[NLRS] Question on emission type

[Dr.Gerald Johnson]

It does take bandwidth in the pulsed signal to resolve to a short 
distance, say 100 feet. That's 200 ns round trip time. !/200ns is 5 MHz, 
and you need quite a bit more bandwidth for a fast rise. I think most 
modern radars are more like 30 MHz wide, maybe more. When my 1296 
receiver worked, I could occasionally hear radars at 1296 that I'm fairly 
sure were down the band at least 100 MHz.

The WSR-88D is pure pulse, but with a stabilized frequency. Most of the 
weather products are based on the pulse response amplitude, not 
the frequency. Only the velocity products make use of the doppler 
data and then only to half its range (computer power ran out). While 
the distributed data is in 1 degree increments, the basic beam is 
narrower which severely complicates cleaning out ground clutter 
down stream because the clutter isn't the same from one scan to the 
next.

Can we squeeze in 1.5 KW pulse as a beacon? It would play heck with  
the WiFi crowd and by blanking our receiver with a noise blanker type 
circuit we could still hear between the pulses. It might require keeping 
the power down but the beacon closer to home, but that might be 
an effective way of moving WiFI and other digital noise from our 
bands. In the future some of that data equipment is planned to have 
avoidance for other signals because the other signals as the 
uncontrolled use rises eat the digital data alive. Cuts back range and 
data rate.

73, Jerry, K0CQ

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Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.