Antenna height?

[Tyke]

Hello all, Can you tell me what the maximum antenna height is. I’m looking at going about 80’ above ground. 

[marcspaz]

There is no "limit" on antenna height from a GMRS rule perspective.  If you have a 1,500 tower, from an FCC rule perspective, you are good.   Now, there are registration and notification requirements for antennas near airports and for antennas over 200 feet.  However, as long as there is no safety or environmental impact, they will simply process the notice/registration into the official record. 

 

There could be state, county or local restrictions, etc.  If you are dealing with an HOA... have fun getting an antenna up at all.  It's always a fight.

[Tyke]

Well thank you sir believe it or not my antenna will be mounted on 2 1/2 pipe reducing to 1’’ pipe at the top,  80’ tall, top and middle attached to tree.  Concrete base and will be hinged to be able to lower it down for servicing. I have to rent a 125’ boom lift to get the reach and height. Weather is slowing me down here. May have to wait till spring. I’ll post pics when done.

[Bugkiller]

I must say, that sounds like something I would like to see a picture of.  Please do post pictures

[PACNWComms]

+1 on showing pictures of this antenna installation. I had VHF and UHF antennas in my attic, until having my roof replaced last summer. I live at the top of a large hill, but when locating my antennas to the eight foot high fence surrounding my property (thinking it was temporary), I found that there was no change in my useful coverage. I still hear and hit repeaters, and what I probably miss out simplex, well if I don't hear it, I don't miss it (ignorance is bliss at times). So, I may leave them mounted to the fence, as it gives me more attic storage. But, seeing that antenna on an 80 foot mast does intrigue me a bit. 

[Muzic2Me]

3 hours ago, Tyke said:

Well thank you sir believe it or not my antenna will be mounted on 2 1/2 pipe reducing to 1’’ pipe at the top,  80’ tall, top and middle attached to tree.  Concrete base and will be hinged to be able to lower it down for servicing. I have to rent a 125’ boom lift to get the reach and height. Weather is slowing me down here. May have to wait till spring. I’ll post pics when done.

Hope its not a Pine. They sway when the wind gets up. Please post pics

[gortex2]

Hope you spend funds on a good chunk of hard line and a real antenna. 

[Tyke]

So this is the antenna base its 2 1/2" schedule 10 pipe you only see the first 3 feet of the 21 foot length. the next section is 21' of 2'" then 21'of 11/2, 21' of 11/4, 10' 1" so i guess ill be at 94'. The base will be able to hinge and will be encased in concrete, again the weather may prevent me from proceeding further at this time. I'm using LMR 400.

Antenna base also has a lug on it for grounding to ground rods, The antenna is about 40 feet from the house, i refuse to tie in the ground to my home grounding system. if we expect lighting ill disconnect coax at the base. When I was on the fire dept ive seen direct strikes to house wiring and i want nothing to do withy connecting a antenna of this height to my house. This is work in progress and will update as things get done, Another person did comment about whether i was connecting the antenna to it well I understand the sway thing in the wind but said pine tree will be topped and most branches removed. so I dont think the sway will be too bad, well see though. Also at this height i might add a decorative weathervane. Stay tuned

Tyke 

[gortex2]

Not sure its worth the work if your using LMR400. 150' of LMR is going to be close to 5 db of loss with connectors (maybe more depending on who assembles) and lighting arrestors. You'd have better luck with it on the roof of the house and 20' of cable. With a 50 watt radio you almost going to maybe have 15 watts at the antenna. RX will be just as bad. With the amount of work your putting into this I would highly recommend a better cable. I run 7/8" at a minimum anytime its over 100' on a tower. 

[Tyke]

Thank you for the input! ill keep that in mind, unfortunately i'm losing a lot now with the duplexer in the Bridgecom repeater so the extra length of the Lmr is not going to help. I will invest later in a 50watt repeater and better cable at some point, with all the work done now i'm at a point of no return. really trying hard at the antenna height. Hell i can put the repeater at the base if I want too eliminating a lot of cable.

