Baffled by verticals. A few questions.

[trapland]

Hi all,

In studying verticals, I'm finding tons of conflicting info and opinions. I have a Hustler 5-band. Here's my questions.

1. When roof mounted, how/where do you do lighning grounding?

2. My antenna manual says roof mount with radials is better than ground mount with radials. Really? Better for what?

3. Is ground mount without radials (good soil) better than roof mount with a counterpoise like this Butternut style. http://http://www.bencher.com/pdfs/00236IZV.pdf http://www.bencher.com/pdfs/00236IZV.pdf

Thanks

 

[n0zna]

I had mine on a fence post away from neibors,so they wouldnt bother it,they had kids.Didnt need radials since it was a metal fence.I ran it for awhile and put up my dipole,gave it to my frend that has local repeater,he live on small lot in town.I made a balum and 124 foot of wire on each end and with tuner does ever band 10-11- though 160...73s de JW

 

[RatsoW8]

You're right..verticals can seem confusing but in reality they are very simple.

Radials are the other half of an hf vertical antenna system. it would be like putting up a dipole with only one leg. The antenna is not balanced. Without radials your hustler will perform poorly even if mounted on the roof. Ground mounted with radials will usually outperform elevated without.

I had a homebrew ground mount vertical for 20 meters with 43 radials laid out aound the antenna and was very impressed with perfrmance.At times it actually worked better for DX than my 20m dipole at 35' did. Try it if you can't install radials on your roof.

 

[Wire Weasel]

I would forget the DC (lightning) grounding. This would only serve to ATTRACT lightning to your antenna and roof/house. Now why would anyone want to do that? Leave it isolated from ground. I've done that with all my roof mounted antennas since 1976. No worries here mate.

As to the radials thing and roof vs. ground, you'll just have to do all the research and make a choice.

Good luck

 

[VA3ES]

Generally speaking, a roof mounted vertical with at least 4 resonant radials (minimum 1/4 wl long) will outperform a ground-mounted vertical with a counterpoise. The reason is that unless you have a vast counterpoise (at least 60 1/4 wl radials, or a huge area of chicken wire) you will have ground losses with a ground mounted vertical. Once you raise up a vertical, the ground losses are greatly diminished (or entirely eliminated).

If your vertical is at least 1/4 wl up, above ground, grounding is difficult. The length of the ground wire becomes resonant and reactive and is no longer a ground wire.

Years ago, I had a Hy-gain 14AVQ trapped vertical on a flat roof, 35 feet up. That antenna had 32 radials, minimum, 1/4 wl long, 8 for each band. Worked like a bomb.

Ground losses cause inefficiencies. You're basically heating up the ground. The whole idea of a counterpoise it to provide the mirror-image a vertical needs to operate properly, and to isolate the antenna from ground losses. Ground losses cause the SWR to hover close to 1:1 because the radiation resistance (50 ohms) is actually provided by the resistive ground losses, not the antenna matching.

Some garbage antenna companies actually promise that their verticals will perform well without ground radials, and provide a good match. Bogus. What the corrupt antenna manufacturer is doing is relying on the high ground loss to make up the feed point resistance, and fool the purchaser into believing he has a good match.

Low ground losses will show a high VSWR before matching. The matching system should resonate and match the antenna to at least 1.5:1. Once done, you're good to go with an efficient vertical.

The only antennas that don't require radial are 1/2 wl antennas and "half-wave fed" antennas, though even the so-called "half-wave fed" verticals still need some radials.

 

[BOOTY MONSTER]

Antenna Notes

 

[trapland]

I would forget the DC (lightning) grounding. This would only serve to ATTRACT lightning to your antenna and roof/house. Now why would anyone want to do that? Leave it isolated from ground. I've done that with all my roof mounted antennas since 1976. No worries here mate.

As to the radials thing and roof vs. ground, you'll just have to do all the research and make a choice.

Good luck

Ok, but wont the coax shield simply be grounded to my equipment ground anyway, and thus bring lightening straight into the shack?! what about grounding the coax right before it enters the house?

 

[trapland]

Generally speaking, a roof mounted vertical with at least 4 resonant radials (minimum 1/4 wl long) will outperform a ground-mounted vertical with a counterpoise. .

Ok, but what about a roof mount with a square counterpoise? Is that better than ground mount? Also again, what do I do about a dc ground?

If I do roof mount with radials, what about a DC ground? Ground the mast and radials? Drop a ground wire from the coax shield to ground?

 

[Moleculo]

Ok, but wont the coax shield simply be grounded to my equipment ground anyway, and thus bring lightening straight into the shack?! what about grounding the coax right before it enters the house?

You should install some form of lightning protection inline with the coax before it enters the house. It's not an complete solution, but it's at least a start. Try these: Impulse Suppresors | Arrestors

If the lightning gets nearby and you're home, disconnect the coax.

