Attic HF/VHF antenna questions

[mirrorshades]

I'm wanting to make an honest effort to get my HF station up and running without needing to run coax out the window/door, so I'm thinking I've got enough room in the attic for a simple dipole on 10/15m and I've heard about "attic antennas" for as long as I've been a ham. Just got two simple questions:

1) For an HF dipole, do I need to worry that I'm going to set my attic on fire when I transmit? Obviously this would not make the wife very happy. Rig is an older Icom IC-735 and I forget the power output but I usually have it toward the lower end. I have wood trusses and maybe a few runs of romex up in the attic, in addition to the usual clutter (if that makes a difference).

2) How in blazes do I get the coax from the attic down to the rig? Is it really a matter of running it down between wall studs, or am I just missing something painfully obvious?

Potentially interested in some sort of 2m/70cm J-pole in the attic as well... I'm less concerned about the "whoops I burned my house down" aspect, but obviously the same question about routing cables still applies. (I don't think there's a straight line down from attic to any room where I'd consider putting a radio.) Do I need to hire an electrician?


Thanks in advance for any help/advice!

 

[wyomingmedic]

The risk for fire is extremely low, but not absent. It can depend a lot on variable such as power output as well as SWR on the antenna. For a resonant antenna at 100 watts I wouldn't worry about it. But be aware that you run the risk of quite a bit of noise due to close proximity to everything.

Running the coax through the house is as easy or difficult as you want to make it. Some folks simply run it across the floor from the attic entrance to the radio. Others go so far as running it through the walls and installing patch panels in the wall. I have a few VHF/UHF attic antennas and I took the time to run every cable through the walls and ceilings. It took nearly a whole day, but the end result is a clean install. But, I have years of experience running cables through buildings as well as all of the cool tools. If you are short on either of those it becomes a much more daunting task.

You can certainly hire an electrician, but you may be opening more of a mess than you want. If you house uses the attic as a plenum, you must use rated cable which is exponentially more money per foot than regular coax. While you as a homeowner can run regular, the electrician may have no choice due to their license.

 

[K7MEM]

I have a IC-735. The output is rated at 200 Watts PEP SSB. I used the IC-735 with attic antenna for 40 meters many years ago and didn't have any issues with fire. You just make sure you have the necessary insulators on each end of the dipole.

A dipole for 10 and 15 meters is good, but that does limit your operations. It would be much better if you had something for 40 and/or 20 meters. If you don't have the room for a full size dipole, you might want to try a Shortened Dipole.

When I needed to route coax down from the attic, I usually found a close closet. A hole in the ceiling in a closet is much less noticeable than any where else. Running the coax inside a wall is great, but if there are any fire breaks in the wall, you will have lots of grief.

Martin - K7MEM

 

[WA8ZTZ]

IMHO, an outdoor antenna is a better option than an attic antenna. You get the antenna away from the electrical noise in the house. Besides, it is no fun crawling around in a hot attic with all the nasty insulation in the summer. With an outdoor antenna, you only have one wall penetration to make.
If you are unsure of how to get through the wall and make a safe antenna installation, don't be afraid to seek the help of a qualified person. Also, be familiar with the Articles in Chapter 8 of the National Electrical Code.

 

[TheSpaceMann]

I'm wanting to make an honest effort to get my HF station up and running without needing to run coax out the window/door, so I'm thinking I've got enough room in the attic for a simple dipole on 10/15m and I've heard about "attic antennas" for as long as I've been a ham. Just got two simple questions:

1) For an HF dipole, do I need to worry that I'm going to set my attic on fire when I transmit? Obviously this would not make the wife very happy. Rig is an older Icom IC-735 and I forget the power output but I usually have it toward the lower end. I have wood trusses and maybe a few runs of romex up in the attic, in addition to the usual clutter (if that makes a difference).

2) How in blazes do I get the coax from the attic down to the rig? Is it really a matter of running it down between wall studs, or am I just missing something painfully obvious?

Potentially interested in some sort of 2m/70cm J-pole in the attic as well... I'm less concerned about the "whoops I burned my house down" aspect, but obviously the same question about routing cables still applies. (I don't think there's a straight line down from attic to any room where I'd consider putting a radio.) Do I need to hire an electrician?


Thanks in advance for any help/advice!

For 2m/440 a Jpole or a ground plane will work in the attic, but of course it would be better if you could get them outside. If you really are stuck having to use indoor antennas, you might want to put up a small 2m/440 beam in your attic. I have used the little Elk 2m/440 beam indoors, with excellent results!

 

[I_am_Alpha1]

Outside I have a GP-15 and a DX-EE on a 30' tilt over mast.

In my attic I have a GP-3, two GP-1s, and a 10M double bazooka.

Of course the outside antennas work better, but we do what we have to (HOA or they would all be outside). I had to relocate some of the attic antennas because of problems...at 50W on 2M and 70cm my DirecTV units went berserk. Others have had similar issues with cable boxes. Once I relocated the antennas to the far side of the house (the furthest away I could go) my problems went away. I was able to drill a hole and drop the feedlines down an interior wall.

Just remember RF radiation is real and distance is good.

 

[N0IU]

I'm wanting to make an honest effort to get my HF station up and running without needing to run coax out the window/door...

