Metal roof question

[okie]

Is your Oil field pipe drill string or completion tubing?

It is completion tubing. I have alot of 4.5" drill pipe but the well tubing is plenty heavy for one 30' joint I think.

 

[Tallman]

Drill string is useless for any project that needs to remain plumb. The pipe can do a hula dance when you try to guy it up.

 

[Marconi]

Okie, sorry to hear about your mishap.

I had to tune my Maco Y-Quad at about 24' feet to get a tune where the match stayed somewhat stable on raising.

It was my first beam antenna and I had no experience in tuning at that early age, but I finally got it to match a little better than 1.50:1.

I had a rotor on it, and the vertical side match would change noticeably when I changed directions. I realize now that could have been due to common mode current (CMC) on the feedline & mast. I did get complaints when using this beam on the vertical side...so that indicates I had CMC radiating badly.

My Eznec model for the Y-Quad also shows CMC as noted.

 

[okie]

My Maco M103C will be here tomorrow so I am going to get everything ready to try this again.
The brown pipe will be well gyed.
The last time the Rohn mast pipe snapped but I had 4 pieces above the brown pipe to the rotor.
This time I will have the rotor as pictured and either one or two pieces of mast pipe above the rotor. With just one I will be at 35'8" to the beam. With 2 it will be just over 40' and get me farther away from the steel pipe.
For those that have 'been there, done that' do you think I can get by with 2 joints of mast pipe above the rotor?

Btw, I am wanting to mount the beam vertical because I mostly talk to stations 50 or so miles away. I know horizontal would make more sense to get away from the steel pipe. The pipe will be well grounded but mounted vertical, the elements on the m103c will be pretty close to the pipe.

Any more advice greatly appreciated. I dont want to buy a 3rd beam in a week!

 

[Marconi]

Okie, you tell us you were talking 50 miles before you got your 1st beam. What were you talking on before?

 

[okie]

Yes I was on occasion. At times I could talk fairly well, other times I could not. I could tell the Y quad was quite an improvement upon the first try.

 

[Marconi]

That wasn't my question. What antenna did you use before you got your Y-Quad?

 

[Shadetree Mechanic]

The more mast you put above the rotor, the more leverage it will have to hurt the rotor. I would keep the mast above the rotor as short as possible or even mount the antenna directly to the rotor. As you have found, the Rohm pipe will be the weakest link. Do you have more brown pipe?

 

[okie]

That wasn't my question. What antenna did you use before you got your Y-Quad?

An Antron 99. I thought I had included that in my origional post. My apology

 

[okie]

The more mast you put above the rotor, the more leverage it will have to hurt the rotor. I would keep the mast above the rotor as short as possible or even mount the antenna directly to the rotor. As you have found, the Rohm pipe will be the weakest link. Do you have more brown pipe?

Ok, thanks. I do have more pipe and may cut a short piece off to raise it up a tad if necessary.

 

[Marconi]

Okie, those clamps you're using to hold the small mast pipe to the side of well pipe do not look to be very durable IMO. What I see so far is mostly all weak on the important load end of the installation.

If those clamps get loose, due to stress and there will be plenty of that in such an install, the clamps could just slide down the pipe.

You need to check and see if the rotor will handle a 15 - 30 lb load. IMO, most of those type rotors were designed for old 3lb TV antennas back in the days, not 20lb loads on top of some thin wall tubing.

Think strong, durable, get if well guyed, and you will be better served.

When you get the antenna all raised up. how are you securing the base of the well pipe?

 

[okie]

Okie, those clamps you're using to hold the small mast pipe to the side of well pipe do not look to be very durable IMO. What I see so far is mostly all weak on the important load end of the installation.

If those clamps get loose, due to stress and there will be plenty of that in such an install, the clamps could just slide down the pipe.

You need to check and see if the rotor will handle a 15 - 30 lb load. IMO, most of those type rotors were designed for old 3lb TV antennas back in the days, not 20lb loads on top of some thin wall tubing.

Think strong, durable, get if well guyed, and you will be better served.

When you get the antenna all raised up. how are you securing the base of the well pipe?

Your correct about the clamps. I plan on getting more pipe clamps. The rotor (according to a search here) made me think it was fine for a 3 element beam. I will upgrade that.
The base is on a tilt with another piece of pipe that is well cemented in the ground. I cut a notch in the pipe and raise and lower it by a cable laying in the notch. When raised there is a gate latch about 12' up on the pipe in the ground I latch with a ladder. The tilt base latches with 4 bolts. That part is well secured.

Again, sure appreciate the advice from all of you. Going to get it right this time!

 

[357magnum]

If " The ( Or just mine ) " Antenna God Speaks " It's Gospel ! Too Mast = Too Many Problems . jmo Been there done that in my early Moon Raker Day's ! What a Kite that thing was & I had support wire running all over the place . Just young & dumb trying to get Max height .

 

[Road Squawker]

The more mast you put above the rotor, the more leverage it will have to hurt the rotor...edit...

I agree, this is too much above the rotor, you are going to have mast failure issues. Both above and below the rotor. That short section between the bottom of the rotor and the top U-bolt will have too much torque on it.

 

[Shockwave]

If the metal roof under the antenna has a large surface area, the effect would be like the roof is the ground. That closer reflection would shift the radiation angle upwards like being mounted too close to the ground. Even if the SWR is good, it's still not an indication of how the radiation angle may be effected.

One of my VHF antennas was nearly crippled when mounted a few feet above a metal roof. Good SWR but much of the signal was shifted upwards, off the distant horizon. The results appeared to be the worst when the antenna was about a 1/2 wave above the metal roof.