Due to the additions in recent years, the introduction of SO2R and the starting up of VHF DXing and contesting I began to feel the need of having proper station wiring without ground loops and multiple ground connections. After seeing the devices developed by HA6PX for HG6N's recent trip to Macedonia (Z38N) I decided to get it done.
The cornerstones of the new design were:
- no ground loops at all. Every device should have a single ground connection
to the shack grounding
- galvanically isolated connections between devices
- redundancy - no change in the setup should require recabling or changing connectors.
If the station needs to be changed from SO2R to SO1R, it should only require
the removal of the SO2R box. Same valid for changing radios or computers.
- simplicity - I tried to keep the number of different cables at minimum.
- and finally to be able to get rid of ALL the temporary boxes and cables which
were created on perfboards, sometimes even in shoepolish
boxes :-) and got permanent status during the years!
The final result can be seen here:
By doubleclicking on the figure it will open up an other window (or if you use a proper browser, in a separate tab) where it can be better studied.
In the figure above the following cabling code was used: The first digit after the J stands for the device plane like J1X is the radio-side of the ISOBOX and J4X denotes the connectors of the radio. The remaining digits identify the connector. When the latetr figure is missing, the cable comes directly out of the device.
All the connections coming out from the PC are RF filtered and galvanically isolated from the other equipments by the isolator box (called ISO BOX on the drawing). The connectors between the PC and the ISOBOX are fully symmetrical straight-through cables with identical connectors on both ends.
The ISO-BOX takes care of the following:
- isolation, impedance and level matching between the radio and the PC.
- isolated CW and RTTY keying
- isolated PTT
- isolated Radio A/B switching
- isolated Band data between the radio and the bandpass filter/6x2 switchbox
- isolated TX GND beween the radio and the amplifier filter
- isolated CAT connection between the PC and the radio
If the ISO-BOX fails for whatever reason, it can be removed from the system without major functional loss and recabling (embedded functionality needs to be replaced eg. a CW-keying circuit needs to be added)
The same is true for the SO2R box as well. "In the very unlikely case of an emergency" the SO2R box can be removed from the system and full SO1R remains.
The prototype works very well, I'm currently busy with designing a proper PCB. As soon as it is positively tested the Eagle PCB files (schematics and board) will be made available here.
