[AMPS] Suppressors, measurements, and acrimonious blather

[Fred Fliss]

W4EF wrote:

Is Wes' raw impedance data for the conventional and
nichrome suppressors published anywhere? Without any
data to study, this debate ends being more like a
political battle than scientific inquiry. Seems like
letting everyone see the impedance data for themselves
would settle the matter.

Mike, W4EF...........................................

----------------

Mike, as things would have it, the answer is "yes" but...as in "yes" but you 
might not be too pleased.

It appears that the suppressors that Wes tested are not the same suppressors 
that Rich provides today.  Rich advises that the length of wire in today's 
supressors is the same as the length of wire used in the unit Wes tested.  
But the one Wes tested was wound about a resistor, whereas "today's" 
suppressors apparently are hairpins.  Rich appears to believe that the 
length of wire is what makes the inductance.  Length of wire, of course, is 
secondary to the area enclosed by the wire and also secondary to mutual 
coupling effects in a coil.  Thus, a hairpin today made of the same length 
of NiCr is a distinctly different component than a coil that is merely made 
of the same length of NiCr.  This is fundamental physics that we do not yet 
have permission to alter.

I have some concerns, too, about the approach taken to this matter.  We must 
seriously consider what our intent is when using a suppressor, or any 
component.  Very recently, Rich provided this quote:

"The combination of both resistance and inductance is very effective in
limiting parasitic oscillations to a negligible value of current.  F.
E. Handy,   1926-edition of  The Radio Amateur's Handbook, page 72."

I find this to be an extraordinary statement.  When one observes writings 
about that time, it becomes evident, if not proved, that parasitic 
oscillations were an accepted norm for the day.  They existed, and the goal 
was merely to keep them from causing troubles.  Thus, this statement holds 
for 1926.  However, with today's better components, and our enhanced 
knowledge of the need for short connections, it should be considered very 
poor engineering practice, indeed, to merely pursue the reduction of 
parasitic oscillations to a negligible level of current.  The only useful 
goal with today's technology is to not allow the parasitic oscillation to 
start in the first place.  This is a very different matter than reducing the 
levels.  Therefore, prudence suggests that we attenuate suggestions based on 
such early work significantly, as our goals have changed dramatically.

This other item is one of some delicacy, and I regret presenting it, but I 
hope the level of stridence on the reflector may abate as a result.  I 
engaged in an email exchange with N7WS a time ago.  He advised me that he 
had, indeed, placed the results of his measurements on the web, but only 
after he had numerous assurances that Rich would never quote the results in 
an effort to demonstrate that supressors were beneficial.  I shall leave it 
to the readers of the reflector to determine whether Rich has violated that 
agreement.

However, you can all see for yourselves this item:  Wes' webpage  indicates 
that the material is copyrighted and can be freely distributed <only> for 
non-commercial purposes.  Unless Rich's suppressor sales activities are 
legally established under IRS code 501(c) as a non-profit enterprise, he is 
in violation of copyright law every time he mentions Wes' measurements in a 
manner that makes his devices appear favourable.

I am really quite disturbed by the level of acrimony that appears to 
accompany this topic.  Although it appears I have targeted Rich, that is not 
the intent.  Inflammatory statements are made on both sides; Rich is simply 
the only emoter on his side of the issue, and his postings are easier to 
identify because of the frequent re-use of unusual phraseology.

Valves are amenable to modelling by the likes of SPICE, and circuit 
parasitic reactances are, as well.  There is no need to pound repetitively 
on the nail of suppressor Q when a few hours work with a nearly free 
software package will show whether it makes sense to do so or not.  If the 
amount of time spent pounding the keyboard to make postings here (I shudder 
to consider what things look like on the un-moderated usenet lists) were 
spent performing responsible analyses, this discussion would not be taking 
place.

Wes' measurements are at:

http://www.azstarnet.com/~n7ws/supp-2a.htm

For myself, once I began designing with valves whose dimensions were less 
than 1/8 wavelength at my operating frequency, I determined that all 
instances of parasitic oscillation were due to poor component layout.  Pay 
particular attention to where ground currents flow.  That tuning capacitor 
has a grounded end.  Where does that ground current need to flow?  To the 
grid of the grounded-grid valve!  Is that distance short?  What about the 
load capacitor?  Do you know where that ground current must flow?  Yes, to 
the output connector!  You see, star grounding is not necessarily correct 
all the time.  Just because a component has a short connection to the 
chassis does not mean it's well grounded.

Whew.  Enough for me for now, I'm at risk of being called the Deuteronomist.

FF
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