[NLRS] 10 GHz Rain Scatter Question

Bruce Richardson w9fz at w9fz.com
Mon Apr 23 02:13:59 EDT 2007


Hi Scott:

Thanks for the Blue Angels link.  Sad.

I was initially going to just send this to you, but I really would like
to hear W0ZQ's, WA2VOI's, and others thoughts.

Well, I don't think we ever tried 10mw on Rainscatter because we thought
it wouldn't be possible. You know, volume of space illuminated, distance
traveled, attenuation, etc. If you take 10mw and distribute it over a
rain shaft 20-70 miles away, you're probably illuminating on both sides
of the shaft. Plus, if you're illuminating from 10,000' to 30,000 feet,
the actual energy being picked up by the droplets is pretty small for
re-radiation.

BUT......... Sigs sure have been strong coming back, at times, now that
we are playing with 2 watts.

Let me pause and do some db math comparing 10mw to 2 watts......10 20 40
80 160 320 640 1280....2000

That's 10dbm to 33dbm -- a difference of 23db-- so you could understand
that they might not hear you if you hear their 2 watts.  That's just 4 S
units on some scales.

Now I think I remember why we didn't try it when we all were 10mw--it
would have been like looking through pin-hole lenses in a cave.
(Someone, help me with another analogy here :-) )  But I think players
SHOULD try with 10mw when the other stations have 2w or more. Sure, they
may not hear you.  But they might. And you will hear them and peak up on
the brightest specular highlight on the rain you are commonly
illuminating.

I must tell you that I did my first rainscatter when I had 400mw. (still
need to finish those qualcomm amp boards :-) )

Pending other responses, I hope you end up trying and are successful. It
would prove 10mw IS possible when a bigger station probes and illuminates
the best shafts.

73
Bruce (in Seattle at the moment)
W9FZ



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