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Discussion Starter · #1 ·
I mounted a CM4228 with amp on my rooftop, but now I need to raise it. The antenna rotor and mount assembly are actually in my attic, with the antenna mast protruding through the roof via a 1" 'plumbing vent' waterproof rubber and aluminum 'flange'. It's a great setup, and this way my amp and rotor are not exposed to the elements (neither are the coax connections). It also helps to keep the neighbor annoyance factor to a minimum.


Now however, I need to raise the antenna up about 6-8' to increase my reception of a local low power DTV broadcast antenna (which my neighbors roof line just barely blocks), and to also reach over the new heater exhaust vent which is just a few feet away. The heater exhaust is located precisely between my antenna and the transmitting tower.


Since the entire shaft and antenna rotate with this setup (the parts sticking through the roof that is), I cannot simply connect some guy wires to stabilize it.


I was wondering if anyone knew of a special guy-wire kit that I could stabilize the mast with when I raise it? I was thinking a 2 part assembly; the top part would have the guy wires attached to it and would twist freely around the mast (like a donut with 3 threaded screws to mount the wires to), and the lower part would clamp to the mast and hold tension from underneath for the wires attached to the top piece.


If this does not make sense, I will post some mechanical drawings when I get a chance.

***edited for spelling***
http://home.earthlink.net/~tim_schaefer/pic/CM4228a.jpg
http://home.earthlink.net/~tim_schaefer/pic/CM4228b.jpg
 

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I thought some guy-wire attachment rings were designed to slip freely around the mast. How freely, I don't know. You're sure that thing is watertight?!


Gerald C
 

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How far away is transmitting tower you are receiveing signals from? I`ve actually seen cases where antenna companies install a preamp and amp like you have pictured, and it actually cause more harm than good. I did a job for woman and thats what original installer did..i took it off and ran direct line to tv and pictures were 100% better. Also you mention having guy wires , but if you are using rotor then they will get all twisted up, unless i`m not understanding you right...... i think from your picture you will be fine raising it up above your vent..that vent can also be source of interferance as it is metal.
 

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(1) What channel is the new station on? You may not need as much antenna as you have up there. If it's high in the band, the 4-bay 3021/4221 could be adequate. I haven't been too impressed with the 8-bay version.


The modified CM4308 on my web site at www.projectorexpert.com may work well for you and provide extra gain.


(2) You could easily support the weight of the mast below the roof line with a thrust collar attached to the beams. The weight of the antenna would sit on thsi collar which is a clmap with roller bearings. The antenna rotot is then simply turning and not trying to support the weight at the same time.


Pete KT2B
 

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Gerald C,


I'm with you.I don't see any way that it "can't" leak,by looking at the picture.He needs to fabricate a cone shaped drip-cap from some flashing material,and fasten it to the rotating mast with a hose clamp.


I'm pretty sure Starks sell a rotor alignment bearing for their cheaper rotor that would work in place of a mast bearing.Actually,I wouldn't be afraid to use 10-12ft of mast above the roofline with the 4228,but make sure the antenna mast right below the roofline is well stabilized.I'd use 1-1/4"rigid conduit out of the rotor,then 1" above that,to mount the preamp/4228,with a pipe cap on top,of course.
 

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Are you sure you need to raise it?

In theory, it makes sense, but, before I would go through all the work, just add a pvc pipe and raise it to see if the results are worth it.


My opinion is that the results will be minor.
 

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Discussion Starter · #9 ·
First, thanks for the replies! GREATLY appreciate the help and ideas. Been out running errands, so this is my first chance to reply.


1. Leaks = 0. The hole in the rubber flange is about 1/2" to 3/4" smaller than the mast protruding through it. The aluminum flange is big, and is covered by at least 6" of shingles on the top edge. I also heavily siliconed the top and side edges both above and below. Finally, I put a huge glob of waterproof grease on the mast when I pushed it through the hole from below, and even put some on top later. This way, no matter how much the mast rotates, the rubber will not wear or get twisted. Took those photos this afternoon, and besides being a bit dusty, the grease looks like I just put it on.


2. I live in Denver, and we have absolutley ZERO full power DTV or HDTV broadcasts here. In fact, the strongest transmitter is PBS, and it is something like 10 KW. (For more information on Denver being the only top 30 market without full power DTV, just read the incredibly long Denver HDTV thread. It sucks, but then, so do the Nuggets!) The channel I am trying to improve reception on is 17, ABC, and it is being transmitted at only 3 KW, no kidding! I spotted the transmitting antenna using binoculars and a ladder on my rooftop (yes, I had 2 people I trust holding the ladder), and currently, line-of-site locates it exactly 28" above the top of my 4228. the ridge line of my neighbors house blocks it. By raising the antenna about 6 feet would give me unobstructed line-of-site. Currently, I can get it at a max of 70-72% on my Dishnetwork 6000+8PSK, but during fast action (football) I get artifacting. Normally, the signal is more like 60-70%


3. Amplifier. As I mentioned above, I am struggling to receive low power transmissions. Tried it without the amp and got marginal results. It most definitely helps, and I will probably remove it once the stations start putting out stronger signals.


