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Thread: Antenna and lead - vent

  1. #1
    Retired Defense Industry Engineer jadnashua's Avatar
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    Default Antenna and lead - vent

    I own a townhouse in a condo. As is typical in this type of environment, there are rules about what you can do on the outside of the building. Being burried in the middle of the complex, my cellphone coverage is lousy. I move a little bit out of the building, and it is okay.

    I bought a cellular repeater after reading some good reviews and checking their fcc approvals. I had hoped to be able to place the "external" antenna in the attic. Second choice was on the deck. After reading the fine print, though, the deck may not be great because the antenna would still be blocked a somewhat, and they say you shouldn't be within 6' horizontally of the antenna without a wall between (cellular signals penetrate walls, but are severely attenuated).

    Someone suggested clamping it to the vent pipe, running the lead down the pipe into the attic, then bringing it out then sealing the hole. The antenna is white, as is the pvc vent pipe, so it would be nearly invisible up there. None of the connections would be within the vent, and it would exit probably 6' above the 'wet' part of the drain. This would probably work, but how many rules would this break, and are they significant? The condo really doesn't like anyone making holes in the roof. An alternative to getting it through the roof was to enlarge the hole in the ridge vent cap which sits under the cap shinges, then silicon it up. Since the coax would be going uphill to make the penetration, it should not leak.

    THoughts?
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    In the Trades Gary Swart's Avatar
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    Check your private message box

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    In the Trades Gary Swart's Avatar
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    Thanbks, Jim.

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    I&C Engineer (mostly WWTP) Lakee911's Avatar
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    Care to clue the rest of us in on the advice given? I'm curious as to what was recommended for the situation.

    Thanks,
    Jason

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    Retired Defense Industry Engineer jadnashua's Avatar
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    He just wanted the brand name of the unit, it's from www.digitalantenna.com if you're interested. Still haven't heard any comments, pro or con. Anyone?
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Plumber jimbo's Avatar
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    Owing a condo myself, I understand the rules and they have to be there for good reason.

    I doubt if it is "legal" to do what you want, so the condo would probably disapprove if they find out. It would probably be fine as far as leaks, etc.

    I would NOT mess with the vent collar and rely on silicone to patch that up. That is a sure leaker, and then the condo will be really pissed!

  7. #7
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    I definitely would not mess with the vent collar, but I like the "run the wire down the pipe" idea. If it's a PVC vent, the best way to take the wire out would probably be to install a wye in the attic and bring the wire out the arm of the wye (installed pointing up) through a cap with a hole and rubber bushing in it. I'm a ham radio operator and have seen and done several such clandestine jobs. Amateur radio enjoys some federal protection for installing antennas where they would otherwise be prohibited, but I don't think a cellphone repeater would qualify. If need be, you could probably suspend the antenna inside the vent so it wouldn't show at all.

  8. #8
    Retired Defense Industry Engineer jadnashua's Avatar
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    I thought about that, but figured the connections might not like it over time. The cable should be fairly impervious, at least for a fairly long time...

    I'll let you know how it works out!
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    A weatherproof antenna connector wrapped with the special gooey black puckey stuff for those connectors will withstand almost anything for quite a while. I'm not sure about the performance of the antenna if it were put wholly inside the PVC pipe, though, although I think cellphones operate at a low-enough frequency that it wouldn't matter. I'll consult with my antenna guru and let you know what he thinks.

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    Hey Mikey, I didn't know you were a Ham. We could have talked for hours had I known.

    I think cellular are still using 800mhz thru 2.4 ghz. Those little waves tend to bounce of things pretty easily. I would try to keep the antenna out of the pipe if possible.

    Jim,

    Maybe you could paint it Skybluepink so it wouldn't show against the sky at all.

    How does this repeater work? Does it plug into house current?

    bob...

  11. #11
    Retired Defense Industry Engineer jadnashua's Avatar
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    The thing operates on both "normal" bands (doesn't work with Nextel and a couple of other odd-balls) 800 and 1900 MHz. Two antennae, one outside, one inside that must be separated by minimum of 20' and at least one solid wall. Outside xmit, variable up to 3W (max allowed), inside, max .6W, again, variable. Inside, on the unit I bought, coverage up to around 1,000 sq ft, but limited by walls. They make just an amp, if your phone has an external antenna jack that is less expensive. You can use it in the car if you get different antennae. Comes with a 12-v adapter for the car, and an ac adapter in the house.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  12. #12
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Default From the guru...

    Here's what he said. I'm not sure you want to go to all this trouble, but if you can find a local ham radio club, someone there might really love to help you.

    "PVC has some dielectric constant that affects the resonant length of the
    antenna - unlike fiberglass. I would suggest that he gets a piece of PVC of
    the same diameter, centers the antenna in it and, if he can, check the SWR
    and adjust the length of the antenna accordingly.

    Years ago I designed a 300 ohm Jpole VHF antenna for the inside of schedule
    40 PVC to put at school shelters so that the klids couldn't vandalize the
    antennas. I had to adjust the length of the antenna because of the PVC. I
    believe I had to make the antennas shorter, since the PVC added inductive
    reactance."

    I think the effect will be more pronounced at higher frequencies, so there might be a problem concealing it in the PVC. However, as implied, you could make a fiberglas imitation vent pipe, put the antenna inside it, and you should be good to go.

    Bob -- next time. I had the rear deck of the car open while we were talking, so you didn't get to see my K2RDB license plate .

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    Well maybe we should put an Amateur Radio forum on the Pumps and tanks forum. That is if Terry doesn't beat me to it. He already has the computer forum here. I thought that was a great idea.

    I didn't know PVC had any effect on antennas whatsoever. You learn something new everyday.

    I have built a bunch of antennas, but they were from HF to VHF. No higher than that.

    That's a pretty cool gadget Jim, I went to the site and read up on it. I can see where they would be a great tool for someone on the fringes of their closest cell tower. Expecially since a lot of folks are pulling the plug on their land lines.

    bob...

  14. #14
    Retired Defense Industry Engineer jadnashua's Avatar
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    I don't own a ladder tall enough to get up on my roof, so I've been thinking of a way to get the antenna up there. My car is not condusive to to moving a ladder, so I don't want to borrow one or buy a new one I won't use often. I came up with this, what do you think?

    Bought a nohub connector and am going to cut the vent in the attic. Going to stick a 3/4" square aluminum tube, attach the antenna mounting bracket to it, and push it up above the top of the vent on the roof through the existing vent. Using some stainless screws, screw the tube to the inside of the pipe with the coax running through the tube. Bring the coax out just above the nohub, and put the thing back together.

    Sound like a plan? If so, now I just have to wait for a day where the attic isn't an oven.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Sounds like a better plan than using a ladder. You could also schedule the job for just before sunrise, when even in FL the attic is quite comfortable.

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