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How get RF through a sealed window?
I gave a presentation on "How Ham Radio Can Help You in an Emergency"
to 70 Emergency Management types last week, and the windows in the building which hosted the meeting were NOT open-able (so I "made do" with an inside VHF antenna and didn't even try to demonstrate HF). But in emergency/expedient situations, it would be really handy if one could pass at HF, say, 100 watts of RF energy through a window (I visualize some foil strips and an inductor or two to "tune out" the capacitance) to an external antenna. I've been told that the April, 1989, issue of Ham Radio magazine carried an article "Easy antenna access for urban apartment dwellers" (for 15 meters) by Bryan Bergeron, NU1N, starting on page 18. I'd sure like to read that article; can anyone send me a copy? -- --Myron A. Calhoun. Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448 NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol) |
How get RF through a sealed window?
wrote in message ...
But in emergency/expedient situations, it would be really handy if one could pass at HF, say, 100 watts of RF energy through a window (I visualize some foil strips and an inductor or two to "tune out" the capacitance) to an external antenna. In an emergency I'd say... uh... just leave the window open? :-) Over on eHam.net there's a recent article on building yourself a simple rectangular wooden panel to stick in the frame of an (open) window. You then just drive holes in the panel as needed to run cables, etc. I've even seen people who didn't have, e.g., a drill or jigsaw do the same thing using a thick-ish chunk of stiff foam (insulation material or even presentation poster board) and an X-acto knife. |
How get RF through a sealed window?
"Joel Kolstad" writes:
wrote in message ... But in emergency/expedient situations, it would be really handy if one could pass at HF, say, 100 watts of RF energy through a window (I visualize some foil strips and an inductor or two to "tune out" the capacitance) to an external antenna. In an emergency I'd say... uh... just leave the window open? :-) But be sure to bring a hefty brick along to create the opening in the first place :) The OP's dilema was that the window COULD NOT open, and therefore some way to pass RF through glass would have been Useful. -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- Lawrence Statton - m s/aba/c/g Computer software consists of only two components: ones and zeros, in roughly equal proportions. All that is required is to sort them into the correct order. |
How get RF through a sealed window?
wrote:
But in emergency/expedient situations, it would be really handy if one could pass at HF, say, 100 watts of RF energy through a window (I visualize some foil strips and an inductor or two to "tune out" the capacitance) to an external antenna. What I have done is plan ahead by drilling two small holes in the glass and plugging them with nylon screws when not in use. That works best on the first floor. :-) -- 73, Cecil, W5DXP |
How get RF through a sealed window?
You'd have better luck with HF than VHF or UHF making it through any solid
object. I have used a homebrew mag loop in a hotel room on several ocassions with some luck..on 20 and 40. I have a 40m dipole in my attic, and I runn less than 5w HF most of the time and I have WAS on several ocassions, I try to WAS every year. 73 -- ========================================= Radio Amateurs - Fill your junk box, from my junkbox! http://www.hamradparts.com 73 de KB9BVN ========================================= wrote in message ... I gave a presentation on "How Ham Radio Can Help You in an Emergency" to 70 Emergency Management types last week, and the windows in the building which hosted the meeting were NOT open-able (so I "made do" with an inside VHF antenna and didn't even try to demonstrate HF). But in emergency/expedient situations, it would be really handy if one could pass at HF, say, 100 watts of RF energy through a window (I visualize some foil strips and an inductor or two to "tune out" the capacitance) to an external antenna. I've been told that the April, 1989, issue of Ham Radio magazine carried an article "Easy antenna access for urban apartment dwellers" (for 15 meters) by Bryan Bergeron, NU1N, starting on page 18. I'd sure like to read that article; can anyone send me a copy? -- --Myron A. Calhoun. Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448 NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol) |
How get RF through a sealed window?
In article -did-not-set--mail-host-address--so-shoot-me, Lawrence Statton N1GAK/XE1 wrote: But be sure to bring a hefty brick along to create the opening in the first place :) The OP's dilema was that the window COULD NOT open, and therefore some way to pass RF through glass would have been Useful. A lot of modern buildings have glass windows which not only cannot be opened, but which have a "low-E" (low thermal emission) coating on the glass. This is (I believe) a very thin layer of vapor-deposited metal. Its RF attenuation is considerable. Some years ago, we had our house windows (1960s-era glass) replaced with new ones using a low-E-coated glass. A previously-workable signal path for 802.11 signals, which got to the back of the house from an access point in the garage by going through the garage door and a couple of exterior windows, suddently became quite unusable - I had to install an additional access point to cover that part of the house. The more obviously shaded or reflective the glass, the more of a problem for RF transmission or coupling this stuff is likely to present. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
How get RF through a sealed window?
But in emergency/expedient situations, it would be really handy if one
could pass at HF, say, 100 watts of RF energy through a window .... Over on eHam.net there's a recent article on building yourself a simple rectangular wooden panel to stick in the frame of an (open) window. You then just drive holes in the panel as needed to run cables, etc.... I can just see me now: * Drive to the High-n-Mighty Hotel where I'm to provide communications for the Red Cross (or Salvation Army) shelter * Ask the desk clerk for someone to help me carry my sledgehammer and other stuff in my grab-n-go kit to the shelter * Walk into shelter where x-hundred shelterees are fast asleep * Take sledgehammer and bash a hole through a window * .... Nope, that's just not gonna work! -- --Myron A. Calhoun. Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448 NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol) |
How get RF through a sealed window?
