a yagi or omni with gain for the long distance, I don't know what I should go with.

 

[MUTNAV]

How much does the curvature effect a site 36-48 miles away

Pretending you are on a flat surface (pretend an airfield or the ocean)

Using the calculator on this links page, an antenna 1000 feet high would get you a little over 38 miles.

Radio Line of Sight Calculator for use on VHF/UHF Ham Bands

There are other modes that could come into play though, troposcatter, knife edge refraction, etc... (besides everyone just being on nice high hills).

If there is a TV or FM station with its antennas near where you are wanting to know about. Try TVFOOL.com or FMFOOL.com.

They can give a reasonable coverage ideas (and I'm not sure, but I think it does take curvature of earth into account).

Thanks
Joel