Here is my home made solution to your problem:

The vertical pieces are just pieces of wood trim that have been primed. It is hidden by the towel, but there is also a piece of wood in the window track to keep the window snug against the wooded pieces and prevent someone from opening the window.

MFJ also makes window pass-through units that work on the same principle if you don't want to roll your own..

 

[geartow]

25 yrs ago I had a 20 meter dipole a 10 meter dipole ,a 10 meter wire ground plane , a scanner antenna and 2 two meter ground planes in my parents attic it was a full floor attic 16 ft from floor to peak. I cut a small hole in floor into cealing of my room where shack was.

 

[jim202]

I have a comment about running cables inside the walls. It depends on the age of the house as to how much of a problem that will be for you. In the older homes it's a piece of cake. The walls should be open floor to ceiling sill. But in the newer homes (about 6 years or so and newer, the code requires fire stops to be inserted in each stud run.

What this means is that maybe about shoulder high or so there is a horizontal stud to block off the chance of fire running up the wall. This means you have no chance of using an outside wall to run cables. But in an inside wall, you generally can buy or borrow a long drill and get up in the attic and drill a hole in the center of the fire stop.

It will take some care to try and place the drill in the middle of the fire stop and not get the sheet rock on one side or the other. I tend to drill like a 1 inch hole in the top sill plate to provide some room to work with up in the attic.

You will need some strong nylon string to allow the retrieval of the drill after you do get the hole in the fire stop. I cut a hole in the room to allow an old construction electrical box to be installed. When you lower the drill, they have a hole in the bit so you can tie the wire or some strong string onto it and pull it back up into the attic. Then use that to pull your coax cable up to the attic.

 

[mirrorshades]

Thanks to all for the information and advice. Let's see what I can come up with.

 

[kk4obi]

Attic fires are real. As a kid I remember how the end of a dipole arced over to a metal glider and set the cushions on fire.

 

[wa8pyr]

I'm wanting to make an honest effort to get my HF station up and running without needing to run coax out the window/door, so I'm thinking I've got enough room in the attic for a simple dipole on 10/15m and I've heard about "attic antennas" for as long as I've been a ham. Just got two simple questions:

1) For an HF dipole, do I need to worry that I'm going to set my attic on fire when I transmit? Obviously this would not make the wife very happy. Rig is an older Icom IC-735 and I forget the power output but I usually have it toward the lower end. I have wood trusses and maybe a few runs of romex up in the attic, in addition to the usual clutter (if that makes a difference).

You should be fine as long as you stick to about 100 watts output, and use the antenna on the bands it's designed for.

I have a full-wave loop for 40m and a G5RV Junior (20-6 meters) in my attic and they work fine.

2) How in blazes do I get the coax from the attic down to the rig? Is it really a matter of running it down between wall studs, or am I just missing something painfully obvious?

Potentially interested in some sort of 2m/70cm J-pole in the attic as well... I'm less concerned about the "whoops I burned my house down" aspect, but obviously the same question about routing cables still applies. (I don't think there's a straight line down from attic to any room where I'd consider putting a radio.) Do I need to hire an electrician?

Exactly what I did, ran the coax down through the wall to my shack (on the second floor, which made it easier).

Look for interior walls with no insulation.

However, if you are using the basement or first floor, look around for an open run to that floor. For example, do you have a laundry chute? If so, you could run the cable down from the attic into the top of the laundry chute, and down to the basement from there.

You might need an electrician to help if you have to run below the second floor.

 

[mirrorshades]

For example, do you have a laundry chute? If so, you could run the cable down from the attic into the top of the laundry chute, and down to the basement from there.

Actually... I do. And it's not quite a direct line down from the attic (it starts on a half-height wall next to the steps), but I could probably get the coax from the attic down and across into the top of the chute. That would definitely be close to ideal, since where I have the rig now is reasonably close to the bottom of the chute. Thanks for the great idea!

 

[Yagi]

For an HF attic dipole I would encourage you to not mount or attach the wire directly to wood. I have an attic dipole that is suspended in the middle from a large metal hook that I screwed in the middle of the highest support beam. A short section of rope goes from the hook down a couple of feet to support the balun. Then either end of the dipole has rope going from the insulator to hooks I put in the rafters at each end of the attic. I have very little nearby electrical wiring and do not have the metal backed insulation but I still found it tricky to tune a fan dipole. I tried to make a 4 band (10m 15, 17 & 20) but ended up scrapping the 17m and making it a 3 band.

Be aware that at attic dipole is much more prone to interfere with things in your house and you will also pick up more interference.

However an attic dipole is a good starting point and I keep my in case weather or something trashes my outside antenna.

I poked around in my attic and found a vent pipe that went from the basement up through my main floor to the attic. I drilled a hole next to the pipe in the attic and in the basement and fished my coax through that. You will need to look around and be creative.

 

[Yagi]

Here is my home made solution to your problem:

The vertical pieces are just pieces of wood trim that have been primed. It is hidden by the towel, but there is also a piece of wood in the window track to keep the window snug against the wooded pieces and prevent someone from opening the window.

MFJ also makes window pass-through units that work on the same principle if you don't want to roll your own..

Scott - that is a nice creative solution to avoid any long term impact of drilling holes. My wife was reluctant to have me drill holes to route coax so I made something similar with a double layer of 3/4 plywood that is heavily painted outside to minimize weathering. Anytime I want to add another coaxial run I drill a new hole and put in a coax bulkhead connector.