Straightforward out-of-the-box solution for extending WiFi range

Discussion in 'Wireless Internet' started by Danny D'Amico, Dec 13, 2013.

  1. Hi Tony,

    Two things I've always wanted to do:
    1. Increase the range of my wifi signal *inside* the house
    2. Connect to access points which are miles away

    What I was documented is the first step, which is to increase the
    range. The second step is to connect to an access point that is miles
    away from that laptop.

    I haven't done *that* yet, but, the potential now exists.

    First, I had to be able to connect to an access point, period.
    It took me a long time to figure out *how* to do that.

    Now that I've done that, my *next* test is to see if I can connect
    to my home broadband router from a couple of miles away.

    It will be fun, to see if I can do that (but I need to find my inverter
    because this particular solution requires 120volts).

    I'll report back if/when I'm successful.
     
    Danny D'Amico, Dec 16, 2013
    #41
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  2. Danny D'Amico

    dave Guest

    There's a store in Chicago that specializes in DX WiFi. They are called
    3gstore.com They also have forums for wireless hacks. Very busy boards.
     
    dave, Dec 16, 2013
    #42
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  3. Danny D'Amico

    miso Guest

    Except power is not valuable in one direction.

    The weak link if the fucking deaf ipad. I'm really starting to think
    Apple designs assuming a coffee shop environment. They don't except wifi
    reception all over the house.

    The reception has sucks for years:
    You will probably need a notebook to use wifi at a distance unless you
    have a lot of WAPs. Notebooks can have full MIMO wifi. At least Dell has
    that as an option.

    If you look at corporate users, the are on select models of Dell, Lenovo
    and HP. I don't think Lenovo makes any really low end gear.
     
    miso, Dec 17, 2013
    #43
  4. Danny D'Amico

    miso Guest

    Stop trying to do math. When the antenna is integral, they spec the
    effective radiated power. But again, power is not going to help here if
    the client is a fucking ipad.
     
    miso, Dec 17, 2013
    #44
  5. Danny D'Amico

    miso Guest

    The noise floor probably consists of other routers on the same
    frequency. This is that 3 miles path, so you are bound to hear all sorts
    of crud.

    There are ways to get omni gain, and directional gain, based on the
    antenna type. For point to point long distance, you want horizontal
    polarization. The cross polarization spec of the antenna will reject
    vertically polarized signals.

    "Horizontal polarization is used over longer distances to reduce
    interference by vertically polarized equipment radiating other radio
    noise, which is often predominantly vertically polarized."

    They then say do whatever you want (horizontal or vertical), but
    horizontal will pick up less crud.

    I never did circular polarization on wifi, but it would reduce
    multipath. The reflected signal would be reduce by the cross
    polarization since the reflected signal has the opposite polarization.
    But the circularly polarize antenna will pick up both horizontal and
    vertical signals, just reduced by 3dB since they are not circularly
    polarized.

    Most people just get two sector antennas and set them up horizontally
    polarized.
     
    miso, Dec 17, 2013
    #45
  6. Danny D'Amico

    miso Guest

    You mean work on both bands at the same time? They kind of get tangled
    in knots. I'm pretty sure these dual band units have band separation
    filters, and they are lossy due to cost constraints. That is the filter
    has an insertion loss which can be quite significant (say 4dB). They
    don't have individual lowband and highband antennas, so they are
    duplexing. The out of band signal is probably bigger than the noise floor.
     
    miso, Dec 17, 2013
    #46
  7. Danny D'Amico

    miso Guest

    A doubt you can get line of sight to a Starbuck. Trees are a pain!

    You would probably have to use circular polarization, like a helix
    feeding a dish.

    Defcon has done wifi shootouts, but they used similar gear on both
    sides. I'm not sure if anyone ever tried to set a record for long
    distance interception. I've done 10 miles in the desert, but there is
    nothing in the way of the signal and and no competing signals. If a
    square law holds, 20 miles would be 1/4 the power. I get my power and
    voltage ratios mixed up, but probably is would need 6dB more gain in the
    antenna. Doable. I'm at 16dB, and gear exists at 22dB.
     
    miso, Dec 17, 2013
    #47
  8. Thanks Miso,

    I'm learning exactly what you say is gospel, even if I don't know it yet!

    I see now that every decibel I get from the antenna is better than the
    decibel I get from the transmitter (simply because the antenna works both
    ways).
    No solution is perfect, but I don't disagree with you.
    That's interesting. I never thought about it, but, I would have *assumed* that
    the newer Apple & Android phones were all MIMO (isn't that really "N")?
    My Lenovo W510 seems to use Centrino, but I don't know if it's MIMO:
    $ lspci| grep -i network
    00:19.0 Ethernet controller:
    Intel Corporation 82577LM Gigabit Network Connection (rev 06)
    03:00.0 Network controller:
    Intel Corporation Centrino Ultimate-N 6300 (rev 35)

    Googling, I see that the Centrino Ultimate-N 6300 DOES have 3 antennas:
    http://www.tomshardware.com/gallery/Intel-Pro-Wireless-6300,0101-331512-0-2-3-0-jpg-.html

    So, at least my laptop is MIMO (I had never thought about that before).
     
