2 wrote:
K7FM had written:
>>I do have a Collins 30S-1 amplifier. It does
>>not have parasitic suppressors.
>
>** Vern Baumgartner, a friend who worked as an engineer at Collins
>Radio told me that Ni-Cr alloy was used as a conductor in the
>4cx1000A's anode circuit.
>
Let's be careful with the facts here. Looking at the schematic of the
30S-1, there is no conventional R/L parasitic suppressor. There is an
"L101" between the anode connector and the HV blocking cap, right where
you would expect a parasitic suppressor to be. The photograph shows a
substantial inductor of 3-4 turns of thick wire, about 0.75-1in diameter
and 2-3in long.
This is the only place where it could make any conceivable sense to put
a parasitic suppressor; but what L101 is made of, the manual sayeth not.
At a glance, there's something connected to the anode called "Z-101"
that looks like a parasitic suppressor, but it is in the path to the
capacitive divider that provides RF negative feedback. In that location,
Z-101 cannot damp the VHF parasitic resonance of the plate circuit.
However, this deliberate additional RF feedback path will also make the
30S-1 behave differently at VHF than amps that don't have this feature.
The 30S-1 is a unique amplifier. It contains many RF, power-supply and
mechanical features that were highly innovative and individual to that
amplifier. Some of these features will only work together as a
"package". Attempts to copy individual aspects have generally not been
successful, because the copiers weren't as smart as the original Collins
engineers, and didn't understand how everything interacts.
In short, the 30S-1 is a dangerous precedent for *both* sides of the
nichrome controversy!
--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek
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