Chuck, How far back should an antenna be from an obstruction (if the obstruction is mandatory and space is limited)?
I found a nice paper with information about empirical RF loss testing through various materials. The main drawback is the tests are for 0.5-2 GHz and 3-8 GHz (skipping 2-3 GHz). Found here: http://fire.nist.gov/bfrlpubs/build97/art123.html Glass test results starting page 141, and wood on page 147. Based on the published results, it seems I might expect signal loss in the 3 dB range when moving from behind glass to behind 1" boards, but I'm not sure I can be as far back as in their testing (1 m from the horn to the specimen). -Chris On Sat, Feb 20, 2016 at 6:38 PM, Mathew Howard <mhoward...@gmail.com> wrote: > hmm... looks like bacon is the way to go, if you can't use glass or ABS > > On Sat, Feb 20, 2016 at 5:33 PM, Chuck McCown <ch...@wbmfg.com> wrote: > >> Well, glass, silicon dioxide is a good dielectric. And dielectric >> materials can make RF lenses. So if it is flat, it will not refract the >> signal and should faithfully transmit it with low loss. >> >> The amount of loss, assuming you are out of the reactive near field >> range, is related to a factor called the loss tangent or dissipation >> factor. It is dependent on frequency. >> >> Air =0 (depends on weather and atmospheric parameters) >> >> Glass = .02 (decreases with higher frequency) >> ABS plastic I use for radomes = .01 >> >> Wood = as much as .4 Commonly in the .02 range @ 3 GHz if dry. >> Walnut wood = 1.4 @ 10 MHz >> Water = .157 >> >> Bacon (smoked) = .05 >> >> >> >> *From:* Christopher Gray <cg...@graytechsoftware.com> >> *Sent:* Saturday, February 20, 2016 4:00 PM >> *To:* af@afmug.com >> *Subject:* Re: [AFMUG] Antennas Behind Wood or Glass in Old Building? >> >> The building is 200+ years old, so most of the glass is old enough. I've >> requested to replace some panes with acrylic sheets, but I don't think they >> will let me. >> >> Thanks for the feedback. It sounds like mounting behind glass is much >> preferred over wood. I have not found good loss estimates yet, but I >> haven't dug into it too far. >> >> >> On Sat, Feb 20, 2016 at 4:59 PM, Eric Kuhnke <eric.kuh...@gmail.com> >> wrote: >> >>> Old windows are not so bad RF transparency wise. It's even possible to >>> use 80 GHz through glass in high rise office buildings that predate 1982 or >>> so, when metallic coatings and special IR/UV coatings on windows started to >>> become possible. >>> >>> It's the *new* windows you have to worry about. >>> >>> >>> >>> On Fri, Feb 19, 2016 at 7:37 PM, Christopher Gray < >>> cg...@graytechsoftware.com> wrote: >>> >>>> I may have an opportunity to install some radios inside a steeple with >>>> some very specific requirements. I'm currently considering 5 GHz and 3.65 >>>> GHz radios for this location. I'd like to do some PTP and PMP links, but I >>>> cannot afford to lose too much. >>>> >>>> I have the option between mounting behind 1" thick solid boards, 2x 1" >>>> thick solid boards, or behind original windows. Are locations with such >>>> barriers even worth entertaining? If so, would it be best to ask for >>>> locations behind wood or glass? >>>> >>>> Thanks you, Chris >>>> >>>> >>> >>> >> >> > >
