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To make a positive posting about why the "board" receiver doesn't exist.
.. . First, I consider my PC. While my very first PC had a bunch of cards, my current one has none except the RAM. The video adapter, Ethernet capability, sound system, modem, serial, parallel, and USB ports are all on a single board, built in. Why? Simple -- it's cheaper. I worked at Tektronix for many years. During that time, Tek made both portable scopes and laboratory scopes, the latter having a mainframe and plug in modules. For a given configuration with the same features, the lab scope was always considerably more expensive than the equivalent portable. Why? Well, the lab scope was always overdesigned for any particular job. The bandwidth of the interface had to handle the highest frequency plugin. The power supplies had to handle the highest current plugins, in any combination -- enough current at 5 volts for a digital analyzer plugin, enough higher supply voltage current for a spectrum analyzer plugin, and so forth. There had to be enough connector pins and supporting circuitry to handle all possible controls on all possible plugins. No single configuration ever used more than a fraction of the built-in mainframe capability. While the portable scope's stages could have optimal gain, in the lab scopes, the signals always had to be normalized to the levels specified for the interface. This often required an extra stage or two for each of the signals being passed (vertical, Z axis, horizontal, and many controls). Power supplies had to be decoupled in each plugin at the interface. And finally, good quality, reliable connectors are much more difficult to find, much more expensive to buy than you'd think -- and even so, they can easily be the least reliable components in the system. Then there's the problem of trying to predict what would be developed in the future when you design the mainframe, so you can build in the necessary interface circuitry. And every new plugin (I've designed them) has to be compatible with every tweak and trick used by all plugins in the past which it might be used with. 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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