Base antenna mast

[CommJunkie]

Is there something specific I should be looking for to use as a mast for a base antenna I plan to put up? Someone once mentioned a fence post, but I would think that would be too heavy.

Also, where can I get chimney straps to mount everything?

Thanks.

 

[SteveC0625]

I think you will find that TV antenna masts are pretty much perfect for CB antennas. Radio Shack used to sell all that stuff: chimney straps, roof tripods, 5 and 10 foot mast sections and a lot, lot more.

 

[W2PMX]

1) Don't mount an antenna on a chimney for 2 reasons. The gasses coming up the chimney will destroy the antenna (there's sulfur in them, so a wet antenna will be attacked by sulfuric acid.) And the stress of an antenna flexing in the wind will destroy the chimney.

2) Anything that's strong enough to keep standing under the load you give it will be fine. But you have to have the wind load figure of the antenna (and the mast itself) and the wind figures for your area to figure out what will work. Most TV masts will be fine (if properly guyed) with a small antenna, even a 5/8 wavelength 11 meter ground plane. Anything larger - well, as I said, you have to know how much wind load the mast has to be able to withstand.

 

[Cruiseomatic]

1) Don't mount an antenna on a chimney for 2 reasons. The gasses coming up the chimney will destroy the antenna (there's sulfur in them, so a wet antenna will be attacked by sulfuric acid.) And the stress of an antenna flexing in the wind will destroy the chimney.

...Snip....

W2PMX, I must respectfully disagree with you on this.

Correction on 1.) Only if you use it will there be gasses. And for 2.) I had an Antron 99 mounted with only 2 straps for close to 7 years on my smokestack and/or chimney which is brick and it was never damaged. It survived hurricanes, tropical storms, you name it. And that is 18 ft. of fiberglass dancing in the wind with only the straps that used to hold an old arrow style television antenna up. But remember to ground everything.

 

[prcguy]

When I was younger and a little stupider I put a 22ft long Hy-Gain Penetrator on 21ft of 1.5" OD fencepost on a chimney mount with no guys. Worked fine for about 2yrs until 70MPH winds buckled the mast and it all came down but the chimney mount was fine.

A good quality SS strap chimney mount can be plenty strong.
prcguy

 

[jhooten]

I was in FRY'S today. Chimney strap kit is $25, 5' mast sections $10

 

[bob-the-scanner-man]

You can also use fencing top rail in place of the mast sections. The top rail is somewhat more durable and it's $10 for 10 feet of it at Lowes and Home Depot.

 

[KJ6HCB]

Kinda like this?

 

[bob-the-scanner-man]

Haha, yeah!

Myself and quite a few other locals here use top rail for our antennas. You can't go too high with it or put a huge beam on it, but for most antennas it definitely gives a lot of bang for the buck!

 

[KJ6HCB]

Thats 2 10' sections. Where they are swedged together at the joint I have them cross drilled and bolted with 1/4"x2.5" bolts with washers - extremely tight with 0 play. Base is in a 5 gallon bucket with 80 pounds of Quikcrete - a swedged piece of pipe in the bottom as well that the mast slips into and then a retaining bolt.

A U retaining clamp with 2 1/2"x3" lag screws through the eaves and... ya - solid as a rock. I just put it up a day or two ago so havent been able to clean up a lot of the stuff, and havent ran all the antennas, but you get the idea. I have 1 more section of pipe Im contemplating adding to the top, but I just dont think Ill need it.

 

[Rt169Radio]

Kinda like this?

So thats what it looks like now.Looks good,was it hard putting it up?

 

[jhooten]

You can also use fencing top rail in place of the mast sections. The top rail is somewhat more durable and it's $10 for 10 feet of it at Lowes and Home Depot.

If you have a McCoy's they have 20' top rail for 18.95. Pretty durable. I have a A99 on a free standing section that has been through some 50+ wind gust.

 

[jonny290]

I'm building an interesting mast this winter, will be neat to see how it works out.

Base will be a 16 foot pressure treated 4x4 sunk 3' into a concrete base, top end will be bolted to the end of the rafters/eaves that overhang there. The mast itself will consist of a 16' 4x4, two 12' 2x4's and one 10' 2x4 on the end, like so:

       --------------2x4------------
===4x4=====                    --------------2x4----------
       --------------2x4------------

There'll be a very slight taper on the 2x4's spacing between one end and the other, obviously. I will cross brace them at a couple locations as well for stiffness.

Overlaps will be 2' so 8' (top) + 10ft (mid) + 14 ft (bottom) gives a total of 32 feet height. Mounted at 1' above ground level on a hinged base gives an even 33. On the end of the 2x4 I am mounting a short piece of mast to stack an Alliance U-110, 6 element 2m/440 yagi and a Diamond F22. In addition I will likely have a discone or 800 antenna on a side mast, just to feed the scanners.

It'll be interesting to work with the material and try to get this thing stiff enough to freestand at that height. My top anchor point is to solid old-growth pine 2x12 rafters at 12 feet above ground level; I intend to tie the ends of 4 of the rafters together with a pressure treated 2x4 + lag bolts and bolt the ground-sunk post's top end to that. The foldover section will be pinned to the ground-sunk post at that height with a big honkin' bolt and nut when it's all in place.

If anybody has any suggestions/number tweaking (besides 'buy a tower'), please mention it!

 

[LtDoc]

An antenna support has to be strong enough to handle the weight of the antenna and any associated cabling. It has to be strong enough to withstand any other forces that will act on that antenna and structure, as in wind. From there, it's more a matter of what you have available to work with.
Does it have to be metal? Nope. Can you use wood, plastic, fiberglass, a combination of materials, whatever? Yep.
- 'Doc

(I'll bet that bucket in the pictures is full of dirt for grounding purposes, right??)

 

[KJ6HCB]

Nope, but the pipe is grounded to a 6' ground rod. Im not worried about it.