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From: rpw3@rigden.wpd.sgi.com (Rob Warnock)
Newsgroups: sci.electronics
Subject: Re: Cable TV question
Message-ID: <88545@sgi.sgi.com>
Date: 2 Mar 91 04:21:48 GMT
References: <471@pyrite.nj.pyramid.com> <17336@milton.u.washington.edu>
Sender: guest@sgi.sgi.com
Reply-To: rpw3@sgi.com (Rob Warnock)
Organization: Silicon Graphics, Inc., Mountain View, CA
Lines: 57

In article <471@pyrite.nj.pyramid.com> dcm@pyrite.nj.pyramid.com
(David C. Miller) writes:
+---------------
| ...I find it frustrating to have to switch between the internal
| and external tuner...
|                            Cable Tuner  +----- Channel 3 out
|                            Descrambler  |
| Incoming cable with          +-----+    v
| scrambled signal on   +------|     |----+
| channel 28           /       +-----+     \+----+
| --------------------+                     |    |------------+
|                     ^\                   /+----+
| cable splitter -----+ +-----------------+   ^
|                                             |
| Device that blanks out channel 28 on      --+
| straight through line, then map channel 3
| from the tuner to channel 28.
+---------------

I have a similar but not identical problem. I don't have cable; I use the
large outside antenna [no rotator] that came with the house I'm renting.
It has a VHF/UHF mixer [inverse "splitter"] up on the antenna along with
a 300ohm/75ohm balun, and feeds the composite signal into the house on a
single 75ohm coax. My problem: Almost all the T.V. stations I'm interested
in are in the direction the antenna points, except a couple, which are on
the other side. And even there, all but one are strong enough that I get
an acceptable signal on back-scatter from the hills "in front" of me. But
the one weak signal on the "wrong" side is also one I'd really like to
receive better. I could put up a second antenna pointing the other way,
but have no easy way to control an antenna switch from the VCR. So the
device *I'd* like to find would do something like this:

	Signal from the
	"front" antenna
	+-----------------+
	                   \+----+      +-----+
	Signal from the     | ?  |------+ VCR |
	"back" antenna     /+----+      +-----+
	+-----------------+   ^
			      |
			Passes all channels from "front"
			antenna, except for one, which
			it selects from "back" antenna.

Any idea what to use for the little black box?

-Rob

p.s. The desired "back" channel is channel 54, and the closest desired
"front" channels is channel 50 (which is, alas, also quite weak), so the
filtering doesn't have to be *too* tight...

-----
Rob Warnock, MS-1L/515		rpw3@sgi.com		rpw3@pei.com
Silicon Graphics, Inc.		(415)335-1673		Protocol Engines, Inc.
2011 N. Shoreline Blvd.
Mountain View, CA  94039-7311