yes, I have. But my stack is supported just above the center where the two pipes meet by a chimney mount and at the bottom, I fabricated or welded if you would call that a rebar that held the entire mast assembly firm into the ground. It has been in for 11 years now and supports a VHF 5/8 over 58 with ground plane at the top with hardline, an 800 MHz 9dB beam with hardline, a UHF 6 dB beam with hardline, the feedpoint for an 80 meter inverted V with 9913, and an AM/FM antenna on an L bracket for the entertainment issue with RG6. I inspect my stack every year for cracks, corrosion, loose connections.
It's something simple until we have the Polish Tower raising party in the fall.
If you have no natural support like the above, then the best option is to consider guy wires.
Two 10 foot masts are not a problem and can support most scanner antennas. What will give you problems is not having a good mounting system and not using guy wires. I've seen 50 foot masts made with TV antenna masts that worked fine as long as the above conditions were followed.
Prior to house remodeling years ago, I used 2 1.25" dia 10' sections of chain link fence top rail pipe. It was secured to a vent pipe mount near the roof peak. It had 1 set of guy wires about 2' above the marriage point of the sections. This supported 1 sole Cushcraft ARX-2B Ringo Ranger 2 VHF 2-meter base antenna. It worked GREAT with absolutely no issues. If not for the remodeling, it would probably still be there.
I had three sections up with the second section eve mounted to the garage and two guy wires on the top 10' piece. Its was properly secured with all stainless steel hardware. Was up for almost two years and never an issue. Also, don't forget to ground the system.
Before the advent of Cable TV, you used to be able to buy telescoping mast up to 50 feet and above
20' each section had guy rings. These were used to secure large yagi TV arrays and CB radio base
antennas. It's too bad that the cost of materials and freight drove those manufacturer's to STOP
making them that high.
You can take about 4 - 10' 6" sections of fence top rail and put them together. You will need to take
long, flat, sections of bracing, mark the holes on one side, drill through BOTH sides and add another
flat bar on the opposite side and bolt together. For the "guys", you eye bolts, opposite directions, and
use guy wire "thimbles" to make it not rub the guy wire in two, then where it comes down, use eye
bolt turnbuckles to make sure when it's in place the wires are tight. Also, make sure that your guy
wires are not ¼ or ½ wave lengths of the receiving band.
At 40' in height, I would not suggest putting anything REAL heavy on top. A VHF Hi-band (150-174
mhz) or a dual band (VHF Hi and UHF (406-512), "J-pole", would suffice.
If you live in a town with a lot of industy or paging systems, I would suggest RG-213 for the coax.
The dual sheilding will help some in blocking those pager "tones". Unfortunatly for me, I'm about
a mile, mile and a half from a pager company that has a 1,000w transmittter. :-( My only solution
is to go with a directional antenna. ;-)
My mast has survived years of monsoons, sometimes with very high wind velocities. Once or twice a year, I go up and make sure the mast is perfectly vertical, and that all wires are tight. I have no doubt I could mount a much larger antenna with no problem, but in a high RF zone like mine, with most important things close by, the "sputnik" you see at the top works quite well for most things. The yagi is for one specific site, of one specific system by the way.
If you do not use guy wires, a 20'+ mast is going to do bad things in the long run.
Just as important, ground your setup properly.
Antenna 40' above ground level. 12 mile line of sight to mobile radios.
Filed down to bare metal, at bottom of mast and used copper clamp to attach ground wires. Sealed the whole thing with silicone #2 (the good stuff). Each antenna has a static discharge block inline right before cables enter the home, and their ground wires tie into the main one. The main ground wire runs down to four ground rods spaced apart properly, all tied together, all tied to the electrical & cable & phone grounds.
All connections are sealed the same way. Silicone #2 doesn't shrink, or fall apart, or deteriorate in UV light.
If you do not ground your setup, wind moving across your antenna will cause static to build up, then discharge into the front end of your radio at some point, which ruins front ends, and makes them deaf to varying degrees, not good.
If a lightning strike occurs nearby, the energy in the air can do the same or much worse.
Oh and without proper grounding, you can burn your house down as well.