[Amps] Nichrome wire for suppressors

[Joe Subich, W4TV]

> I personally saw the results, as strictly an observer, of a 3CV1000 
> military amp prototype that defied all attempts to stabilize until a 
> 1/2" wide ribbon of Mumetal was wound around the big Globar. It then 
> passed all tests 2-30 mHz using a reactive dummy load to 
> simulate VSWR's of up to 4.5:1 of either sign.

I don't think that anyone is arguing that resistive loading isn't 
a valid and useful approach to dealing with parasitics.  Commercial 
amplifiers of all kinds have used that approach, including nichrome, 
when the use of bulk resistances does not work (e.g., excessive 
resistance in the B+ line, insufficient space, excess reactance, 
etc.).  

However, Measures' claims are simply at variance with physics. 
Due to skin effects, the resistivity of nichrome has only minor 
effect on the behavior of the suppressor at VHF frequencies - it 
simply adds proportionally more resistance to the parasitic 
suppressor at HF, MF and LF frequencies.  Unless the tubes in 
question are unstable in or below the operating range, this 
added resistance is of no value and the same effect can be 
obtained by adjusting the value of the fixed resistor in the 
suppressor.     

73, 

   ... Joe, W4TV 
 



> -----Original Message-----
> From: amps-bounces at contesting.com 
> [mailto:amps-bounces at contesting.com] On Behalf Of Carl
> Sent: Wednesday, February 11, 2009 10:22 AM
> To: Vic K2VCO; Gudguyham at aol.com
> Cc: Amps at contesting.com; Gary at doctorgary.net
> Subject: Re: [Amps] Nichrome wire for suppressors
> 
> 
> And here is a third comment on the subject.
> 
> BOTH are partially wrong, Measures for his ideas about 
> parasitics being 
> the cause of everything bad that happens.
> 
> Long before W8JI came along and declared himself the messiah of all 
> things some commercial and military amps used nichrome or 
> mumetal as the 
> suppressor inductance. If you go back to the 90's archives I 
> mentioned 
> it a few times and then gave up as a few people will not 
> accept anyones 
> ideas but their own.
> 
> I personally saw the results, as strictly an observer, of a 3CV1000 
> military amp prototype that defied all attempts to stabilize until a 
> 1/2" wide ribbon of Mumetal was wound around the big Globar. It then 
> passed all tests 2-30 mHz using a reactive dummy load to 
> simulate VSWR's 
> of up to 4.5:1 of either sign.
> 
> So, before anyone goes off half cocked and believing everything they 
> read on the Internet please consider the above.
> 
> Carl
> KM1H
> 
> 
> 
> 
> 
> 
> 
> 
> ----- Original Message ----- 
> From: "Vic K2VCO" <vic at rakefet.com>
> To: <Gudguyham at aol.com>
> Cc: <Amps at contesting.com>; <Gary at doctorgary.net>
> Sent: Tuesday, February 10, 2009 11:15 PM
> Subject: Re: [Amps] Nichrome wire for suppressors
> 
> 
> > Gudguyham at aol.com wrote:
> >>
> >> In a message dated 2/10/2009 10:36:09 P.M. Eastern Standard Time, 
> >> Gary at doctorgary.net writes:
> >>
> >> Anyone  have a suggestion where I can find quick & easy 
> find about a 
> >> foot of  nichrome wire to be used in parasitic suppre
> >>
> >>
> >> Does anyone dare answer this?
> >
> > Sure. The use of nichrome wire in VHF parasitic suppressors is
> > controversial. A very good
> > explanation of VHF stability in vacuum tube amplifiers which argues 
> > *against* the use of
> > nichrome wire can be found at <http://w8ji.com/vhf_stability.htm>.
> >
> > If you want to see the opposite side, look at Rich measures' site, 
> > <http://www.somis.org/>. He also will sell you a kit including wire 
> > and the appropriate solder and flux to make a nichrome suppressor.
> >
> > Personally, I think that although many of Measures' ideas are
> > useful -- I like his fast
> > t/r switching circuit -- he is wrong about the nichrome and W8JI is 
> > right.
> >
> > That wasn't bad, was it?
> > --
> > 73,
> > Vic, K2VCO
> > Fresno CA
> > http://www.qsl.net/k2vco
> > _______________________________________________
> > Amps mailing list
> > Amps at contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps 
> 
> _______________________________________________
> Amps mailing list
> Amps at contesting.com http://lists.contesting.com/mailman/listinfo/amps