Wall mounting questions

[hmburgers]

I'm going to pull the trigger for an exterior antenna--thinking of the Scantenna (ST2?) as I am receive only and 90% in the 470MHz band for my listening with the other 10% being 2-meter ham listening and a bit of 800MHz for the State PD.

I have to go wall mounted because I am not willing to go on my 12/12 pitch roof.

The house is a Cape style, no dormers, so my plan is to use a set of 4" or 6" wall mounts next to the second floor window under one of the gable ends--essentially the mounts will be placed where a decorative shutter normally is.

The top of the window is about 6' shy of the peak of the roof, so I think I would need a minimum of a 10' mast to get the top of the mast up near the peak. I'd probably need more like 15' to get the antenna itself above the peak. I think between the 4-6" push from the wall and and Scantenna itself I think it should be OK if the antenna is not actually above the peak...

A few basic questions...
- What distance should there be between the wall mounts? I've read 20" is the minimum... but is there a rule of thumb based on mast length?

- Is there a rule of thumb for how much mast should be sticking out of the bottom mount? How about how much should be exposed at the top beyond where the antenna has been mounted?

- As to the mounts themselves... I don't have an extension ladder that reaches as high as this window... I'm confident I can get the mounts installed by leaning out of the window, but can I reasonably expect to mount the antenna to the mast, get the mast+antenna assembly out my window, and then the mast into the wall mounts? Or is that crazy? Seems like with an antenna at the end of a 10' mast I'll have a lot of weight, plus the leverage will be working against me...

Another option is that I could put the wall mounts about 6-8' below the window (that's about the max working height of my ladder) and then use a very long mast from there to the peak... if I did this I was thinking I could mount everything from the ladder using the two holders, and add a third mount further up the wall by leaning out of the window. I think that would be quite strong, but would look fairly ugly on the side of the house because it would be something like a 20' pole the majority of which would be along side the house rather than majestically soaring into the air carrying my fabulous ~8' antenna

Thanks for any tips...

 

[Rt169Radio]

Have any pictures of where you want to mount the antenna?

 

[Blackink]

Well, I can tell you how my ST-2 will get mounted on the roof. Some of this info might apply to your situation and some of it won't but I thought I'd pass it along. Eventually when I do get the thing up there, I'll post pictures but I just don't have the time I need to finish the job right now.
Here's what I do have done:
This pipe mast is what a 10' piece of 1 1/4" conduit is going to go into. I have the longer end of the pipe mast pointing up with the shorter end fastened to the base. The base has been bolted to my metal roof with 2x4 reinforcements under the metal roof right next to an un-used chimney with 4 chimney mounts attached to the longer end of the pipe mast. The conduit will be bolted to the pipe mast with 3 - 5/16"x2" bolts.
I do have the antenna bolted to the conduit pipe a couple inches down from the end of the pipe.
4 guy wires, 1/8" diameter are attached to the conduit pipe 12" down from the top of the conduit pipe (about 8-9" below where the ST-2 antenna is attached). Eye bolts are attached to the side of my house and to the roof where turnbuckles will be used to tighten up the guy wires. All the the eye bolts have been reinforced on the inside of the roof area.
I've gone up and down the roof (4-12 pitch) several times with just the 10' conduit pipe after getting the Dish pipe mast secured to get holes drilled through the pipe mast AND the conduit, measure for the guy wires, etc.
I don't expect a problem lugging the conduit with the antenna, the guy wires, and the coaxial cable attached to the conduit pipe, up on the roof and secured to the pipe mast when I get the chance to do it.
I certainly won't do it on a windy day though.
I do have an 8'x5/8" copper grounding rod hammered into the ground with 3' exposed, I'll use about 10-15 feet of #6 grounding cable/wire attached to a grounding block about 25' below the antenna and where the coax will be going into the house.
I've done all the work myself and I'm looking forward to getting the project completed, hopefully in the next week or two. It's been a job but it'll be a good install when finished.
All exposed connections are or will be sealed/waterproofed with this stuff (works great as I've used some on the 300-75ohm transformer connection already). When you apply this tape, stretch it as you go overlapping a bit each time as you wrap and you'll get a watertight seal for sure.

This is how my set-up will be and I'm sticking to it !!!
Good Luck with your external antenna mount.

I'll post pictures when available.

 

[hmburgers]

Have any pictures of where you want to mount the antenna?

Proposed:

The yellow dots represent the proposed mount mounts. There is about 30" between top and bottom. The house is vinyl over original wood, so I will need to bore out a 1-2" hole in the vinyl to get to something solid. My plan was to use a 4-6" stand off mount where the legs of mount could poke through the vinyl shutter (obscuring the removed vinyl and making the mounts less obvious.