 

[hookedon6]

..again, what do I do about a dc ground?

If I do roof mount with radials, what about a DC ground? Ground the mast and radials? Drop a ground wire from the coax shield to ground?

just about anything you may want to know about any BTV is here http://www.dxengineering.com/pdf/BTV-INSTALL-GUIDE-Rev0a.pdf

 

[Captain Kilowatt]

I would forget the DC (lightning) grounding. This would only serve to ATTRACT lightning to your antenna and roof/house. Now why would anyone want to do that? Leave it isolated from ground. I've done that with all my roof mounted antennas since 1976. No worries here mate.

As to the radials thing and roof vs. ground, you'll just have to do all the research and make a choice.

Good luck

WW, this may piss you off but I really don't care so here it goes.

You are either lucky or very stupid and I suspect a little of each but weighing in heavier on the latter. First of all lightning rods and grounds do NOT attract lightning. I have heard this all before and it is simply NOT true. I would have thought that you would have known that. The coax cable is already connected to the antenna providing a ground path for an electrical charge to build up easily. It does not even need a ground path for this to happen BTW and that is the reason trees get hit. They don't have a ground to attract the lightning either. When the charge builds up to the point of arcing to the sky, yes lightning actually goes start from the ground up to the sky in the first stage and not from the sky down as most people think, you are going to want a good heavy DC path for that energy to be conducted to the earth and a simple grounded coax shield is not going to do it. If what you say were true we could have saved thousand and thousands of dollars and not grounded our broadcast towers and just let the coax cable shield handle it.

 

[wavrider]

CK is 100% correct on the lightning and ground topic. Not that I needed to verify that but his post is verified by many electrical codes and also with proper antenna installation procedures.

If roof mounted then run a heavy gauge solid wire from the antenna mount to a good ground rod, or several ground rods spaced a few feet apart.

Lightning is wicked stuff and I have seen my yagis and towers get hit many times living in the lightning capitol of America. Florida.

Any and all precautions need to be taken if possible but never the less when lightning strikes it is devastating.

Some people never install ground cables or rods and have never have been hit, you roll the dice and take your chances

 

[trapland]

So I'm getting the idea that a ground mount is preferable to a roof mount for several reasons. Check me on this:

1. Safer for lightning. Nice straight path and you can ground your coax at the antenna and the house.

2. Takeoff angle is better for DX. Flatter means longer distance for the first hop.

3. Ground radials are way easier than elevated. Just put a bunch out there and dont worry about the length. You also dont have to tune the length.

4. 90% of the info available concerning verticals is about ground mounting. Even though the manual that came with my antenna suggests that elevated mounting is better, the excellent DXEng info that Hookedon6 offered, almost discourages roof mount. It's all ground.

Thanks all. I've decided to improve my existing ground mount and not piss off my wife with that "damn aerial on the roof".

73

 

[Captain Kilowatt]

Outside of town here there was an older fellow I knew that had an A-99 mounted on the eave of his house using brackets. There was no ground other than the coax cable shield. Lightning struck the antenna and converted it into shards of fiberglass. It followed the coax cable down to the kitchen where he had the radio installed. The coax was routed down from the attic behind the kitchen cabinets which were blown off the wall. Oh yes, it set the house on fire as well. With a decent ground cable and rods he could have prevented the $35,000 damage inflicted to his house because he didn't spend at tops $50-100 to do it right.

I had a Gates FM broadcast transmitter get hit multiple times in a single storm. I actually watched from a distance and saw it get hit four times before saying to hell with it and going home as it was not safe to enter the site during the storm. When all was said and done I lost a rectifier stack in the 5000 volt plate supply with none of the program link gear or audio gear on site damaged at all. That's the difference between doing it right and not doing anything at all.

 

[wavrider]

So I'm getting the idea that a ground mount is preferable to a roof mount for several reasons. Check me on this:

1. Safer for lightning. Nice straight path and you can ground your coax at the antenna and the house.

2. Takeoff angle is better for DX. Flatter means longer distance for the first hop.

3. Ground radials are way easier than elevated. Just put a bunch out there and dont worry about the length. You also dont have to tune the length.

4. 90% of the info available concerning verticals is about ground mounting. Even though the manual that came with my antenna suggests that elevated mounting is better, the excellent DXEng info that Hookedon6 offered, almost discourages roof mount. It's all ground.

Thanks all. I've decided to improve my existing ground mount and not piss off my wife with that "damn aerial on the roof".

73

Raised verticals are easier to work with as far as radials, only need about four to make it work as good as 120 ground laid radials.

Maybe a small tower, 15 to 20 feet, let the wife plant some flowers around the base, and use your ground radials as guys so double duty, will work fine and wont have all those ground radials laying in the yard to mow around.

Either way the vertical will work good, just do not expect to much from it on 20 meters and above as height is might on the upper HF frequencies.