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
Benefits of  adding QSK 2500 to Your Amplifier

 Benefit 1:   QSK  2500 makes your $800 to $3.5K Amp equivalent to the $7K amp  in pile ups.

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

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

 Benefit 4:   In rag chews, you can monitor the channel for interference while transmitting.
QSK 2500© Transmit/Receive Switch:
  • ARRL review:   QST, September 2016, pages 52-55.
  • 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)
  • 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
  • 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)
  • No hot switching of Amplifier T/R Relay on the first dit or dah of each transmission
  • QSK relays & Amplifier T/R relay protected against hot switching due to transceiver removal of Amp Key signal prior to the decay of transmit RF envelop
  • SSB VOX:  Use the QSK 2500 to reduce your amplifier's loud T/R relay noise.   (click here 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
  • Introductory Price:     $379  (shipped in the USA)
         PayPal or Credit Card purchase:    Send email to
                                                                          A PayPal invoice will be sent to your email address.
        Check purchase :       Checks will be cleared before shipment.  (Make payable to:  W. Rodgers K3HZP)
             send to:
                                                                       DX Connection                                                                                
                 W. Rodgers  K3HZP                            website:                       
                 5727 Buckfield Court                            phone:   260 432-8223
                 Fort Wayne, IN 46814                           email:

  • 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)

RF delay
5ms (min)
8ms (min)
total T/R actuation time(1)
15ms (min)
18ms (min)
longer settings in Xcvr
“          “        “      “
fixed in Xcvr
“       “      “
“       “      “
“       “      “
“       “      “
   “       “      "   
“       “      “
“       “      “
         (1)  Amplifier T/R relay actuation times ‘typically’ range from 13ms to 15ms.
         (2)  QSK 2500© key/paddle output delay selectable range is 3ms to 16ms.  Factory setting is 10ms.
Table 1:  Time available for actuation of Amp T/R relay
  Yaesu FT-1000MP MKV
  Elecraft K3
  Kenwood TS-480, TS-590S,
                    TS-590SG, TS-2000
  Icom IC-7000
  Yaesu FTDX-9000, FT-2000
  TenTec Omni VII & Orion I/II
  Ten Tec Eagle
  ICOM  IC-706 MKIIg
  ICOM  IC-735
QSK 2500©
key delay(2)
(factory setting)