If you just had the xtal headphones there, the audio power developed across the xtal element would be of a very high impedance with very, very little swinging AUDIO voltage being able to be produced to activate that type of headphone.
Much akin to a similar situation which you could try by a completely aside test and using a similar low freq AC situation ...for your clarification of what is occurring ....with the connecting of a DVM ....with its being set to its AC voltage mode / range ....with one test lead going to the AC lines ground and the other metering lead going to the lead of an ~500 pf ceramic or silver-mica capacitor . (Much in the order of the loading presented by an xtal headphones loading) You then touch the other free lead of the capacitor to the hot lead and prepare to read the voltage level that is coupled through. What are you expecting now ?.....125 VAC....100 VAC....75 VAC.........nope, not hardly, it being merely a fraction of that high of an AC voltage level.
Much in the order of your xtal headphone coupling into the like AC / audio of that receiver.....however .... if that resistor that you mentioned was installed, there would be the making of a completed AC and DC power loop with an appreciably higher level of voltage being able to be developed ACROSS that "load" resistor.
With that xtal headphone now being across that now much healthier swinging audio level, the audio
being now produced by the phone will go up appreciably,as was previously experienced with merely the crystal element being in circuit by itself .
The xtal headphone mainly reacts to a varying static voltage( presenting very little loading down) whereas a magnetic headphone with its thousands of turns of fiiiine wire and hundreds of ohms of resistance is definitely loading down the circuit more and requiring a higher power level to produce its sound.
Should you want to further experiment, sub in a 1 meg pot for that load resistor, using center tap and one of the outer terminals and shunt the xtal headphone across the "variable load resistor" then give the unit a test on a decently received signal with the expectation that there will be a roughly optimal setting found. If too high of a loading resistance the volume will be down and if the resistance gets too low there will inherently be less resistance for any voltage to be developed across.
73's de Edd
:What does a 40K resistor do to make the sound louder and clearer when using between the headphone leads of a crystal detector? Thanks.
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:If you just had the xtal headphones there, the audio power developed across the xtal element would be of a very high impedance with very, very little swinging AUDIO voltage being able to be produced to activate that type of headphone.
:Much akin to a similar situation which you could try by a completely aside test and using a similar low freq AC situation ...for your clarification of what is occurring ....with the connecting of a DVM ....with its being set to its AC voltage mode / range ....with one test lead going to the AC lines ground and the other metering lead going to the lead of an ~500 pf ceramic or silver-mica capacitor . (Much in the order of the loading presented by an xtal headphones loading) You then touch the other free lead of the capacitor to the hot lead and prepare to read the voltage level that is coupled through. What are you expecting now ?.....125 VAC....100 VAC....75 VAC.........nope, not hardly, it being merely a fraction of that high of an AC voltage level.
:
:Much in the order of your xtal headphone coupling into the like AC / audio of that receiver.....however .... if that resistor that you mentioned was installed, there would be the making of a completed AC and DC power loop with an appreciably higher level of voltage being able to be developed ACROSS that "load" resistor.
:With that xtal headphone now being across that now much healthier swinging audio level, the audio
:being now produced by the phone will go up appreciably,as was previously experienced with merely the crystal element being in circuit by itself .
:
:The xtal headphone mainly reacts to a varying static voltage( presenting very little loading down) whereas a magnetic headphone with its thousands of turns of fiiiine wire and hundreds of ohms of resistance is definitely loading down the circuit more and requiring a higher power level to produce its sound.
:
:Should you want to further experiment, sub in a 1 meg pot for that load resistor, using center tap and one of the outer terminals and shunt the xtal headphone across the "variable load resistor" then give the unit a test on a decently received signal with the expectation that there will be a roughly optimal setting found. If too high of a loading resistance the volume will be down and if the resistance gets too low there will inherently be less resistance for any voltage to be developed across.
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:73's de Edd
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::What does a 40K resistor do to make the sound louder and clearer when using between the headphone leads of a crystal detector? Thanks.