By counting the rows of the siding (about 3" tall) I believe that the distance from the bottom of the shutter to where it hits the roof line is about 24-26 rows of siding, or about 75". If I were using an 8' mast I could leave 3-5" below the lower mount point and hopefully about 10" above the roof line. If I went for a 10' mast obviously another 2' above roof line. Either way the antenna itself will be partly above and partly below the roof line. The mock up shot was just to illustrate where I wanted the antenna it isn't to scale and I realize it might actually be lower. The trees do not overhang the roof and would not be in physical contact w/ the antenna, there's a good 6'.

The original shot, plus another angle. The radios will be located in the basement at the front of the house, so the coax will enter near where the electric meter is. Figured I could drop straight, then run along the bottom of the siding. There is already a ground rod there for the electric service.

 

[KC8ESL]

Our houses are almost an exact mirror of each other. I opted to put my mast up down by the edge of the roofline about as high as my extension ladder would safely go. Used a 5' mast to get to the roofline, added a rotator, then put a 10' mast on top of that with my antenna. Tip of the antenna is over the center peak of the roof by about 4ft. Only thing that direction is Canada so I don't really care.

I can post a picture later.

 

[hmburgers]

I can post a picture later.

Thanks, I'd appreciate the look.

With 15' total mast size, how did you get the antenna up there? Just hoist by hand? Do you need guy wires at that height?

 

[KC8ESL]

Incredible upper arm strength and an impecable sense of balance I wasn't aware that I had... lifting the antenna/mast isn't bad, but once you've got 17' of mast and antenna above you and coax is dangling, swaying from side to side, while balancing on a ladder AND trying to get the mast into the rotator then tightening the nuts, you begin to rethink your choice of hobbies at that particular moment.

No guy wires. It is actually very happily set up even in high winds. I haven't gotten around to it yet, but I have a Hy-gain 5ele 2m yagi and a 2m/70cm fm yagi I want to put on the mast which is why I have the rotator up there.

Honestly considering renting a cherry picker from the local DIY store for 4 hours one weekend. I'll get it much higher at the peak then. It'll also make gutter cleaning a piece of cake if I do that.

 

[WA2E]

My concern is the antenna looks like it will be too close to the electric line. I understand the going on the roof issue but that vent line looks ideal.

 

[hmburgers]

My concern is the antenna looks like it will be too close to the electric line. I understand the going on the roof issue but that vent line looks ideal.

About the electric line, yeah I had forgotten that the aerial drop actually made contact w/ the roof further up until I took the picture. I know the goal is usually the mast length is same or less than half the distance to the lines, in this case that would be pretty tough to do... I may need to either abort the idea, or just mount the antenna on the side of the house at the shutter and not elevate it...

I won't use the vent pipe for a few reasons... it's even closer to the electric lines... it's on the front of the house and would look ridiculous... I'd rather not have cables draped on the roof or near the electric lines... I don't want to attach anything to the vent pipe which was never intended to support weight or deal with much lateral movements (wind on the antenna making it act like a sail).

I'd consider the other side of the house, but it's very highly visible (I have a corner lot), so it would be quite unsightly, worse than the front actually... I'd also have to double (or more) the length of the coax to get to the radios...

The other reason I like this particular location is that due to my vinyl siding I'm going to have make some cuts in the siding to reach solid mounting surfaces. I'd love those cuts to be behind the vinyl shutter so that I can minimize the appearance. I believe I can slice the shutter at the top and bottom to create thin channels that I can slip around the legs of the wall mount, if the mast is ever removed I think the mounts would be relatively hard to see because it's not an exposed side of the house and it's up high so you'd have to specifically look up to see anything... Anywhere else and I'd have to use vinyl mounting blocks which would be extremely obvious.

That said, I'm now thinking I may take the other poster's idea of moving closer to the eves (on the back of the house) ... I have access to the back side of that wall area for about the first 4-5' because that is knee wall attic. Since my radon numbers are in the mid-7's I've considered adding an active radon vent pipe right there because it's the same corner that my sump pump pit is in--the radon vent pipes are fairly common (and accepted) thing to see around here, and it would provide a perfect spot for wall mounting and would be a good way to hide the cables running down the house as well. I'll have to think harder about this...

 

[pjtnascar]

Having done a few of these installs (mast next to upstairs window) I would suggest you get about 5' spacing between mounts for this type of antenna. The issue with electric wires has already been mentioned so I won't repeat. Just be careful and remember the more vertical spacing between brackets the more stable your installation will be.

As an FYI: My install here in NJ is next to a window with a 4 1/2 foot vertical spacing, a 10 foot mast and a 17 foot A99 antenna and it survived hurricane Sandy when many trees, roofs, houses, etc. did not.