Homebrew Spiderbeam, not using the commercial kit...

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by AE7F, Jan 4, 2012.

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  1. WB4CMB

    WB4CMB Ham Member QRZ Page

    Jeff
    I appreciate, Thanks
    I've been running all sorts of things thru my mind, that could be dangerous as my eyes will prob cross and smoke may come out my ears.
    Even thought about reinforcing the spreaders with something, maybe put it on the spreaders after they are bent by rigging. The compression
    of this material when the spreaders try to sag would resist the spreader sagging. Maybe only run this material on p/o the spreader. Metal might work for avoiding as much
    sagging but would definitely interact. However the metal could serve as a driven element. Might add too much weight anyway.
    Enough lame brained ideas!
    I will ck out the SB folk's masts. Still wondering abou the chimney strength? I've seen some straps and mounts but for small antennas.

    Thanks, Ray
     
  2. AK5B

    AK5B Ham Member QRZ Page

    I wouldn't try a chimney mount unless it was for an even lighter and smaller wind load antenna; the twisting and torsional forces at work might eventually loosen the mortar and then you've got big problems.

    The SB masts are really one of the coolest things going, in my opinion. I have an older sort of knockoff called a New Wave Portapole (no longer in production as far as I know) that I plan to use for my new cobweb and then potentially later on once I build some sort of SB. Further down the road I plan to upgrade to one of their fine telescoping aluminum masts along with a tripod base as well (ground mount). While they're not inexpensive they are still a fairly affordable way to gain some serious elevation for a SB, hexbeam or other lightweight wire beam. Another nice feature is that they can be erected with a minimun number of personnel (perhaps even solo if the guy ropes are preset and it's raised on a totally calm day).

    In case you haven't already seen SB's US website, here's a link:

    http://www.spiderbeam.us/

    Btw, what about a separate 5, 6 or 7-element 6M SB as an alternative to a 6-10-15-20 SB? Might be easier to design and build in the long run and offer better performance as with any monoband design.

    73, Jeff
     
  3. AE7F

    AE7F Ham Member QRZ Page

    The home brew spiderbeam I just constructed would be too much to mount to a chimney. The reason is that my design is heavy. I have something like 8' of metal standpipe as well.

    After watching this antenna helicopter around in 50mph winds earlier this week, I don't know if I'd trust a chimney mount... I would be inclined to bracket mount to the side of the house/cabin. If you have a patio deck at the 2nd or top level, you might be able to lower the mast and drop the antenna to work on it. If it were safe to get on the roof, you could do all of the work at roof level and simply rotate the antenna as needed, but I thought you said earlier it is a metal roof. It doesn't sound like walking around like a cat on a tin roof at 30ft is very safe....

    Otherwise I would check into a push-up mast. Rick at spiderbeam told me they have something in the $1k-1.5k range but I wasn't clear if he was referring to the mast + antenna.
     
  4. AE7F

    AE7F Ham Member QRZ Page

    I still have not had time to raise the antenna - it's still at 10ft. Need to tighten everything up but I plan to get it on the mast this weekend. The weather will be above 50f for a few days.

    However, I just made my first contact with the spiderbeam on the 10m band with VP2MOM on the first try. My beam is pointed westerly so this was either a long-path contact or a contact off the backside of the beam. QRZ calculates this as a 3300+ mile contact.

    I'm not sure how the beam will perform but hopefully it is directional with some gain over a dipole. I think I will take down my 10m 3el monobander now, however. In its place will go a 2m beam.
     
  5. WB4CMB

    WB4CMB Ham Member QRZ Page

    My roof is not metal but there is a lot of metal attached to the roof, ie solar collectors. evap cooler. Another problem I have is I don't really have anyplace to put guy screws/posts, unless I guy to house. Even then I don't really have room in small backyard to attach even 1 guy. Self supported mast/tower??? I need to look up how much a crank up mast would be.
    Congrats on the SB contact/s. Ray
     
  6. AE7F

    AE7F Ham Member QRZ Page

    What are the dimensions of your yard? If you draw a circle around an antenna mast or tower in the center of the circle, what kind of radius do you have for guying? I am using earth screw anchors. You can get as many as you want for safe guying: http://www.homedepot.com/h_d1/N-5yc...talogId=10053&langId=-1&keyword=earth anchors
     
  7. WB4CMB

    WB4CMB Ham Member QRZ Page

    To continue:
    1. I could attach mast or tower to side of house anywhere from ground level to about 20 ft. I would have to use some type of "stand off" from outside wall to mast/tower to compensate for distance from side of house, the eaves do stick out. My back yard is about 60 ft by 30 ft., front yard is tiny. There is only about 20 ft between my house and neighbor's houses on both sides. Would attaching guys to house be OK. I would hate to make holes in roof to roof structual members but possibly could.

    2. It sure is expensive to get back into Ham Radio. XYL is NOT exactly symphathetic(sp) either. I could write a check for all this stuff commercially plus a rig and it would clear, but that check to the DIVORCE LAWYER probably wouldn't.

