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Re: [TenTec] OMNI VII QSK users with good ears....

To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Subject: Re: [TenTec] OMNI VII QSK users with good ears....
From: "Paul Christensen" <w9ac@arrl.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sun, 9 Dec 2007 20:07:32 -0500
List-post: <mailto:tentec@contesting.com>
> The Omni VI/VI+ used a reed relay for T/R switching, even tho they may 
> have
> used diodes in the circuit.  Remember all the complaints about how some
> folks could hear their relay and others couldn't?  :-)

The mechanical mounting of a T/R relay has a profound effect on acoustical
noise.  To reduce noise of any relay in a T/R circuit, the idea is to reduce
the effects of the PCB or chassis functioning as an acoustical sound board
(e.g., like that found on a piano or violin).

Even on the Omni Six series, the noise of the T/R reed relay varied from 
nearly zero to annoying,
depending on how the relay was inserted during manufacturing.  The distance 
of the reed relay's body from the PCB generally established the level of 

By contrast, the Omni Six's open-frame amp relay is quite loud.  There are 
other noiseless solutions for that, including the bypassing of the amp relay 
with a high-voltage, high-current MOSFET switch, capable of silently 
switching nearly any AC or DC amp key line.

The idea propagated by others that a "Y" adapter used on the Omni Six's 
TXOUT/TX EN line through a steering diode to the amp is a bad one and leads 
to hot-switching on some amps without such timing protection.  I know it 
works for some folks, but they're lucky in that the amp senses the hot 
switching -- until the protection circuit fails.  Those two amp sequencing 
jacks are meant ONLY for amps that accommodate a bi-directional handshake.

Paul, W9AC

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