You'd have better luck with HF than VHF or UHF making it through any solid
object. I have used a homebrew mag loop in a hotel room on several ocassions with some luck..on 20 and 40. Even in an emergency situation, I just don't think it would be a good idea to string some kind of an antenna above the heads of shelterees and then start soaking them with RF, especially depending on the HF frequency in use. In fact, I suspect the FCC's RF-exposure regulations would frown on one doing so! -- --Myron A. Calhoun. Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448 NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol) |
How get RF through a sealed window?
"Lawrence Statton N1GAK/XE1" wrote in message
-did-not-set--mail-host-address--so-shoot-me... The OP's dilema was that the window COULD NOT open, and therefore some way to pass RF through glass would have been Useful. Oops, sorry I missed that! |
How get RF through a sealed window?
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How get RF through a sealed window?
Perhaps.
In an emergency situation though, you do what you need to do and try not to let the regulations keep you from saving lives and/or property..while still keeping the regs in mind. When I use my portable mag loop for 20 and 40, from my hotel room, I try to place it outside my room...but that hasn't always been possible. At my low power I would have to guess the RF I'm bathing in should only be slightly more harmful than the X rays leaking out of my cheap "Made in Turdistan" TV set. I certainly wouldn't attempt using this setup with much more than a few watts of power. As for my attic dipoles, I have never tried to measure the exposure level in my home. I'll check in to that..but again, at 5w or less it can't be too dangerous. 73 -- ========================================= Radio Amateurs - Fill your junk box, from my junkbox! http://www.hamradparts.com 73 de KB9BVN ========================================= wrote in message ... You'd have better luck with HF than VHF or UHF making it through any solid object. I have used a homebrew mag loop in a hotel room on several ocassions with some luck..on 20 and 40. Even in an emergency situation, I just don't think it would be a good idea to string some kind of an antenna above the heads of shelterees and then start soaking them with RF, especially depending on the HF frequency in use. In fact, I suspect the FCC's RF-exposure regulations would frown on one doing so! -- --Myron A. Calhoun. Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448 NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol) |
How get RF through a sealed window?
But in emergency/expedient situations, it would be really handy if one
could pass at HF, say, 100 watts of RF energy through a window (I visualize some foil strips and an inductor or two to "tune out" the capacitance) to an external antenna. What I have done is plan ahead by drilling two small holes in the glass and plugging them with nylon screws when not in use. That works best on the first floor. :-) =============================== Might be OK for single - ,but NOT for double glazed windows. A solution for HF 'might' be an inductive coupler/matching unit , with half of it including an inductor on the outside with the other inductor and 'tuning bits' inside .Both inductors 'in-line' for best possible coupling. If an outside variable capacitor is to be used ,its shaft could possibly be magnetically coupled with a manipulator fitted inside ,using strong magnets . Home-brewing Ham Radio equipment is and remains an interesting ideas-provoking activity . Frank GM0CSZ / KN6WH |
How get RF through a sealed window?
"Brian Murrey" wrote in message
ink.net... In an emergency situation though, you do what you need to do and try not to let the regulations keep you from saving lives and/or property..while still keeping the regs in mind. Slightly off-topic, but see: http://www.truck.net/showdetail/rec_id/1182. Bizarre... |
How get RF through a sealed window?
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How get RF through a sealed window?
wrote in message ... I gave a presentation on "How Ham Radio Can Help You in an Emergency" to 70 Emergency Management types last week, and the windows in the building which hosted the meeting were NOT open-able (so I "made do" with an inside VHF antenna and didn't even try to demonstrate HF). But in emergency/expedient situations, it would be really handy if one could pass at HF, say, 100 watts of RF energy through a window (I visualize some foil strips and an inductor or two to "tune out" the capacitance) to an external antenna. I've been told that the April, 1989, issue of Ham Radio magazine carried an article "Easy antenna access for urban apartment dwellers" (for 15 meters) by Bryan Bergeron, NU1N, starting on page 18. I'd sure like to read that article; can anyone send me a copy? -- --Myron A. Calhoun. Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448 NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol) I have drilled a hole in a window frame and passed a piece of RG-58 through it. A 2M rig in my den is that way right now. It's easier to justify doing it to your own home than to a place you're visiting |
How get RF through a sealed window?
Myron,
I built a set of tuned rings to couple a 4MHz signal from an ultrasound transducer to its processing/signal generation box. I used a small copper ring (only about 6") split at one point with a resonating capacitor across the gap on the ultrasound box side. The coax was connected across this gap also. On the transducer side, use an identical loop and capacitor but make a series resonant circuit (capacitor in series with one of the feedline leads). Loops were separated by about 1/4 inch. I know this configuration (parallel resonant on the transciever side, series resonant on the "antenna" side) worked the best. It worked well in terms of passing the signal through undistorted (looked at amplitude and phase on both sides of the circuit, only got a bit of a phase shift, no amplitude loss) I don't know about power handling. If you use hefty capacitors, there should be no problem. Bandwidth could be quite low with high-Q circuits, but maybe you could use variable caps. I think your idea with capacitative coupling with inductors to tune out the reactance would work fine too, but I haven't tried that. Anyway, the inductive thing works OK. I got the idea from a older (1950's?) ARRL antenna book that touted it as a way to allow rotation a parallel-line fed beam. You'd certainly need a set of coupling rings for each band of interest, or switched or variable capacitors. Low E glass would get some eddy currents going. I don't know how conductive it really is though, so ... who knows? 73, Dan N3OX www.n3ox.net |
How get RF through a sealed window?
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