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RF (Antenna) plumbing

Discussion in 'Electronic Design' started by Don Y, Dec 31, 2011.

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  1. Don Y

    Don Y Guest

    Hi Michael,

    So, this addresses the splitter *and* buffers. Instead of inserting
    an amplifier upstream (to compensate for the insertion loss of the
    splitter), this gives me unity gain *across* the slit AND buffers
    each output (as Joerg has suggested)?

    So, the only losses I have to deal with are the ~5dB in the cable
    Hacking together a small supply is never a problem.
    Anything special about the box? Or, will any (suitably sized) box work?

    (not a problem for my application)
  2. Don Y

    Don Y Guest

    Hi Gary,

    OK, so roughly the same as DTV.
    We don't use cable so its not an issue. I am more concerned to make sure
    the wiring scheme *can* accommodate CATV when/if the need arises.

  3. Joerg

    Joerg Guest

    There is one TV jack. If the TV needs to be in another corner we'd just
    run a longer cable to it. After all, it's only for the duration of a
    sickness that might possibly strike some day.

    Both have TV jacks. The back porch also has CAT-5 but normally unplugged
    for security reasons.

    You must have built the house from scratch. There would be no way to get
    CAT-5 to all those places here.

    The real AC is never on anymore because we have an evap cooler now. The
    time constant of that cooling is several hours, so we have a totally
    revolutionary control concept: Walk over there, reach over, turn big
    knob :)

    For some other stuff we have several handheld RF remotes.

    We used to have X10 for all that, with a central controller that can be
    reached via any of the remotes. But the PLC part, comm standard, and the
    hardware are all of sub-par quality so I ripped most of it out again.

    I dropped my efforts to do that. It's impossible in an existing house
    like this because there is no decent hardware at reasonable prices. Huge
    untapped market, the big players simply don't get it.

    You'd probably have to sit down and rebuild a relay.

    Well, yeah, one would never mount those out in the rain. Although
    there's cabinets if you had to. But the electrolytic in there would
    likely croak soon.

    That's whar thems condensers were invented for :)


    One guy in this area had his roof starting to sag after that.
  4. Joerg

    Joerg Guest

    Beats me why many "RF designers" can't get it into their heads that the
    very first component in any RF amp after the coax jacks shall be a choke
    to ground.

    In our case it's ok since they are inside and behind the preamp. But
    IIRC there's five transistors in each.

    That's inexpensive indeed.
  5. Don Y

    Don Y Guest

    Hi Joerg,

    Different perspectives. A neighbor was bedridden for several
    years before just passing away. Another friend just diagnosed
    with ALS. I.e., it's not uncommon for people to spend considerable
    time "trapped" in a room.

    Plus, a future owner would probably have kids and they would want
    media access in those rooms.

    "Wire is cheap" :>
    I just change the routing tables to prevent them from going anywhere.
    We re-routed the HVAC supply ducts. At the time, that gave us
    easy access to many of the "interior" walls in the house. Birdboards
    give us (continued) access to one of the exterior walls. And, the
    "end" birdboards give us access to two of the other exterior walls.

    In two places, I had to cut small holes in the ceiling to get the drop
    *down* into the wall. But, doing so carefully make these easy to

    The drops for the front porch are currently tucked up in the ceiling
    *by* the front porch -- waiting for me to get a chance to remove that
    paneling and stucco the porch. (No rush for those drops since we
    couldnt leave anything *out* (TV, etc.) on that porch as it isn't
    We stopped using the cooler a few years ago. *I* prefer the moist
    air (at least during the dry part of Summer) but I only get one "vote".

    But, the furnace and cooler are also controlled. I had hoped to
    install motorized skylights so the cooler/ACbrrr tradeoff could be
    dynamic and automated. But, with only that one vote... :>
    Ive put reed switches on the floor to detect when the garage door is
    fully closed. A long-throw opto-interrupter to detect fully open.
    A sensor in the freezer to monitor temperature (and provisions to
    monitor the compressor therein -- is it running "a lot" yet failing
    to cool, adequately?). The same for the hot water heater (though
    waiting to replace it before instrumenting that control).

