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Author Topic: 75A3 mechanical filters  (Read 3022 times)
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John K5PRO
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« on: September 11, 2006, 04:05:04 PM »
I have heard or read that Collins Radio made a change in 75A3 production and went from their 455B-3 to a 455C-31 for the 3 KHz filter that was standard in these receivers. Is there a difference in the characteristics of these two filters, besides one having 3100 Hz and the other 3000 Hz bandpass? I also read (maybe in Electric Radio) that the termination capacitance in the stock receiver changed from 330 pf to something like 130 pf in later production.
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WA5VGO
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« Reply #1 on: September 12, 2006, 07:04:45 PM »
I believe the early filters had about 10 db more loss than the later ones.

73,
Darrell, WA5VGO
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John K5PRO
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« Reply #2 on: September 12, 2006, 07:39:49 PM »
Wow, thats significant (-10dB). Being inside the IF amplifier, I wonder what that does to overall RX performance?
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w3jn
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« Reply #3 on: September 13, 2006, 02:31:04 PM »
In most any well-designed receiver, tHere's always excess gain available.  It's made up in the AGC.
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