[amsat-bb] curious question

[Greg D]

Agreed!

Good point about polarity choices.  It's kind of interesting to consider
the diffraction effects that large, long hunks of wet wood might have on
a 70cm signal.  Probably less so on 2m, given the wavelength.

Oh, I forgot to mention that green wood is pretty much a killer on 2.4
ghz.  Think of what makes your microwave oven work.  I suspect, but have
not tried it yet, that the 1.2 ghz uplink to AO-92 on weekends might be
affected if you don't have a lot of power to start with. 

For some time, a bunch of years ago, our home internet was delivered via
a commercial Wi-Fi-based service.  I was a bit of a test subject, being
on the fringe needing to burn a bit of an RF hole through yet more of
our dear oak trees.  What was interesting was that the presence of rain
didn't make much of a difference on that band.  Wood, wet or "dry" still
absorbed signal quite well, and as the trees grew over time, the signal
degraded to the point of stopping service.  Fortunately, the cable
internet folks came through about the same time and we switched.

So there is a point, somewhere between 70cm and 13 cm, where trees
become a crippling factor.  Below that, they're mostly just shade.

Greg  KO6TH


Bryan KL7CN wrote:
> Well said, Greg -- to clarify my original comments:
>
> 1. Arboreal QSB is real, but...
> 2. It's not that significant.
> 3. Switching polarity helps quite a bit.
>
> I really only notice it when operating FO-29 on passes during the height of the Spring when the leaves seem to have the most moisture.
>
> Otherwise, it's not a general concern. But it is fun to say "Arboreal QSB".
>
> -- bag
>
> Bryan KL7CN/W6
> Location: CM98, usually
> E-Mail: bryan at KL7CN.net
> Telephone/SMS: 408-836-7279
>
>> On Sep 14, 2018, at 14:13, Greg D <ko6th.greg at gmail.com> wrote:
>>
>> Hi Bob,
>>
>> Trees probably do have an effect, but unlike others, I've not found it
>> to be a significant problem.  At least, not one where I need to plan my
>> passes around which trees might be in the way.  The only time they did
>> was with AO-40, where transmitting on 70cm directly into a huge oak tree
>> would have the signal bounce back and interfere with the 2.4 ghz
>> downlink.  One could map out where the limbs were based on the results.
>>
>> In an area of the country where shade in the summer is prized more than
>> many other things, taking a chain saw to a heritage-sized oak tree in
>> pursuit of a QSO just wasn't an option.  So, AO-40 contacts to the
>> south-east never happened.  Then "unintended chemistry experiments in
>> space" made it no longer relevant.  {sniff}  The only issue I have with
>> the trees now is to keep them trimmed appropriately so they don't snag
>> the antennas as they swing round.
>>
>> Greg  KO6TH
>>
>>
>> Bob- W7LRD wrote:
>>> Hi All- Just wondering-in the real world how much attenuation is there with trees?  I am surrounded with fir trees, a huge maple tree and cedar tree, (I live in the north west).  I run  a IC-910, preamps at the cp yagis.  
>>>
>>> 73 Bob W7LRD
>>>
>>> Seattle
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