Tower antenna question..

[acyddrop]

This isn't *strictly* a tower antenna question but I don't know where else to post this and figured someone here would know the answer to these two questions:

I will be installing an 80M, 40M, 20M, 17M, 15M, 12M, and 10M beam and a 160M, 80M and 40M wire antenna. Is there any need to install an HF vertical antenna that would also cover 80M thru 20M? I'm already planning to buy a vertical for portable and mobile use, could someone suggest a good vertical for 80-20 (or at least 40M and 20M)?

Second question unrelated specifically to antennas:
I'm planning to install a 100ft Rohn 25G 130MPH tower to support at least a 2m and a 440 antenna at this point (going with two antennas and not a dual band). But I'd also like to put up an HF vertical if it's worth while and a 23cm antenna as well. Is it possible to attach all these verticals at the top of the tower. I was thinking of something like some 1 1/2" galvanized pipe and attaching each antenna to the ends of the pipes in sort of an X configuration at maybe 20-30' apart from end to end. But there must be a solution for something like this.

Thanks in advance.

 

[LtDoc]

Is it possible to put all of those antennas on one tower? Yes, but it won't be easy. Jow about horizontally polarized and vertically polarized antennas, both needed? No sure way to answer that question, it depends on what you are attempting to do/hear. Having both horz/vert antennas for the same band can certainly be handy in some situations, but not absolutely necessary.
One option would be to load the tower it's self on the lower bands. Certainly not 'plug-n-play' but also not that uncommon.
If it were me looking for a multiband vertical antenna, and if I had the room, and if I could afford it, the '18-HT' (HighTower by Hygain) would be my choice. It requires a very good ground radial system, but it's the best I've ever heard. Oh well, one'a these days...
- 'Doc

 

[acyddrop]

That Hytower setup certainly looks fantastic, and the reports of it on eHam are favorable. Looking at the price as of now doesn't fuss me either given the amount I've spent on towers and antennas up to this point. It also looks like I'd be able to erect it close to the shack then just use a wire puller for running a few 60-100ft ground planes. I saw some people stating it required 60+ ground planes all of significant length, which is absolutely out of the question. I could at most be able to run 10-15 such 1/4 wave radials for 80M and down and would result in like 1/8th wave for 160M if I got the choke for it. Obviously 15 radials even on my high end is a far cry from the recommended 60+ radials. Though people reported good luck with just four 80 foot long radials too. The height is certainly reasonable for what would be a backyard install though. What are you thoughts on a max of 10 to 15 radials?

I've also decided to MAYBE lose the idea of a 3rd tower and just put up the 2m, 440 and 23cm antennas on masts 20-30 feet above the shack. I'm not looking to do any kind of great distances on any of those bands (100-150 miles at most with 50-100 watts would be more than enough for me on 2 and 440). If I did that I'd certainly have the money for one of these HF verts. I could also hang a 2m or 440 repeater antenna off the side of one of the towers if I ever decided to, I've seen the brackets for that kind of thing. I've been considering the idea of running an Echolink node/repeater and giving back to the community.

Is it possible to put all of those antennas on one tower? Yes, but it won't be easy. Jow about horizontally polarized and vertically polarized antennas, both needed? No sure way to answer that question, it depends on what you are attempting to do/hear. Having both horz/vert antennas for the same band can certainly be handy in some situations, but not absolutely necessary.
One option would be to load the tower it's self on the lower bands. Certainly not 'plug-n-play' but also not that uncommon.
If it were me looking for a multiband vertical antenna, and if I had the room, and if I could afford it, the '18-HT' (HighTower by Hygain) would be my choice. It requires a very good ground radial system, but it's the best I've ever heard. Oh well, one'a these days...
- 'Doc

 

[k9rzz]

What are your goals and aspirations? That will determine what your antenna system should be.

5BDXCC? Skip the 80 meter yagi (seriously???) and put up a 4 square of verticals. Then from 40 on up you don't need verticals since yagis up 100+ feet will be fine for DX.

However, good verticals need a good ground. No room for radials? put in what you can and forget about it.

 

[n5ims]

This isn't *strictly* a tower antenna question but I don't know where else to post this and figured someone here would know the answer to these two questions:

I will be installing an 80M, 40M, 20M, 17M, 15M, 12M, and 10M beam and a 160M, 80M and 40M wire antenna. Is there any need to install an HF vertical antenna that would also cover 80M thru 20M? I'm already planning to buy a vertical for portable and mobile use, could someone suggest a good vertical for 80-20 (or at least 40M and 20M)?

