Hi Folks, I wonder if someone can help me out. I am an absolute beginner in "hollow" state electronics (on first project). I recently bought a 1920's homebrew bcast set but the tubes are duds and are expensive and hard to find. I want to keep the same tank circuit ( Amrad basketweave variometer with paralell trim cap) but completely reconfigure the rest of the set. Currently it is set up for Det to AF amp.I was thinking of having two tubes that actually do some work,rather than having one of the tubes "loaf" as a detector.I have never seen this done before (and maybe there is good reason why), but I was thinking of Ant to tank to RF amp stage to passive detector ( Cat's whisker as light contact galena or medium contact pyrite -or- maybe even a disguised 1n34 ) to AF amp (to G). (Is overvoltage/ overcurrent a concern for a diode ie with set on full rf amplification on local blowtorch station using big ant?) I figured the RF amp would be better after the tank, hopefully to amp what has been selected, rather than broadband blast everything into the tank.I be would using type 30 triodes, possibly with the set's existing rheo's. Although these aren't authentic 1920's tubes ( I think 199's are in it now) , they are cheap and easy to get. ..... Also is there really any difference in output result of my proposal versus these other layouts: two stages of RF Amp then Det (passive or tube) -OR- Det (passive or tube) and two stages of AF Amp? Will all three have same net gain output? .... And as a side question , What would be the results of running a 2 volt fil at 1.5 v (25% undervoltage) as a preservation technique, is there a serious loss of amplification ( or detector sensitivty, if used as a det)?......As a footnote , I am an an avid crystal set builder ( antique repros),have fiddled around with solid state stuff and am a ham.However my deeper electronics knowlege is quite "polarized" (pun intended) and at times I need help. Any help is greatly appreciated, KLN

It's always best to have the tuned circuit first in a set. The detector used was the grid-leak type which detected and amplified, so the tube didn't actually loaf. You may have problems using a triode like the 30 as an RF amp and may have to go to a neutralized circuit or fiddle with bias voltage. A crystal detector can be used, but it should be coupled to the RF amp through an RF transformer consisting of a 2 winding coil with about 20 turns of #36 wire on the primary and a secondary of about 100 turns of the same on a 2" tubular form. Fixed crystal detectors were used in the 1920s so a replica using a 1N34A would be fine..

:Hi Folks, I wonder if someone can help me out. I am an absolute beginner in "hollow" state electronics (on first project). I recently bought a 1920's homebrew bcast set but the tubes are duds and are expensive and hard to find. I want to keep the same tank circuit ( Amrad basketweave variometer with paralell trim cap) but completely reconfigure the rest of the set. Currently it is set up for Det to AF amp.I was thinking of having two tubes that actually do some work,rather than having one of the tubes "loaf" as a detector.I have never seen this done before (and maybe there is good reason why), but I was thinking of Ant to tank to RF amp stage to passive detector ( Cat's whisker as light contact galena or medium contact pyrite -or- maybe even a disguised 1n34 ) to AF amp (to G). (Is overvoltage/ overcurrent a concern for a diode ie with set on full rf amplification on local blowtorch station using big ant?) I figured the RF amp would be better after the tank, hopefully to amp what has been selected, rather than broadband blast everything into the tank.I be would using type 30 triodes, possibly with the set's existing rheo's. Although these aren't authentic 1920's tubes ( I think 199's are in it now) , they are cheap and easy to get. ..... Also is there really any difference in output result of my proposal versus these other layouts: two stages of RF Amp then Det (passive or tube) -OR- Det (passive or tube) and two stages of AF Amp? Will all three have same net gain output? .... And as a side question , What would be the results of running a 2 volt fil at 1.5 v (25% undervoltage) as a preservation technique, is there a serious loss of amplification ( or detector sensitivty, if used as a det)?......As a footnote , I am an an avid crystal set builder ( antique repros),have fiddled around with solid state stuff and am a ham.However my deeper electronics knowlege is quite "polarized" (pun intended) and at times I need help. Any help is greatly appreciated, KLN