As Chuck mentions, for some reason pine trees are worse. That doesn't
account for different kinds of pine trees. IDK, but there has been
speculation about the length of the needles relative to the wavelength.
However, that's just anecdotal.
I can say that some kinds of Eucalyprus trees are just murder WRT
penetration. Had one at 200 yards on a 3 mile link. Just awful SNR.
--
bp
part15sbs{at}gmail{dot}com
On Mon, Feb 8, 2021 at 5:05 PM Chuck McCown via AF <af@af.afmug.com> wrote:
> I only know that folks in areas with pines have reported worse loss than
> other types of trees.
>
> *From:* Jaime Solorza
> *Sent:* Monday, February 8, 2021 4:13 PM
> *To:* AnimalFarm Microwave Users Group
> *Subject:* [AFMUG] What kind of signal loss ?
>
> We installed a licensed 928.xxx/952.xxxMHz link for SCADA project. We were
> only hired to install some VFD controls, the radio and antenna on a
> supplied 10 ft. mast installed by general contractor.
> They opted not to pay for a site survey from us months ago.
> When we were on site, I told the project mgr. that some existing trees a
> few feet in front of the antenna and the ten foot height were going to
> severely affect signal. He said go ahead and we will deal with it later.
> Later arrived. The link works with zero packet loss and all equipment
> responds as requested. The lift station is operational at -106dBm!!!
> The SCADA manager noticed that and now wants us to get it into the mid
> -60s range...I explained to him that we need to clear the trees to get a
> stronger signal.
> Five watt radio at mountain with 90ft of 1/2 inch Heliax and 12dB sector
> antenna...with 12dB yagi and same power at Lift Station...my calculations
> with trees show a -63dBm. I tried entering the trees (pine) but it threw
> the calculations way off.
> Trees are 30 ft. high and about 30 ft. in front of antenna and then
> several more about 250 ft. in path.
> How much absorption are these trees causing based on typical path analysis
> on empirical evidence?
> Thanks
>
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