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Re: audio modulated VTTC

Original poster: "rheidlebaugh by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rheidlebaugh-at-zialink-dot-com>

I don't understand your problem. I use a streight forward class "C" Hartley
oscilator with self generated bias, No external bias supply. The use of the
4-400 family of tubes with no cathode, but direct filament heated, are more
problem but they should work in a Hartley oscilator mode as well.  Just coil
wire feed back with few components.
  Robert  H 

> From: "Tesla list" <tesla-at-pupman-dot-com>
> Date: Wed, 29 May 2002 07:53:25 -0600
> To: tesla-at-pupman-dot-com
> Subject: audio modulated  VTTC
> Resent-From: tesla-at-pupman-dot-com
> Resent-Date: Wed, 29 May 2002 08:30:19 -0600
> Original poster: "Herwig Roscher by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <herwig.roscher-at-gmx.de>
> Hi list,
> I've built an audio modulated VTTC and find the quality of the
> radiated AF not to be overwhelming at all. Plasma tweeters are
> kind of VTTC and are reported to generate high quality AF - at least
> at high modulation frequencies.
> Searching the web, I've found, that most VTTCs are Armstrong
> oscillators, operated in "C-mode" (no true C-mode, which requires
> a constant grid bias). One of the advantages, claimed for this type
> of oscillator is, that it is selfstarting and selfregulating.
> Plasma tweeters nearly almost are Huth-Kühn (in this part of the
> world)-oscillators (feedback by increased capacity between plate
> and control grid). This type of oscillator seems to have start
> problems and it is necessary to touch the terminal with a well
> insulated screwdriver to stimulate the oscillations.
> Because of simplicity and low distortions I would like to use the
> plasma tweeter type of oscillator for my VTTC. But I am not
> prepared to accept the start problems, as they are a huge menace
> for the toob.
> What are the reasons for the a.m. problems and is it possible to
> overcome them? Are there other types of power oscillators which
> combine easy selfstart and good modulation quality and could be
> used for VTTCs?
> Cheers,
> Herwig  
> ---------------------------------------
> Greed is the root of all evil!
> ---------------------------------------