[Top] [All Lists]

[AMPS] construction of parasitics

To: <>
Subject: [AMPS] construction of parasitics
From: (2)
Date: Fri, 20 Jul 2001 06:42:52 -0700
>re: parasitic construction.
>Hi Bill,
>I also had problems one of the first times I tried to 
>construct and install one of Rich's parasitic kits in 
>a floor console model Henry.  The resistors got 
>really hot and failed. 

/\  What mode and which band were you using at the time of R-supp 
failure, Skipp?

>The problem also surfaced on a very cranky SB 
>220, I was working through from years of neglect. 
>So I did the proper math home work to figure out 
>the coil inductance values for my suppressors which 
>were right in line with Rich's paperwork. My math 
>and testing came up with inductance values about 
>85 to 95% of the suppressor kit values.
>Upon construction of my own model suppressors, 
>I noticed that very small changes in the physical 
>construction added or subtracted from the inductance 
>values.  Indeed, it's very possible to construct two 
>almost exact physical size inductors that differ in 
>inductance value a dramatic amount.  To much 
>inductance is really bad news in a suppressor made 
>with low wattage resistors. 
>To complete the amplifiers I constructed a batch 
>of coils with similar inductance values and ran them 
>through my test equipment (HP Network Analyzer 
>and a Sencor LC-102) to match up and tweak 
>the coils. 
>Rich's paper work mentions the resistors do/should 
>run warm/hot in operation. Using his values, parts 
>and information they do indeed run hot at the high 
>end of the HF bands.  The tweak is the guy who 
>doesn't have lab test equipment to ensure the 
>suppressor inductance value is not a significant 
>amount over the desired value, else they have a  
>potential to fail in certain longer duty cycle conditions. 
>My fix was to actually "upgrade" the suppressor resistance 
>value to a higher watt rating and use close measured 
>and matched coils, being careful to er on the side of 
>slightly less than the desired inductance. 
>My results then and to this day have been dramatic, 
>not one of the many cranky amplifiers I've reworked 
>has shown parasitic probablems since my retrofits. 
>That includes my very cranky BTI 3-1000 amplifier 
>with a really squirly aged tube.  
>Rather than argue over any of this, I'll just throw out 
>that I prefer to use higher watt MF resistors than the kit 
>supplied values and I pay very careful attention to 
>the inductance values.  In my examples, slightly less 
>L might not be enough (for the most part it often is), 
>and too much L is almost always bad for the resistors 
>when things are running full tilt. 
>Your results may vary.. my results are still on the air. 
>skipp    wv6f
>      I've added all three of the 
>vhf arcos amps and some tube data sheets.
>--------- Forwarded message ----------
>From: "bill thomas" <>
To: <>
>Date: Thu, 19 Jul 2001 13:44:41 -0500
>Subject: [AMPS] Re: Parasitics
>Message-ID: <>
>I once had a Henry 2K-3 in which I installed Mr. Measures' suppressor
>I thought I was doing a good thing.  The first time I put it on 15 meters
>several of the resistors exploded much as a shotgun shell would do. I 
>promptly went back to the Henry factory suppressors and never had another
>problem, nor did I have a problem prior to that.  For some stupid reason
>was convinced that that bit of nichrome was going to save me from eminent
>disaster.  In my 25 years of hamming, never have I experienced a
>with my Henry 2K-3 (2x3-500z's), My AL1200 (3cx1200A7), or my Henry 3K 
>Classic X (8877).
>This suppressor kit thing reminds me of the travelling salesman selling
>all elixir out of the back of his wagon.  "Guaranteed to cure your gold 
>sputtered meatballs...."
>Bill Thomas   k1xt
>Get your FREE download of MSN Explorer at
>FAQ on WWW:     
>Administrative requests:

-  R. L. Measures, 805.386.3734,AG6K,  

FAQ on WWW:     
Administrative requests:

<Prev in Thread] Current Thread [Next in Thread>