Ground independent vertical for HF

[videobruce]

That was the term that was in the ARRL Handbook chapter 21 that seems to be the only option for where I live (in a city) for a roof tripod mounted antenna for HF.

So my question is, since I couldn't really find anything specific other than a "C Pole" using that term, does anyone know if such a animal exists?

Before anyone asks, I really can't go the 'dipole' route due the lack of trees, nor can I go with the at ground level mounted vertical. Other than a dipole in the (full, walk up, not a crawl space) attic which I really don't even want to try. There is also the length issue, the sky is not the limit.

I don't have a HF rig yet, I'm studying using the ARRL General Class License manual (which isn't going that great ).

Positive suggestions welcome.

 

[videobruce]

BTW, one of those "Hexbeams" won't work, no way I could mount it up on a 2 1/2 story 'double'.

 

[prcguy]

In my experience all the “no ground plane” HF vertical antennas can also be called “no workee so good” HF vertical antennas. This includes the Comet CHA-250 and many others. If you can get an HF vertical on the roof can you use very thin wire for radials that can’t be seen at a distance like thin enameled magnet wire, etc?

 

[videobruce]

I understand it would be a compromise like all 'compact' antennas.

 

[prcguy]

I understand it would be a compromise like all 'compact' antennas.

With a little research and creativity it doesn’t have to be a compromise. What bands are you interested in?

 

[W4AXW]

That was the term that was in the ARRL Handbook chapter 21 that seems to be the only option for where I live (in a city) for a roof tripod mounted antenna for HF.

So my question is, since I couldn't really find anything specific other than a "C Pole" using that term, does anyone know if such a animal exists?

Before anyone asks, I really can't go the 'dipole' route due the lack of trees, nor can I go with the at ground level mounted vertical. Other than a dipole in the (full, walk up, not a crawl space) attic which I really don't even want to try. There is also the length issue, the sky is not the limit.

I don't have a HF rig yet, I'm studying using the ARRL General Class License manual (which isn't going that great ).

Positive suggestions welcome.

Hard to offer suggestions since you only mention what you can't do rather than what your situation might allow, such as space and access, what bands and operating modes interest you, local or DX or both, etc.,etc.

 

[videobruce]

Here is the current setup. The tripod on the right would move the Comet dual band (top) to the 'lower 'arm' on the right. That area would be for the vertical (minus the 'L' extension) above the TV yagi. The discone be be removed. (That window is actually a 'roof hatch' door which is how I get up there).

 

[videobruce]

One thing I should of mentioned, this would be a purchase of a existing item, not a scratch built which is well above my pay grade.

 

[WA8ZTZ]

IMHO, a typical HF multi-band vertical (4/5BTV, 14AVQ, etc.) would be too unwieldly to be mounted on that tripod.

However, that existing discone may work on 10 meters. 10 is hot right now as we reach the peak of solar cycle 25.
You can get on 10 phone with a tech license.

 

[prcguy]

IMHO, a typical HF multi-band vertical (4/5BTV, 14AVQ, etc.) would be too unwieldly to be mounted on that tripod.

However, that existing discone may work on 10 meters. 10 is hot right now as we reach the peak of solar cycle 25.
You can get on 10 phone with a tech license.

If the tripod is mounted securely it will easily handle the antennas mentioned. Of all the no ground plane antennas I’ve used, the Cushcraft R7 was not bad and it seems it’s been replaced by the R8. It’s 28.5ft tall and fairly efficient. The classic trap verticals like the 4/5BTV, 14AVQ, HF6V, HF9V should also work ok with a lot of thin invisible ground wires.

 

[WA8ZTZ]

If the tripod is mounted securely it will easily handle the antennas mentioned.

You must live in a place where there is no wind.

If the legs of the tripod don't pick up the rafters underneath the roof deck (sheathing), forget it.
If they merely attach to the sheathing, there is no way the installation of a tall vertical will survive a serious wind event.
This is especially true if the sheathing is OSB... nail or screw retention is much better in plywood.

Notice that the OP lives in Buffalo NY. Winter storms come screaming off the Lake driving a foot (or more) of
snow with them.

 

[prcguy]

You must live in a place where there is no wind.

