brucec@iddic.UUCP (Bruce W. Cheney) (07/25/85)
I am considering mounting a tribander beam on my roof (XYL says no to towers). I would be very interested to hear of other people's experiences trying to do something similar. Any good, practical, reference material tips would also be appreciated. NI7M brucec
jak@ky2d.UUCP (Jim kutsch) (07/27/85)
I had a TA33 Jr on my roof for a year then replaced it with the full TA33 about 2 years ago. It is on a 10 foot tripod and I am using alight duty TV type rotor. It is not guyed and has survived several NJ winters. My only tip is to use threaded rod to bolt it to the roof, not wood screws. Use long rods and place a long 2x8 (or 2x10) under the rafters to spread the stress across several rafters. Good luck. 73, Jim KY2D
price%marlin@Nosc (James N. Price) (07/27/85)
------- Bruce--I have a pseudo-roof mounted beam, and I went thru the same drill and quandries about what to do. What I elected to do, somewhat due to simplicity, somewhat due to geometry, was to use a 30' telescoping TV mast alongside the house. The mast is drilled thru the eaves of the house, thus allowing it to be well secured at that point as well as easy to pull up while standing on the roof. It's easy to mount the antenna, too, because all work can be done at eye level on the roof vice on ladders. If you opt for an actual roof mount, I suggest a triangular tower section with a tilt-over base, again for the sake of mounting the antenna and raising it. You WILL need to bolt the tower section THRU your roof, which can be a problem for some houses (like ours which has open beam ceilings thruout!). And you will need to guy it well since you don't want the antenna to take your roof off in a good wind! And remember about using non-resonant lengths of guy wires. I have a TH-3JRS which is no big shakes as a beam, but it beats the heck out of dipoles and verticals! I wouldn't advise roof-mounting an antenna too much bigger than that--the wind load is really incredible, even on the smaller beams. Hope that helps. 73-- Jim Price, K6ZH, San Diego, CA (619) 225-2665 PRICE@NOSC.ARPA -------
jhs%Mitre-Bedford@d3unix.UUCP (07/27/85)
Some comments: 1. Be very careful climbing around on your roof. And on ladders on the way up and down, too. Also, be extremely careful to avoid having ladders or antennas (or YOU) come in contact with power lines which may enter the house somewhere near where you are working, or which may pass by your house near roof level. 2. One DISADVANTAGE of a roof-mounted antenna is that it might possibly attract a lightning strike to your house. A lightning arrester on the house might be a good idea. (This might be a good line of argument to get the XYL to reconsider the tower issue!) (Or maybe to reconsider her choice of OM.) NOTE: A VERY effective lightning arrester can be made by taking a length of very finely stranded welding cable and stripping it back 6 inches or so and "fraying" the end of the wire into a bushy "head of hair" made up of the individual tiny strands of wire. This is mounted with the "hair" pointing upwards, up high on your tower, above the beam if possible, and grounded to the tower or else the heavy cable is itself run down the tower and to a good ground system -- preferably several independent ground rods tied together. Keep the grounding cable straight insofar as possible, as curves become inductive and encourage lightning bolts to jump off for something nearby that they like better. According to Don Clark, a transient protection consultant used extensively by FEMA (the Federal Emergency Management Agency), installations protected with this "head of hair" approach simply NEVER have lightning strikes. The fine points of the wire cause such an intense electric field that the air around them breaks down and leaks off the charge in little sparks rather than one big one! According to Don, you should give the gadget a "haircut" about once a year, because little spherical beads of copper form at the ends of the fine strands, indicating that they are carrying heavy currents at times. Eventually this will decrease the E-field intensity at the ends and reduce the protection the device gives. Snipping off the little beads will restore its performance. Eventually you will of course have to use another piece of welding cable to replace the used-up end. 3. If you are still not cowering in fear, you might find W6SAI's book The Antenna Handbook a useful source of ideas on roof mounting. The ARRL Antenna Handbook also has some wisdom in it. Basically, there are little bitty sections of tower that are designed to go on a rooftop. It is also possible to use TV mast for small beams. Guy wires are a good idea in either case. 4. Be careful what you attach to or guy to -- in a severe windstorm, it is possible for a large, roof-mounted antenna to be stronger than the things it is attached to and to pull off sections of roof or chimney or whatever. (Another argument for your XYL!) 5. You might look into Dick Austin's itty-bitty little triband beam, which is small and light enough to install very