>>>>>I applied the term "bogus" to the system I described, not the one that
>>>>>is actually in the Heath Warrior.
>>>>// blowin' smoke
>>>>>Just a plain fact. The circuits are different.
>>>// Is the theory of operation different?
>>Basic electronic theory remains the same, but the circuit is different
>>so the ways they operate are too.
>>// Is neutralization at the operating frequency. or at the
>>anode-resonance frequency (c. 80MHz)?
>We were just told that neutralization is carried out at the high end of
>the operating range.
// I do not accept everything I am told. Some men tell the truth but
other men have less couth.
>It's just another kind of balanced bridge, so it should improve
>stability at the VHF resonant frequency too,
// Why and how? Below the grid-resonance frequency, regeneration
should not be possible since the grounded-grid acts as a shield between
out and in.
> provided that phase-
>inverting transformer is sufficiently broadband.
// It seems unlikely that phase shift would not change from HF to VHF.
Examination of the values used in g-g amplifier "neutralization"
circuitry suggests that they are not intended for VHF signals. Also,
frequency dependent phase-shift will take place through the tube's
internal feedback-C. In the original "Plywood Box"/tetrode-with-handles
amplifier, I used a Bruene neutralization bridge. (Figure 5 on my Web
site) Nevertheless, the P.B. initially had an intermittent parasite c.
68MHz which had the disgusting habit of stentorianly reducing the glitch
resistor to largish dust particles. The fix was to reduce Rp (and VHF
gain) at the anode-resonance by replacing the Cu straps with straps cut
from 0.1mm stainless-steel (Ni-Cr-Fe) shim-stock. [free samples still
>More specifically, it
>won't make VHF stability worse than the un-neutralized condition unless
>the phase of the feedback has somehow reversed itself between 30MHz and
>80MHz (which is easy enough to ensure).
// Owners of newer model versions of MFJ/Ameritron amplifiers that were
originally not neutralized reported more grief in the new version.
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
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