...snip...
>Wes also measured just the wire alone. Was this in coil configuration or
>just straight wire?
>
coil
>Anyone who has worked at VHF/UHF knows that you do not use nichrome,
>stainless or other materials with a high RF resistance....at any power
>level. It kills the Q, and dissipates power.
Yea, verily
>So why would it not be a
>good material to resist VHF energy in a HF amp?
This was essentially what I was thinking when I tried resistance-wire VHF
parasitic suppressors in 1986. Perhaps this is similar to what amateur
radio pioneer and Handbook Editor F. E. Handy was thinking when he
experimented with the idea in the 1920s. In the 1926-edition of The
Radio Amateur's Handbook, on page 72, Mr. Handy says:
- "The combination of both resistance and inductance is very effective
in limiting parasitic oscillations to a negligible value of current." -
- OTOH, Mr. Rauch says otherwise.
>NiCh60 has a 24% iron
>content as well as Ni and Ch. If this is standard resistance wire at DC,
>as used in meter shunts, then why is it not performing the same function
>at RF?
>
Because you are not applying the 'EXACTLY correct' principals of
Rauchian Science?
>The tests were run at the microwatt level, what happens at the KW level
>with RF heating?
>
Resistance-wire alloys maintain fairly constant volume-resistivity with
changes in temperature.
>Why was the ESR not listed for the AL-80 suppressor when it was for the
>NiCh60? The omission is quite glaring to say the least.
>
Beats me, Carl. However, Wes did measure the VHF-Rp and VHF-Q of both
types of suppressors.
>The more I look at the "results" the more questions arise. An ESR of 58
>at 150MHz for the NiCh60 looks impressive to me. With the hairpin loop,
>the whole curve would just shift upwards and reduce the losses at 30MHz.
The hairpin loop/U-inductor has the same inductance as a coil inductor.
The advantage of a U-inductor is that it loads the VHF-resonance of the
enclosure. The trade-off is that U-inductors are difficult to decouple
from each other in multi-tube amplifiers.
>A bit of fine tuning on an Impedance Analyzer would be indicated here to
>produce a better curve.
So it would seem. However, the major constraint is NOT DESTROYING Rs at
29mHz. If one wants better VHF performance, double Rs and double Ls --
as I did when I came up with the 200nH, 200 ohm VHF suppressor. The
improvement in Rp at 100MHz was fairly impressive. The sticky wicket was
the 42W of 29MHz dissipation destroying Rs. In a nutshell, the advantage
of resistance-wire suppressors is that they allow the user to lower VHF
Rp without increasing the dissipation burden on Rs.
>
>The AG6K kit also includes 4 1 Ohm anode fuse resistors and an additional
>pair of NiCh60 wires for connection to the plate blocking cap. In all
>fairness, since this is all in the kit, it should have been tested that
>way.
IMO, the admittedly inane-appearing, unequal-length double nichrome wire
suppressor seems to be a useful adjunct to the Rs/Ls suppressor. In a
TL-922, omitting the double-nichrome-wire VHF suppressor is apparently
Not a really great idea.
- however, there seems to be no way to use a Z-analyzer to measure the
VHF Rp in the anode circuit of a working amplifier. The best test
appears to be the one Wes performed.
>
>The ARRL is distancing themselves from all of this and refuses any
>official comments. Just as they have distanced themselves from the
>Maxwell issue. Both issues have their own proponents at the League, just
>as we do here but they are not at individual liberty to be open about it.
So it seems, Carl. IMO, a problem in Newington is that the Mark and Dave
direct too much control over the so-called Directors. 17 or so
kilobucks/year in "shaking hands money" appears to be one of the means.
> At least we are discussing it, the ARRL just play politics.
Agreed. The irony is that when Dick Erhorn and Tom Rauch were telling
Mark Wilson that there things in my '95 Handbook manuscript which were
"unproven", Mark could have used equipment in the ARRL Laboratory to
compare copper-wire VHF suppressors with resistance-wire VHF suppressors
-- as did Wes. .It seems to me that Mark should have known that testing
was a good idea because, in the Summer of 1990, Mark used a
resistance-wire VHF suppressor in his Alpha 77. When the factory's
suppressor was in use (at W1AW, before Mark bought the 77 at auction),
numerous, mysterious 8877 failures occurred. So how does Rich know
this? It's what Mark told me on the telephone when he ordered suppressor
retrofit-kit (s/n 1252) for the 77. I asked Mark why he thought the
Alpha 77 had a VHF stability problem. He said because he read the
article on VHF parasitic-oscillations in the October 1988 issue of QST.
>
>I appreciate your offer of amps for independent testing. But would it
>really be a fair test? ..
......snip...
>After all Rich is selling retrofits to known problem amps...not good
>ones. ...
... snip...
Alas, this is mostly the case -- an inescapable and troubling fact that
nearly kept me from getting involved in selling retrofit kits back in
1988. However, some users purchase suppressor retrofit kits for new
amplifiers. Last week, the owner of a brand new AL-1500 phoned me to
order a retrofit kit. It doesn't take a genius to see that no VHF
suppressor whatsoever in an 8877 HF/MF amplififer is Looneytunes.
AFTER QST printed the somewhat eyebrow-raising critique of "The Nearly
Perfect Amplifier" in the 9/94 issue [p.72] - AND Mark Wilson refused to
allow any rebuttal or discussion of it in QST, presumably Mark and Dave
figured that the problem would just go away. Obviously it did not,
thanks to the Internet, thanks to Mr. Rauch and his faithful followers.
Rich---
R. L. Measures, 805-386-3734, AG6K
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