[HamWAN PSDR] Results of 7.23 mile 5.885GHz signal test

Kenny Richards richark at gmail.com
Mon Apr 1 11:28:37 PDT 2013


You might want to search the archives of the PNWVHFS mail reflector, I seem
to remember a thread about a year ago where this kind of thing was
discussed.  It was in the context of getting people their VUCC for 2.4 and
5Ghz, which requires only four grids.  The thread discussed having a group
of operators at a particular mountain site and an experience rover drive
through four grids and give out contacts.  All the shots were line of sight
and well tested.

I'll poke around and see if I can find it, but it might provide some
options now that the weather is getting nicer.


On Sun, Mar 31, 2013 at 8:05 PM, Bart Kus <me at bartk.us> wrote:

> Our primary test site turned out to be inaccessible, so we had to fallback
> to another test site.  We ended up NOT having clear line of sight over the
> 7.23 mile shot.  In fact, about 900 meters of the shot went through the
> tops of evergreen trees.  That makes this test invalid.
> Having said that, the received signal strength from the +10dBm transmitter
> was about -100dBm, which is 40dB below projected values.  So about 105dB of
> path loss if you discount the cable losses.
> We then hooked up the modems which run +30dBm and they were able to
> establish a 39Mbit air speed link.  Link quality was about 60% both ways.
>  Throughput tests showed 30Mbit(min) to 33Mbit(max) data transmission rate.
>  Speeds were the same in both directions.  It was nice and steady, with
> good ping times throughout.  Very well behaved despite the harsh
> conditions.  The radios reported -75dBm signal. The math predicts -85dBm
> should have been reported.  The radios are not calibrated measurement
> devices though, so a 10dB error is not surprising.
> This whole test needs to be re-done with actual line-of-sight conditions
> to get a good reading on path loss in free space.  A couple sites look
> possible on satellite but need to be verified on the ground for
> suitability.  They're only 6.9 and 6.7 miles long though.  It's tough
> getting good clear long distance shots in publicly available places.  If
> anyone wants to volunteer to help out with follow-up tests, let me know.
>  If you know of a good long distance LoS option, also let me know.
> --Bart
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