    Other things are much easier to accommodate. E.g., the doorbell.
    There are "panic cords" in the bathrooms ("Help! I've fallen and I
    can't get up!" :> ). I also ran controls for a motorized
    projection screen in the living room (I consider the big TV's to
    be an eyesore -- much nicer if the "screen" disappeared into
    the ceiling).

    Things like the thermostat and irrigation controller are a bit more
    involved because they need to operate in the absence of "supervisory
    control". I.e., if the automation server crashs, you don't want the
    house to heat up *or* cool off extraordinarily. So, (part of) the
    control loop has to reside in those "motes" -- not just the I/O's
    (as is the case for the garage door, etc.)
    Again, in our case, we took advantage of the opportunity to run wire
    to all of those places. If we had an attic or basement, this would
    have been much easier.

    Once you have wire in place, it becomes relatively easy to script
    many of these things:

    for door in doors
    if (doorbell[door]) {
    locations = locate_occupants();
    for l in locations
    route_video(l, door);
    The amplifier I have is intended to be outdoors. Presumably
    taking into account the fact that it rains AND the sun shines on it.
    Yes but I wonder if they'd ever *notice*? This (partial) wall supports
    (part of) a 25' 4x12 that carries the living room ceiling. It also
    acts to psychologically isolate the living room from other arts of the
    house (by breaking sight lines). *They* obviously decided the wanted
    to *open* those sight lines -- without thinking about other reasons for
    the wall's presence! :-/

    [I was lucky to come across a set of prints for this house so know
    where the footers are poured. "Gee, look at this footer in the center
    of the house... right under this funky little wall..."]
  6. mike

    mike Guest

    How are you combining the multiple sources at V?
    I'd pay some attention to dynamic range. If you have weak
    signals and strong signals, you may run out of it.
    I had a situation where I cascaded so many splitters that
    there wasn't enough signal. Adding an amplifier at the front
    end made the whole system worse cause it overloaded the front end
    of the less attenuated stuff.
    Using a distribution amplifier designed for the job and ditching
    most of the splitters helped a lot.

    Having quality stuff everywhere helps, but I don't have any of that.
  7. Don Y

    Don Y Guest

    Hi Mike,

    "V" is actually intended to be an antenna symbol:

    There are two. Plus two CATV feeds. So, to answer your
    question: I'm *not* combining anything! The DTV antenna
    feeds a splitter that drives the drops intended for OTA
    reception. The FM antenna feeds a splitter that drives
    the drops that feed HiFi's. The CATV lines feed a splitter
    that ...
    I'm more concerned about the way I've routed the cables
    and where I've decided (schematically and physically) o
    locate the various "components" involved. E.g., amp
    ahead of splitter -- instead of at the load end of a drop...
    Well, I'm not breaking the bank with this (I had to buy some RG6Q
    F connectors is my biggest out-of-pocket) but don;t want to make
    any obvious mistakes. Opening up the ceiling again to fix something
    would be painful. OTOH, I could very easily convince myself to just
    *ignore* any problems! :>
  8. Joerg

    Joerg Guest

    Ok, but that warrants a lot more changes and you might then throw in
    another wire drop. For example right now our master bedroom has no LAN.
    But it'll be easy to run if the need would arise.

    That's what causes problems in a lot of kids these days. I am glad my
    parents did not allow that.

    If it's a new house, yes, otherwise it can be a pain in the neck to fish
    it through. Fire stops are special fun.

    Oh, I just hop into the basement. And while down there, I grab a nice
    bottle of Belgian Trappiste ale :)


    I was lucky. At frst my wife said "But I don't want an ugly monster like
    So-and-so has", referring to a friend who generally just kludges such
    stuff. So I promised her I'd do a really nice and clean install and now
    she loves it. I even made a winter cover that matches the wall. Beats me
    why the mfgs do not sell any, they are literally leaving money on the table.

    Pretty impressive. Most stuff is automated here as well but it is not
    networked. Because I haven't found any reliable comms method that is
    reasonably priced. But I do not really central servers too much.

