The fact is that hams, for sure, wouldn't pay all the extra money a well
designed plug in system would cost. Of course, I might be wrong --
anyone who thinks so (one particular person comes to mind) should get busy
designing and developing one. Perhaps there's a fortune to be made.
Certainly there's a market for a much simpler plug in system with much
less versatility than the oscilloscope system I described, as a few
manufacturers have shown. The question is, how far can this be taken
before the market dries up due to the increased cost?

Roy Lewallen, W7EL
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Would a relatively 'low cost ' plug in card system perhaps be possible by
using standard PCI (computer) or similar card connections for the 'non RF'
connections ,with standard 50 Ohms miniature connectors for all RF
connections.
It would mean that all RF card modules would have a standard RF in- and
output connector using 'miniature coax'.
It would of course mean that all the card modules involving RF would have a
universal 50 Ohms in- and output impedance.
The latter is already promoted by looking at designs in the book
'Experimental Methods in RF Design'

The above referred type of PCI card connections (or any other agreed card
standard )could then be standardised with specific 'edge connections' used
for 'ground' , +5V , -5V , +12 to15 V ,-12 to 15 V , etc

The above would facilitate home brewing and make it possible to combine home
brewed modules with specialised commercial modules. It also would enable
testing modules with standardised (impedance wise) test equipment.
Ready made or blank (single or double sided) PCBs would have identical 'card
fingers' also those supplied as part of a complete kit.

I feel that the amateur radio community would very much benefit of such a
standardised card system.

Although the amateur radio market place is relatively small , with modules
physically standardised , there would be an opportunity for a modest
'cottage industry' .

Frank GM0CSZ / KN6WH