Author Topic: Old AFB weather radar AN/FPS-77(V)  (Read 148 times)

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Offline Bafb

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Old AFB weather radar AN/FPS-77(V)
« on: November 26, 2018, 11:14:47 AM »
We are about to display this old Blytheville Air Force Base weather radar equipment and hope someone can help us with a one paragraph description of what we have. Something to go on a card next to the unit so the public can have some idea of what they are looking at.  Any help from this group is appreciated

Offline Jstx

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Re: Old AFB weather radar AN/FPS-77(V)
« Reply #1 on: November 26, 2018, 11:35:25 AM »
Bing is your friend:

Manufacturer: Lear Siegler Inc.
frequency:   5 450 … 5 650 MHz
pulse repetition time (PRT):   3 086 µs
pulse repetition frequency (PRF):   324 Hz
pulsewidth (τ):   2 µs
receive time:    
dead time:    
peak power:   300 kW
average power:   200 W
instrumented range:   200 NM (≙ 370 km)
range resolution:   300 m
beamwidth:   1.68°
hits per scan:    
antenna rotation:   0 … 5 … 8 min-1

The AN/FPS-77 is an operating in C-Band storm detection radar. It was developed as a low-cost, medium-range weather radar set to provide information on severe storms for local use. It couldn't measure Doppler frequencies. This radar was the predecessor to the NEXRAD and used over 200 vacuum tubes.

The antenna assembly includes an 8-foot parabolic reflector, fed by a J-type bended feedhorn mounted at the focal point of the reflector. The antenna could be made to sweep automatically in azimuth or elevation, or the antenna could by pointed in a fixed direcion for height or distance analysis.

Target returns are displayed on three scopes at the console and a single scope at the remote indicator. Pertinent data displayed by the three scopes include true range, height, azimuth bearing, and target density. The video is shown on PPI type indicator and an earth curvature–corrected RHI-indicator, both with rotating deflection coils. An additional A-scope with a diameter of 5 inch used electrostatic deflection. The CRT image storage was made by a Polaroid camera.

The AN/FPS-77’s PPI used an interesting but not totally successful dark-trace storage tube that could be operated in lighted environments. It used a long persistent phosphor that indicated the echos in black, not light green. The PPI echos would remain on the CRT up to 1 hour. The scope was back lighted so the black storm images on the scope are shown as a shadow. The images were erased with a heating filament inside the CRT.

The AN/FPS-77(V) were purchased in two increments from 1964 to 1966. In total, 103&nsbp;of these radars were built.

Offline mldenison

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Re: Old AFB weather radar AN/FPS-77(V)
« Reply #2 on: November 26, 2018, 12:57:37 PM »
I used this radar while a weather forecaster in the USAF - late 60's and early 70's.  I had a pair of the magnetron magnets from a burned out magnetron.  Unfortunately, they were stolen in a move and have never found another set.  They were massive!
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Offline W Thomas

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Re: Old AFB weather radar AN/FPS-77(V)
« Reply #3 on: November 26, 2018, 08:19:56 PM »
With 200 tubes those units could sure give some free heat in the winter!
Worked with a few Collins 20V2's that heated half the studio building in the winter :grin:

With 26° here now I would like to have one heating my living room,IF I could afford the power bill  :lol:

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