    Danny D'Amico, Dec 17, 2013
    #48
  9. Hi Miso,

    My fault for not being clear.

    What I had meant by "double the decibels" is that I've noticed that
    seemingly, the same equipment (like the dish for the Rocket M2 versus the
    seemingly exact same dish for the Rocket M5) always has a 3 decibel
    (i.e., doubling) higher gain on the 5GHz equipment as on the 2.4GHz equipment.

    So, without actually looking it up, I always assumed that a given set of
    equipment is double the power if it's 5GHz.

    But, maybe I'm wrong. Googling, I found this gain calculator:
    http://store.freenet-antennas.com/linkbudget.php

    Reading the "Antenna" section, I see a parabola is a parabola, so, I can
    safely assume the Rocket M2 (2.4GHz) and the Rocket M5 (5GHz) do use the
    same dish reflector.

    Plugging in the numbers, into the "Parabolic Antennas" calculator of
    1/2 meter for the dish diameter, I get 22 decibels of gain at the
    2.4GHz range, and 29 decibels of gain at the 5 GHz range. So, that's
    actually a quadrupling of gain, simply by bouncing a higher frequency
    into the reflector.

    So, for any given size equipment, I always assumed (perhaps incorrectly),
    that the 5GHz equipment inherently had twice the gain.
     
    Danny D'Amico, Dec 17, 2013
    #49
  10. Hi Miso,
    This is interesting, the polarization issue. I really never thought about
    polarization, so, I'm reading (and re-reading) your post, to get the facts
    into my head.

    For example, I had never realized that, for long distances, one polarization
    would be any different than the other - but - as you noted - most things
    are vertically polarized - so - to reduce noise - I'd want the opposite
    polarization for long distances.

    Thanks for that insight! You seem to be years ahead of me in knowing what's
    what.
     
    Danny D'Amico, Dec 17, 2013
    #50
  11. I'm so new to polarization, that I had never heard of circular polarization.

    Googling, I find this "patch antenna", which describes what you said about
    penetrating obstructions:
    http://www.radiolabs.com/products/antennas/2.4gig/non-line-of-sight-panel-wifi-antenna.php

    Here's what they say which agrees with what you had said:
    "circular polarization means the antenna is better able to receive a clear
    signal due to the fact that the signal is both vertically and horizontally
    polarized at the same time. This effect enables the signal to penetrate
    through small obstructions and "twist" its way through trees, leaves and
    small structures. "
     
    Danny D'Amico, Dec 17, 2013
    #51
  12. Hi Miso,

    I'm a retired accountant.

    I have to do the math!

    And, it has to all add up!

    :)

    BTW, they must expect us to use just the feedhorn for the Nanobridge M2,
    because it shows right here in the router configuration that I can select
    the 3dBi gain of the feedhorn alone, without the additional 15dBi gain of
    the reflector dish:
    http://farm4.staticflickr.com/3831/11419600465_455bec7924_o.png
     
    Danny D'Amico, Dec 17, 2013
    #52
  13. Just by way of testing, I clipped the 23dBi NanoBridge M2, with just the
    3dBi feedhorn into my Ethernet port of my laptop, and I went to the farthest
    reaches of the house to test if it mattered how I rotated that 3dBi antenna.

    With the laptop on my lap, I held the feedhorn like a flashlight, pointing
    the invisible beam directly at the router at the other side of the house,
    pointing up at the ceiling, pointing down at the floor, and pointing directly
    away from the router (with the cat5 "tail" of the feedhorn denoting direction).

    With the Nanobridge M2 transmit power dialed down to 6dB, which is the
    lowest it would go, I got the following signal strengths:
    http://farm3.staticflickr.com/2826/11419588365_0209969676_o.png

    -38dBm, -40dBm, -52dBm, & -61dBm

    All of these are fantastic signal strength numbers for connectivity, but,
    they're still too strong to make much of a conclusion about usefulness.

    Since my signal strength is so powerful, even at the very lowest possible
    settings, I'm going to need to go a few hundred yards to maybe a mile away
    from my home broadband router to see how much the directionality really makes
    a difference.
     
    Danny D'Amico, Dec 17, 2013
    #53
  14. Danny D'Amico

    miso Guest

    Wifi is just like ham radio. Same issues.

    The sector antennas are always able to do horizontal or vertical
    polarization, but sometime the pattern isn't appropriate to more than
    one polarization.