Tyke

[gortex2]

If this for a repeater you will never get your expectations with LMR 400 at that distance. As said a mount on your house would work better on the repeater. Setting up a repeater with inferior equipment will not help expectations. If you just use 3db thats half your power. If your already at 25 watts after the duplexer your even worse than what I had given you before. I think you need to rethink what your trying to do. At this point youd be better off buying the RT97, mounting it on top of the pole with the antenna and run power up the 150'. 

[SteveShannon]

14 hours ago, Tyke said:

So this is the antenna base its 2 1/2" schedule 10 pipe you only see the first 3 feet of the 21 foot length. the next section is 21' of 2'" then 21'of 11/2, 21' of 11/4, 10' 1" so i guess ill be at 94'. The base will be able to hinge and will be encased in concrete, again the weather may prevent me from proceeding further at this time. I'm using LMR 400.

Antenna base also has a lug on it for grounding to ground rods, The antenna is about 40 feet from the house, i refuse to tie in the ground to my home grounding system. if we expect lighting ill disconnect coax at the base. When I was on the fire dept ive seen direct strikes to house wiring and i want nothing to do withy connecting a antenna of this height to my house. This is work in progress and will update as things get done, Another person did comment about whether i was connecting the antenna to it well I understand the sway thing in the wind but said pine tree will be topped and most branches removed. so I dont think the sway will be too bad, well see though. Also at this height i might add a decorative weathervane. Stay tuned

Tyke 

Here’s an article, written in English rather than “regulish”, on correct grounding for antenna systems.  You really ought to reconsider your grounding.

https://reeve.com/Documents/Articles Papers/Reeve_AntennaSystemGroundingRequirements.pdf

[mbrun]

@Tyke I strongly encourage you to ground and bond your system correctly. If you have any cable from an antenna system entering your home, you really do want it grounded and bonded to your main electrical ground. But it must done properly. Done improperly, or not at all, you could at times have a very unsafe voltage potential between things in your home and the shield and/or center conductor of your feed line. Doing it properly is not difficult, but does come at some added expense. Also, if you are insured, take a hit, and have a savvy insurance company, they may not cover you if they can deduce that at least the NEC minimum requirements were not followed.

Good luck on your project. I look forward to seeing the appearance of your final installation.


Michael
WRHS965
KE8PLM

[Tyke]

Well thank you sir believe it or not my antenna will be mounted on 2 1/2 pipe reducing to 1’’ pipe at the top,  80’ tall, top and middle attached to tree.  Concrete base and will be hinged to be able to lower it down for servicing. I have to rent a 125’ boom lift to get the reach and height. Weather is slowing me down here. May have to wait till spring. I’ll post pics when done.

[Tyke]

Ok thank you all for your input well taken, so I’ve decided to the following correct me if I’m wrong. 
My antenna is roughly 40’ feet from from the house. I understand all the grounding that was discussed. I’m going to place the repeater at the antenna in a radio house, I’ll monitor the temp and humidity levels as this is my trade. l only need about 80’+- of coax I’ll use the 7/8 hardline as mentioned above. Notice the chart below I think the numbers look great. The BridgeCom 40 watt output with duplexer is only 28 watts out. This is unacceptable to me wish I had done more research prior to the purchase, but this is all a learning curve and fun to figure out. Now I also like the fact I do not have a coax running into my house no one can say that all the grounding in the world would stop a direct hit by lighting from tracing the coax and into the house I can’t stomach the thought. Any other suggestions would be great. 

[SteveShannon]

Nobody suggested that you shouldn’t disconnect your coax, but if you don’t tie your grounds together with #6 or #4 copper your coax will tie them together. Your radio will have one ground potential and it’s possible your antenna will have a different one. 
Just be sure and install an arrester as mandated by NEC. 

[Phyberoptic]

I'd rather have 10 watts at 80' than 50 watts at 20' as far as coverage goes.

