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Subject: [TenTec] OMNI VI TROUBLE
From: geraldj@ames.net (Dr. Gerald N. Johnson, P.E.)
Date: Sun, 01 Nov 1998 21:51:30 -0600
What you want is rather difficult to achieve. If a station is running
SSB within 2 or 3 khz of your frequency that station has spectrum
components that are WITHIN your receiver passband. They aren't copyable
but they are there. Likewise your signal is nearly 3 khz wide and you
are in their receiver pass band. Just because the dial shows a number
different by 2 khz doesn't mean its not causing QRM.

To be more specific. Take an operation on 75 meters, Lower Side Band.

Suppose you are tuned to 3970. That means you are listening from
3967.300 to about 3969.700 Khz. with your 2.4 Khz filter. The filter
isn't perfect so there are some components beyond that.

A station transmitting on 3968.000 LSB has components from 3964.3 to
3967.700. Overlapping your receiver passband.

A station transmitting on 3972.000 LSB has components from 3969.300 to
3971.700 Khz. Again operlapping your receiver passband.

Maybe if we'd transmit a little carrier the receiver could reject
components that didn't have the same phase and thus reject the other
transmitters, but without carrier that's a tough thing to accomplish.

I don't think TenTec has a solution perhaps other than suggesting the
1.8 Khz filter and using the RF gain and RF attenuator to reduce the
signal strength of the unwanted signal. I think you do need a towel.

73, Jerry, K0CQ

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