[Heathkit] Re: parasitic suppression - Better Title

[rbethman]

Carl,

I submit that unless you have had a PhD, *and* wrote reference material 
during the '30s and '40s, that your last paragraph is indicative of 
*your* interpretation.

Reference F. E. Tereman, July 1933 and also "Radio Engineers' Handbook", 
1943, pp 500 - 503.  Specifically referring to *Low-Frequency parasitics*.

You may *not* be enamored with the name and description - However, it is 
indeed the terminology used to describe them.  William Orr simply 
continued this terminology.

My reference to the aluminum rod had NOTHING to do with LF parasitics, 
it instead *is* the neutralizing capacitor used in Heath radios. I only 
added that for S & Gs.

The Heath applicability in regard to *Low-Frequency parasitics*, shows 
in the DX-60 where the dual triode 6DE7 modulator has had its cathode 
taken to ground to resolve this issue in an audio stage.

I'm sure that this will show up in other Heath designs, and in many 
other tube equipment used and or built by hams from the 60s on.

This was *never* meant to get into a knowledge contest or argument.  It 
simply seems that you and I have a proclivity to butt heads, as this 
*is* the second time that this has occurred.  The other being over 
painting methodology.

73!
Bob - N0DGN
>
> LF parasitics are usually caused when the grid bias choke and its 
> associated bypass capacitor create a resonance that is able to pass 
> thru the anode circuit with little attenuation. This was very common 
> in amplifier stages of the 30's and 40's where bypass capacitors were 
> highly inductive. For this reason many designers did away with the 
> choke and replaced it with a carbon resistor of 1K Ohms or 
> thereabouts. A ferrite bead over the grid lead will also help suppress 
> that oscillation. Ive used a combination of ferrite and low inductance 
> ceramic capacitors to tame notoriously unstable RF and IF amps in late 
> 20's to mid 30's receivers. An amplifier at any power level, from 
> milliwatts to serious QRO can be unstable; the higher the gain the 
> more likely it becomes.
>
> Before responding with further confused statements I suggest that you 
> read up on some 30-50's application notes from RCA, GE, Philco and 
> others that address LF oscillation, it really should not be called a 
> parasitic since it is not created inside the tube or the anode tank 
> circuit.
>
> Carl
> KM1H