XG91 horizontal mount problem

I've got two XG91s ganged side by side. Used the horizontal mount option. Got our first big wind yesterday and found out the mount is inadequate for horizontal mounting. Reception got bad and I walked up the hill and found one antenna pointing up at the moon. They use dinky little bolts and cannot be tightened enough to restrain. Bolts are smaller than 1/4" - maybe 10/24. Not so much an issue with vertical I guess for several reasons - including the option of using a second mount on top. Can't use a second mount when horizontal. When I bought the XG91s, I thought they DID come with two mounts since that's the way they usually show it in ads - and on the boxes they come in. Small print though reads "extra mount optional."

Took it down and made a new crossbeam mount with a pressure-treated 2"X4", some steel plate, and two vertical pieces of galvanzied 1 1/4" EMT pipe on each end. Now they are still ganged side by side but using the vertical mount mode instead. Seems much stronger now, but the next big wind will tell for sure. At least now, if I have to, I can add the second mount on top (at the boom itself). If they do shift, then cannot go up or down anymore, but could change compass points.
Hopefully not since it's quite a project to get up and work on it. Being 30 feet in the air on a stand-alone pole, I have to bring a big backhoe-loader up there. Raise the bucket as high as it will go and then put a 32' ladder against it. Even then, I have to lower the mast 6-7 feet so I can reach. Once the ground gets snow-covered, I won't be able to get up until spring.

If I ever have to put up any XG91 again, I'm going to make sure I've got the "optional" second boom mount. Never had this problem with any other antenna, but never had an antenna with such a weak mount.

Your problem was not the XG 91 antenna, it was your engineering.

I think that if you have high winds, sooner or later you are still going to have problems with the treated lumber board.

If you read some of the solutions that I have posted for other forum members problems , I explained to you how you can buy Chrome Moly or Stainless Steel tubing, where you can go to any shop that works on racecars and have them cut, weld and bend it for you in any shape you wish.

When fabricating mounts, wood is a poor substitute for steel.

You will probably find out that you wasted your time.

Weight is one issue and wind sheer is another and the third problem will probably be failure of the wood.

You would have probably done better to laminate several pieces of treated plywood, not particle board, but actual plywood. Since plywood does not have any grain to it, it is less susceptible to splitting and cracking and failure and is several times stronger then a piece of 4 x 4.

For $20 - you could have probably gotten someone to weld you a mount that would have lasted several lifetimes.

It isn't necessary to have two mounts on the XG 19.

I installed one two years ago that has seen 65 mph sustained winds for two days straight, ice storms, snow storms that dumped 1 foot of snow in 4 hours and several hail and rain storms that would have blown Noah off the ark. All with the original mount.

You have to be very particular where you put the mount when you put the antenna together. It took some figuring out because it didn't show anything in the instructions.

A little dab of anti seize on the threads and tightened with a pair of vise grips to a torque of about 45 ft lbs and I have never had one come loose.

I would say that your original mount failed due to the fact that the antenna's were moving around too much, bouncing up and down in the wind. You probably need a stronger mast pipe.

Your problem was not the XG 91 antenna, it was your engineering.

I guess the company that builds these antennas offers the "optional" second mount just for the fun of it?


I explained to you how you can buy Chrome Moly or Stainless Steel tubing

I'm capable of fabricating, welding, and bending steel tubing, regardless if some mix of magnetic or non-magnetic stainless alloy, plain ductile steel, or aluminum. I have a MIG, TIG, stick, and gas welder here in my shop along with several sorts of tubing-benders up to 2 1/2" OD. The issue is - I didn't want a metallic crossbeam to start with. A non-metallic crossbeam is recommended for best gain with ganged antennas. Usually, a high-strength fiberglass crossbeam is used. Just so happens I couldn't find any locally, unless I bought a high-priced tool and such a handle, and robbed the handle for this job.


When fabricating mounts, wood is a poor substitute for steel.

Not true in all cases. In fact, that is kind of silly. Wood in some applications has been shown to be superior to steel and/or concrete. That because of wood contruction being very flexible and corrosion resistant.
In this application, I agree that there are better materials, e.g. fiberglass. Anythng metallic in this particular use is inferior.
Some species of wood have tight straight grains and others do not. Like anything, you need to pick and choose. The treated wood I used is very straight southern yellow pine which has the strength of some of the best hardwoods and probably an above ground lifespan of 40 years. Note that the power lines that run through my farm were installed ca. 1945. All treated southern yellow pine or white cedar poles and crossbeams and still being used.


Since plywood does not have any grain to it, it is less susceptible to splitting and cracking and failure and is several times stronger then a piece of 4 x 4.

Plywood certainly does have a grain. It has many grains facing different directions if done properly.
The opposite facing grains and layers of glue in between is what gives it strength. And, that depends on the plywood, amount of plies, and source of the veneer used. There are also high strengh "ply-beams" that use whole 2X4 wood face-glued with opposing grains.

I installed one two years ago that has seen 65 mph sustained winds for two days straight, ice storms, snow storms that dumped 1 foot of snow in 4 hours and several hail and rain storms that would have blown Noah off the ark. All with the original mount.

