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Author Topic: Installing a Low VHF-Q/Low VHF-Rp Parasitic Suppre  (Read 1028 times)
W1DY
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Posts: 29




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« on: February 07, 2004, 10:16:36 PM »

Please HELP!!!!!!

I just bought a Low VHF-Q/Low VHF-Rp Parasitic Suppressor Retrofit-Kits from Richard L. Measures, AG6K.
 
It includes nickel-chromium-iron alloy wire; 430'F / 221'C tin-silver solder and nichrome soldering flux, glitch protection and RF-NFB resistors; capacitors; 200a-peak glitch protection diodes; instructions; diagrams and a condensed version of the Oct 1988 QST article.

Well... I thought I could install this myself....
But after looking through the kit and reading the instructions...(5 times) I'm lost....(not that good at relating the schematic to what is actually inside the amp and where)

I really need a Picture or 2 to Jog me and give me the ability to get my bearings on just how to assemble..and what goes where!

A couple of pictures of an actual install is really going to help a LOT!...

If anyone has installed this kit in an AL-80B...and could take a couple of snapshots of the install...It would be a great help!..

I have already installed Ameritron's Grid Protection board in the amp...but according to Mr. Measures, it is too slow to protect against VHF-Rp Parasitics. (It just helps keep me from making a big mistake while tuning.

If there is anyone that can guide me...I know that I can find them here on Eham.!

Wendy
W1DY




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W1DY
Member

Posts: 29




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« Reply #1 on: February 07, 2004, 10:43:29 PM »

OOppps...
Forgot to put an e-mail address...for anyone that can help...

wquinn2@yahoo.com

Thanks again!
Wendy
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N3ZKP
Member

Posts: 2008




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« Reply #2 on: February 08, 2004, 10:29:29 AM »

Windy,

Just out of curiosity, why did you purchase this kit? Are you having trouble with the 80B going in to oscillation? That normally isn't a problem with this amp.

Lon
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W1DY
Member

Posts: 29




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« Reply #3 on: February 08, 2004, 12:59:29 PM »

It seemed like a cheap insurance policy.

After seeing how hard the band switch is to get to...I decided an ounce of prevention is worth a pound of cure.

I just thought it was better to be proactive rather than put my head in the sand and Hope nothing bad happened.

Wendy
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W8JI
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Posts: 9304


WWW

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« Reply #4 on: February 09, 2004, 09:47:16 AM »

Wendy,

I've looked at that "parasitic stuff" for years now, and I'm convinced it is 98% nonsense. You'd be better off leaving your amplifier alone.

N7WS also made measurements, and concluded the same. Eimac and a dozen others (including the retired chief engineer of Collins Radio)also disagree with it, and pretty much dismiss it as "bolognia".

For actual measurements and a demonstration of what causes arcs and failures you can see:

http://www.w8ji.com/Amplifiers.htm

Just write off the few bucks you spent to experience, and don't fix something based on false science.

73 Tom
 
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AB5Q
Member

Posts: 202




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« Reply #5 on: February 09, 2004, 05:38:00 PM »

I'll agree with Tom on one point, if the amplifier is not having problems don't bother modifying it.  You might induce other problems as a result of modifying the circuit.  In addition, soldering nichrome is not exactly as easy as soldering tinned copper with 60%/40% Sn/Pb.  The AL80B tank circuit layout is much better than its predecessors.  You should not have the same instability problems experienced with the AL80/AL80A.

In my situation, I have modified two amplifiers that experienced damage as a result of parasitic oscillation. In both cases Rick’s parasitic kit solved the instability problem.   In one situation an amplifier vaporized the contacts on three band switches within the first year of ownership.  I proceeded to install Rick's parasitic suppressor kit and in the fourteen years following I haven’t had any further problems.  When I analyzed the before and after affects of the modification, based on my observations I have reason to believe that Rick’s theories do have merit.
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W8JI
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« Reply #6 on: February 09, 2004, 10:31:36 PM »

Hi Rick,

There was never a stability problem in the AL80A caused by tank layout, so the AL80B changes fixed nothing. As a matter of fact, the layout in the AL80A was actually a bit better than the layout in the AL80B, but either is pretty good overall.

Arcing is pretty well explained for real factual scientific reasons. I have a tutorial at:

www.w8ji.com/amplifiers

about arcs and what causes arcs.

73 Tom
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