Stacking vertical over beam

[vdubb16]

Ive got 58ft of Rohn 25 currently with a A-99 ontop. Id like to put a beam up again, probably another maco Yquad. The last one i had up was on a rotor with a 5 ft mast that the antenna was mounted to the tip of the top cone section...

I used 5 ft of mast to try to get the vertical elements to clear the tower as much as possible "not knowing if if would cause any issue with tuning or radiating pattern." Will it?

This alone in my mind seem like it would be rather straining on the rotor during strong winds.

Id like to mount a rotor inside the cone somehow and run a long mast to mount the YQuad and then the a99 above in on the same mast. Ive found the bushing for the top cap leaving the max OD for a mast of 1.5" This i seems to be the better way to do things especially having a rather heavy combination of antennas on it, yquad at 15lbs and antron guessing at 5-7lbs.

Now to the rea questions, How will i go about mounting the rotor inside the top section of the tower?

Also 1.5 inch mast is alil small i think, but its what ive got to work with to do this. any suggestion on tube to use.

Will the mast being up through the Yquad to the a99 interfere with the function of the beam?

 

[n5ims]

A few questions here. You indicate that your tower is Rohn 25, so this is a good start, but what type is your top tower section. There are several different options and the solution is different depending on what's up there. You could simply have used a standard section or one of the top sections (Texas Towers, Rohn 25G Top Section Page).

For the 25AG4, you can get one of the Rohn thrust bearings (Texas Towers, Rohn Thrust Bearing Page) that most closely mates with your mast size. If you topped it off with a standard tower section, you can get a thrust bearing plate to mount on the top to install one of the thrust bearings as well.

For the most of the other top sections (AG2, 3 & 5) you can run your mast through the top section's center tubing, with the mast diameter limited to which model you purchased. It's recommended that a bearing be used instead of simply sliding the mast through a top section's tube, but both will work. The bearing will provide support and reduce or eliminate any binding from metal rubbing against metal that would happen from simply using the tube to support the mast.

For either of the above solutions, you'll also need the accessory shelf (ROHN 25G Tower Top Single Accessory Shelf R-AS25G) so you can mount your rotor inside of the tower to mate with the mast. The lower you mount the shelf (and associated rotor), the stronger it will be.

This has much of what I've mentioned with sizes, etc. http://www.3starinc.com/manuals/25G-16.pdf

 

[vdubb16]

Thanks for your reply,

this is easy as in i was referencing the same website in my search before posting here.

ROHN 25AG 9 Foot Top Cap Tower Section with 2 inch O.D.
This is the top section that i have,

ROHN 25G 1.50 inch Tower Bushing for 25AG 45AG Tower Top Cap Section R-TB75
this is the bushing which i was thinking would do the trick for the tube at the peak, however 1.5" was the largest opening bushing i could find. with a thin coat of 5th wheel grease yearly or bi yearly to keep things smooth. and save on having to buy a bearing. Its a tilt over tower so servicing is a simple turn of a winch.


The accessory shelf you posted i must have overlooked through my browsing, thats definatly within the budget. Thanks!


Now the only questions are with the antennas and mast issue. Will the mast going up to a omni conflict with the vertical element of a quad. My mind tells me yes, but i dont know all. or any ways around it.

I could use something non conductive maybe to minimize adverse effects on performance, but what?
Also the coax that leads to the omni... it would be lmr-400, but would that also cause a conflict?

 

[n5ims]

Thanks for your reply,

Now the only questions are with the antennas and mast issue. Will the mast going up to a omni conflict with the vertical element of a quad. My mind tells me yes, but i dont know all. or any ways around it.

I could use something non conductive maybe to minimize adverse effects on performance, but what?
Also the coax that leads to the omni... it would be lmr-400, but would that also cause a conflict?

Glad to help out.

I haven't seen this done with a quad, and agree it may affect performance somewhat, but wouldn't expect a great deal of issues (the bottom part of the quad already has a mast near it's vertical section so all you're doing is making the top part match - this may even improve things, who knows!) I have seen it done quite often with a horizontal HF beam with the VHF/UHF omni on top with little interference found. I have even seen stacked VHF beams below an omni VHF vertical do fine, although when transmitting on one of them there is desensing on the other antenna's radio.

LMR-400 is quite stiff and may not work well around the rotor (never tried it though). You may want to use something more flexable to allow the coax to move easily while the rotor is turning. The beam's coax will have the same issue though. A short length of RG-8 from the antenna to just below the rotor where it could change to the LMR-400 might be good (if possible use N connectors and definately waterproof the connection) or if you haven't got the LMR-400 you may try the LMR-400 Ultraflex instead (LMR400 Ultraflex Coaxial Cable) since it should flex similar to RG-8.

 

[vdubb16]

Glad to help out.

I haven't seen this done with a quad, and agree it may affect performance somewhat, but wouldn't expect a great deal of issues (the bottom part of the quad already has a mast near it's vertical section so all you're doing is making the top part match - this may even improve things, who knows!) I have seen it done quite often with a horizontal HF beam with the VHF/UHF omni on top with little interference found. I have even seen stacked VHF beams below an omni VHF vertical do fine, although when transmitting on one of them there is desensing on the other antenna's radio.

LMR-400 is quite stiff and may not work well around the rotor (never tried it though). You may want to use something more flexable to allow the coax to move easily while the rotor is turning. The beam's coax will have the same issue though. A short length of RG-8 from the antenna to just below the rotor where it could change to the LMR-400 might be good (if possible use N connectors and definately waterproof the connection) or if you haven't got the LMR-400 you may try the LMR-400 Ultraflex instead (LMR400 Ultraflex Coaxial Cable) since it should flex similar to RG-8.

I never really thought about that, the mast below to the tower is would already be in the vertical elements plane. so i reckon it cant cause that much of an issue leading the rest of the way through. I do have 50 some ft of another coax im unsure what it is. same size as lmr 400 but with stranded center conductor. It got nicked by something all the way to the center conductor about 20 ft in. i was using it for jumpers, i could measure out what i need for a wire balun and use that to attach to the antennas. Its much more flexible than the lmr.