7-9                                                   
                 ART-13 Keying Circuit for CW

                Eliminate the CLACKING and reduce Relay "Maintenance"

                               
6-14
       This page on the ART-13 contains information and techniques dedicated to the ART-13 transmitter. This web page assumes that the reader has possession of the ART-13 A and B manuals. The Philco "Training Manual is also a valuable source of info.
      Perhaps some of my adaptations or mods offend those that want a "perfect" radio. My goal is to modify the radio to suit my needs and to make the mods easy to reverse.
That clacking relay during CW ops is very annoying and relay contact maintenance can be very time consuming and may eventually require replacement of the relay. .
   Disclaimer: The photos and technical information on these pages reflect projects that the author has either tested, repaired, modified or fabricated. Be sure and check my simple sketches for errors prior to construction. Most of the projects can be constructed using simple hand tools but the use of tools such as a hand saw and a electric drill can be hazardous. Soldering irons are very hot and often produce temperatures in excess of 700 degrees F.  Soldering radio and electrical circuits produces noxious fumes and can be addictive. Do not inhale. Seek out therapy if necessary. Group sessions are recommended.
 

          

               Discussion of the Main R/T relay
             Bypassing the Main R/T relay for CW keying.
             813 Screen Keying
             813 Screen and HF Oscillator CW keying.
             Mosfet Screen Keying Circuit
             Mosfet HF Oscillator keying.

               

 

 

 

                          


                 A discussion of the main R/T relay                   


                                

       The ART-13 "Keying" Relay K102 is very busy. All 10 contacts open and close each time the relay is activated via the "Key Line" when keying CW. In addition the glass antenna relay contact switches from Receive to Transmit.
   It is important that all contacts be adjusted in accordance with the manual for precise closing sequence, contact gap, and contact pressure.

                 Be careful making adjustments which effect the glass vacuum antenna relay. It is easy to damage the relay.

               
 

                

      A Jones plug for connections is located on the side.
 

                      

              All of the contacts are activated when K102 is activated by the "Key Line". Relay contacts 5-13 and 3-9 provide the actual keying of the RF stages. The Vacuum Antenna Relay (Contacts shown at top) is also actuated each time the CW key is closed.
                 

               

              The main keying relay K102 and the Vacuum Antenna Relay are located on the top of the chassis

   

                       

                 A short video depicting the K102 relay action.
                        ART-13 K-102 Video.

   

                             

             The internal contacts have provisions for contact pressure and sequence.

   

                           
                                   K102 Relay Adjustment

      There are also numerous adjustments for the delicate glass vacuum antenna switching relay. Only one of several adjustments is shown above.

          
                          

             Bypassing the RT relay Contacts for CW keying
           Repeated keying of a RT relay K102 that is in need of adjustment during CW ops may result in pitted contacts on the smaller contacts. The Vacumn Antenna relay needs careful adjustment.             Overall the entire relay system is very noisy during CW ops.
  

           Key the ART-13 R-F Carrier circuit on CW with a separate keying circuit. During transmit the main RT relay contacts and the vacuum antenna relay will remain closed reducing wear and tear and noise.

                   

  

                     
                            
                        Q. I have been keying my ART-13 on CW for years and have never  experienced a problem.
                    A. Good for you.

                         Q. I have adjusted K102 on several of my transmitters and never had a problem. All you have to do is read the manual.
                     A. Good for you. I wish the manual would explain how to reduce the Clacking during CW ops.

                        Q. What about phone operation? Will modifications of the RF carrier keying effect it?
                    A. No.       More details below.

                    Q. I hate the Clack Clack noise of the ART-13 when keying.
                    A. Me too. It is not my favorite CW transmitter.

                    Q. What's the big deal ? - if my relay fails I will just find another one and plug it in.
                    A. Good luck with that.   Its not exactly "Plug and Play".                 

                    Q. Are there relay adjustment instructions in the manual?
                    A. Yes several pages for all versions of the relay.

                    Q. Do I have to remove the relay to make the adjustments.
                    A. It makes the process easier for several of the adjustments.

                    Q. How do I power the relay if I remove it from the transmitter?
                    A. Use alligator clips and power the relay coil on terminals 14 and 15.

