Have you discussed potential exterior camouflage enclosures? There is also the option if the siding is not a material part of the antiquity and you are skilled with a hand plane to frame out a section of the wood and hand plane until it is very thin and then fill the void with an rf transparent acrylic to regain the sstructural strength and minimize the loss. On Mar 14, 2016 11:43 PM, "Christopher Gray" <cg...@graytechsoftware.com> wrote:
> 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 >>>>> >>>>> >>>> >>>> >>> >>> >> >> >
