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Thread: House structure signal degradation?

  1. #1

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    Question House structure signal degradation?

    How much does the stick wood structure, drywall, and asphalt roof shingle of a house affect the radiation patterns and signal quality of a 2m/70cm vertical ground plane antenna?

    Very low
    Low
    Moderate
    High
    Very high

    Is there equipment to objectively and quantitatively analyze the affect (within an amateur budget)? Cost? Link?

  2. #2
    GTGallop's Avatar
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    Is the antenna inside the living quarters?
    Is it a two story?
    Is it in the attic?
    Is it near any HVAC / Water Heater / Plumbing / Duct Work?
    Is it on the eve of the roof?
    Is it on the peak of the roof?
    Is it mounted more than one wavelength higher than the peak of the roof?
    Does the roof have solar?
    Does the attic have a radiant barrier?
    What is the length, gain, type of 2/70 antenna. Are we talking a Dipole or Slim Jim, or a Colinear J, or a Rango? Is it an automotive antenna meant for a car or is it a true base station antenna?

    Mostly your radiation patterns and degree of take off are impacted by antenna design. Your SWR and signal strength and quality are impacted by environmental factors. The only true way to know is to get out in an open field with no obstructions and put that antenna on a mast way up in the air and measure it with an antenna analyzer. Then put it in the house in question and measure it again. There will certainly be SOME impact. How much and what kind remains to be seen.
    KG7NDC

  3. #3

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    If the house is in the way of the antenna system, then there are quantifiable effects. If the ground plane is above the obstructions of course, then it should be a virtual circle polar pattern wise,

    If the house is in the way then the factors will be absorption, reflection and diffraction. Refection and diffraction require a barrier that in not transparent to RF. Metalised windows with films or metallic compounds in the glass, will reflect, and a number of metallic obstructions will work together to detract. Absorption figures for building materials in common use don't appear to be published. Heat and even audio energy have proper figures you can use for calculation, but nothing I can find for RF, so you'd have to do the tests yourself. Signal strength measurement devices would do the trick, but what a job! trying to walk around a house maintaining a constant distance from your antenna is going to be damn near impossible I'd guess.

  4. #4
    K7KBN's Avatar
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    No two houses are the same; no two antennas are the same. Nor locations within/outside the house. Experiment and see what works best for you.
    73
    Pat K7KBN
    Semper ubi sub ubi.

  5. #5
    Super Moderator 5B4AJB's Avatar
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    Moisture content will play a lot here as those materials absorb and hold water, which attenuates R.F. especially at VHF and above.

    Dry season:- Very Low, Low, Moderate
    Wet season:- Moderate, High

    There is something you can build & use to figure out your radiation pattern, it's one of the most basic Amateur tools and used to be a requirement - a field-strength meter.

    It is simply a tuned circuit with a detector diode and an s-meter, a short antenna wire and a metal case for you hand to earth it. Some C.B. SWR meters have a socket for a field-strength antenna and are usually quite good.

    If you need more sensitivity (and who doesn't?) build one with an amplifying transistor and battery, it doesn't have to be anything fancy, you can build it dead-bug style on top of your multimeter. It is useful to have a potentiometer somewhere to be able to set the gain if you do build a powered one.

    Take your time to map out your signal, some way of remotely keying the transmitter (a friend) is handy here. It's worth touching the meter's antenna on nearby metal objects to see how much energy is being held by them...

  6. #6

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    If the exterior of the house is stucco (which we have a lot of in Southern California) then there is wire mesh underneath the stucco. This will really degrade the signal. Also, if the house is insulated with batt that has a foil side to it, that's also going to degrade the signal.

  7. #7
    GTGallop's Avatar
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    Quote Originally Posted by K6CPO View Post
    If the exterior of the house is stucco (which we have a lot of in Southern California) then there is wire mesh underneath the stucco. This will really degrade the signal. Also, if the house is insulated with batt that has a foil side to it, that's also going to degrade the signal.
    Anyone building stucco homes in Western Washington needs to have their head examined. But anything is possible. If only Snaky Jake would reply back to answer all of our burning questions to help him.
    KG7NDC

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