                    Q. What tools are needed to adjust the relay?
                       A. Here is a link to several pages (Relay Adjustment) of the manual.

                                        
                       
        All models of the ART-13 use the same method of keying the RF carrier.
 

                     
                                     Click to enlarge

     During  CW operations the main R/T relay coil (K102) is activated via the "Keyline" for each dot and dash. The relay contacts 5-13 and 3-9 key the 813 Screen voltage and the HF Oscillator cathode.

         
 

              
                     
              The lower Key Jack J103 will be rewired for the new keying circuit.
                The Throttle Switch (TS) J101 wiring will remain intact.

               

        After rewiring the Key Jack J103 for a alternate keying circuit the TS Jack J101 can still be used for the original keying of the transmitter. However the Key Jack circuit will need to be closed to provide a carrier.

        Several ART-13 users have installed a RT switch using the TS jack. More info below.

 
                

                      

                J103 and J101 are standard 1/4 inch jacks on the "Keyline"..

 

                      




                        813 Screen keying for the ART-13

        During bench testing small relays were used initially for keying the RF carrier. The smaller relays were very quite when compared to the larger relay K102 that remains "closed" during transmit.

           It helps to read all of the relay info below before going to the Mosfet keying circuit.
 

       

                

        My first attempt at "Stealth" keying and to test the keying concept - - - I just keyed the 813 screen with a small relay. The smaller relay was very quite. No more Clack Clack.

    
 

           

            My first attempt at screen keying was to simply remove the 813 screen feed lead from terminal 7 of modulation transformer T101 and use a small relay.

         Later I removed the large Jones connector J116 from the side of the RT Relay for access to the screen voltage terminal #13.

                   
                       Relay K102 uses a 15 pin Jones Connector
               


    
 

                    
                           Jones Connector Diagram

 
                      

      During key up conditions when keying just the 813 screen the HF oscillator ran continuously and approximately 3/4 watt would bleed through the 813 circuit (with no screen voltage) and make it to the antenna via the ART-13 matching network. This small RF carrier could easily be heard in the station receiver. During good HF conditions distant stations could often hear the low power signal in the back ground and it was very annoying to hear the constant carrier when monitoring on my receiver.

   Another issue. When keying the 813 screen seperately via T101 terminal 7 (by passing the connector wiring) the CW sidetone circuit will not be keyed and will be on continuously. I never use the sidetone to monitor my keying so that was not a real problem.
              But read on for Plan B.

 
           

                          

                The Key Jack 103 shell is grounded to the chassis and is rewired. The original "Tip" wiring was carefully removed and insulated. A single wire is connected to the tip contact and fed to the new keying circuit.
 

                    

           The Key Jack is grounded via its frame.
                      



            813 Screen and HF Oscillator Keying
 

                 

       Plan B: The 813 screen voltage and HF Oscillator Caathode were then keyed by using a relay to key circuits connected to Jones Connector terminals 9 and 13. The main Relay K102 contacts between 5 and 13 and 3 and 9 will still be closed during transmit. In addition the Glass Antenna relay will be in the transmit position and not clack back and forth. The relay for keying the 813 screen voltage should be rated for 400 volts.

                  Keyer circuits using Mosfits for the 813 screen and oscillator cathode will be shown later so read on but for now I played with the small relays.  
 

                

       Smaller "quite" Relays can be used for keying the 813 Screen and if necessary the 837 Oscillator cathode. I used a "high voltage" vacuum relay (SPST) to key the 813 screen voltage and a small enclosed relay for the Oscillator cathode.

           

             Q. Why use relays to eliminate keying a relay? It doesn't make any sense.
             A. You can barely hear these smaller relays when keying and they reduce the maintenance on the main RT relay K102 contacts which will now remain closed during transmit. In addition the glass antenna relay also remains closed during transmit. However read on as a solid state Mosfet keyer is presented below.

             Q. Why not key the set with high voltage transistors or Mosfets?
             A. I used relays first as it was simple and to test the concept but later switched to a Mosfet keying circuit. Circuits presented below.
      
