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How I Deal With Stucco...

Discussion in 'Amateur Radio News' started by WJ6F, Mar 26, 2017.

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  1. WJ6F

    WJ6F Ham Member QRZ Page

    100% Agree!
    This state is not small business and 2A friendly at all. Yes, I do own a small business.
     
    N6PJB and K9ASE like this.
  2. K6BRN

    K6BRN Premium Subscriber QRZ Page

    And you were OK with Grey Davis?
     
  3. MW6ZAN

    MW6ZAN Ham Member QRZ Page

    Interesting topic i would think this way of building in the usa, would make life easy for the radio amateur, as your living in a metal screened building that would stop a hell of a lot of qrm. Also having a metal roof what a fantastic ground plane for a multitude of anennas to experiment with. Of course external mounted antennas would be a must as attempting to use a handy from the kitchen may present problems. 73
     
  4. K6BRN

    K6BRN Premium Subscriber QRZ Page

    Stucco homes being a Faraday cage is a myth, I'm afraid.

    The wire mesh in stucco is not even close to RF-tight. I've lived in several stucco homes - watched them built from the ground up and noted all of the wire mesh under-layment - but can easily hit repeaters miles away with 1 watt from an HT, from any floor.
     
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Try it in the same structure having no windows or doors.

    Also, try it on 40 meters, where a wavelength is 135 feet.
     
  6. K6BRN

    K6BRN Premium Subscriber QRZ Page

    Hi Steve:

    Really? NO DOORS OR WINDOWS? (trying not to laugh) Ummmm... do you live in a permanently sealed bomb shelter with no way out? Interesting.

    I'm not aware of ANY homes that have no windows OR doors - we were talking about homes, right? Usually they have windows, doors, roofs - your know - the usual stuff. And I'm not inclined to check our bomb shelters, since I don't live in one. Nor do most people. But at least they have doors.

    And - why would I care about a 40M antenna INSIDE a home. Any antenna INSIDE a home is a severe compromise. Go ahead - tell me you've worked the world using a magnetic loop on 40M, from your basement. (But, you probably don't have a basement, since you live in L.A. ) To quote one of my favorite comedians "Well, good for you!"

    You are really stretching, here., and I'm missing the point. Or you're really bored, today. That's OK. Friday is just two days away.

    See you at HamCon West this Friday. Maybe we can discuss stucco homes there. And homes with aluminum siding. Been in those, too.
     
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I think you missed the point I tried to make.

    You wrote,
    "Stucco homes being a Faraday cage is a myth, I'm afraid.

    The wire mesh in stucco is not even close to RF-tight."

    My comment addressed that. That you can work repeaters using a low powered hand held on VHF inside a stucco sided home does not mean the stucco itself isn't a very good shield, and is actually quite RF-tight. The reason it "works" is due to apertures like windows and doors (and maybe ceilings and the roof) that don't contain any stucco and let the RF blast right through almost unimpeded.

    The stucco itself is quite an RF shield.
     
  8. WA7PRC

    WA7PRC Ham Member QRZ Page

    Rule of thumb: for good RF shielding, openings should be a fraction of the wavelength. Generally, λ/10 (or smaller) is a good target. :)
     
  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    The wire lath used for stucco has wires spaced to make about 1" squares. A wavelength of 10" is about 1100 MHz.

    Based on the 1/10 wavelength formula (which I think is pretty accurate), "stucco" would be an effective shield on at least 15 amateur bands, from 1.8 through 902 MHz.
     
    WA7PRC likes this.
  10. K6BRN

    K6BRN Premium Subscriber QRZ Page

    Not sure why this is relevant since the root topic is homes built of stucco and not RF screening for its own sake. But... OK.... I'll bite. Remember, you "asked".

    Stucco screen would make a crappy RF shield - and does, even without windows and doors. There is an entire expertise devoted top this in the field of EMI/EMC compatibility and control. It includes a study of RF permeability/penetration of metals, diffraction effects of screening materials and much more. I've worked in enough RF test and measurement labs, including screen rooms, anechoic test chambers and vacuum chambers to witness that RF squeaks through any available gap, at any frequency. And since the relevant dynamic range of a perceptible, usable and relevant RF signal, from HF to microwave, can span 90 db or more (1,000,000,000:1), it really does not take much RF to leak through for it to be relevant.

    If I had a 160M antenna in my home, was transmitting 100W and my incredibly tight DIY RF shield was 99% effective (it would NOT be chicken wire) I'd still be putting out 1 watt of RF into uncontrolled space . Any QRP'er will tell you that 1W is more than enough to make many, many contacts, And on RX, that 99% represents a loss of about 20db, or about 3 S-units. Ever received a signal coming in at better than S6? It would be received loud and clear in the the "shielded" house.

    So... what's a shield. Well, for comparison, RF screen rooms are usually double or triple walled (4-pi) metal, with copper strips along all seams and a vault-like door with copper fingers along the edges, a perimeter bezel with conductive compression gasket and locking dogs. And they still leak a small amount, especially if not maintained or if the door is not properly locked down (its a pain to do and some less experienced engineers try to get away with just a "closed" door - not a good idea).

    So... I guess it all depends on how you define a shield. Want a few db of loss? OK, use chicken (stucco) wire and get rid of the windows and doors.

    Want to stop the signal entirely? That's a hard problem.

    And back to my previous point - the stucco home I own does not behave any differently (in terms of RF) from the one I have with vinyl siding, or the one with wood siding. They all leak RF like a sieve.

    Hey, you haven't said when you'll be at Hamcon West. Going?

    Brian - K6BRN
     
  11. WA7PRC

    WA7PRC Ham Member QRZ Page

    At the world's largest OEM of RF-driven sealed CO2 Lasers, that was the technique we used for our kilowatt-up RF sources to drive Lasers on 40.68 and other frequencies. Even though 40.68 is an ISM frequency and it's OK to radiate, it was good to "keep the Genie" in the bottle to prevent RFI. One of our sources would do 10kW RFOUT.
     
  12. K6BRN

    K6BRN Premium Subscriber QRZ Page

    Ummmm.... no.

    It's NOT OK to radiate unlimited amounts of RF on ANY frequency. Safety standards govern that when ITU, Federal and local spectrum use regs don't. You had a leaky screen, not a shield, probably to knock down stray emissions to some presumably man-safe levels. And it was apparently a cheap one if it really used chicken wire. Hope you had a good EMI/EMC team on call and did frequent testing/monitoring. Excess RF emissions at that frequency usually causes eye damage, and not because of the optical emissions of the lasers. I presume you were trained on that if you worked in the area. But maybe not. How's your vision?

    At the worlds largest producer of satellite comms equipment, we did a little bit better. And were continuously monitored by ourselves and government watchdogs. Rusty chicken wire was not something anyone with serious shielding aspirations gets away with, at ANY frequency. We didn't, because we couldn't. And we would have liked to, because chicken wire is cheap.

    Brian - K6BRN
     
    WJ6F likes this.
  13. WA7PRC

    WA7PRC Ham Member QRZ Page

    Assumptions.
     
  14. K6BRN

    K6BRN Premium Subscriber QRZ Page

    More like an educated guess from an engineer who has had to run RF-heavy labs governed by OSHA regulations, and guided by your statements regarding construction technique and purpose. Remember: GIGO.
     
  15. WA7PRC

    WA7PRC Ham Member QRZ Page

    Yes, a guess... aka assumption.
     

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