Re: Thoughts on a Ham Bus


My problem with the bus concept is that some but not all connections between analog modules are amenable to bussing.  

Control or signal lines that are needed by more than one module -- such as clocks, power, ground, control lines (+tx, +rx, band select, USB/LSB select, IF filter select, PTT, key, T/R relay) -- fit the bus model well.  Modules using these lines would not be location-dependent on the bus -- they could be plugged in in any sequence.  

The signal paths in a typical transmitter/receiver, however, are point to point and form a serial chain of modules -- eg. antenna T/R relay (and optionally LPF) -> BPF ->  RF amp -> Rx mixer -> xtal filter -> Product detector -> Audio preamp -> Audio filter -> Audio power amp.  I can't see an obvious answer to how to make these serial point to point connections on a bus.  

If I were to prototype this, I'd most likely run these signal paths in coax along the sides of the modules, not using the bus but floating the coax lines above the bus, between modules, perhaps with SMA or some connector type.  This compromises the bus model a bit (not all connections come in or go out of the edge connector/header, two module connection/disconnection points) but to put these connections on the bus complicates the bus and couples small signals and sensitive amplifier inputs to long parallel bus lines.

So the best I can imagine is a pseudo 'Hambus'. with control lines on the bus and signal interconnections not on the bus  

73 Paul VK3HN.    

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