[Elecraft] help/ QSK 5

[Dale Boresz]

Ron Spencer wrote:

>Has anyone interfaced a K2/100 to the QSK-5 which is the external qsk box
>from Ameritron? I am wondering what signal (and where it was taken off the
>K2)  was used for what Ameritron calls the Key 2 or the qsk signal from the
>radio.
>  
>
Hello Ron,

I have interfaced the QSK-5 to my K2 S/N 3039 + EC2/KPA100/KAT100 and 
Ameritron AL811-H amplifier, and it works great - BUT - I had problems 
with it when using Ameritron's configuration as shown in fig. 2a. of the 
QSK-5 manual. Specifically, the relay in the AL811-H was too slow, and 
at times, the K2 would 'see' an open circuit and go into limiting, 
requireing me to either back down the K2 power control, and bring it 
back up, or reset the power to the K2, in order to be able to get it to 
transmit again. In a discussion with an Ameritron engineer, he 
acknowledged that the problem sometimes does occur, and his 
recommendation was to take advantage of the FET which is kindly provided 
in the QSK-5 (Q7), for the purpose of controlling the amplifier's bias 
line, enabling the AL811-H relay to remain continuously energized. A 
welcome advantage to this arrangement is that the QSK operation is very 
quiet since the amplifier's relay remains energized. Also, since FET Q7 
controls the bias to the amplifier based upon the T/R signal from the 
K2, the bias is turned on milliseconds before the amplifier is driven, 
and turns off again milliseconds after the keying stops. So the 
resulting idle power (and heat) is significantly lower than it would 
otherwise be.

I don't know what kind of an amplifier you're using, but I think this 
would be a relatively simple modification to make to most amplifiers.

My connections to/from the QSK are as follows:
QSK-5 (Amp Out) ---------- AL811-H (RF Out)
QSK-5 (Antenna) ---------- ATR-30 (Xcvr) [ATR-30 is Ameritron's 
high-power antenna tuner]
QSK-5 (Amp Relay) ---------- AL811-H (Relay)
QSK-5 (Key 1) ---------- Grounded
QSK-5 (Key 2) ---------- KPA100 (PA Key Out)
QSK-5 (Xcvr Out) ---------- KAT100 (Ant1 or Ant2).  If not using KAT100, 
then KPA100 (Ant)
QSK-5 (Amp In) ---------- AL811-H (RF In)

The following two connections, are brought out to the AL811-H bias line, 
which must be cut. The bias line is a blue wire which physically runs 
from the (+) side of meter M2 to the internal amplifier relay. This blue 
wire is cut, and the two ends connect to FET Q7 of the QSK-5 as follows:
QSK-5 (Point "I" - Q7-D) to the end of the blue wire which is connected 
to the AL811-H amp relay.
QSK-5 (Point "J" - Q7-S) to the end of the blue wire which is connected 
to the AL811-H (+) terminal of meter M2.

In case you're wondering how I brought the two lines out of the QSK-5 
case, I pushed one of the two pilot lamps on the back panel, back inside 
the case, (they're wired in parallel anyway) and pass the two wires 
through the now open rubber grommet.

That's it! Although I don't use the amp very frequently, I'm not above 
turning it on if the other station is having a particularly difficult 
time copying me, and the arrangement has worked flawlessly and is very 
quiet!

Of course, you'll want to initially test this arrangement with as little 
drive to the amp as possible. In fact, I'd recommend that you place the 
K2 into "Test" mode so that it won't transmit, and with the amplifier 
turned on and the OPR/STBY switch in OPR (relay energized) and the K2 
not keyed, you should see no idle current reading on the plate current 
meter of the AL811-H. Then, key the K2 (while still in test mode), and 
you should see the plate current meter should indicate about 150 mA 
until you stop keying the K2. That tells you that the QSK-5 is 
successfully controlling the amplifier's bias line. Then, place the K2 
into the normal 'Oper' mode, and slowly bring up the drive while keying 
the rig and watch the amplifier output, until you're comfortable that 
all is well.

If you have any questions, feel free to contact me directly.

Best 73,
Dale Boresz / wa8sra