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General Radio Discussion / Dead End Q vs Z Match
« on: August 17, 2024, 0110 UTC »
Hey All,
Just a theory question, maybe not so modern in origin, but a curiosity.
Back in ancient times, one method of matching the Z of a simple / single tank crystal radio to either the detector or the antenna was through the use tap of leads run to a panel mounted tap switch.
But this method left all unused leads hanging in dead end effect , spoiling the tank Q.
Cases were made that the increase of energy transfer via Z matching “ could “ (??) overcome the Q hit of dead ended leads into a net “ up” (by HOW much ? ) of RF energy recovery.
I admit, my grasp of this “ battle of the two phenomena “ isn’t as much up to snuff as I would like.
Does anyone envision any physics state that could result in a net “ up” via Z matching, despite being “ fought “ by Q loss.
I understand the layout “convenience” of a front panel tap switch.
But is this ALWAYS an undesirable building technique ?
FWIW, I use a “hump” of coil turn that slightly arcs up and then back down to the winding.
That way the “ connection point” on the coil doesn’t break the coil plane very much, nor does it have any twists.
A single lead with a flat ( non toothed ) copper alligator clip is brought TO the coil. Viola, no dead end leads left hanging .
Definitely not as convenient as a rotary switch, but I feel it is probably a more efficient way to go.
Again, just trying to get some theory input on a question that has puzzled me for a while.
de NQC
Just a theory question, maybe not so modern in origin, but a curiosity.
Back in ancient times, one method of matching the Z of a simple / single tank crystal radio to either the detector or the antenna was through the use tap of leads run to a panel mounted tap switch.
But this method left all unused leads hanging in dead end effect , spoiling the tank Q.
Cases were made that the increase of energy transfer via Z matching “ could “ (??) overcome the Q hit of dead ended leads into a net “ up” (by HOW much ? ) of RF energy recovery.
I admit, my grasp of this “ battle of the two phenomena “ isn’t as much up to snuff as I would like.
Does anyone envision any physics state that could result in a net “ up” via Z matching, despite being “ fought “ by Q loss.
I understand the layout “convenience” of a front panel tap switch.
But is this ALWAYS an undesirable building technique ?
FWIW, I use a “hump” of coil turn that slightly arcs up and then back down to the winding.
That way the “ connection point” on the coil doesn’t break the coil plane very much, nor does it have any twists.
A single lead with a flat ( non toothed ) copper alligator clip is brought TO the coil. Viola, no dead end leads left hanging .
Definitely not as convenient as a rotary switch, but I feel it is probably a more efficient way to go.
Again, just trying to get some theory input on a question that has puzzled me for a while.
de NQC
. ). 
