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Title: 75A3 mechanical filters Post by: John K5PRO 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.
Title: Re: 75A3 mechanical filters Post by: WA5VGO 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 Title: Re: 75A3 mechanical filters Post by: John K5PRO 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?
Title: Re: 75A3 mechanical filters Post by: w3jn 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. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
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