QSK definition
Click to watch: 
Adding QSK 2500 to unmodified SB220 Amp
Click to watch:
How QSK 2500 meets T/R Relay Timing

Ham Radio QSK (full break-in)
DxConnection:  QSK 2500 Amplifier T/R Switch
eham reviews
Benefits of  adding QSK 2500 to Your Amplifier

 Benefit 1:   QSK  2500 makes your $800 to $3.5K Amp equivalent to a $7K Amp  in Contests &
                      DX p ile ups.     
                            i.e.  ALS-1306, ALS-1300, ALS-600, AL-1500, AL-1200, AL-572, AL-82, AL-80B, AL-811H, SB-220,
                                   HL-2200,  SB-200, SB-201,  Drake L-4, VL-1000 Qradra, TL-922A, TenTec Centaur, Centurion, Titan, etc.

Benefit 2:   QSK 2500 keeps you in sync with a DX station & increases your chances of working it.
                               (You can identify calling stations that are not running QSK! )

 Benefit 3:    QSK 2500 reduces the number of times that you have to hear that loud clunky Amp T/R

 Benefit 4:   In rag chews, you can monitor the channel for interference while transmitting.
QSK 2500© Transmit/Receive Switch:
  • ARRL QSK 2500 review:  QST, September 2016, pages 52-55   (click for QST review)  
  • Converts any HF Amplifier to QSK (full break-in) without amplifier modifications
  • Amplifier independent:  Adds QSK to new amplifiers as you upgrade  (no need for QSK in new Amps)
  • Compatible with all HF transceivers supporting QSK (full break-in);     (160 thru 6 meters)
  • RF Power: 2500 Watts  CW/SSB/Data modes at < 1.5:1 VSWR   (1500 Watts at < 2.5:1;  1250 Watts at < 3.0:1 )
  • Duty cycle:  Continuous
  • Acoustically quieted and sealed relays for quiet operation
  • RF losses:  Almost lossless relays (much less than PIN diodes), silver plated SO-239s           
                          ARRL measured loss:     <0.05dB from 1.8 - 50MHz 
  • LED indicators:  Power (green), Transmit (red)
  • Interfaces to amplifier key voltages up to +/-200V  (No additional amplifier interface hardware   required.)
  • User adjustable Amplifier Key delay from 2 sec to 10 sec (factory setting = 3 sec
  • User selectable key/paddle input delays from 3ms to 16ms (factory setting = 10ms)
  • May be used without key/paddle input delay if transceiver has adequate RF delay      (Click to  FAQ page
  • No hot switching of Amplifier T/R Relay on the first dit or dah of each transmission
  • QSK relays & Amplifier T/R relay are all protected from hot switching caused by transceiver removal of the Amp Key signal prior to the decay of the transmitter's RF envelop
  • SSB VOX only:  Use the QSK 2500 to reduce your amplifier's loud T/R relay noise.    (Click for details)
  • DC power input:  17 to 25 volts at 200ma (max);  120VAC power adapter (i.e. wall wart) included
  • Very compact enclosure:   5 ¼ in W x 2 in H x 3 in D   (excluding SO-239 connectors)
  • Weight:  < 1 lb
  • Factory option to use the Kenwood transceiver +12VDC Amp Key output
  • 1 year Limited Warranty  (See  QSK 2500 User Manual ) 
  • Price:  $379 includes free shipping (to continental USA addresses)   (Adding QSK to Amps since 2015)
        Credit Card or PayPal purchase:      Send an email to [email protected]
                                                                                 An invoice will be sent to your email address allowing payment online.
         Check purchase :      Checks will be cleared before shipment.  (Make payable to:  W. Rodgers K3HZP)
                      Send check to:
                                                                         DX Connection                                                                                
                  W. Rodgers  K3HZP                            website:  http://qsk2500.myfreesites.net/                       
                  5727 Buckfield Court                            phone:   260 432-8223  [If no  answer, leave a call-back number.]
                  Fort Wayne, IN 46814                           email:   [email protected]

  • QSK 2500© connecting cable set:                              $19.00   (with QSK 2500 order only)


  • 2 each 6’ cables with male phono connectors,
  • 1 each 6’ cable with mini (1/8”) male stereo connectors
  • 1 each mini (1/8”) female stereo to 1/4” male stereo adapter.
  Note:   These cables are for connecting the QSK 2500© to your transceiver and amplifier.  Adapter plugs (not supplied)
                may be required for your particular transceiver or amplifier.            

QSK 2500©  (back view)

Table 1:  Time available for actuation of Amp T/R relay

RF delay
5ms (min)
8ms (min)

total T/R actuation time(1)
15ms (min)
18ms (min)

longer settings in Xcvr
“          “        “      “ (3)
fixed in Xcvr
“       “      “
“       “      “
longer settings in Xcvr
fixed in Xcvr
“       “      “
“       “      “
   “       “      "   
“       “      “
“       “      “
  See footnote below (4)

  Yaesu FT-1000MP MKV
  Elecraft K3
  Kenwood TS-480, TS-590S,
                    TS-590SG, TS-2000
  Icom IC-7000
  Yaesu FTDX-9000, FT-2000
  Yaesu FT-450
  TenTec Omni VI & VI+
  TenTec Omni VII & Orion I/II
  Ten Tec Eagle
  ICOM  IC-706 MKIIg
  ICOM  IC-735
  ICOM IC-7300

QSK 2500©
key delay(2)
(factory setting)

         (1)  Amplifier T/R relay actuation times ‘typically’ range from 13ms to 15ms.
         (2)  QSK 2500© key/paddle delay selectable range is 3ms to 16ms.  Factory setting is 10ms.
         (3) Based on the K3 User Manual, use the default 8ms delay in the K3 plus the 10ms delay in the QSK 2500 for ‘external’
              keyers, computer-generated CW, etc.    When using the internal K3 keyer or the internal K3 memories, set CONFIG: TX
              DLY to 18ms in the K3.  Plug the key or paddle directly into the K3.  The paddle or key lines are NOT routed though the
              QSK 2500 for this configuration.
         (4) The preferred configuration for the IC-7300 is to set its RF Delay to 20m, (i.e .set TX Delay HF to 20ms) and route all key,
               paddle, computer, etc. inputs directly to the IC-7300, instead of through the QSK 2500.  This allows using the IC-7300
               internal keyer and memories.  No hot switching of the Amp T/R relay can occur at the end of a dit or dah (as described
               in the Aug 2016 issue of QST) because of the QSK 2500 protection circuits.