    For example, say you bought a sector antenna that was vertically
    polarized and designed for coverage over a wide horizontal region but a
    narrow vertical region. That makes sense for a lot of vertically
    polarized applications, like you are covering a yard. But if you rotate
    that antenna so it is now horizontally polarized, you now have narrow
    coverage in the horizontal direction and wide coverage in the vertical
    direction, which is pretty useless.

    For long distance, you want a laser beam. Since that can't be achieved,
    you generally want it tight in both elevation and azimuth. That is
    beaming is often done with dishes.

    If you look at microwave links, they often have two dishes. One is
    horizontally polarized, the other is vertically polarized, That gives
    them isolation between the dishes. Generally one is TX and the other RX.
    You don't want your TX signal leaking into the receiver.
     
    miso, Dec 17, 2013
    #54
  15. Danny D'Amico

    miso Guest

    I haven't done much non line of sight wifi. But in SIGINT, you deal with
    scattered signals. Reflections, knife edge diffraction, even atmospheric
    ducting. So you never know the polarization. Circular works well in that
    case.

    When you design comm gear, well perhaps only back in the days I was
    doing so, you would put in "hooks" in the gear to see the constellation
    or eye pattern, depending on the complexity of the modulation. The hook
    would be some secret multiplexing of pins on the chip so the internal
    demod could be viewed. Often as simple as just providing hooks to drive
    dacs. These schemes provide great insight to the effect of noise and
    multipath. It wouldn't surprise me if the developers of these wifi chips
    had special drivers just for that purpose.

    The wiki is OK on this topic: The constellation is the more interesting of the two. You can watch your
    phase lock quality by seeing the constellation rotate back and forth. If
    a dot crosses a boundary, that is a bit error.

    The eye pattern is useful in aiming the antenna. You move the antenna
    around until the eye is as wide as possible. A wide eye means the bits
    are less likely to be in error.

    I did my MSEE with emphasis on communications and worked in the field a
    bit on baseband mod/demod, Not RF but wireline. But the theory works for
    both. Wireline reached a dead end, so I moved on to other design areas.
     
    miso, Dec 17, 2013
    #55
  16. Danny D'Amico

    miso Guest

    It is a bit more complicated than that. Meditate on a very simple
    antenna, say a quarter wave monopole. The signal in the aether has a
    field strength, generally expressed in volts per meter. If you compare
    two quarter wave monopoles, with one being twice the frequency of the
    other, it will also be half the size. [Wavelength being inversely
    related to frequency.] Same field strength, half the size, hence half
    the received signal being sent to the receiver. So generally lower
    frequencies are better than higher frequencies if you want range, but
    only for the same type of antenna.

    Now there are things you can do to improve the reception of high
    frequencies. When I mentioned that the higher frequency antenna is
    smaller, that refers to the aperture of the antenna. The smaller antenna
    has less aperture. To increase aperture, you make a more complicated
    antenna. Stack simple antennas to make one that have more aperture. You
    now have a bigger sponge by combining smaller sponges.

    This all can be related to photographic lenses. The opening of the front
    element of the lens is the aperture. The focal length of the lens is the
    gain. This all gets confusing, hence the use of various calculators to
    predict received signal level.

    Now for a dish, and I may not be correct here, but I believe the
    aperture of the dish is just the damn diameter of the dish. Whatever
    frequency you chose, the aperture is the same. The gain however goes up
    with the frequency. But I think you don't gain any signal strength when
    the dust settles. For one thing, your feed horn for the dish is now
    smaller, i.e. it lost aperture.

    This would be a good Jeff L. question, though he seems missing in action.

    Generally there are no free lunches in electronics. The only benefit to
    going higher in frequency is there is less atmospheric noise. At least
    to a point. In satellite reception, you can have the noise of the sun
    kill your signal.
     
    miso, Dec 17, 2013
    #56
  17. This makes sense, as everything in radio transmission is a tradeoff.
     
    Danny D'Amico, Dec 18, 2013
    #57
  18. Again, you have a great perspective on how to explain why we use the dishes
    for point to point over long distances!
     
    Danny D'Amico, Dec 18, 2013
    #58
  19. Luckily, in WiFi, you know everything. (At least you do!). :)
     
    Danny D'Amico, Dec 18, 2013
    #59
  20. Danny D'Amico

    miso Guest

    But that isn't a WAP with integral antenna. If the device just has a RF
    port, then you need to know the characteristics of of the antenna to get
    the effective radiated power.

    I'm not sure what the limit is in those ISM (free) bands, but there
    probably is some limit and the vendor doesn't want you to exceed it.

    Maybe you can do the first wifi moon bounce.
     
    miso, Dec 19, 2013
    #60
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