Second question unrelated specifically to antennas:
I'm planning to install a 100ft Rohn 25G 130MPH tower to support at least a 2m and a 440 antenna at this point (going with two antennas and not a dual band). But I'd also like to put up an HF vertical if it's worth while and a 23cm antenna as well. Is it possible to attach all these verticals at the top of the tower. I was thinking of something like some 1 1/2" galvanized pipe and attaching each antenna to the ends of the pipes in sort of an X configuration at maybe 20-30' apart from end to end. But there must be a solution for something like this.

Thanks in advance.

You need to rethink your tower choice or the size and number of antennas on that tower. The Rohn 25G design wind load rating at 130 MPH is 6.5 - 9.0 sq-ft. A simple tri-bander or a 2 element 40 meter beam by themselves would use up 5.5 of that, leaving very little for all of the others you plan to put up. Put them both up there (along with the rotator, coax, etc.) and you're well above the load rating.

Moving up to the standard 45G would give you a bit more room with the 130 MPH ratings of 9.2 - 11.7 sq-ft. The tougher 45GSR (solid leg version of the 45G) would bring that up to 20.5 - 29.1 sq-ft. You don't want to overload your tower, especially if you live in an area where there are strong winds or especially any chance of ice (or even heavy snow). It only takes a small amount of ice buildup to brind down a tower that's just amount above the design load limit.

Note, the ranges for the wind load is based on where the tower is located. In an area with very mild weather (no ice, minimal snow, very rarely strong winds) rate the larger number while areas with strong weather (hurricanes, strong storms, or ice/snow likely) would rate the lower number.

 

[acyddrop]

Sorry, I'm not getting an 80M beam. I'm using a wire dipole between the towers for 160M and 80M. I'm getting 3 beams, two of which cover multiple bands.

Cushcraft 40M 2 element beam
Bencher Skyhawk: 20M, 15M and 10M (no traps)
Bencher Skylark 17M and 12M (no traps)

The 40M will be at 140 feet the other two will be at 120 feet. Both rotated with a K0XG orbital ring rotator. I'd like an HF vertical for increased flexibility over beams alone. There are applications where the verts will be highly useful. Currently my usage break down is going to be something along the lines of 30% ragchewing, 40% data modes (where-ever I can hit), 25% DXing and 5% contesting. Though my rigs and antenna setup should afford me a lot of flexibility regardless of what I want to do. I would also be able to help in disaster situations (hurricanes, etc) due to UPS and a Generator on site here (I put the generator in ages ago due to the 2004 & 2005 seasons). Eventually I'd love to also be able to give back to the community and operator an echolink repeater for the south Florida area.

I'll also have 3 VHF/UHF antennas on masts connected to the shack up between 30 and 40 feet (2m, 440 and 23cm verticals). My goals on those bands are fairly less lofty, I'll be happy if I can talk 50-200 miles max on 50-100 watts (D-Star, Echolink and IRLP not withstanding). 10 watts on 23cm I think.

What are your goals and aspirations? That will determine what your antenna system should be.

5BDXCC? Skip the 80 meter yagi (seriously???) and put up a 4 square of verticals. Then from 40 on up you don't need verticals since yagis up 100+ feet will be fine for DX.

However, good verticals need a good ground. No room for radials? put in what you can and forget about it.

 

[n5ims]

Sorry, I'm not getting an 80M beam. I'm using a wire dipole between the towers for 160M and 80M. I'm getting 3 beams, two of which cover multiple bands.

Cushcraft 40M 2 element beam
Bencher Skyhawk: 20M, 15M and 10M (no traps)
Bencher Skylark 17M and 12M (no traps)

The 40M will be at 140 feet the other two will be at 120 feet. Both rotated with a K0XG orbital ring rotator. I'd like an HF vertical for increased flexibility over beams alone. There are applications where the verts will be highly useful. Currently my usage break down is going to be something along the lines of 30% ragchewing, 40% data modes (where-ever I can hit), 25% DXing and 5% contesting. Though my rigs and antenna setup should afford me a lot of flexibility regardless of what I want to do. I would also be able to help in disaster situations (hurricanes, etc) due to UPS and a Generator on site here (I put the generator in ages ago due to the 2004 & 2005 seasons). Eventually I'd love to also be able to give back to the community and operator an echolink repeater for the south Florida area.

