DX Connection QSK 2500 User manual

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DX Connection
QSK 2500© Instruction Manual
1) Description
The DX Connection QSK 2500© allows operating a non QSK amplifier in QSK mode (or SSB VOX mode) with
no amplifier modifications. No amplifier T/R relay interface is required. The QSK unit will interface to
amplifiers whose key jack presents less than 200 volts positive or negative polarity to the QSK unit. The
QSK 2500© adds a nominal 10ms delay to the transceiver’s normal RF delay to eliminate hot switching of
the amplifier’s internal T/R changeover relay before the first dit or dah of a transmission. After the first
dit or dah, the amplifier remains keyed up for the remainder of the transmission preventing excessive T/R
relay switching. The QSK 2500© returns the amplifier to standby 2 sec to 10 sec (user settable) following
the last dit or dah of a transmission. The QSK unit incorporates hot switching T/R relay protection caused
by some transceivers removing the amplifier key signal before the RF envelop has decayed. The QSK unit
senses for RF on the amplifier RF input connector and only switches from Transmit to Receive when the
RF envelop is no longer present. A functional block diagram is included later in this manual.
The QSK 2500© Key/Paddle input jack accepts a straight key, an external keyer, a bug, a paddle (to use the
transceiver’s internal keyer), computer generated CW, or anything that keys the transceiver by grounding
a circuit(s). The input device must sink about 1 ma to ground and accommodate 5 volts open circuit.
These requirements are compatible with the transceiver’s Key/Paddle Input jack requirements.
2) Specifications
a) RF Power: 2500 Watts CW/SSB/Data modes
b) Antenna VSWR: < 1.5:1 at 2.5KW, < 2.5:1 at 1.5KW, < 3.0:1 at 1.250KW
c) RF losses: almost lossless relays (much less loss than PIN diodes), silver plated SO 239 connectors
d) QSK internal relays: acoustically quieted and sealed for quiet operation
e) No hot switching of QSK internal relays
f) Provides T/R relay high voltage interface for both new and older amplifiers: The QSK 2500© input
presents a 5VDC 1ma signal to transceiver Amp key jack. The QSK 2500© output keys (to ground)

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amplifier T/R relays up to +/ 200VDC and 150ma. (No need for MFJ ARB 704 or Jackson Harbor Keyall
Interface.)
g) Amplifier TX to RX hot switching protection: QSK unit returns to Rx mode only after the RF envelop has
decayed preventing hot switching the amplifier T/R relay.
h) Amplifier RX to TX hot switching protection: QSK unit adds nominally 10ms (see next item) of delay to
the transceiver’s internal 5 to 15ms time delay (see Table 1 below) before the start of the transceiver RF
envelop output. The 15 to 25ms total time delay allows the amplifier T/R changeover relay ample time
to switch to TX prior to the first dit or dah of each transmission. The amplifier remains keyed after the
first dit or dah of each transmission preventing excessive T/R relay switching during the transmission.
(The 5 to 15ms initial key delay is not available in SSB VOX mode because the Key/Paddle input delay
channel is not used in SSB VOX mode.)
i) QSK timing delay: The Key/Paddle output to the transceiver is delayed 10ms from Key/Paddle input with
the factory settings. This should accommodate almost all transceiver/amplifier combinations. However,
solder jumpers are provided to adjust this timing delay from 4ms to 16ms to accommodate custom
transceiver/amplifier timing requirements. (See comment above on SSB VOX mode.)
j) Amplifier keying delay following the last dit or dah of a transmission: User adjustable from 2 sec to 10
sec (factory setting: 3 sec) SSB VOX mode is fixed at 30 sec
k) Duty cycle: continuous duty
l) DC power input: 17 to 25 volts at 200ma (max) [120VAC power block included.]
m) Two LED indicators: Power On (green), Transmit (red)
n) Acoustically quieted, sealed relays for quiet operation
o) Key/Paddle input jack: 1/4” stereo
p) Xcr Key/Paddle output jack: 1/8” mini stereo
q) Amp Key ‘IN’ phono jack: 5VDC open; 1ma shorted (transceiver keys to ground)
r) Amp Key ‘OUT’ phono jack: keys Amp T/R relay to ground. Accepts T/R relay voltages +2 to +200 VDC
or 2 to 200 VDC, 150ma (max)
s) Power jack: 2.1mm male (center positive)
t) Size: 5 ¼ in W x 2 in H x 3 in D (excluding SO 239 connectors)
u) Weight: < 1 lb.
v) Optional cable set: One 6 ft long 1/8” mini stereo cable, two 6 ft long RCA cables, plus one 1/8” to 1/4”
stereo adapter.
w) Factory option to use the Kenwood transceiver +12VDC Amp Key output signal: Contact DX Connection
for information.
x) 1 year Limited Warranty
(back view)