    We have a Frank Lloyd Wright style house and retrofit runs are painful
    to impossible in most areas. You push into a ceiling and 4-5ft later ...
    thwock ... full impenetrable stop.

    I'd do it without scripting. Plus 99.xx% of buyers are not programmers.

    Ouch! That sounds like they wrecked the static integrity of their house.

    I can crawl underneath ours and actually see where they are.
  9. Don Y

    Don Y Guest

    Hi Joerg,
    Adding ANY wiring (e.g. drops) here would typically be done on the
    *outside* of the house OR by carefully boring through the roof
    HOPING to it the interior of a wall (*insane*!). So, when you have
    he chance to string wire, you string everything imaginable!
    That's why having access to the HVAC soffits was such a blessing!
    Can't run cable *in* the ductwork but you can run it *along* the
    Hard to automate "run into basement"! :>
    Our cooler shares the same distribution ductwork as the furnace and
    ACbrrr. So, switching among them is relatively easy -- *except* heat
    and AC typically happen with windows *closed* (while the cooler needs
    a vent)
    My first pass just used wiring to bring the field *to* the controllers.
    Then, I redesigned t move the controllers out *to* the field. Since I
    was using PoE for the telecom and multimedia stuff, this seemed a
    natural extension: run everything over ethernet and use the PoE
    feature to get power to the various motes.

    But, I now wnt to go back to a slower technology to cut down on
    the size/complexity of the PoE switch. ($$) This is unfotunate
    as t means I will need to have a second system of power management
    instead of just treating the automation nodes/motes as "yet another
    powered device/peripheral" (e.g. a second battery backup scheme
    and an independent set of management criteria)
    I'm not interested in buyers! :>
    Yup. I figure the footer and support wall were put there for a reason!
    So, I wonder when his sh*t will hit the proverbial fan! :-/
  10. Joerg

    Joerg Guest

    Don Y wrote:


    How did you do that? A giant "cold air SPDT relay"?

    One company makes ceiling vents for that. Forgot the brand but they open
    into the attic when pressure from the cooler builds but close through a
    temp fuse when there is a fire. Not sure how well they hold up in winter.


    Hmm, but don't we have some moral obligations for after when we leave
    this earth? Paying for assisted living would also require fetching a
    pretty penny for the house. Unless you'be been a state employee with a
    super-fat pension plan. It'll be tough to sell if the installation is
    deemed "weird". If the home inspector doesn't understand or doesn't
    approve of it people usually nix the deal.

    Probably when he sells and the buyer comes in with a smart home
    inspector. Not sure about the law but I assume they'd have to report an
    unsafe structure, and then all hell would break loose.
  11. Don Y

    Don Y Guest

    Hi Joerg,
    [Of course, the ACbrrr shares the furnace ductwork due to the location
    of the Acoil on the top (exhaust) side of the furnace.]

    The supply ducts are located high in the rooms. So, it is convenient
    for a roof mounted, downdraft cooler to push chilled air *down* into
    the ducts. Barometric dampers are located below the cooler (yet above
    the ducts) and above the A-coil (yet below the ducts) acting as one
    way valves, of a sort.


    But, these leak. So, when I *know* the heating/cooling season is
    over, I install baffles below/above the ducts alongside the dampers
    for a tighter seal.
    I wanted to just install motorized skylights -- and vent them when the
    cooler needed to run. This would have the added benefit of bringing
    light into rooms. (we like *lots* of daylight in the house)
    You will note that I said *remove* the kit when leaving the house! (in
    an earlier post) That's the reason that I'm going to the effort of
    installing more conventional infrastructure (regular telco wiring,
    CATV drops, etc.).
    No doubt! If not sometime *before* that! ("Bob, why is the living room
    ceiling sagging?")
  12. Joerg

    Joerg Guest

    I thought I had understood it but this throws me off guard. That kind of
    damper is usually mounted under where a rood-mounted the evap cooler
    pushes it's cool air inside, isn't it? Also, doesn't code require a
    fire-shutoff function?
    Yeah, the leaks is what I am concerned about. Usually manufacturers do
    not understand this and homeowners are on their won, and must kludge.
    Took me a couple of hours to make a decent looking cover box for the
    evap cooler inlet. SWMBO wanted one that blends into the textured wall.

