Repeater Antenna

[LeoG]

Running a 50w repeater right now putting out about 40w after the duplexer.  The antenna is only about 40' above the ground which is 100' above sea level.  It's below the tree line which I think is what's killing me.  But the plan is to get the antenna above the tree line, and it won't be by much.  Right now I'm using a generic dipole with a 7.2dBi gain.  I've seen the same type of antenna sold by many companies so I'm sure it's probably just a generic make and relabeled.  This particular one was sold by Retevis and is their MA-09.

Not sure how much I want to spend.  But I live in a treed and hilly area so what I've seen is I don't want a really high gain antenna because the pattern won't work well with the hilly terrain.

So should I just stick with this antenna or is there something else I can use.  Not looking to put a really long antenna up like I seen with one of the Comets.  I've also seen some folded dipoles but don't know enough abou them to know if they'll work better than a straight dipole.

The mast will likely be 70-75' tall and the antenna on top of that.  We shall see.

Enlighten me please. 

[Guest]

I can not recommend the comet 712efc 9db at 10’ or the comet 9nc 12db at 16’ enough.  My old 20w set up with the 712 got 200miles depending on weather.  Now with the 50w set up and the 9nc I get the same 200miles full quieting. You didn’t mention the length or type of coax?  
 

assuming 50’ of lmr400 your current set up is radiating about 140w

your same set up with a 9db antenna would radiate 217w

and with a 12db it would radiate 433w. 
 

both a  great step up.  Assuming you get the antenna up as high as you can your going to notice a big difference especially with a 12db 9nc 
 

[LeoG]

So what about my hilly terrain?  I know you live in the land of the flat and that would absolutely work for you.  Not so sure around here.  But that's why I'm asking, because I really don't know.  The mast, in theory, will be on a hinge so I can take the antenna up and down, but that is only going to be for a rare reason I hope.  It's probably going to be more like a total of 70' of Hyperflex 13 with 2 runs in between the lightning protection.

[Guest]

Same recommendation.  Except it’s not going to work as far.  Height, and radiated watts is still key to any of this.  460mhz does not bend or bounce.  hilly terrain needs height  to get over the hills.  There is no special antenna that is going to help get around or over hills.  
as with any of this, start with the highest wattage radio you can get. In gmrs case 50w according to the rules.  The the best and shortest length is f coax you can run. THen the the highest gain antenna you can and get it  up as high as you can get.  Now if you have unlimited funds there are professional antennas that are 20 or more feet high that have water fall effects and 16db or more gain but those are in the several $1000s range.  And even with those they are not going to bend the signal around or over a hill.  

[AdmiralCochrane]

I read in the first post he is using a 50w GMRS radio.

[WRYZ926]

A higher gain antenna will have a flatter radiation pattern. A 6 dB antenna works well in hilly areas while a 9dB or greater works better in flatter areas with its flatter radiation pattern.

I am running the Comet CA-712EFC and the base is 22 feet above the ground. There are some hills and valley around me and my signal shoots right over the valleys. I get a range of 50-55 miles with the local terrain and forested areas with my antenna setup. I'm running a 30 ft section of LMR400 to the outside wall and a LMR400 jumper from the inside of the wall to my radio.

[LeoG]

That's the thing I worry about is the pattern missing the low areas.

[LeoG]

So what happens if you put a high gain antenna like the 9NC on a mountain top 1000 feet above the floor?  Does it skip over a lot of nearby area?  Does it not reach down at all?  If your antenna is up that high do you use a lower gain antenna so the beam of radiance aims more downward?

[SteveShannon]

30 minutes ago, LeoG said:

So what happens if you put a high gain antenna like the 9NC on a mountain top 1000 feet above the floor?  Does it skip over a lot of nearby area?  Does it not reach down at all?  If your antenna is up that high do you use a lower gain antenna so the beam of radiance aims more downward?

Yes, a high gain antenna sacrifices up and down while enhancing horizontal. 
The antenna we use for our 2 meter repeater is a vertical array that uses phasing to tilt the gain downward like a shallow cone. 

[LeoG]

So how do I read this?

Is this an approx to what this says?  My numbers other than beam width/angle.  Is this a 3dB width meaning the 9dB angle would be less?

 

[SteveShannon]

Max is 9.78 dB (assuming dBi) at theta = 90°, horizontal. That’s the blue horizontal line to the right, and it’s 9.77 dB along the green horizontal line to the left (theta = -90°).

The red lines are about angles above and below horizontal. Theta is the angle along the circle.

So at theta = 84° (which is the upper red line in the diagram) the gain is 5.74 dB. That’s 6° above horizontal.

At theta = 95° (the lower red line) the gain is 6.77 dB.

Everywhere within the 11° angle between theta = 84° to theta = 95° has gain greater than 5.74 up to 9.78 and back down to 6.77. 

[WRUE951]

A few years back I had a homemade UHF J-pole mounted in a tree and had very good results.   Don’t hesitate giving one a try,  Supper easy to build.  

[LeoG]

So the area I'm trying to get to is 6.35 miles away, there is a 120 ft difference in height and it has line of site.  So the angle of incidence is 0.21º.  So it seems I'm basically near the center of the lobes.  Guess I don't have to worry about this since my 80ft above ground ain't no mountain.