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3) Interconnections
The Control interconnections are shown in Figure 1. The RF interconnections are shown in Figure 2.
Referring to Figure 1, the CW input device (i.e. key, paddle, bug, computer, keyer, etc.) connects to the
¼” Key/Paddle stereo input jack on the QSK unit. For single line input devices such as a key, keyer, bug,
computer CW, etc., a stereo jack must still be used. The center pin is used for CW; the sleeve is left
unconnected. Paddles connect to the center pin and the sleeve in the normal manner (dit center, dah
sleeve).
Note: A stereo plug is no longer required for new QSK units when not using p ddle. The QSK
2500 utom tic lly dis bles the ring ch nnel t power up if it is found to be shorted to ground.
The delayed CW appears at the Xcvr Key/Paddle mini stereo jack on the QSK unit. This jack connects to
the Key or Paddle input on the transceiver.
The transceiver’s Amplifier Key jack connects to the AMP Key IN phono jack on the front of the QSK unit.
The transceiver keys to ground a 5VDC 1ma signal from the QSK unit. (Contact DX Connection to use
Kenwood’s +12 VDC for QSK 2500 keying.) The QSK’s AMP Key OUT phono jack connects to the amplifier’s
AMP Key IN (or ‘antenna relay’, ‘T/R relay’, or ’transmit input’) as shown in Figure 1. It keys the amp T/R
relay to ground. No QSK setting changes are required for keying either positive or negative amp T/R relay
voltage polarity.
A 17 to 25 volt, 200 milliamp, ‘wall wart’ type DC power supply (included with the QSK unit) connects to
the ‘Pwr In’ jack on the front panel. The power supply requires a 2.1 mm power plug (center positive).
See this video for an example. Adding QSK to unmodified Ham Radio Amplifier - YouTube
4) Example Interface to Ameritron AL-811 amplifier series
The QSK 2500© interface to the Ameritron AL 811 series of amplifiers is shown in Figures 5, 6, and 7.
5) Operation
The QSK power switch places the unit in either ‘AMP mode’ or ‘ByPass mode’. In AMP mode, the QSK unit
is active and performs the expected switching of the RF signal.
The QSK unit must be in AMP mode nytime th t the mplifier is to be used reg rdless of the
oper ting mode, i.e. SSB, CW, RTTY, PSK, etc.
If the amplifier is not to be used, then the QSK unit can be set to ByPass mode which turns it’s DC power
off and routes the Key/Paddle input jack to the Xcvr Key/Paddle output jack. See Figure 3. The QSK unit
can be set to AMP mode for transceiver only operation if the amplifier power is turned off or the amplifier
key input is disabled. Some amplifiers can be disabled by a switch on the front panel. For this case, it is

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not necessary to set the QSK unit to ByPass to operate without the amplifier. However, the amplifier RF
ports must remain connected to the QSK unit.
6) Adjusting Amplifier Keying Delay
After the last dit or dah of a transmission, the amplifier is held keyed for a short time to prevent excessive
switching of the amplifier T/R relay. The nominal factory setting is for a 3 sec delay which satisfies most
users. Faster CW operators tend to prefer shorter delays and slower operators tend to prefer longer
delays. This setting is not critical and is mainly a user preference. (It does not affect QSK receive or
transmit timing.) A 20 turn screw adjustable potentiometer is located next to the PIC16F676 chip (see
Figure 1a below). It allows setting the delay from 2 sec to 10 sec. After djusting the potentiometer, the
QSK2500© must be switched off nd b ck on for the djustment to t ke ffect. Also, see video:
Adjusting QSK 2500 Delays high resolution Rev YouTube .
Method 1:
The safe method is to adjust the potentiometer a few turns with the QSK unit turned off, and then turn it
on to see how the delay time has changed. Be sure to remember (or write down) the direction of the
adjustment and the number of turns so you can estimate which direction to turn the potentiometer screw
the next time and how many turns. The adjustment is approximately linear.
Method 2:
Be careful to not short any of the PIC16F676 pins. The delay can be set with the QSK unit powered up by
measuring the voltage on pin 8 of the PIC 16F676, and according to the following formula.
Potentiometer voltage = (desired delay in sec 2.0sec)/10.1sec * 5.0volts
Remember: The QSK unit must switched off and back on for the dela change to take effect.
7) Selecting SSB VOX mode
SSB VOX mode is selected by shorting to ground the tip of the Key/Paddle input plug during power up. If
CW is not used, a 1/4 inch plug with the tip shorted to ground can be inserted in and left in the
Key/Paddle input jack. If both SSB VOX and CW are used, the tip must be shorted to ground for 2 seconds
during and immediately following QSK 2500 power up. Holding the key down or holding the dit input
with a paddle during power up works fine.
When SSB VOX mode is selected, the QSK 2500 holds the amplifier keyed for 30 seconds following the last
voice transmission. (CW cannot be used while in this mode.) The QSK 2500 is keyed by the ‘AMP in’
being grounded by the transceiver’s amp key output shorting it to ground. This is no change from CW
QSK mode.
To exit SSB VOX mode, remove the tip short to ground and turn the QSK unit off and back on.