    And brings wasps and other nice guests inside :)

    That I never do. I want it to be so that I can essentially drop the keys
    and move out. Of course, it'll never be that way but I try to strive for

    I wonder when the first homes with "engineered beams" show such
    problems. Probably all it takes is a leaky toilet or bathtub.
  13. Don Y

    Don Y Guest

    Hi Joerg,
    One is located "above the roofline" (to be accessible AND above the
    ductwork) but *below* the cooler (to place it in the outlet air flow).
    This is what make it troublesome to "baffle", manually (i.e., you have
    to climb onto the roof)

    The other is located in the outlet duct of the furnace -- just above the
    A-coil (thereby blocking airflow BACK into the furnace from the cooler).

    AFAICT, they are identical devices.

    Of course, the one in the furnace is very readily accessed.
    Apparently not. Note that it (rooftop) only opens when air wants to
    be blown DOWN through it. As soon as the cooler shuts off, it snaps
    closed (annoying to hear the louvers slap shut).
    Oh, I'm *sure* they "understand it"... they just don't *care*! :>

    Coolers are often covered (weatherized) in the winter so someone is
    up there to cover the cooler -- and can insert the baffle.

    The biggest appeal to the dampers is NOT the heating vs. cooling
    switch but, rather, the ACbrrr vs. swamp cooler switch. Previously,
    we would use the cooler for most of the Summer (hot, dry) and just
    resort to the ACbrrr during Monsoon. The automatic dampers made this
    really easy (though switching to AC from cooler has to be done with a
    bit of care as the moisture content of the air -- from the cooler
    plus the fact that RH is rising, in general, when we want to make
    that switch -- can be a chore for the AC to address).
    No, you put a screen on the window.

    We are debating a 46" square skylight for the kitchen (anything larger
    starts to present significant structural challenges). But, are worried
    about the thermal load it will place on the cooling system.

    (It's amazing how hard it is to get concrete data that you can *relate*
    to for things like this!)
    I'm not willing to live with what "normal" folks would consider
    acceptable! :> E.g., most folk see nothing wrong with lots of
    "equipment" (hifi, dvd, cd, tv, etc) cluttering up the place.
    I don't want to see *any* of that, here! So, the burden falls
    on me to come up with ways of *hiding* it.

    The bigger worry is, "what happens if some ill befalls *me*!" :>
    Yeah, each time I look at that stuff, I (intellectually) understand how
    it works. But, it doesn't leave me with a warm, fuzzy feeling thinking
    something as "flimsy" as that might be keeping the roof up over my head!
  14. Joerg

    Joerg Guest

    Ah, so you made yourself a "poor man's SPDT switch for air flow".

    I do not believe that passes muster WRT the code.

    Ever since I discovered a major boo-boo in the design (!) of our pellet
    stove and I as an EE had to tell those MEs how to do it right, my
    confidence in the "understanding" part has been shaken.

    Oh, and when the cooler arrived and was unpacked, guess who had to
    balance the squirrel cage?

    For our small one they don't even make a jacket. Plus those jackets can
    be a perfect recipe for mold because warm moist air from inside hits a
    very cold surface.

    On our roof that wouldn't last a long time. Some of the birds out here
    have several feet of wing span and corrspondingly powerful beeks.
    Sometimes you'd think a roofing contractor was up there.

    Why? It's basically just a window, and I am sure you can get automatic
    shutters for it to avoid being pelted by a scorching sun.

    Exactly. And that can happen faster than we think.

    IME, if I don't have a warm and fuzzy about something it is mostly
    indeed junk over the long term :)
  15. Don Y

    Don Y Guest

    Hi Joerg,
    Moe like a "diode switch" :>
    It is apparently accepted practice, here. I.e., *we* didn't
    do it, the HVAC installer did. The previous system used
    removable baffles (present on *every* house that has a swamp
    cooler). I.e., anyone with a swamp cooler has an *opening*
    through the roof that is "open" throughout the cooling season
    (i.e., the damper *closes* ours when the cooler is not blowing
    I suspect the covers are effectively "decoration". Hard to imagine
    they do much/anything to improve thermal efficiency.

