> >I guess it becomes a question of what the goals are. If you want
> >less of a loss difference between HF and VHF, a more resistive
> >conductor makes sense. If you want more loss at VHF with less
> >disturbance at HF, use a thin resistive plating over a good
> >conductor would be better.
> >
> >73, Tom W8JI
>
> Hi, Tom, and fellow "Ampers!"
>
> I brought up in another group several months ago the Henry suppressor that is
> used on the current 8K-Ultra and other models. I thought it was an ingenious
> idea, and I still do, although no one on the thread at the time seemed to get
> as excited as I did. For those of you who are not familiar with the
> suppressor,
> it is a 5 inch piece of brass strap bent into a one turn coil. The width
> of the strap and the diameter of the coil is 1 inch. The suppressor is then
> chrome plated to a depth sufficient to create the correct RS for the circuit
> for which it is intended.(a 3CX3000A7, in this case) The skeptics informed
> me that this was not chrome plating, but some other material. I visited the
> Henry factory where it was indeed confirmed to be chrome. The advantages of
> such a device are obvious...at VHF, it looks lossy. At HF, it looks like a
> big, wide piece of brass strap. The RS is "built in," so there is no parallel
> resistor required to burn up on 10 meters, or fail during a fault. It does
> the job for which is was designed...it stabilizes the "system." The chrome
> plate is as beautiful as a car bumper for years! It has a little something for
> everyone...the nichrome camp, the silver plated copper camp, and folks like I
> who truly admire a simple solution to a very complex problem. I don't know if
> this was an "in-house" Henry development, or from someone on the outside, but
> I would like to shake the man's hand some day!
That's right Phil, it is a good idea. Chrome over copper would give
even more slope with frequency.
To obtain higher slope in the AL-572 (it uses four 572B tubes) and
AL-1200, as well as some other commercial 40 MHz amplifiers I did for
Lockheed, GE, and others, I used a capacitor in series with the
resistor across the suppressor inductor.
On ten meters (or 40 MHz) the capacitor's reactance shifts current
out of the resistor so there is little heat. On VHF, the capacitor is
selected to cancel the inductive reactance of an inductive metal film
resistor. The resistor and cap are series resonant, and so
the path through the resistor dominates the anode system.
Another scheme is to parallel resonate a small value inductor with a
fixed cap at the frequency of self-oscillation , and put the
resistor across the resonant circuit.
The best systems minimize loss at HF by INCREASING the slope of
resistance change with frequency, and parking maximum suppressor Rp
on the undesired frequency.
73, Tom W8JI
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