Hi,
The goal of this configuration is to reduce the RF output power from my IC-703+
I have now built a cable that allows my Digirig interface and Neptune HF 50W to work together with my IC-703+.
The only thing left is to improve the Y-split section to make it more robust.
This is how I built it:
- I purchased a straight 4-pole TRRS extension cable (male to female) and a solderable TRRS male plug.
- I already had an RCA cable available.
- I cut the TRRS extension cable in half and stripped back the conductors. Since the wire colors did not follow any standard, I identified each conductor with a multimeter and noted the wire colors and corresponding connector terminals.
- I also cut the RCA cable, stripped the conductors, and verified them with a multimeter.
I then soldered the wires to the TRRS male plug. The TRRS female connector remains wired straight through to the male connector.
The radio’s ACC pin 2 (PTT) and ACC pins 3/7 (Ground) are connected in parallel inside the TRRS male plug to feed both the Digirig interface and the Neptune 50HF amplifier.
After soldering, I checked all connections with a multimeter to verify continuity and ensure there were no shorts. Everything tested exactly as intended.
Next came the bench test using a 50-ohm dummy load.
I connected the microphone and verified that pressing PTT correctly keyed the Neptune 50HF amplifier. It worked exactly as expected.
I then connected the remaining Digirig cables, started WSJT-X, and performed a Tune operation. The PTT from WSJT-X also keyed the Neptune 50HF amplifier correctly.
This is currently a prototype, but the next step is to refine the Y-split assembly into a more mechanically robust and reliable cable that can withstand regular use.
I have now tested the system, and it works very well.
I have tested both digital modes and SSB, and the system operates without any issues in this configuration.
The Neptune HF 50W amplifier is very easy to drive. With the IC-703+ set to its lowest power level, I get an output of approximately 10 to 45 watts, depending on the operating band.
If lower output power is required, an RF attenuator can be inserted between the transceiver and the amplifier.
If your antennas are not resonant on the bands you intend to use, it is recommended to place an antenna tuner after the amplifier.
For my tests, I used a horizontal delta loop (triangle) installed about 13 metres above ground. So far, 14 MHz has provided the best performance.
I am sharing this in case anyone is considering a similar configuration.
Best regards and 73,
Anders
SM6UUZ | LB0MI