[WRYZ926]

6 hours ago, LeoG said:

So the area I'm trying to get to is 6.35 miles away, there is a 120 ft difference in height and it has line of site.  So the angle of incidence is 0.21º.  So it seems I'm basically near the center of the lobes.  Guess I don't have to worry about this since my 80ft above ground ain't no mountain.

You should be good to go.

[LeoG]

Well... ordered the COMET CA-712EFC antenna.  The NC9 is a bit much I think.  Time will tell.

[Lscott]

15 minutes ago, LeoG said:

Well... ordered the COMET CA-712EFC antenna.  The NC9 is a bit much I think.  Time will tell.

A buddy at my Thursday night coffee group was looking at prices for a high gain commercial grade repeater antenna for his Ham setup at a school. Not cheap.

https://www.commscope.com/globalassets/digizuite/262263-p360-db420-b-external.pdf

 

[SteveShannon]

Yeah, those are heavy duty tig welded aluminum and capable of withstanding a lot. The one on our 2 meter repeater is a Comprod?

https://store.trustclarity.com/Comprod-874F-70HDWTM-Heavy-Duty-4-Dipole-Array-for-138-174-MHz-Top-Mount/dp/pId=422212465103940?gad_source=1&gbraid=0AAAAACbFVBrehveY9E-VtwdZkWeYVUs95&gclid=CjwKCAjwl6-3BhBWEiwApN6_kqakg3AdIOXY28uYJNwcnVCETlz3y9MNX0vw8leXnzZJTJfkw1CYthoC4fsQAvD_BwE

[LeoG]

35 minutes ago, Lscott said:

A buddy at my Thursday night coffee group was looking at prices for a high gain commercial grade repeater antenna for his Ham setup at a school. Not cheap.

https://www.commscope.com/globalassets/digizuite/262263-p360-db420-b-external.pdf

 

My family isn't THAT important

[WRXB215]

58 minutes ago, LeoG said:

My family isn't THAT important

Oh Lord! I almost fell out of my chair on that one. 

[WRUU653]

6 hours ago, LeoG said:

My family isn't THAT important

 

5 hours ago, WRXB215 said:

Oh Lord! I almost fell out of my chair on that one. 

Truely made me laugh as well, that was gold! 

[Lscott]

7 hours ago, SteveShannon said:

Yeah, those are heavy duty tig welded aluminum and capable of withstanding a lot. The one on our 2 meter repeater is a Comprod?

https://store.trustclarity.com/Comprod-874F-70HDWTM-Heavy-Duty-4-Dipole-Array-for-138-174-MHz-Top-Mount/dp/pId=422212465103940?gad_source=1&gbraid=0AAAAACbFVBrehveY9E-VtwdZkWeYVUs95&gclid=CjwKCAjwl6-3BhBWEiwApN6_kqakg3AdIOXY28uYJNwcnVCETlz3y9MNX0vw8leXnzZJTJfkw1CYthoC4fsQAvD_BwE

That’s a reasonable price compared to the DB-420. 
 

[Crosswire3]

I just came across some used commercial stationmasters and super stationmasters if you want something affordable and serious. 

[LeoG]

Already got my antenna on the way.  Should be here Wednesday.  5.25dBd gain would likely be a good higher altitude antenna though. 

[piggin]

On 9/18/2024 at 9:25 PM, LeoG said:

That's the thing I worry about is the pattern missing the low areas.

I have 2 antennas up and neither one is epic. One is a Comet GP3 ham 2m/440 antenna good for 5.1 DBD and One is a Laird 4503. (3DBD) The Laird is fed with only 20ft of LMR600 equivalent feedline and is fantastic here in the mountains of WNC for hearing activity in the city of Asheville and the surrounding area. The Comet has more gain is is great for more distant repeaters and really eliminates a bunch of stuff down low closer in. The effect is comical and obvious...its like a local/distance switch!  Depending on the topography you can find a good compromise that is doable for both. The Laird is Lower than the comet. With the comet up much higher

I have heard many guys on a repeater 100 miles away say I am the most distant station they have ever worked in my direction. There is a higher ridge between us and a higher gain antenna here might not exploit the knife edge diffraction I am using to work them. Pattern makes a big difference! High power and a fat radiation pattern can be very good in the mountains while a very high gain antenna will delete your close pals! It really depends on where you are and who you want to talk to. The Laird is to talk to my daughter when she is walking about. The Comet is great to talk to distant repeaters. Good Luck!!!

[piggin]

For close in the minor lobes will be fine.Based on what you want to do you made a great choice. Peak wind velocities here and mounting points pretty much rule out 2 or 3 piece radome antennas for me. I like my low gain one piece radome antennas for the durability and low wind load. If I lived on the plains My antennas would be very different! Your new antenna should work well. My Comet is fed with 60 feet of LMR600 equivalent. A giant upgrade from the 100 ft LMR400 foot section I used previously. 

You should be GTG. Please post again and tell us how it works for you. Anecdotal reports are invaluable...looked down on by some but they still have a huge value and do nothing but add to the knowledge base.

Thanks!