    3. One way I can prob save a bit on SB Or a quad too. My son in law is a metal fabricator. He says he could make the spider plates for me. He might even be able to help me with a tower/mast. Think I would use one quarter in top and bottom plates, would add weight tho. The SB push up mast is really neat and I'm sure it's top quality but I just can't afford that right now.

    4.In the SB plans, do the fibreglass spreaders go inside metal tubing that is p/o the spider OR do the fiberglass spreaders go right up to center of spider and butt up against each other? Maybe I should have seen/understood the plans better, wouldn't be the first time I missed something!

    5. Oh well. I've never claimed to be the sharpest knife in the drawer. But I should have thought of this before. Another important advantage of the SB is that it would allow fairly long spacing between wire beam elements, I've read that"Gain is a function of boom length."

    6. The instructions/plans I downloaded are in metric. I did ck the English language choice. Is there something else I should do to get this in ft/inches? Or maybe i could just use a metric tape. The plans say don't use a yardstick as this could lead to error with just a very small cm error. I would imagine with the "coupling" this would be very true. Have any of you found out just how bad/critical this is?

    7. I spoke before about gluing or putting a small bolt thru sections to hold them in place. After further thought (More Smoke From Ears) pinning or a small bolt would be much better than glue. This would allow for dissasembly if you wanted to move the antenna or if one section broke would allow for replacing only that section. If using thin fiberglass this would prob NOT be recommended.

    Here I go pestering and causing trouble again!

    Thanks Ray
     
    Last edited: Mar 9, 2012
  8. AE7F

    AE7F Ham Member QRZ Page

    I think you can come up with a solution. I would however create a new posting in another thread specifically titled to draw people in who have experience with what you need. So for example, if you decide that bracketing to your house is the way to go, make a new thread and specifically ask about that. The reason I say this is you might have spiderbeam people looking at this thread but maybe not the tower/mast/guying experts.

    You know, I am and have been going through the same challenges as you in terms of settling on an antenna but then having some significant challenges in terms of even getting the antenna up in the air. I have a large enough yard but have had some other specific challenges, which have caused my project to be delayed. I hope to finally get the antenna in the air this weekend though so that I can test it and post results here.

    Don't get discouraged.

    I took about 10 years off and it was a sad reality to come back to radio and discover the same thing you have. You wouldn't believe how many times I've heard others say the same thing. Even used radio equipment can be pricey. It's not worth a divorce. Sometimes you have to just do little bits here and there to get from A to Z. Depends on the XYL...

    That will help. Having someone who can work with metal or who is otherwise able to creatively build stuff will really help. I'm sure he can weld, which is also useful.

    The 6-way hub I used (from creativeshelters.com) only cost like $30-35 bucks shipped. It was a little more expensive than some on their site because it is larger. I got one that would fit the standpipe I wanted to use and also the PVC pipe as well. You can get the hub that works with 1" pipe and its even cheaper. It is also machine welded and the metal is coated. I couldn't get one fabricated as nicely for that price and if you go through this thread from the beginning, I looked at many other hub options as well. Charles gave me the idea and Jeff also came up with an inexpensive hub for his cobwebb antenna.

    The spiderbeam hub design uses metal tubes sandwiched between sheet metal plates. The fiberglass spreader poles insert into the metal tubes and go right up against the standpipe for a good, secure joint. The 6-way hub I use is pretty much the same. The only difference is the spiderbeam hub is adjustable for different mast diameters and my 6-way hub is not. My spreaders go into the hub and butt up against the metal standpipe tube.

    Give yourself some credit...

    Yeah, it's a long boom. 16.4ft x 2. I once asked the sb guys how they were claiming 4+dBd of gain on this length of boom. The reason is because I was planning on building a homebrew log periodic, and on a 30ish foot log periodic, I was only able to calculate ~3ish dBd of gain. The sb guys said theirs was an interlaced yagi and this is what they advertise it as. I compared several competing antennas and found that the spiderbeam is a tremendous bang for the buck, especially if you build it yourself for less. I think you are barking up the right tree.

    PM me your email address and I will email you the version that shows the critical items in terms of inches. I converted everything myself and they sent me the conversions after my antenna was already up! DOH.... Anyway, I double-checked and every one of my calculations was exactly the same - a good thing!

    Yeah, the spreaders rotated around during the 50mph winds we had earlier this week. Even strong tape would probably be enough but I am going to try and remedy this issue as well. In a way it may not such a bad thing. It distorts the spreader geometry but the flexing and twisting allows the beam to equalize the guy stress all around. I think it might actually distribute stress around the beam rather than concentrating it on the joints or guy points. ?? I don't know.

    One thing I do know is this is version 1 of my build anyway. If it performs, I will stick with the spiderbeam concept for awhile. If it performs really well, I'll stick with it for a long while.

    I hope this build will last 1 season but if the spreaders fail, I will go with MaxGain spreaders on the next go around and will simply drill and pin them. They are more than capable of this because I have seen and worked with their tube. I have no doubt that if you used MaxGain spreaders you would have a very tough antenna - probably tougher than the commercial kit.
     
  9. WB4CMB

    WB4CMB Ham Member QRZ Page

  10. AK5B

    AK5B Ham Member QRZ Page

     
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