             Q. What about the glass antenna relay? How do you key it for antenna change over?
             A. K102 is constantly closed during transmit and that keeps the fragile glass antenna relay switched to the transmit position.

              Q. How to you keep K102 and the Vacuum relay closed during transmit?
            A. I used a simple toggle switch labeled Trans/Receive wired to a quarter inch plug and inserted into the TS jack.

            Q. Where do I plug in my key?
            A. The "Keyline" jack J103 (1/4 inch jack) is rewired to activate the new keying circuit.

              Q. Why all this fuss? I am losing interest.
              A. You obviously do not work very much CW with the ART-13. The Clacking of the main relay during CW is very distracting. In addition I hated the K102 contact maintenance. The glass vacuum antenna relay is scary.

              Q. I do not want to add mods that harm the original wiring of the set.
              A. All wiring is easily reversed to its original state.

              

 



            

 

 

            
           The two relays - - one for the 813 screen and the other for the HF Oscillator cathode are held in place with a piece of clear lexan. The Screen keying relay is near the modulation transformer.
 

                  

              When Screen and Cathode CW keying circuits are used and phone operation is desired then use a "Shorted Plug" for constant carrier. This restores normal PTT RF operations.Your microphone PTT will function and you can even insert a key into the TS jack and key with the original keying circuit.
                                 



                        813 Screen Mosfet Keyer
 

             
             Click to enlarge modified schematic from "Jackson Harbor Press."

        The screen voltage for the 813 can by keyed using Mosfets driven with a Photocoupler.
                 Complete isolation of the high voltage is achieved.

 

            TLP591B Photocoupler is available from Mouser.

 
 

           
                         Click to enlarge

 

                  When using Mosfets in series the ratings are doubled.
 

             
           A slightly modified "Keyall" Keyer board (Kit) by Jackson Harbor Press

     Jackson Harbor Press " WB9KZY" provides a dual Mosfet kit for keying. Initially a 3300 ohm resistor was used in series with the 28 volt power for keying the Photocoupler. On later circuits for other ART-13 transmitters I used a 2200 ohm resistor. A Max current of 25 mA is usually the recommended MAX current for the internal coupler LED and the minimum recommended is 5 mA. The 400 volt screen supply is connected to the two "Collector" tab terminals at the top. The polarity of the two tabs can be either way and positive voltage can be applied to either tab.

          I fabricated a keying circuit similar to the Jackson Harbor Circuit and it is shown below.

 
 

                    
                           K4CHE Ugly Screen Voltage Keyer
                                    

      The Opticalcoupler / Dual Mosfet circuit is easy to fabricate on a Proto Board or Perf Board but the Jackson Harbor Keyall" kit is a lot neater than my 20 minute creation shown above. I did wire up another version which is shown below.

           

 
              

                                         
                                    Screen Voltage Keyer

           Another perfboard (perforated board) version. Note the 2200 resistor for dropping the 28 volts and the use of a 8 pin socket for the 6 pin IC.
                    Four (4) components - a quick project.

 

                 
                  
               Q. Why not use a single mosfet?
               A. You can but be sure and observe polarity. Dual mosfets give you higher ratings and you do not have to observe polarity.
              Q. I don't have a 6 pin socket.
              A. Use an 8 pin or take a larger socket and trim with sharp dikes.
              Q. On the "Ugly" board shown above you put the components on the copper side instead of sticking the leads through the holes?
              A. Sometimes I do things differently. A through hole version is shown above.
 

          

               Disconnect Jones Connector pin 13 wiring and insert screen voltage keyer.

             Use pin 15 for a 28 volt source for keyer boards. Do not remove original pin 15 wiring.
 

                 

           The screen keyer board can be enclosed in scrap sheet plastic.

                Use a Heat Gun to bend the plastic scrap. Use a vise and clamp the plastic while bendng. The clear plastic can be scrounged from a package of batteries.
                             
       There is plenty of room for the "813 Screen" keyer next to the modulation transformer.
 

 

                       



                  HF Oscillator Cathode Mosfet Keyer      
                
 

                  
                                       Oscillator Cathode Keyer

   A keyer for the HF Oscillator cathode was constructed using an HSR412. Spec sheet shown below.