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8) Optional Key/Paddle Delay timing
The factory setting for the delay from the QSK2500© Key/Paddle Input jack to the key/paddle Xcvr Output
jack is 10ms. This value is suitable for most amplifier/transceiver combinations. The user is encouraged to
use this setting unless this delay is known to be too short. Table 2 below shows that by adding the
appropriate solder jumpers, the timing can be adjusted from 3ms to 16ms. There are pairs of holes
located next to pins 2, 3, and 4 of the PIC16F676 for the jumpers (see Figure 1a below ). A 1/4” long bare
#22 solid wire makes a suitable jumper. The delay should not be lowered below 10ms unless test
equipment is available to assure hot switching of the amplifier T/R relay does not occur at the start of the
first dit or dah of each transmission. See Adjusting QSK 2500 Delays high resolution Rev YouTube .
Note: M ny commerci l extern l QSK units (including PIN diode types) do not protect g inst hot
mplifier T/R rel y switching t the st rt of the first dit or d h of e ch tr nsmission.
9) Limited Warranty
The QSK 2500 is warranted to be free of defects in materials and workmanship for 1 year to the original
purchaser. This limited warranty is for either the repair or replacement of the QSK unit only. There is no
coverage for anything other than the QSK unit. This warranty is exclusive of abuse, misuse, accidental
damage, acts of God or consequential damages, etc. A DX Connection Return Authorization (RA) is
required for warranty service. Email or mail a copy of the purchase receipt and a description of the
problem to DX Connection to obtain a Return Authorization. Upon receipt of the Return Authorization,
return the unit shipping prepaid to DX Connection. DX Connection will pay return shipping. 73
Cont ct: DX Connection em il: [email protected]
W. Rodgers K3HZP phone: [phone]
5727 Buckfield Court
Fort W yne, IN 46814 website: http://qsk2500.myfreesites.net/
YouTube video 1: Adding QSK to unmodified H m R dio Amplifier - YouTube
YouTube video 2: Adjusting QSK 2500 Del ys high resolution Rev - YouTube
YouTube Video 3: QSK2500 TR Rel yTiming - YouTube

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Figure 1a Delay potentiometer & jumper holes adjacent to PIC processor
Table 1 Total time for Amp T/R relay to switch
(factory delay setting= 10ms)
tr nsceiver tr nsceiver
RF del y
QSK 2500©
key del y
(f ctory setting)
total T/R
actuation
time
comment
Yaesu FT
1000MP MKV
5
ms (min)
10ms
15ms (min)
longer settings in Xcvr
Elecraft K3
8ms (min)
“
18ms (min)
“
“ “ “
Kenwood TS
480, TS
20
00
,
TS 590S, TS 590SG 10ms “ 20ms fixed in Xcvr
Icom IC
7000
8
ms
“
18
ms
“ “ “
Yaesu FTDX
9000, FT
2000
15ms
“
25ms
“ “ “
TenTec Omni
VII & Orion I/II
15ms
“
25ms
“ “ “
Ten Tec Eagle
17ms
“
27ms
“ “ “
ICOM IC
706
MKIIg
12
ms
“
22
ms
“ “ “
IC
756 PRO
, PRO II,
IC
746 PRO
10ms
“
20ms
“ “ “
ICOM IC
735
5
.5
ms
“
15
.5
ms
“ “ “

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Table 2 Changing QSK timing delay (Optional)
Jumper 2 adjacent holes together located next to the PIC16F676 pin specified in table.
pin 2 pin 3 pin 4 QSK delay Comment
10ms
factory setting (no jumpers)
jumper
8ms
add 1 jumper
jumper
6ms
add 1 jumper
jumper
jumper
4ms
add 2 jumpers
jumper
3
ms
add 1 jumper
jumper
jumper
12ms
add 2 jumpers
jumper
jumper
14ms
add 2 jumpers
jumper
jumper
jumper
16ms
add 3 jumpers

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mplifier
(b ck)
QSK 2500
©
(b ck
)
tr nsceiver
(b ck)
tr nsceiver
QSK 2500
©
(front)
mplifier
out
key/paddle
IN
key, paddle,
keyer
computer, bug, etc.
(stereo
or mono
plug
)
key/paddle
key/paddle xcvr
Amp Key
Amp Key
In
Amp Key
IN
Pwr In
RF OUT
RF IN
RF OUT
antenna
RF IN
RF OUT
ANT
XCVR
Figure 2 RF Connections (back)
Figure 1 Control Connections (QSK 2500© front)
DC power: 17
25 volts
200 ma
2 to +200 VDC to gnd or
-2 to -200 VDC to gnd;
150ma (max)

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Ke /Paddle jack
Xcvr Ke /Paddle jack
17 – 25 volts DC
power to QSK
Figure 3 Circuit for power switch set to ‘Bypass’
input to QSK
Amp out
Amp in
Xcvr
Ant
Figure 4 RF circuit in ‘receive’ & ‘off’ states
X
c
v
r relay
control
B+
Amp relay control
B+