[VHFcontesting] Setting up TE RF amp for use with a sequencer.

[Terry Price]

Folks,

The answer to the pin 5 and 6 question is pretty simple. A small portion of
input RF to the amp is coupled to a couple of diodes that rectify the RF
(AC) and make it DC and apply it to the base of a transistor. Once the
voltage reaches about .6v above the emitter voltage, the device turns on
and the collector goes low (it's a NPN transistor). The jumper between pins
5 and 6 ties the emitter to ground which ensure this circuit works. Cutting
the jumper will disable the RF sensing circuit. If you put the "mode"
switch into the FM position and just ground pin 2, you achieve the same
results. All the FM/SSB switch does is to add some delay to hold the relays
in inbetween syllables on SSB or characters on cw, it does NOT change the
bias on the devices from AB to C. Using this amp with a sequencer, the PTT
will be keyed long before any RF is generated if things are corrected set
up.

So the short answer is, just connect the center conductor of a shielded
cable to pin 2 and the shield to pin 6 (GND) and this becomes your PTT or
"hard key" line. Keep the mode switch in the FM position to eliminate the
delay.

73 and keep on contesting!!

Terry Price - W8ZN
Directive Systems and Engineering
703-754-3876


On Sun, Dec 15, 2019 at 6:30 PM John Young via VHFcontesting <
vhfcontesting at contesting.com> wrote:

>
> Taking pin 2 to ground turns on the PA with 5 and 6 still internally
> connected.
>
> However with 5 and 6 internally connected the rf sensing is still enabled
> which defeats part of the purpose of the sequencer.  The amplifier can turn
> on if RF gets to it even if the PTT ground to rf amp lead from the
> sequencer is not grounded.
>
> I have had my 991A on 6m buzz my 1.25m amp, same thing happened with the
> W4IY Elecraft on 6m in september.  If I had been using a hard keyed pre amp
> on 1.25m it would have been fried.
>
> I opened up the amp and there is no obvious sign of the pin 5-6 internal
> shorting wire.  Maybe you have to cut a trace now?
>
>
> Calling TE Tomorrow.
>
> 73
> John
> KM4KMU
> On Sunday, December 15, 2019 John Young via VHFcontesting <nosigma at aol.com>
> wrote:
>
> The TE manual gives some simple instruction for hard keying the amplifier
> but out an abundance of caution I want to verify my understanding of them
> before I start cutting wires and adding relays.
>
> The DEMI sequencer gives a sequenced PTT ground to enable the amplifier.
> The TE  instructions are to cut the internal  shorting wire between pins 5
> & 6 and then connect the PTT ground to pin 2.
>
> To enable the RF amplifier the TE instructions are:  1) Connect pin 5 & 6
> then 2) connect pin 2 to PTT ground.
>
> My interpretation of these instruction are:
> I need to use the PTT ground to close a relay that connects pins 5 & 6 and
> then use an output from this relay to close another relay that connects the
> PTT ground to pin 2 on the amplifier.
>
> Is this correct?
> Is there a better way?
>
> 73
> John
> KM4KMU
>
>
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