[Tyke]

Hi steve, so are you saying that if I have my station house located 40 feet from my residence I still need to tap into my home grounding system for my antenna mast and coax ground,at this point I’ll have no connection of any coax inside my house. I just feel that a direct strike (worst case) as we all know lighting has a mind of its own, could travel into my home grounding system where it normally would not have. I understand that by grounding the mast and eliminating static charges to ground will help avoid a direct strike and different voltages between the radio, coax and mast. I figured locating the Equiptment away  from the house if it gets hits there is no connection to my house, if the station house blows up my repeater goes flying and antenna falls at least it’s not affecting my home directly, I’m not being sarcastic at all, as mentioned I’ve seen strikes on houses, fires, cracked foundation walls and blown off siding I do not want this near me. And at least if we get a pop up storm and I’m not able to disconnect my equiptment in time it is what it is. Your thoughts?

Tyke

[gortex2]

If your house is 40' from the "radio shack" you can just ground the antenna at the radio shack. There is no need to run to the house. With that said remember that your "ground" wire from the repeater will be going back to the house via some sort of 110v power source unless your having a drop from the power company. If thats the case you definitely want surge protection on the 110 volt leads also going into the radio shack. 

8 hours ago, Phyberoptic said:

I'd rather have 10 watts at 80' than 50 watts at 20' as far as coverage goes.

The issue with cable is not all the transmit power. The more critical issue in any repeater is RX sensitivity. If your loosing 5 db in the receive line your almost killing portable use to the repeater. This is what many dont think about. 

[mbrun]

Hi steve, so are you saying that if I have my station house located 40 feet from my residence I still need to tap into my home grounding system for my antenna mast and coax ground,at this point I’ll have no connection of any coax inside my house. I just feel that a direct strike (worst case) as we all know lighting has a mind of its own, could travel into my home grounding system where it normally would not have. I understand that by grounding the mast and eliminating static charges to ground will help avoid a direct strike and different voltages between the radio, coax and mast. I figured locating the Equiptment away  from the house if it gets hits there is no connection to my house, if the station house blows up my repeater goes flying and antenna falls at least it’s not affecting my home directly, I’m not being sarcastic at all, as mentioned I’ve seen strikes on houses, fires, cracked foundation walls and blown off siding I do not want this near me. And at least if we get a pop up storm and I’m not able to disconnect my equiptment in time it is what it is. Your thoughts?
Tyke

The only thing you can actually do to ‘avoid a direct strike’ to you antenna is not put one up at all. You have no control whatsoever on whether you will you will or will not get hit, so I suggest dropping that idea completely. When you install things per the NEC, it is all about life safety and property protection improvements. When you follow the NEC you are improving your odds. If you choose not to comply with the NEC and other professional recommendations, that is your choice. There are those that simply don’t know better, and those that choose not to know better, and many have survived unscathed. Others not so much.

If your tower were completely off-grid powered with no coax running to the house and no AC power running from the house to the tower, you could make an argument for not bonding your tower ground to the home’s earthing system. After all, your home and your neighbors homes are not bonded together. However, as has been said, if you run power from your home to the tower either to power the equipment or to serve as utilitarian power, you’re still connecting your home’s ground to the tower, only now doing it poorer manner because you are now using the small ground conductor in your small 120v power cable, rather than using an appropriately sized bonding conductor. Doing it correctly merely brings the potential between tower ground and home ground closer to a zero potential under a wider variety of conditions. Zero potential is what you want.


Michael
WRHS965
KE8PLM

[SteveShannon]

Tyke,

Perhaps I misunderstood.  Will you be running any physical connections between the house and the tower?  Coax, power, Ethernet cable, cables for monitoring other conditions (you might have mentioned some kind of telemetry)?  If not, then you don’t need to worry about it.  I thought you were proposing disconnecting the coax from the house whenever you anticipate lightning. I apologize if I misunderstood.

