[FSG-public] Link from Tampa to St Pete - Quick question

[Bryan Fields]

On 1/4/17 10:37 PM, Luis V. Romero wrote:
> Are you guys doing the link between the two HamWAN sites via RF?  If so, what
> is the link budget?

The radios are at -63 now at 140 Mbit/s.  We need -70 or better.  I think we
need to tweak it a bit more, it can improve.


> Since you tested it in the winter, I suspect lots ofFresnelzone issues and
> reflection off of the bay plus tropo issues in the summer.

Yes, but we can maintain a link to -90 and the radios will modulate down (with
a drop in throughput)


> How do I know this?  I had a2 watt/30dBi gainHorizontal pol7GHz hop from
> across the street from RayJay to Riverview over Hillsborough Bay and in the
> summer, the path was a mess due to temperature inversion layer differences
> over ground vs the bay… Needed diversity receive antennas at Riverview.  I had
> a hell of a time with that path! Thank god for Fiber – The RF path was the
> secondary STL for WFTS.

Who decided to do horizontal pol over the water?

We run MiMo with H&V polarity.  there is a much better dispersion fade margin
in modern digital radios.  The older analog radios needed a very hot signal to
make it work due to the limited recovery due to fades built in.

> 
> The path over the bay is BRUTAL in the summer, especially in the early
> morning/late evening.
> 
> Wonder how this will affect that link.  It will be interesting to
> see. Don’tknow how much fade margin you guys have in the link budget.

I need to start graphing it.  It's going to be fun, and it's ham radio :D


-- 
Bryan Fields, W9CR
Florida Simulcast Group, Inc.