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R. Hayward EVLA Feeds CDR – Feed Radomes17 Feb. 2005
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EVLA Feeds CDR
Feed Radomes
R. Hayward EVLA Feeds CDR – Feed Radomes17 Feb. 2005
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Radome Windows
• All of the feeds will require a radome (or weather window) to provide environmental protection.
• These radomes must:• be low loss • be non-absorbent, • have good UV characteristics• provide a moisture seal• protect against insect/bird/rodent access
• All but the Ka & Q-Band receivers have their feeds protruding through the Feed Cone roof.
R. Hayward EVLA Feeds CDR – Feed Radomes17 Feb. 2005
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Feedcone View of Radomes(excluding L-Band)
S
C X
K
KaQ
Ku
L
L, S & CRadomeswill use aStronger,
Low FrequencyRadomeMaterial
X, Ku, K, Ka & Q Radomes will use aLow-Loss
HighFrequency
RadomeMaterial
R. Hayward EVLA Feeds CDR – Feed Radomes17 Feb. 2005
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“K-Band” Style Mount
• K, Ku, X, C, S (& even L) use similar style of mounting
• Feed is mounted to the Feed Cone and the Receiver is then mounted to the Feed
• Radome membrane covers the mouth of the feed
• Esscolam 10 for L, S & C
• Gore RA7906 for X, Ku & K
R. Hayward EVLA Feeds CDR – Feed Radomes17 Feb. 2005
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Radomes for Low Frequency Bands
• Esscolam 10 will be used onL, S & C-Band Feeds
• 72” by 72” sheets
LS
C
R. Hayward EVLA Feeds CDR – Feed Radomes17 Feb. 2005
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“Q-Band” Style Mount
• Q & Ka use similar style of mounting
• Feed is considered to be part of the Receiver
• Rx bolted to Feed Tower• Air-tight seal formed
between Rx and Tower• Radome membrane covers
the top of the Feed Tower• Gore RA7906
R. Hayward EVLA Feeds CDR – Feed Radomes17 Feb. 2005
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Radome MaterialsEsscolam vs. Gore-tex
• Esscolam 10– Loss similar to Esccolam 8– Thickness 0.024”– 72” wide sheets– OK below 8 GHz
• Gore RA7906– Thickness 0.012”– 45” wide sheets– Best above 8 GHz
R. Hayward EVLA Feeds CDR – Feed Radomes17 Feb. 2005
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Radome Windows at W-BandGore RA7906 vs. Gore 3T20
W#8 : Effect of Goretex Window sSNA Sw ept LO1 Data
W08-RCP-Old&New-Goretex-Window-28-Sept-2004.xls28 Sept 2004
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Frequency (MHz)
Trx
(K
) RCP Trx with No Window
RCP Trx with RA7906 Goretex
RCP Trx with 3T20 Goretex
R. Hayward EVLA Feeds CDR – Feed Radomes17 Feb. 2005
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Radome Windows at K-BandGore 3T20
K#28 With Cryo IsolatorsTest Feed w ith Orange Mylar vs. Orange Mylar + Goretex 3T20
15 July 2004K28-Trx-Test-Feed-Orange-and-Goretex-Elev-Loads-18-26-Cryo-Iso.xls
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Frequency (MHz)
Trx
(K
)
RCP Trx - Orange
RCP Trx - Orange+Goretex
R. Hayward EVLA Feeds CDR – Feed Radomes17 Feb. 2005
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Radomes for High Frequency Bands
• Originally purchased 8m of 3T20 ($3200)
• Now obvious that RA7906 is preferred
• Reuse existing K & Q RA7906 membranes
• W.L. Gore has agreed to allow us to return the 3T20 and replace it with RA7906– incur a 20% restocking fee ($640)