Yes, and are you claiming you used the horizontal mount feature? I doubt it. I suspect you had a vertical mount on a vertical mast, which is comparing apples to oranges. My statement was in regard to the horizontal mount feature. I know, for sure, that with this use of mount, this antenna mount does not have the strength to sustain 65 MPH winds if 90 degrees to the length mast.

A little dab of anti seize on the threads and tightened with a pair of vise grips to a torque of about 45 ft lbs and I have never had one come loose.

Anti-sieze compound has absolutely nothing to do with something not staying tight. It's not a thread-lock compound. Good to have to make later removal possible, yes. I buy it by the quart and use it on anything ferrous exposed to the weather, road salt, etc.

To claim you are torquing 10/24 bolts at 45 ft lbs is simply rediculous. Maybe 45 inch pounds that would also break them? Breaking point on on a grade 2, 10/24 bolt is 24 inch pounds. Max torque is supposed to be 18 inch pounds, and the XG91s come with wing-nuts, probably so nobody tries to tighten with a wrench and break them. The 45 foot pounds you mention will break a grade 5, 3/8" bolt. Even the biggest antennas I've worked with use 1/4" or 5/16" hardware, all grade 2 or 5. A torque of 6 foot pounds will break the 1/4" hardware, and a torque of 13 foot pounds will break the bigger 5/16" hardware.

The antennas were too close together. The spacing tends to be around 50" for horizontal spacing with the 91 xg.

The structure over the mast should be in a shape of an H. This will allow 2 points of attachment for the antennas.

There is a heavy duty mounting hardware available shaped like a upside down V that should be more than enough to mount the structure to the mast. the mount used to be available at solid signal.

I have a problem with a support mast made from wood.

Google "mounting 2 91xg antenna" and you should find about 17300 things to read through.

Your problem was not the XG 91 antenna, it was your engineering.


I've got a non-antenna question for you. Why do many of your posts seem to require condescendence by the audience?

Hopefully it's not intentional, but I've gotten that feeling many times -from your replies to me and others. Hopefully, with many . . . the focus here is information sharing and gathering. Not a convenient forum for scolding people who don't do as you say.

You may, or may not have a lot of expertise in whatever field you work in. I'll add though, that some skills can cross lines of professions and be generally useful - when it comes to figuring things out in related fields. I've worked for 40 years in many skilled trades, including as a house builder, heavy equipment operator, electrician, welder/fabricator, and diesel mechanic. Yet, you respond as if I'm a clueless idiot that will never survive unless I follow only your advice, without question.

I've got no problem when someone can point out an error , or come up with a better idea on something. That is not the same at telling something they are foolish, or wrong, or cheap, or what ever you're in the mood to put into a response.

In this particular case, no - my "engineering" is not the problem. The problem is a inadequate single mount with very small hardware when used in horizontal mast mode. Also a problem of having a site where winds make u-turns and point almost straight up at times. It's an effect when you live in a sort of bowl surrounded by mountains. I've had two 40 foot long steel buildings get ripped out of the ground, lifted straight up, then blown across my fields. I suspect my particular wind situation might differ a bit then your's.

I'll add that those two steel buildings were not installed by me. The company that sold them to me insisted on using their own anchor system, rather then mine. Obviously, their's did not work.

The antennas were too close together. The spacing tends to be around 50" for horizontal spacing with the 91 xg.

The optimum spacing depends on the targetted channel. I used computer software for my initial spacing, and then tested on site. It seems to hold true in my case.

XG91s when used for best reception on channel 50 come up as thus:

31.9" (2' 7-7/8") spacing when horizontally mounted

30.9" (2' 6-61/64") spacing when vertically mounted

For lower channels, they get spaced further apart. The 50" you mention might indeed work well for some lower channels. I haven't checked since I'm not trying to get any.

I am only after channel 50 and tested them. The 32" spacing worked the best. Not by much, but better just the same.

As to mounts, there are many good designs and kits around for ganging. I would of done my first attempt with a better mounting, except the weather had turned bad and I ran out of time.

A-tech is one of many, but they post some interesting test-specs.

http://www.atechfabrication.com/products/dual_antenna_boom.htm

Didn't I read somewhere that using metallic booms between two horizonally stacked antennas creates another element to the antennas and can mess up their reception so fiberglass was recommended for horizonal boom mounts, or you needed to keep the antennas 3 ft away from the horizonal element?

Didn't I read somewhere that using metallic booms between two horizonally stacked antennas creates another element to the antennas and can mess up their reception so fiberglass was recommended for horizonal boom mounts, or you needed to keep the antennas 3 ft away from the horizonal element?

Yes, I read the same in several places, about the metallic boom causing problems. Not about the above-boom spacing for all antennas. Some of the observed specs are specific to certain antennas and the channels targetted.

Didn't I read somewhere that using metallic booms between two horizonally stacked antennas creates another element to the antennas and can mess up their reception so fiberglass was recommended for horizonal boom mounts, or you needed to keep the antennas 3 ft away from the horizonal element?

Generally that's true, but the 91XG has an offset mount that minimizes the problem.

Note that if you do opt for an insulated mount it's necessary to dangle the coax away from the antenna with no support. Eventually that will cause the coax to fail.