IMO, we must always assume hot switching is occurring on any amplifier
WITHOUT a very fast TR relay (i.e. vacuum relay).
Therefore the lead delay time should be at least 20ms but 25ms is a safer
value. If you know the exact speed of the relay, from the spec sheet,
perhaps it can be 10ms slower (15ms delay), but it doesn't hurt to just use
25ms.
You will also need a hang time delay with these open-frame relays and it
should be adjustable up to about 1 second. SIMPLE SIMON to implement; you
need only one electrolytic capacitor and a potentiometer. Piece of cake!
If you do this, there is no need to trace the timing with a dual-trace
scope.
Mind you, it's a great idea to do that, but most people don't have the scope
and may not know how to do this.
ALL OF THIS TIMING HAS BEEN MEASURED IN THE LAB ALREADY, LONG AGO!
WE ALREADY KNOW WHAT IS REQUIRED!
BTW, don't worry about side effects from the 20 to 25ms delay.
The human brain does not detect the delay while keying unless you are keying
at over 50wpm.
73 - Rick, DJ0IP
(Nr. Frankfurt am Main)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Peter
Bertini
Sent: Sunday, January 05, 2014 5:08 AM
To: tentec@contesting.com
Subject: Re: [TenTec] inverse question re amp QSK keying
It fails on non Ten Tec QSK amps because Ten Tec amps provide a relay
closure to activate the RF CW signal. This ensures the timing allows for the
reed or vacuum relays to have proper switching and settling time before RF
is applied.
I'm using an Omni VI and Paragon II with a QSK ready SB-220 amplifier. In
the case of the Omni, the T voltage provides adequate timing (using a mosfet
switch) to activate the amp. In the Paragon II I found the mute voltage
allowed for a 15 mS delay between activating the amplifier and RF output
(again using a mosfet switch.
)
Caveat emptor... any similar mods require some bench evaluation using a dual
channel scope to verify that hot switching is not occuring.
Pete
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