[CW] "Amp Sequencer"

Thu May 19 04:27:31 EDT 2005

Hello Jim,

The web page (see below) says that it is "near QSK".

What happens is that it inserts 10 ms delay after you close the key, 
switching the amplifier circuit relay (which will close within 10 ms) then 
energizing the transmitter will will go into transmit - it will stay on 
through the length of the pulse - then the sequencer will allow the amp 
relay to close.

Switching pulses are sent first to the amplifier relay, delayed by 10 ms to 
and then sent to the transceiver (but with the same length), ... ... ...

It is obvious to me now that the switching pulse to the amplifier has to be 
lengthened so that it is around 15 ms (delay time of the pulse sent to the 
transceiver, plus whatever time it takes for the r.f. to reach zero...)

So if we have a 20 ms pulse (a dot at 50 wpm), I think it figures as such:

20 ms pulse sent.

Time = 0
Relay voltage sent to amplifier relay.
10 second buffering delay by sequencer
Amplifier relay is fully closed @ T+10 ms
20 ms pulse starts to be sent by the transceiver @ T+10 ms
5 ms rise time  finishes @ T+15 ms
20 ms pulse finished by transceiver @ T+35 ms
5 ms decay time @ T+40 ms

So we have a minimum of 40 ms that the linear amplifier relay will be open - 
which is equal to a 50 wpm dot and the associated interelement space (both 
20 ms long).

So at 50 wpm, you will never hear between dots, but you will hear between 
letters as that would be 60 ms - but the window will be only the same size 
as a 50 wpm dot!

I've seen vacuum relays that switch in 6 ms close, 6 ms open - so that's 12 
ms.

I have no idea how long it takes for a key to be closed and a transceiver to 
start sending r.f.

I wanted to put vacuum relays in my NCL-2000 but Carl, KM1H is saying that 
because of the screen circuit, it isn't advisable, also because of hot 
switching.

Thanks for the help.

73

David N1EA

----- Original Message ----- 
From: N2EY at aol.com
To: n1ea at arrl.net ; CW at mailman.qth.net
Sent: Wednesday, May 18, 2005 9:03 PM
Subject: Re: [CW] "Amp Sequencer"

In a message dated 5/18/05 7:52:20 PM Eastern Daylight Time, n1ea at arrl.net 
writes:

Recently I saw in "QST" an advertisement for a new "Amp Sequencer".

http://netcertus.com/cgi-bin/netc/net.cgi?page=ampsequencer

This sequencer acts immediately on the keying pulse from the key (or from
the Push-to-Talk keying line) to close the relays on an r.f. amplifier (it
also handles sequencing the switching of additional preamps), then delaying
via a buffer the keying signal to the transmitter (transceiver) by an
adjustable delay (or a factory default delay) to allow the amplifier relays
to close, then the transceiver to be keyed, r.f. to be generated and
amplified, then after the key (or PTT) is released, the amplifier is
switched off after the adjustable delay (or factory default delay), the
preamp is turned back on.

What it amouns to is about a 10 ms delay before the start of the CW, and a
equal delay in holding the amplifier on.

Is this meant for true QSK, or simply as a foolproof form of TATTOO 
(Transmitter Automatic Turner On-er/Offer)?

The web page says that 10 ms delay isn't objectable, but I would think that
a 250 ms (1/4 of a second) would be nutty, but I don't know.

Is a 10 ms delay before you hear audio for your keyer irritating?  60 wpm
has 25 dots per second, which means it has a pulse length of 1/50 of a
second (1:1 dot:space ratio).  1/50 of a second is .02 seconds or 20 ms.  So
perhaps at 60 wpm where the delay is 50% of the dot it might be irratated.

Vacuum relay can do a lot faster than 10 ms.

But the delay could be eliminated (to the ear) by using an external keyer,
you hear the audio, the amplifier switches, the delayed key pulse goes to
the transceiver, (you have to turn the sidetone off) and the r.f. goes out
for 10 ms longer than the keyer is making a noise, then the amplifier turns
off.

Sounds sweet.

Any better units out there?

The modern trick for QSK is to use vacuum relays or PIN switches, and a rig 
that is set up for separate rx antenna input, so only one relay has to 
switch.

I have an old National Radio NCL-2000 amplifier which is tuned grid, tuned
plate (not grounded-grid) and runs two 8122 RCA ceramic tubes.

I'd like to run QSK but I don't want to hot switch the amplifer.

btw, the NCL 2000 is grid driven, but has a passive grid circuit.

73 de Jim, N2EY

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