HF Antenna Multiplexer

   1 to 3-ports (triplexer)

​  Share one wideband HF antenna with 3 receivers on     three dedicated frequency bands

  Add an additional unit for 3 receivers more

​  Works in reverse too

  Bonus pre-selection band-pass filtering in every        branch 


Fig. 2. The 40-m band-pass filter response, as an example, before inserting it into the triplexer. The tracking gen power is at -20 dBm.

ORDERING:  EUR 64.66 + s&h

​The prices do not include 24% Greek VAT applicable only to individual buyers from European Union. 

The Module includes a  high-quality built & tested ENIG FR4 PCB (106 x 49 mm) that comes with female SMA conenctors soldered in place together with a black aluminum box with all mounting hardware. We will email you asking about the three HF frequency ranges you need it prepared.

The shipping is with registered mail  (your signature is required upon delivery). 

The shipping cost is USD 3.99 for total value under USD 9.99, USD 7.99 for total value under 49.99, USD 11.99 for total items value under 99.99, USD 15.99 for total value under 199.99 and free for total value grater than USD 200.00. 

The shipping is with registered mail with tracking info and delivers to USA, Australia in about a week to 12 days max, or less than a week for Europe. 


The SV1AFN's HF antenna multiplexer, is a bidirectional device with every port working as an input or an output and has 3 branches, each tuned on a center frequency chosen from 1.8 - 30 MHZ. All ports are of 50 Ohms nominal impedance. The 3 filters on the triplexer branches, offer high isolation between the branches and make them insensitive to arbitrary terminations.

​Although the multiplexer works in reverse too, lets describe its operation as a wideband HF antenna receiving triplexer.

A multi-band or a wide-band HF antenna connects to the input SMA connector. There is a DC path, a discharging resistor connected to ground, a Gas-Plasma Discharge Tube for statics and overvoltage protection and a parallel SMA connector, used only for expansion with a second similar unit. If not used, it should left open, without any termination.

Then, up to three series tuned filters can be placed to form a diplexer or a triplexer and each branch is isolated more by using band-pass filters. For example, if there is an antenna working from 1.8 MHZ to 30 MHZ, it can be connected to the input, and then 3 separate receivers can be connected on each branch. Each receiver can only work on the designated frequency range simultanuously with the other 2 receivers, each receiver on his own frequency range,  without using a splitter or a multicoupler which either would add losses and noise or introduce IMD by using an LNA to overcome its losses.

The arrangement as described above, can be duplicated, for up to 6 receivers, by using 2 triplexers and connecting their inputs in parallel with the antenna. Again, all ports will have 50 Ohms impedance without mismatches, additional losses or reflections.

The idea works in reverse, too! Think of every receiver to become a transceiver. Then, by using one multiband antenna, up to 6 transceivers can be simultaneously operated, each one either receiving or transmitting, or tuning their Antenna Tuner Units etc., without interfering each other! Of course I am talking about a different project, with much larger inductors and capacitors which can tolerate the currents and voltages of the higher power. But the idea is exactly the same and even this unit can be used for low power levels (up to +10 dBm).​

Another idea for reverse operation, is to use one unit to pre-select the 3-bands and then use a second to feed one receiver with only those three bands pre-selected, without switches to select each band.

This project is only offered built and tested on order, because it needs tuning and optimization. But If you may need anything to help experimenting, drop me a line with email.

Fig. 3. The 40-m band-pass filter response, after inserting it in the triplexer. Notice the 14 MHZ and 3.8 MHZ rejection, add this to the rejection of the other filters on 7 MHZ,  to find the isolation of the ports (> 95...120 dB).

​Fig. 1