• Please, remember that triplexer  must see 50 Ohm load on every triplexer port during an adjustment process.
  • Please, pay attention to a fact that triplexer is a balanced filter system and graphs should be as symmetrical as possible. The best way to measure symmetry is from Antenna port.
  • If the triplexer is not symmetrical than toroids located closer to Antenna port can get warmer than it should be. 

All photos made with  1590F Hammond enclosure.

  • The first step is to use an empty triplexer board as a template to make all required enclosure holes. 9 of them for standoffs and four large 16mm in diameter holes for connectors. You need another 8 or 16 holes to secure connectors on the enclosure. 
  • Please, make your decision where to drill all holes. You can install the triplexer board inside or on the lid of the 1590F enclosure. 

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L20-5 and L15-4 air coils are quite sensitive to how you mount your board inside enclosure. Because of small inductance of each coil the wire between a triplexer board and an enclosure UHF connector is a significant part of the coil. 

If a connection wire would be longer/shorter  or the board would be installed directly on connectors, those air coils should be adjusted. It’s hard to give exact value of those coils, but after a couple tries you will see the way to go. You can use smaller coil diameter or spread/compress turns to change a coil inductance. 

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The board requires good grounding to perform as expected…please, never try to tune it without been installed into enclosure.

I do not remember how much time it took me to do all works the first time, but I can predict at least 3 hours as a reasonable time frame to complete the triplexer assembly.

After triplexer assembly completed and board installed it is a time for tuning the triplexer.

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If toroid coils are good and capacitor values are close to required values, the procedure is quite easy with a company of VNA as a helper. I would try to give some recommendations based on my experience.

  • I am using two-detectors N2PK VNA with a Reflection Bridge. It allows me to see Insertion Loss and SWR(Return Loss) the same time (Transmission and Reflection mode simultaneously). I connect Reflection Bridge output to a triplexer band port and the 2nd VNA detector to the triplexer antenna port.
  • Do not forget to terminate unused band ports with 50 ohm loads. Sometimes, especially for 10M band if your load is some kind of Dummy Load connected to triplexer by a coax cable, the actual SWR is never close to 1. As a result you can expect a bad SWR for the triplexer measurements.
  • The best way is to use a 50 ohm load connected to the triplexer connector directly. You can solder a regular non-inductive 50 ohm resistor on the board as well.

Step 1. Always start tuning with LC trap adjustments. Change inductance to get LC trap frequencies as close to calculated values as possible. Spreading turns will change frequency up and compressing will change it down.Please, adjust all LC traps before you start any triplexer band.

  • LC trap resonance frequency values influence all triplexer parameters.

If you move LC trap frequency away from calculated value, you have to adjust another LC trap to find a new balance for the band.

  • 0.2-0.3% frequency change is a very safe margin for LC trap frequency adjustments. 0.1% is 21 KHz for 15M band, as an example. 
  • Please, do not be confused by software calculation and feel confident to adjust LC trap peak into the band. The rule of thumb here is to keep SWR and Insertion Loss low while changing LC trap peak point.

You can do some test. Please, adjust LC trap frequency as calculated, than change one LC trap frequency (any direction) to see how SWR and IL changed. After that, change another trap frequency to see if you can simply return SWR and IL back to values before the test. You can see than doing that you can improve parameters of the particular band or get it worse. It is a good idea to do it to every band filter to understand if you have the maximum from the triplexer.

  • After setting all LC trap frequencies you can go to Step 5 below to tune from antenna port where all band connected to each others. 
  • Try to make RL graphs as symmetrical as possible by adjusting parts directly connected to the antenna port (coils for 20 and 15 meter band and capacitor for 10M band).

Step 2. I always start with 10M band. If 10M band LC traps are as calculated and other capacitor values are close to required value this band could be in a good shape right away. Sometimes I am lucky …not always.

Usually, SWR (Return Loss) requires adjustments.