reasonably on a TV mast. I believe it uses twin-lead to feed it and requires a tuner and a balun, but it is possible to run a short length of coax and put the balun outside the house if you have problems running twin lead in and out. This unit has about 4 to 5 dB of gain over a dipole, and like all Austin antennas, this is what you would actually measure on an antenna range. The better small tribanders run 7 or 8 dB if you are lucky, i.e. about a half S-unit better. If you are lucky. Austin is in Sandown, NH. His mailing address is PO Box 357, ZIP is 03873. His phone is (603) 887-2926. Dick will probably also be willing to give you good information on which competitors' antennas are reasonably good if you choose to pick one which is coax-fed. He tends to be very helpful and objective when it comes to discussions of antennas, although he of course would be happy to sell you one. That's AT LEAST all I know, maybe a lot more! 73, John S., W3IKG
roode@uci-icsa (Dana Roode) (07/31/85)
I've often considered mounting something on my roof. Did you have any trouble with rain leaking in? What did you do to seal up the holes where your threaded rod went through? Dana Roode, WA6NGO roode@uci-icsa.arpa
jak@ky2d-2.UUCP (Jim kutsch) (08/03/85)
> I've often considered mounting something on my roof. Did you have any > trouble with rain leaking in? What did you do to seal up the holes > where your threaded rod went through? > > Dana Roode, WA6NGO I have had no trouble in nearly 3 years now with rain leaking in. I used a heavy application of roof patching cement (tar base stuff) under the legs of the tripod. Then, after tightening down the threaded rod, I put a heavy coat of the stuff all over the top of the tripod feet covering the top of the threaded rod and the nuts. So far, not a drop of water has come through. I have, however, been wondering how to seal the holes if I take the tripod down. I guess I'll dump some more of this tar stuff over the holes. Hope this is useful. 73, Jim ky2d ...!mtunh!jak
Karz.Wbst@Xerox.ARPA (08/07/85)
Bruce, I have a roof mount for my Hygain Explorer 14 that I'm quite pleased with. My antenna mast is mounted on the back side of the roof a few feet from the peak. I built a "frame" for the mast mount out of 3 pressure treated 2X4s about 25" long that lie across the joyces and are bolted to the joyces with lag bolts. The 2X4s are parallel to each other and spaced about a foot apart. They are not quite parallel to the roof line and are caulked on their "uphill" sides so that they won't dam up rain water. The frame serves to distribute the load of the antenna across the joyces. I purchased 2 2' lengths of fireplace lentil at a local brickyard. The lentil has an "L" shaped cross section. I drilled holes in the lentils and mounted them on the "frame" parallel to the fall line of the roof (that is, almost perpendicular to the 2X4s) and with the "feet" of the "L"s pointing outward. I spaced the lentils the mast diameter apart. I then drilled a hole through the mast about an inch above the bottom and corresponding holes in the lentils. The mast pivots on a 1/2" bolt through one lentil, the mast, and the second lentil. The antenna is held up by aircraft cable guys anchored to the roof with lag bolts. The mast is 12' high. I used roofing cement around all lag bolt holes and have had no problem with leaks. The antenna has been up 2 years this month, and I've had no problems whatever, but I do make a point of checking the installation twice a year since the failure of any one lag bolt will bring the system down. Except for the driven element, the system is a "plumbers delight" (just one big short), so I feel that the #4 copper ground wire from the mast gives pretty good lightning protection. Nevertheless, I keep the feedline disconnected from the rig and grounded when not in use as an added precaution. I hope my experiences is of some help to you. Bob Karz K2OID
brucec%tektronix.csnet@csnet-relay.arpa (08/09/85)
Thanks for your reply, the information was quite detailed and helpful. Maybe we'll meet on the air sometime ?? Bruce Cheney NI7M tektronix!iddic!brucec
Karz.Wbst@Xerox.ARPA (08/10/85)
Concerning sealing the holes when a roof mounted tripod is removed: When I roof mounted my beam (Message of August 6 with the creative spelling of "joist" and "lintel"), I missed the joists with a few holes and had to seal them up. My approach was to drive a short length of roofing cement coated wooden dowel (purchased at any hardware store) into the hole so that the top of the dowel was recessed about 1/4" below the roof surface. I then filled the space above the dowel with more roofing cement. I've had no problems whatever with this kind of patch. 73 Bob Karz K2OID
Karz.Wbst@Xerox.ARPA (08/10/85)
Bruce, Meeting on the air sounds like a great idea. I have a TS930s operating barefoot with the capability to operate 80 through 10 meters. I would think that 20CW about 0200 UTC would be a good place to start with movement to the phone band if conditions permit. I'm free most evenings at that time. Let me know. 73 Bob Karz K2OID