If the legs of the tripod don't pick up the rafters underneath the roof deck (sheathing), forget it.
If they merely attach to the sheathing, there is no way the installation of a tall vertical will survive a serious wind event.
This is especially true if the sheathing is OSB... nail or screw retention is much better in plywood.

Notice that the OP lives in Buffalo NY. Winter storms come screaming off the Lake driving a foot (or more) of
snow with them.

My area is known as “Hurricane Gulch” to the local sailors. If you don’t bolt into the rafters then all bets are off.

 

[videobruce]

Both tripods (5' of different manufactures erected at different times) are bolted with lag screws to rafters. I made damn sure of that!! I had the legs out to their maximum for best support. The one on the left just replaced a much older 3' that had rusted thru legs. The north side of the house roof was replaced (tear off) and I had the roofers help me with that installation. The other I did myself.
Yes, there is a 'wind' problem that has gotten worse the past few years with all the other weather issues due to global warming, thou this isn't the south or the mid-west with tornado's.

Let me digress a bit. I've been doing alot of reading for my General license and I came across the issue of 'RF burns' from un-bonded equipment which is a separate subject in itself. I'm concerned about reverse currents (if that is what they are called) when some antenna installations 'leak' (my term) RF back down the shield of the cable.
It's not that I'm against ground radials, both of my V-U antennas have ground, but there is a huge difference in the length involved. Stringing ground lines across the roof really isn't practical for my roof.
All of that is kinda confusing to me and hard to describe here. The "ground independent' design sounded like a good idea when I first read about it after briefly looking over the more common choices.

Question; I had a Diamond X50 that had three radials that were 6-8" in length which are too short to be true 1/4 wave radials at least for VHF. What good could those be, especially when there are only 3 of them?

 

[AK9R]

Question; I had a Diamond X50 that had three radials that were 6-8" in length which are too short to be true 1/4 wave radials at least for VHF. What good could those be, especially when there are only 3 of them?

I believe that they are intended to keep stray RF from the antenna from travelling down the outer shield of coax.

 

[videobruce]

Isn't that design relevant for HF?

 

[W8KIC]

Here is the current setup. The tripod on the right would move the Comet dual band (top) to the 'lower 'arm' on the right. That area would be for the vertical (minus the 'L' extension) above the TV yagi. The discone be be removed. (That window is actually a 'roof hatch' door which is how I get up there).

It's a shame that chimney isn't just a little bit taller, as well as how it flairs outward towards the top of it. Some years back, I installed a couple of heavy duty chimney straps on my parents home chimney, which was quite a bit taller than the one on your roof. The mast was installed and on top of that, a Cushcraft R7 was mounted and it stayed up for many years as it endured the strong winter winds of Northeast Ohio. It was a very good set up and I worked LOTS of DX with it. With MFJ no longer in business, trying to find a vertical antenna (other than from what's left of their inventory, as well as the inventories of a few dealers) with the Cushcraft or Hy-Gain name on it will be problematic to say the least.

 

[videobruce]

That chimney is my workbench up there. With that mostly flat top, I lay tools and parts there since there is no where else to do so other then the pouches in my belt which isn't as convenient.

 

[prcguy]

It's a shame that chimney isn't just a little bit taller, as well as how it flairs outward towards the top of it. Some years back, I installed a couple of heavy duty chimney straps on my parents home chimney, which was quite a bit taller than the one on your roof. The mast was installed and on top of that, a Cushcraft R7 was mounted and it stayed up for many years as it endured the strong winter winds of Northeast Ohio. It was a very good set up and I worked LOTS of DX with it. With MFJ no longer in business, trying to find a vertical antenna (other than from what's left of their inventory, as well as the inventories of a few dealers) with the Cushcraft or Hy-Gain name on it will be problematic to say the least.

Another vote for a chimney mount and R7/R8 type antenna. Most chimney mounts will hold the mast out several inches to clear overhanging bricks at the top.

 

[WA8ZTZ]

Another vote for a chimney mount and R7/R8 type antenna. Most chimney mounts will hold the mast out several inches to clear overhanging bricks at the top.

Stand-off chimney mounts... good idea... set the mast on a metal plate where it contacts the roof so as to protect the shingles.
The OP may want to consider guy ropes as well considering his location (sustained gale 8 force winds with ice and snow load).
Another whole issue but it needs to be considered is proper grounding of the entire installation for lightning protection.