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From: "Steve Andrew"
Subject: Re: 10.7MHz video demodulator
X-Newsreader: Microsoft Outlook Express 5.00.2615.200
Date: Sun, 19 Jan 2003 22:33:47 GMT
NNTP-Posting-Date: Mon, 20 Jan 2003 09:33:47 EST
Organization: BigPond Internet Services (http://www.bigpond.net.au)
Michael Black wrote:
> John Woodgate (email@example.com) writes:
>> I read in sci.electronics.design that Steve Andrew
>> wrote (in <6OjW9.2073$m47.10729@news-
>> server.bigpond.net.au>) about '10.7MHz video demodulator', on Sat,
>> Jan 2003:
>>> I cannot say what bandwidth your R8500 has at 10.7MHz
>>> but my ICOM R7000 bandwidth is around 5-6MHz so you should be able
>>> to receive the sound and colour carriers as well.
>> It sounds suspiciously like masochism to design a 6 MHz bandwidth
>> with a centre frequency of 10.7 MHz. The asymmetry problems must be
> I suspect it's not designed there, just incidental.
> Likely, there is a roofing filter at some higher IF, and that
> to be 6MHz or so wide. Though, who knows whether that wide an IF
> is due to design limitations, or they deliberately made it that wide
> for the sake of this TV adaptor. If the latter, it seems pretty
> since it must impact on the rest of the design, and TV sets are
> good for that sort of thing. More likely, if it's deliberate, it's
> there for panadaptor type things (a visual representation of the
> signals in that 6MHz or so band segment) and the TV adaptor is again
> So the point that being tapped is at the output of the mixer that
> brings the signal down to 10.7MHz, before any filtering (or minimal
> filtering) comes into the signal path. There may be a good reason
> the overall design which makes the output point at that frequency
> rather than at the higher IF.
The 10.7MHz IF output is taken directly from the second mixer without
any filtering that I'm aware of. (ICR-7000). Frequency response
extends from 10.7MHz to roughly 16MHz. I don't know if this is
intentionaly done to be used with a TV adaptor or a panoramic adaptor.
I've found another article that covers the ICR-7000 being used for AM
Further info can be found at
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