I'll also have 3 VHF/UHF antennas on masts connected to the shack up between 30 and 40 feet (2m, 440 and 23cm verticals). My goals on those bands are fairly less lofty, I'll be happy if I can talk 50-200 miles max on 50-100 watts (D-Star, Echolink and IRLP not withstanding). 10 watts on 23cm I think.

My earlier post used your 100' size for the towers. As you go higher, the supported wind load gets smaller so be sure to factor this into your tower selection (height and tower size).

The 2 element Cushcraft 40M beam is 5.5 sq-ft wind load.
The Bencher Skyhawk is 8.5 sq-ft wind load.
The Bencher Skylark is 6.5 sq-ft wind load.

Add at least 1 - 1.5 sq-ft for the rotor and coax as well as any additional antennas on the tower. They should be below the tower's max rating for your area. Since you're in Florida (they do have hurricanes there I believe), you should use the lowest rating provided for your tower at your installed height.

Let's say you put both the Bencher antennas on the same tower. You also have a few smaller VHF/UHF antennas side mounted on it as indicated. Your wind load would be 8.5 (Skyhawk) + 6.5 (Skylark) + 1.5 (rotor) + 4 (for the odd small VHF/UHF antennas). Your tower should be rated for at least 20.5 sq-ft of wind load (really should be more for safety). This assumes your base and guy anchors are built to spec and the guys are also installed with the correct size, quantity, locations, etc. for the tower design, height, soil conditions, etc.

 

[acyddrop]

I'm having the towers, guy wires, and beams (etc) installed professionally. I want it done right from the start. The towers are both Rohn 55g type towers rated for 130mph winds. I did a bit more research on the Hy-tower and it works best with 24 ground radials, which gives ~3db gain I think I can eek out that many, I may have to move the damn thing back by the rest of the towers, which means I'll have to run heliax to it. I'd hope to get it closer to the shack (which is attached to the house) and just use RG-8X or similar since it would be a 50ft run or so. Hopefully my tower/antenna expert can help me out.

My earlier post used your 100' size for the towers. As you go higher, the supported wind load gets smaller so be sure to factor this into your tower selection (height and tower size).

The 2 element Cushcraft 40M beam is 5.5 sq-ft wind load.
The Bencher Skyhawk is 8.5 sq-ft wind load.
The Bencher Skylark is 6.5 sq-ft wind load.

Add at least 1 - 1.5 sq-ft for the rotor and coax as well as any additional antennas on the tower. They should be below the tower's max rating for your area. Since you're in Florida (they do have hurricanes there I believe), you should use the lowest rating provided for your tower at your installed height.

Let's say you put both the Bencher antennas on the same tower. You also have a few smaller VHF/UHF antennas side mounted on it as indicated. Your wind load would be 8.5 (Skyhawk) + 6.5 (Skylark) + 1.5 (rotor) + 4 (for the odd small VHF/UHF antennas). Your tower should be rated for at least 20.5 sq-ft of wind load (really should be more for safety). This assumes your base and guy anchors are built to spec and the guys are also installed with the correct size, quantity, locations, etc. for the tower design, height, soil conditions, etc.

 

[LtDoc]

The Hy-Tower...
You may have to more it further away from the shack but that doesn't necessitate the use of heliax feed line. Since it's about the same price (locally) I might use LMR-400, but that's not needed either. RG-8 or RG-213 would work just fine. Keep in mind that it's an HF antenna. I also seriously doubt if you'd ever see a 3 dB gain from it. It's a ground mounted multiband 1/4 wave vertical, so no gain. Any/all ground mounted vertical antenna will benefit from having a 'better' ground than is normally found with plain old dirt. That means the more radials you have the better. Having 120 radial like most commercial vertical antennas would be nice, but not really necessary for amateur use. Making that radial pattern symmetrical would also be nice, but it isn't absolutely necessary either. A bit 'lop-sided' typically doesn't hurt anything especially if the alternative is no/less radials in the field.
There are degrees to "less than perfect". I've never seen a 'perfect' antenna yet, they are all compromises in some way. You do what you can and then live with the results.
- 'Doc

(The perfect number of radials, as far as I'm concerned, is twice as many as you've gotten in the ground before you are totally sick of messing with them. I hate messing with ground radials! )