If there’s never going to be a physical connection, then disregard what I said.

[Tyke]

Hi Steve you did not misunderstand, I do understand the 120 volt feed out to the tower is also susceptible to all the conditions you have mentioned, I do have the ability to do solar if I choose to, the Hvac monitoring will be wireless although the repeater has a very wide range of temperature parameters I’d be more concerned with the humidity levels being outside they did not give those parameters. So I may install (2) 125 amp/hr lifepo batteries with solar or some other type of battery as lifepo’s won’t charge when it gets too cold. This is work and decision making in progress and all the help you and others is well appreciated. I’m going to miss having the repeater in my rack in my office but the coax run is just to long for me. Also the antenna will be positioned so that if it falls and goes thru the house it will not hit my side of the bed. Shhhh she does not know thatand mabey I’ll plug the repeater into the neighbors outdoor plug. (My problem solved) What did you think of the line losses in the above charts I know they may not be exact.

Tyke

[Tyke]

Also this is all for testing purposes, if I like it and the performance is good, although we don’t have a lot of radio traffic so far, I’d  be willing to put up a real tower and gain more height and do things more inline with a professional installation. For now it’s a hobby and I’m also trying to hit a certain repeater about 30 miles away, I understand there are ways to link via the internet but that’s above my ability at this point, and I don’t think I would want to do that anyways it’s fun just trying to get the height and wattage out there. My radio is a Wouxun 50 watt. Without the repeater I could seem to break into that repeater I believe I got a squelch tail (if I’m saying that right) I can hear him but can’t seem to get the power out I’m interested to see what happens with the 80-90ft tower. My ground elevation is roughly 1020 ft then I’ll go up with my tower 80 to 90 feet, most of the surrounding areas are lower then me 500 to 900 approximately.

Tyke

[SteveShannon]

I don’t think you’ll ever notice the loss from 40w to 28w.  Your antenna height will more than compensate.

Just a couple more things about lightning protection.  Proper grounding puts everything at the same ground potential.  That allows the soil to absorb any voltage that would be conducted on the shield rather than following the shield into your home and equipment.  

But without a lightning protector on the center conductor of the coax which must be connected to the ground system, the high voltages associated with static electricity or a lightning strike to your actual antenna have a straight shot into whatever is connected to the coax, including your repeater.

Even a temporary installation should have a good ground and lightning arrester.  In your instance I believe the lightning arrester would be right at the soil level where your antenna coax enters your radio shack and tied into the ground system for the radio shack, which is also bonded to the utility service ground.  

Inside your house I would use an antenna switch that opens up the connection from the incoming coax and connects the incoming coax center connector directly to ground. 

I have read good things about Alpha Delta lightning protection. I’m a new ham and just learning what’s necessary and available for amateur radio.  My background is electric utilities and utility SCADA where grounding systems were literally the foundation upon which everything was built. 

https://www.alphadeltaradio.com

[Lscott]

20 hours ago, Sshannon said:

Inside your house I would use an antenna switch that opens up the connection from the incoming coax and connects the incoming coax center connector directly to ground.

I wouldn't recommend that. Lighting strikes are very high voltage and current. Chances are the RF switch would have the internals destroyed, melted contacts and so on, and the current will take whatever path to ground it can find, including jumping any gaps inside of the switch. Your best bet, provided you know a storm is coming, is disconnecting the coax from any equipment and keeping the ends away from anything conductive. A few people claim they put the ends in thick glass jars.

Even near strikes can induce high voltages in the cable ruining to equipment, similar to an EMP event. A lighting arrestor won't guarantee no damage will occur but will go a long way in reducing any that does.

One thing that people don't think about is build up of static electricity, even on bright sunny days. If there is no way to bleed it off the voltage that builds up can destroy RF front ends in radios. You may have seen it mentioned in the specifications but never really thought much about it, some antennas are built with a DC ground, due to the driven element(s) would otherwise be isolated, for exactly the above reason.