    One of my pending improvements is to install a spiral staircase to
    make it easier to get onto the roof (think: getting OLDer! :> )
    so I can just stuff the cooler with a thermal block/insulation
    in the heating season. I've already replaced the fasteners for the
    access doors so that they can be removed without tools...
    The window "looks up", not "out". And, the vent position usually only
    "cracks" the skylight. So, it's a relatively small target -- and,
    "uninteresting". E.g., we've never had any problems with the Harris'
    Hawks, etc. in the neighborhood. OTOH, the little "critters" can't
    say likewise! :>
    But we *want* it unshuttered during the daylight hours. Shutters/blinds
    would actually only be useful at night to trap the heat in the winter.

    I've heard horror stories that the space under these can be
    significantly warmer. And, seeing that this would be the meal
    prep area (i.e., where we spend a fair amount of time), increasing
    light at the expense of added *heat* isn't appealing (I'd rather
    just add more light fixtures).
    Yup. But, then again, it wouldn't be *my* problem! :>
    Well, I don't get that feeling from "metal studs". Yet, I have grown
    accustomed to using them liberally! OTOH, I don't use them for the
    same sort of structural support that I might use dimensioned lumber.

  16. Joerg

    Joerg Guest

    Don Y wrote:


    Amazing that the code allows that in your area. Out here the fire
    marshall would probably have a hissy fit.


    That is what neighbors thought, too. Until the day when they heard a
    commotion in the kitchen and a racoon was duking it out with their cats,
    over who gets to eat the stuff in the bowls and who does not. He had
    made a hole in the screen and was rather unimpressed by our neighbor
    showing up in the kitchen.

    I think they make modern IR-repelling glass or something like that. It
    ain't grampa's old skylight no more.

    Not guaranteed either. My wife and I visit Alzheimer's places as
    volunteers. Some people live there for years or decades. Some
    permanently in wheelchairs.

    I would _much_ prefer metal over wood. Not this flimsy coke can strength
    stuff but real posts and such. Unfortunately those are unobtanium in the
    US and importing costs too much in freight. So we'll be forever forced
    to fix rot on decks and such.
  17. Don Y

    Don Y Guest

    Hi Joerg,
    Never saw a racoon, here. Bobcats and bears, yes. Racoons, no.
    But you can't *relate* to the number on a spec sheet! Just like you
    (meaning some *real* person) can't quantify how much warmer you feel
    standing in the sunlight than in the shade.

    I can look up the specs for a window (skylight) but can't, from that
    number, decide how comfortable/uncomfortable it would be to stand under
    it for any length of time.
    If *I'm* in that state, then it's still "not my problem" :>
    You can buy steel buildings, etc. It's just too expensive to be
    practical. (A house I had in Illinois used a steel I-beam as the main
    carrying beam)

    The metal studs are more convenient than dimensioned lumber for
    non-load-bearing framing -- it is *really* nice to be able to trim
    things with a pair of tin snips instead of a saw (electric or hand).
    But, I wouldn't count on such framing to support anything (perhaps
    other than a simple drywall partition).
  18. Joerg

    Joerg Guest

    Don Y wrote:


    They are junk, IMHO. Once during an EMC debug job I had trouble getting
    a panel off a large machine. So I pulled some more, then even more ...

    The panel suddenly gave up and I flew backwards into a wall. My shoulder
    made a major hole in a wall and bent some of those coke can strength
    "studs". The guys from production (on the other side of this wall) came
    running out to see if I was ok. I did not feel any pain whatsoever, the
    wall just went like that, as if if was cardboard.
  19. Joerg

    Joerg Guest

    Much of it was US-engineered and US-manufactured. More industrial stuff,
    not low end gear. Some European ones, too.
    I think the BRF92 and BFR93 are at the core of most designs. Almost
    impossible to beat in price.

  20. Joerg

    Joerg Guest

    That must have been back in the days of the Pilgrims :)

    It's a really old TO-50 can and nobody carries it these days. Well,
    Arrow lists them but there is no stock.
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