           An 8 pin IC socket may be used - just use 6 pins.

 

                 Many Thanks to "Mr. Wizzard" - Al Klase N3FRQ for introducing me to the HSR IC series. Its a great switch and has many applications.  

             
 

            

        Insert the HF Oscillator Cathode HSR412 keyer at pin 9.
 

                
                            HSR412 HF Oscillator Cathode keying circuit.

         When using the Mosfets in series either "D" (Drain) can be the input regardless of polarity.

                 
                      Click to enlarge.

                           The HSR412 has a 400V rating with excellent circuit isolation. It all most makes you believe in a "Free Lunch".
 

               

           Loosen the relay mount and move the relay slightly and then you can have easier access to the female Jones connector J116.

            For Screen keying remove the connections from Pin 13 of the Jones Connector J116.
                (There are two wires going to pin 13 - just attach and add a single extension wire to simplify connections.) Connect the keyer between the pin 13 connections that you removed and pin 13 on the Jones connector.

            For Cathode keying remove the wire from Pin 9 (3rd row) and connect the HSR412 keyer between the wire you removed and the connector pin. Do not confuse pin "6" with pin "9".

       

  
 

                     
             Rear view connection diagram of the Jones Connector.

 
 

                    

     Power for keying circuits can be obtained by "solder tacking" a wire onto pin 15 but do not remove the pin 15 wire from the Jones Connector.

                 Pin 13 wire information to confuse you: On the ART-13 original wiring there are two wires connected to Jones Connector Pin 13. One wire is connected from Pin 1 of the main power connector J108 Dynamotor output (410V DC) and the other wire wire feeds numerous circuits which consist of the R117,118,119,120 resistor combo which feeds Audio Amp, Low freq Osc, and HFO plate. If you are curious you can ID the wires. . Have fun tracing it out on the schematic. With the meter probe grounded the Pin 1 dyn will show continuity between the main power connector pin 1 and the other wire will exhibit the resistance of R117, 118 etc.
 

                               

      You may have to remove the glass vacuum relay end connections when moving the relay.

 

                    

             Use the proper "Torx" tool for removal of vacuum relay connector set screws.
 

            

               Plenty of room for the 813 Screen and HF Oscillator Cathode keyers. The boards are enclosed in thin sheet plastic.
 

       

               I made a small wiring distribution board for the +28 volt (Red) and Keying lines (Blk).

 

              

    Plenty of room on a 2 inch perf board for the 813 Screen Voltage Keyer.

 

                      

                   I ran out of 6 pin IC sockets.

           TLP591B is available from Mouser.
 

                     

             HSR412 Cathode keying circuit can utilize a 1 inch perf board.

 

              

                Q. Will using two different keyer boards (813 Screen and Osc Cathode) result in a keying sequence problem.?
                A. No sequence problem was noted. "Unmodified and Modified" Oscilloscope video and photos are below.

 
 

               
                   

      Click her for Scope video of ART-13 Standard Keying without modification.   
 

                

       Click here for ART-13 Mosfet Keying Scope Video.

 

                            
                ART-13 Standard Keying no Modification.

                             
              ART-13 Modified keying with Mosfets.

             The above photos appear to indicate that 'Mosfet Keying" on the Test transmitter provides a cleaner pattern. However the ART-13 relay K102 contact sequence could possibly be "Fine Tuned" for a better pattern.
                        The same transmitter was used for all testing.
                 

            

              During Phone Operations insert a shorted plug for normal PTT and Constant Carrier.
 

                        

        Note that the Throttle Switch "TS" jack is on the same keying line as the Key and Microphone.
 

                      
                               TS (Throttle Switch) jack

 

     The TS (Throttle Switch) a Standard 1/4 jack can be used for an easy connection for an external TR switch. You can mount the switch at a convenient location at your operating position. The upper Test switch still functions and was not changed.

 

           Remember that if you get home sick for the relay Clack Clack sounds you can always close the Mosfet RF keying circuits with the "Shorted Plug" and then insert your key in the TS jack.

                "That's about all I know bout ART-13 keying."

  

                     Return to top.

                  Return to K4CHE Index.    

                 ART-13 CDA-T Info