Jeremy,
think of mechanical tolerance issues for a minute; let's say, a shaft
and a bearing for example; take 1/4 inch diameter, with some tolerance
and take the specifications; imagine the diameter specs are .250 inch,
but to make sure it fits, the hole in the bearing might be specified at
0.251 +/- .002, and the shaft might be specified at 0.249 +/- .001 so
as you grab parts out of bins, these tolerances vary, so you could end
up with bearings ranging from 0.249 to 0.253 inches, and shafts ranging
in diameter from 0.248 to 0.250; if the parts are from opposite ends of
variance, they are either loose, or too tight; and some are just right.
Take it to an electrical circuit; the parts have tolerances too, and for
caps and inductors, the resulting resonant frequencies are different;
now take the toroids; how evenly the windings are spaced affects it
somewhat in value. The transistors will vary in parameters also, having
slightly different gain and requiring slightly different biasing to get
that gain.
This is why the circuits have adjustments, such as the trimmer caps and
resistors; so that you can get these circuits to perform "as designed".
Imagine now that all of the components have some tolerances, and you can
see that "plug and play" is not so easy in the analog world, and we end
up with these variations.
Then there is the measurement issue on top of that; our watt meters have
the same issues, and calibration issues as well; so we might all be
using the same watt meter, and if I take my radio to all of us, it will
measure slightly different output, based on slightly different
temperature, slightly different impedance of load, slightly different
supply voltage, and variations in watt meters.
That is where knowing the resolution and accuracy of the test equipment
come to play.
Probably more than you wanted to know, but there are a lot of variables
contributing to the variations reported, to say nothing of damaged parts
and shorts and stuff that throw it all off.
73 de W5SV, Dave
Jeremy Cowgar wrote:
Why the difference, they are all the same rig why would it change from
rig to rig?
Jeremy
KB8LFA
_______________________________________________
Elecraft mailing list
Post to: [email protected]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
