Discussion in 'Amateur Radio News' started by WJ6F, Mar 26, 2017.
This state is not small business and 2A friendly at all. Yes, I do own a small business.
And you were OK with Grey Davis?
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
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.
Try it in the same structure having no windows or doors.
Also, try it on 40 meters, where a wavelength is 135 feet.
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.
I think you missed the point I tried to make.
"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.
Rule of thumb: for good RF shielding, openings should be a fraction of the wavelength. Generally, λ/10 (or smaller) is a good target.
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.
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