4. WOW! The CM 9525 looks exactly like what I was envisioning (GMTA!). I'm not worried about the antenna getting blown over, just want it to be stable when it is windy. I will include a below roofline photo. The rotor is 'quad' mounted to a 6', 2"x12" piece of microlam which is bolted to the roof ridge beam and to a rafter below. Solid as a rock. Like I said, just do not want the antenna wobbling around on windy days atop an 8-10' mast(yes, we get nasty thunderstorms in Denver).
http://home.earthlink.net/~tim_schaefer/pic/rotor.jpg
 

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What model preamp are you using, and with how much gain? Denver has four 5,000Kw UHF transmitters clustered together (analog channels 20, 31, 53, and 59), so if you use a high (25-30dB) gain preamp, they may overwhelm the weaker, digital signals. A medium (15-18dB) gain preamp may be optimal for your situation.
 

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I guess my question is why go to this much trouble? The rotor was designed for exterior use, why protect it? There are many rotors out there that have been up for 20 or 30 years and still work fine.


I would think a basic tri-pod assembly would do what you want, and depending on placement should be unobtrusive.
 

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Discussion Starter · #12 ·
1. I'm only interested in getting the OTA HDTV broadcasts with my setup. Tried it both with and without the amp, and the digital stations all came in much better with the amp in place. It is a model 7775 with an advertised gain of 26 dB. Have not tried any other amps. Any suggestions for the 15-16 dB you mentioned?


2. My roof has a 12/12 pitch with several dormers. The best place for mounting the antenna, due to other obstacles, is near the peak. The tripods looked easy, but did not provide the flexibility to place the antenna where it needed to go. My house was nothing but studs with sheeting on the roof, so it was very easy to mount my contraption in place and to bore the mast hole exactly where I wanted it through the sheeting. When the roof was finished, I simply located the hole and slipped the 'flange' into place. Yeah, the rotor is weatherproof, but I wanted to keep the neighbors as happy as possible while still erecting a rooftop antenna. It also makes accessing it (winter) a lot easier.


Currently trying to locate the CM 9525, but both Stark and Warren are out of them. Anyone know of a source?


Thanks again.
 

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I noticed that your neighbors have chimneys. If you have a chimney I feel that a chimney mount is one of the best. It is sturdy and easy to install. I have a chimney mount. The chimney is on the rear part of my house and I put the mast on the rear corner of the chimney. As a result, it is not very visible from the street.


Don't worry about the weather affecting the preamp or rotor. They are designed for the elements if installed correctly.


Get a chimney mount that has at least 1/8 aluminum in the mast mounting bracket. I used thinner aluminum at first but they blew down in 6 months. My current mount has been up for 11 years and has with stood 70 mph winds.


Rick R
 

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Quote:
Originally posted by Jetlag
Any suggestions for the 15-16 dB you mentioned?
Winegard makes NINE PREAMPS with UHF gain of 19dB. The differences are in VHF amplification and input configurations.
 

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Discussion Starter · #16 ·
Rick_R, thanks for the reply, but both of my chimneys are spoken for:
http://home.earthlink.net/~tim_schae...c/Dish500a.jpg http://home.earthlink.net/~tim_schae...c/Dish300b.jpg

As you can see, I have a Dish 500 (110/119) bolted to one of them, and a Dish 300 (61.5) bolted to the other. The UHF antenna is mounted toward the rear of the house and can only be seen from way out in the alley behind the house, so the neighbors don't mind. The Dish 300 is on the back of the house, and can also only be seen from the alley.


The TB-105 looks like it will work, and will also try one of the other amps. Maybe I could sponsor a UHF amp shootout? ;) At least until we get full power OTA HDTV here. Thanks!
 

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OK. I'm curious. What's the cover on the Dish 300?


And did you just mount the foot to the chimney brick with masonry screws?! (I guess I wouldn't trust the tensile strength of brick.) But if it works for you.... :)


Gerald C
 

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Discussion Starter · #18 ·
The cover is on the Dish 500 and it looks a lot better than having the big logo displayed (you can see this one from the front yard and street), plus I got it for free... Since E* is not paying me to advertise their product, why turn my chimney into a billboard?


Anchored both "feet" using four 4" threaded sleeves epoxyed into the chimney. Bore a 5/8" hole, slip a plastic mesh sleeve into it, fill it with super-fast dry epoxy, then insert the threaded sleeve. I let them cure over night, then simply anchor the mast foot with 4 stainless steel bolts. The bolt size allows just a bit of 'slack' with the pre drilled hole in the foot, just enough to tweak the mast to true vertical before tightening. If I ever remove the DSS dishes, just simply remove the bolts. If I want to get fancy, I could always mix some color matched mortar and cover the exposed sleeves, done deal. Did I mention that I'm a qualified electrician and plumber? I restore old homes on the side to pay for my HT ventures.


Normally, attaching an antenna in this fashion could weaken the chimney structure over time due to wind vibration, but since I took apart and restacked the top 4 feet of the front chimney, and put a new cap on the rear one, I was not to concerened about the structural integrity of either of them.


I ordered the TB-105 and already have some guy wire and a mast. Will be sure to let you know how it turns out. Will also do some evaluation of a 19dB amp I ordered, and will post those results (good or bad) as well. Thanks once again for all of the help.
 

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Just a thought..for around $300-$400 (depending who does the labor) you could have your roof free of everything and have a tower mounted with all your equipment.
 

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I hope I am not beating a dead horse. However in the picture of the chimney on the left, the corner in the picture between the dish mount and the camera looks to me that it could have a chimney mount attached to it.


The straps go all the way around the chimney but they could be below the dish (or one above and one below). The mast mounts are on the corner. The mast would get the antenna well above the dish to cause either the antenna or dish any trouble.


Just a thought.


Rick R
 
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