[HamWAN PSDR] dBm musings [was 8 ft horizontally = 9dB increase]

[Dean Gibson AE7Q]

Prior details in the eMails below ...

Shortly after the -75dBm report below, I started to see the value drop 
to a usual range of -77-80dBm, with occasional excursions down to 
-83dBm.  I spent three long sessions (one getting wet) out on the roof, 
to no avail (I carry an Android tablet logged into the MikroTik radio, 
to observe the effects of small adjustments).  The variations did not 
seem related to rain, although a wet antenna seems to drop the signal 
about 2dB.  Interestingly, during the night there was little change, but 
the commute hours seemed to generate the most fluctuations.  I think 
that's because the line-of-sight path runs about 20ft above 132nd St SE, 
a busy street connecting I-5 and Highway 9 at the north end of Mill 
Creek.  Perhaps the signal is bouncing off of vehicles?

I originally thought that perhaps the decrease from the initial -75dBm 
to -78dBm was perhaps due to foliage growth (this is Spring, after 
all).  However, in the last week I've seen a very slight increase 
(1-2dB) in the average signal level, so I don't know what to make of 
that.  Perhaps someone has been picking flowers, or Bart has been 
climbing the SnoCo DEM antenna tower and making adjustments (just joking)?

Anyway, the reason for this idle posting is just to record my 
observations for others to consider.  I have thought of raising my 
antenna a couple feet using a similar gutter mount.  I then considered 
that would probably place the center-of-mass above the gutter, which 
would make the whole thing unstable in a strong wind without a 3rd 
attachment point.  What appears to be the lower "attachment point" in 
the images, is in fact just contact bracing, with gravity providing a 
constant contact.  That's nice when the whole thing is stable with 
regard to pivoting around the gutter axis (as it is now), not so nice 
otherwise.  Yes, I could weight the lower end down to lower the center 
of mass, but right now the weight is enough to make hanging the thing on 
the gutter difficult, when standing on a slanted roof ...

-- Dean

On 2014-03-29 08:09, Dean Gibson AE7Q wrote:
> Antenna inside (-89dBm), to test the site:
>
> http://www.ae7q.com/misc/media/5.9GHz-1.jpg
> http://www.ae7q.com/misc/media/5.9GHz-2.jpg
>
> Antenna just outside the window (-84dBm), from inside:
>
> http://www.ae7q.com/misc/media/5.9GHz-3.jpg
> http://www.ae7q.com/misc/media/5.9GHz-4.jpg --  God left a gap in the 
> (many) trees, right in the path to Paine field ...
>
>   ... and from outside ...
>
> http://www.ae7q.com/misc/media/5.9GHz-5.jpg -- frontal view
> http://www.ae7q.com/misc/media/5.9GHz-6.jpg -- in the line of fire ...
>
> Move the antenna 8 feet east for a 9dB signal strength increase 
> (-75dBm = three green lights (power/Ethernet + two signal "bars") ...
>
> http://www.ae7q.com/misc/media/5.9GHz-7.jpg -- frontal view
> http://www.ae7q.com/misc/media/5.9GHz-8.jpg -- in the line of fire ...
> http://www.ae7q.com/misc/media/5.9GHz-9.jpg -- side view
>
> The nice thing about the mounting, is that there is NO attachment to 
> the house, which makes adjustment trivial (sliding the mounting hooks 
> in the rain gutter).  Even the Ethernet cable goes through 
> pre-existing screening in attic vents.  The whole thing can be removed 
> from the house without a trace in 20 minutes (10 minutes, if one is 
> young and agile, which I am neither). It's (reasonably) light-weight 
> (another plus, for the same personal reasons).
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