[TenTec] Transmit not stopping when PTT is released

[Rick - DJ0IP / NJ0IP]

OK guys, it's time to take the hammer and hit the nail on its head:

The BTI LTK 2000 amp is a very hefty amp with a single 3-1000z triode.
Although it is a 1960s amp, it does have a 12vdc T/R relay.
I assume it is an open-frame relay and very hefty, so it will need on the
order of 25mS to switch (including its 2 mS settling time).

The Orion provides a pre-dit delay and an adjustable post-dit delay (hang).

The pre-dit delay will key the amp 15 mS prior to the first dit being sent.
Unfortunately this is not long enough for safe keying and it is not
adjustable.  It's simply too short for a large open-frame relay.  
ADDITIONAL DELAY IS PROBABLY REQUIRED TO PREVENT HOT SWITCHING.  (10 to
15mS)

The post-dit is like a VOX Hang.  
It keeps the amp keyed after the dit as been sent.  
This is also adjustable in the Menu under "EXT T/R Delay 1" and "EXT T/R
Delay 2". 
I would use about 200 to 250mS.

NOW THE SWEET/SOUR MESSAGE

AS SOMEBODY ELSE SAID, THE TRICK IS TO HAVE THE MicroKeyer KEY THE TX, NOT
VICE VERSA.
(THIS INCLUDES CW MODE AS WELL AS DIGITAL MODES!)

In order to assure Rod can key the amp without hot switching, he has
everything he needs already.
However he will need to key the MicroKeyer using its built-in Winkey keyer,
therefore he cannot use the Orion's built in keyer.
Doing this will assure the amp does not hot switch in CW.

The MicroHam MicroKeyer II has adjustable delay for handling all of the
keying.
These adjustments are found under "Device Configuration" within the "PTT"
tab:
 
 <> Its "PA PTT" switches the linear on before the TX is keyed. (Pre-dit
delay). The PA PTT signal can key the amp with either a relay, or a
transistor (up to 48 volts and 800mA). It is selectable.  Should be fine
with the transistor BUT CHECK THE KEYING CURRENT of the linear's T/R relay)
BEFORE SWITCHING TO TRANSISTOR KEYING!  
IMPORTANT:  You can adjust the PA PTT hang time in the software.  The
adjustment is called "PA PTT tail".  It defines the time the PA PTT signal
remains closed, after PTT1/2 signal has ceased. (try 200 to 250mS). 

 <>"PTT1/2" keys the CW; plug it into the Orion's PTT (input) jack and run
the Orion without its internal keyer.  This will probably need to be set for
10 to 15mS before triggering the next one (PTT1/2).  This specific
adjustment is called "PTT lead" and sets the time between the signal
triggering the PA PTT and the beginning of the signal triggering the PTT.
Again, this will need to be set to 10mS, perhaps even 15mS, which in
addition to the Orion's own pre-dit delay of 15mS will give you 25/30 mS
total pre-dit delay.

VERY IMPORTANT:  YOU MUST operate the WinKeyer in (CW) "Semi Break-in Mode"
(NOT QSK).  
In QSK mode, the delay timing is NOT active which will cause "burn baby
burn" to the Amp's T/R relay.  

Unfortunately, in order for this to work, you have to key the MicroKeyer,
NOT the transceiver.
So as I said, Rod will have to deploy an external Keyer for CW.

The MicroKeyer has two inputs (PTT IN and Foot Switch).
Either one will generate the process.
The External keyer can plug to either of these.

In digital modes, the MicroKeyer also keys the Orion's PTT line.  It uses
the PTT1/2 signal.
PTT1 and PTT2 are identical; this enables you to key two things
simultaneously.
The simplest way to set this up is to connect either of these lines to the
Orion's PTT INPUT (not output).

And that's all I have to say about that.

73
Rick, DJ0IP


-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Bob McGraw
- K4TAX
Sent: Friday, December 06, 2013 3:28 AM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Transmit not stopping when PTT is released

In most cases with a non-QSK amp some form of delay system should be
employed.  This system provides a delay at initiation of transmit such that
amp relays close and settle before RF is applied.  Then at the end, a delay
to hold the relays closed until the completion of the last character.  At
end when the CW key is released the character must still be sent.  If the
radio is using the CW key for control of the TX/RX control then likely the
amp could un-key before completion of the RF envelope.  Thus hot switching
may occur.

I don't recall the timing sequence of the Orion II.

With the Tentec QSK circuit the key is closed and this sends the signal to
the amp to switch from RX to TX mode. After the amp has switched it then
sends a signal back to the transceiver to deliver the RF.  At the end of the
transmission, the RF sensing circuit in the Centurion and Titan keep the
relays in the amp engaged until the end of the RF envelope before the relays
are allow to switch from TX back to RX.


73
Bob, K4TAX