Some time ago N4IS ordered a triplexer board  to build a triplexer to use with his Waller Flag receiving antenna on low bands (1.8, 3.5 and 7 MHz). I’ve never thought of using triplexer that way, but it turned out to be a good idea to have all three low bands available from a dedicated receiving antenna to any radio in SO2R setup.

Using a software, I designed a new low band triplexer for him for 160-80-40 meter bands and later, I built the triplexer for low bands.

In a regular RX/TX operations, it can be used with multi-band vertical or wire antenna. If you do not need 160 meter band, you can use it as a diplexer simply terminating 160 band port with 50 ohm load (You have to build 160M band part of schematics anyway).

  • Low Band Triplexer can be used as a Diplexer for any band combinations (40-80, 40-160 or 80-160). Unused port should be terminated by 50 Ohm load.

Below is all information for low band triplexer I built for a regular TX/RX usage. 

  • I use the same Triplexer board for both Low and High bands.

low_band_triplexer_008

Please, see some parts values from schematics below. On a triplexer PCB 20M is 160M, 15M is 80M and 10M is 40M.

lowband_sch1-0

lowband_sch2-0

As expected all numbers for a low bands triplexer are a little bit better than those for a high band triplexer.

  • Insertion Loss is below 0.08dB
  • Return Loss > 26dB (VSWR < 1.1)
  • Band Isolation is better than -32dB
  • 100 Watt output power 100% cycle
  • 200 Watt PEP

Please, use pictures above as a reference for the coil types and number of turns to the table below. Capacitor values can be +-1% of calculated values.

You can see Low Band Capacitor List.

Name       Value Core/Caps Type # of Turns or Caps
L160-1    4040 nH T130-6 19
L160-2    1260 nH T130-17 15
L160-3    3310 nH T130-6 18 
L160-4    433 nH T130-17 8
L160-5    895 nH Air Coil 9t 15-20mm in diameter
C160-1    1557 pF Mica or TDK HV  Any values (4 to 5 caps)
C160-2    1192 pF Mica or TDK HV  Any values (3 to 5 caps)
       
L80-1    2758 uH T130-6 16
L80-2    4198 uH T130-6 19
L80-3    1082 nH T130-17 13
L80-4    610 nH Air Coil 7t 15-20mm in diameter 
C80-1    709 pF Mica or TDK HV  TDK Low-Dissipation
C80-2    1806 pF Mica or TDK HV  Any values (4 to 5 caps)
C80-3    466 pF Mica or TDK HV  Any values (4 to 5 caps)
C80-4    3200 pF Mica or TDK HV  TDK Low-Dissipation
       
L40-1    1255 nH T130-17 15
L40-2    1638 nH T130-6 12
C40-1    484pF Mica or TDK HV  TDK Low-Dissipation
C40-2    1551 pF Mica or TDK HV Any values (5 caps) 
C40-3    590 pF Mica or TDK HV  TDK Low-Dissipation
C40-4    4513 pF Mica or TDK HV Any values (4 to 5 caps)
C40-5    2184pF Mica or TDK HV  TDK Low-Dissipation
  • T130-2 can be used instead of T130-6 with 2 turn less than showed in the table above (L40-2 should be 11 turns for T130-2).

Please, see some graphs below. 160M band tuned mostly for 1.8-1.9MHz range.

K3AL_Triplexer_2_40

K3AL_Triplexer_2_80

K3AL_Triplexer_1_160

HP 1500W 40-80-160 meter band Triplexer built as well. The same good parameters and low Insertion Loss achieved.

The problem building such a Triplexer was a capacitor choice. Doorknob capacitors I am using are too large in diameter to make up large required capacitance and some 1000V Mica capacitors were used together with doorknob capacitors to make up the required values.

Large inductors made using large Iron Powder toroids where a high current expected and smaller double toroids used for LC traps.

Unfortunately, all those “extra” parts mentioned above made HP Triplexer more expensive.

“Smoke” continuous test was done with 1300W output power for a few minutes run on each band port and all was good, no overheating found and some coils was a little warm (without any air cooling applied).

  • Low Band Triplexer can be used as a Diplexer for any band combinations (40-80, 40-160 or 80-160). Unused port should be terminated by 50 Ohm load.

Please, see a photo below.

IMG_1628