The first thing to try is to change 15 and 20 meter band LC trap frequencies. Change LC trap frequency by spreading/compressing turns a little to get the best possible outcome. I always do it to get the best numbers even if SWR value for 10M band is below 1.1.

Usually, LC trap adjustments should do the job and you can achieve SWR better than 1.1 (RL better than 26dB).

If required 20M LC trap peak is quite far from 14MHZ, please do not worry, just keep 20M isolation around -40dB as this value is a very good number. Good SWR and Isolation Loss much more important than band isolation value.

  • 15M band L1C1 resonance frequency influence SWR of a 10M band as well.

If your 124pF or 127pF are quite off from required values it could require more work to do, like to increase/decrease capacitance by 2-3pF to see the difference. You are better off to make sure that your capacitors within 1% of calculated values before installation. 

If  VSWR is not below 1.1 you can try to change 127pF value up or down to improve the Return Loss. The 127pF capacitance value “moves” maximum Returm Loss up or down by frequency.

At the very beginning, do not spend too much time trying to make 10M band perfect. Get SWR for a minimum value and reconnect your VNA to the next band….you will come back to 10M band later to finish the procedure.

Step 3. There is no difference what band to choose next. Let’s start with 20M band. This is the most “flexible” band. LC traps usually not a problem to tune, and all the rest components left are coils. It is good as it is very easy to adjust inductance, but because of it you can get lost in all possible inductance variations.

There are 3 coils beside LC traps. I would start checking 14MHz Insertion Loss adjusting L1, L3 and L5 coils. L1 and L3 are to pay attention to at this point. Please, get the minimum IL you can and use LC trap coils to improve band SWR.

  • Please, change inductance by compressing/spreading turns by a very very little steps. I would recommend to set your VNA frequency range a little bit wider that 20M band at this stage of Insertion Loss/SWR measurements.

Step 4. The 15 meter band is different as it is actually BPF and for a minimum Insertion Loss both L1C1 and L4C4 resonances should be as close as possible. You can measure those resonance frequencies, but I never did. Please, use your VNA to control Insertion Loss for the band by adjusting those two coils, L1 and L4. As soon as  resonances are close you will see how IL becomes improved. 15M band BPF is a very wide filter to pay attention to its actual center frequency. As soon as you get an acceptable Insertion Loss you are good to go.

For SWR as always, please try LC trap coils to get the best result if required. The LC trap resonances are very sharp for 15M band and there is not too much room to play with those LC traps to improve SWR as it was with other bands.

If your SWR is not below 1.1 ( 26dB for Return Loss) use L1 to improve SWR and adjust L4 after that to improve Insertion Loss.

L1 and L4 coils are very sensitive to adjustments and required a very little changes at a time during tuning procedure.

Step 5. Now, if all bands are good it is time to reconnect your VNA to measure SWR from the triplexer antenna port. Now, VNA Reflection Bridge should be connected to antenna port and detector connected to any band port (all other bands loaded by 50ohm). For this measurement all IL graphs should be the same as described above but SWR graph has three minimum points, one for every band. Use the same approach described above to get it better than 20dB for Return Loss.

The graph below shows 15M band and SWRs (green line) from antenna port. If your triplexer balanced well SWR line is symmetrical.

  • You can start Step 5 right after all LC trap frequencies setup.

After that knowing that Antenna port balanced for  all bands it is much easier to align every band port.

  • It is acceptable if SWR(RL) graph is not the same symmetrical like on the graph below but you should have SWRs in a good range around 1.1 value for every band.

The triplexer specification is very good and you can have a very good triplexer even without tuning the triplexer to the maximum possible point.

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  • Later version of triplexer enclosure 1411RU used to have connectors on a side of the enclosure. The difference is that air coil’s one end soldered directly to UHF connector.
  • Please, see a picture below.

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1411RU (8″ wide) and 1411UU (10″ wide) enclosures are on a photo below.

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