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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: Tue, 11 Dec 2007 22:31:03 -0500
List-post: <mailto:tentec@contesting.com>
> I strongly urge one to use the "keying loop" provided by the Tentec Omni 
> VI
> Plus system.  Although it requires different and additional circuitry 
> within
> the amp, it allows the switching to take place before RF is generated by 
> the
> transceiver and subsequently applied to the amp thus the amp T/R relay has
> switched and settled.

Good solution, but the extra circuitry required within an older non-TT amp 
to establish a keying loop is beyond the means of most users.  The sampling 
of the Omni Six's "T" buss results in the closure of most amp relays before 
RF is applied and has been tested with vacuum relays, PIN diodes, and even 
fast open-frame relays with success.

But Bob raises an excellent point.  The amp's internal relay still needs to 
be fast enough no matter what scheme is used for QSK or semi-break-in.  But 
let's say that the HA-14 cannot switch in time without hot-switching when 
sampling the Omni Six's "T" buss..  No problem.  Simply move the Key-All 
sample input line from the Omni's "T" buss right back to the input of the 
lifted base resistor of the TO-92 transistor used to key the Omni's loud 
relay for the amp.  The Omni will not key the amp with lightning speed, but 
this is exactly the condition wanted with sluggish amps.  The T/R delay time 
can also be set with variable drop-out time from the Omni's menu.

With either sampling point, the Omni will still key the amp silently, and 
that is his goal.

I should have also mentioned that any time this portion of the circuit is 
modified, a scope is an absolute necessity to ensure that hot-switching does 
not occur.  At the very least, this needs to be observed once after the 
modification is complete and tested at low transmit power at high WPM 
speeds.  I use a commercial Bird RF sample, but an inductive sample loop 
coupled close the rig's PA is adequate for a scope sample.  If hot-switching 
is occurring, it will be very apparent on the scope.

Paul, W9AC

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