[MAMS] April 2011 Microwave Activity Day

[Dr. Gerald N. Johnson]

On 4/4/2011 4:39 PM, Zack Widup wrote:
> Surprisingly, my dish wasn't damaged, even after it literally flew
> over my car WITH the tripod at one point. I did get a scratch in the
> car.

At CSVHF last summer Bill Clark didn't seem to think that the stock 
Direct TV dish was made very well anyway, that its precision was poor.
>
> My IF rig was damaged when the table blew over. I don't think a radome
> would've kept either the radio or the dish from blowing over.

Actually I was thinking of a RADOME big enough to hold dish, gear, and 
operator. It would practically have to be mounted on a truck with 
stabilizing jacks like a crane or bucket truck and heavy enough to hold 
it down in the anticipated wind.
>
> Next time I won't bother to try to set up if the wind is that
> ferocious. I suppose I could've carried some sand bags for weight but
> there's only so much you can fit into a Toyota Corolla!

We probably need to do some checks of path losses vs wind speeds for 
various times of the year. I suspect that under the wind conditions you 
had, signals are down seriously, like 20 to 40 dB on a 40 mile path, 
making outings and exercise in futility. I've seen more variation than 
that to Des Moines repeaters and packet nodes over the years, but I've 
not bothered to compare to wind speeds. The 4th edition of Kraus 
published for Asian consumption has many chapters on propagation and 
includes computations for refraction and obstacle gains at microwave. 
I've not read it all yet, but it may supply some research references if 
not some insight to these wind effects.
> :-)
>
> Zack W9SZ

73, Jerry, K0CQ