I'm of the opinion that Rich is probably one of the smarter guys in this
group.(there are a lot of smart guys here) Just face the facts...What he is
teaching you about parasitics is correct. I know the amp builders that I
associate with all agree with him on this subject. It just makes sense. Lets
move on. This subject is very used up. No one is going to change their minds
publicly on this one way are the other anyway.
Jay
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]On
Behalf Of amps-request@contesting.com
Sent: Sunday, March 09, 2003 7:21 PM
To: amps
Subject: Amps Digest, Vol 3, Issue 44
Send Amps mailing list submissions to
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When replying, please edit your Subject line so it is more specific
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Today's Topics:
1. Re: Nichrome magic (rlm)
2. Re: SB-220 cap arc and the local broadcast station (Tom Rauch)
3. Re: SB-220 cap arc and the local broadcast station (Tom Rauch)
4. Ameritron alternative (Ragnar Otterstad)
5. Re: AL-80B questions (Tom Rauch)
6. Tuned Input (Ed)
7. Re: AL-80B questions (Ian White, G3SEK)
8. Re: Clipperton Bandswitch wafer (Tom Rauch)
9. Re: Tuned Input (rlm)
10. Re: AL-80B questions (rlm)
11. Re: SB-220 cap arc and the local broadcast station (rlm)
12. Re: AL-80B questions (rlm)
----------------------------------------------------------------------
To: <amps@contesting.com>
Date: Sun, 9 Mar 2003 12:20:06 -0800
From: rlm <2@vc.net>
To: "Tom Rauch" <w8ji@contesting.com>, " AMPS" <amps@contesting.com>
Subject: Re: [Amps] Nichrome magic
Message-ID: <200303092030.h29KUiKZ024891@contesting.com>
Content-Type: text/plain; charset="US-ASCII"
MIME-Version: 1.0
Precedence: list
Message: 1
>> >How soon we forget things like that.
>>
>> How soon you forgot our telephone conversation wherein you told me that
>> you had seen parasitic-oscillation damage in many of the 400 Heath
>> SB-220s you had repaired. I wonder if Tom remember what he said when I
>> told him he used essentially the same suppressor design in the SB-1000 ?
>
>
>No many how many times you repeat that story, it does not become real Rich.
The seemingly lifelong excursion on the wide river in Egypt continues.
So Tom, do you remember asking me if I was recording your (Paul
Pagel-recommended) telephone call? Do you remember telephoning Paul
Pagel?
>The only stability problem I am or ever have been aware of in a SB220 is
the
>same one that occurs in other amps using that silly super-cathode
circuitry.
>
Bzzzt. Story adjustment.
>I have spice models of a typical grid impedance on my website.
** are children allowed to view them?
>It has
>nothing to do with VHF, except as it needlessly makes the grid connection
>physically longer than needed. This is similar to what VK6APK did. He made
>the grids leads long, tying them in common.
>
>That is a bad idea in ANY amplifier, since it moves the frequency of
>self-neutralization lower while decreasing the ground effectiveness greatly
>at the grids.
>
>73 Tom
- R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K,
www.vcnet.com/measures.
end
------------------------------
To: <amps@contesting.com>
Date: Sun, 9 Mar 2003 15:54:31 -0500
From: "Tom Rauch" <w8ji@contesting.com>
To: <amps@contesting.com>, "skipp isaham" <nospam4me@juno.com>
Subject: Re: [Amps] SB-220 cap arc and the local broadcast station
Message-ID: <013001c2e67e$162e5c40$1c8001d8@akorn.net>
References: <20030309.092332.-292253.0.nospam4me@juno.com>
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Reply-To: Tom Rauch <w8ji@contesting.com>
Message: 2
> I tried all the cleaning, de-burring type tricks before I
> bought the late version cap. In my opinion, lack of
> proper parasitic suppression and an otherwise eager
> capacitor caused the previous owner (two different
> brands of) tube failures.
You can not clean and polish a capacitor and restore voltage.
Although the article mostly was written for gamma matching, I give sme
details why in my gamma and omega matching page.
Capacitors are micropolished, the general procedure is plates are roughly
deburred and then tumbled in walnut shells.
> After the standard updates were in place (which
> include my own type of suppressors), full tilt key-
> down into the load didn't even touch weak signals
> into the adjacent FM receiver. Sometimes the
> music stinks, but it's not the amplifiers problem...
Most FM receiver problems are through power line or direct radiation into
receiver IF systems. They are particularly sensitive to 7 and 14MHz signals,
since the IF's are at 10.7
Tighten a screw, move a cable, and the problem changes.
I have Motorola Micor 147 MHz repeater here, and when it was in my workshop
my 7 and 14MHz signals would totally wipe out the receiver, opening the
squelch when no 2m signals were present. My cure was to unplug the phone
line to the repeater, and reroute it slightly.
73 Tom
------------------------------
To: <amps@contesting.com>
Date: Sun, 9 Mar 2003 15:57:05 -0500
From: "Tom Rauch" <w8ji@contesting.com>
To: "skipp isaham" <nospam4me@juno.com>, <amps@contesting.com>,
"Pete Smith" <n4zr@contesting.com>
Subject: Re: [Amps] SB-220 cap arc and the local broadcast station
Message-ID: <013601c2e67e$71e201e0$1c8001d8@akorn.net>
References: <5.2.0.9.2.20030309124945.01ab9c60@pop.dc2.adelphia.net>
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Reply-To: Tom Rauch <w8ji@contesting.com>
Message: 3
> One of the big imponderables in Heath amps, it seems to me, is how well
> they were built in the first place. I was lucky, and the guy who built
> mine seems to have known what he was doing -- the workmanship is
first-class.
>
I took a shot at servicing Heath gear as a subcontractor back around 1970.
It was a disaster because of the poor construction and wiring errors.
You would not believe how bad some of the stuff was built!
73 Tom
------------------------------
To: <amps@contesting.com>
Date: Sun, 9 Mar 2003 22:09:08 +0100
From: "Ragnar Otterstad" <otterstad@enter.vg>
To: "Amps" <Amps@contesting.com>
Subject: [Amps] Ameritron alternative
Message-ID: <MBBBJCHIMOLLDEAHAJGKEEHBEKAA.otterstad@enter.vg>
Content-Type: multipart/mixed;
boundary="----=_NextPart_000_000D_01C2E688.81C35C80"
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Their versions are using more heavy duty components than Ameritron
equivalents.
73 Rag LA5HE
http://www.lauk.karoo.net/
------=_NextPart_000_000D_01C2E688.81C35C80--
------------------------------
To: <amps@contesting.com>
Date: Sun, 9 Mar 2003 16:25:16 -0500
From: "Tom Rauch" <w8ji@contesting.com>
To: "Joe Isabella" <n3ji@yahoo.com>, <amps@contesting.com>
Subject: Re: [Amps] AL-80B questions
Message-ID: <014001c2e682$61f55440$1c8001d8@akorn.net>
References: <20030309183756.43683.qmail@web14101.mail.yahoo.com>
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Reply-To: Tom Rauch <w8ji@contesting.com>
Message: 5
> Bottom line, the mods fixed the arcing, and I spent less than $3.00.
> I'd like to ask Tom why these work -- he seems only to say that
> parasitics don't exist, and the mods don't make sense. If that's the
> case, why is my amp now working so much better? The filiment mod is
> very clear to me, same with the step-start mod. Why is this such a big
> deal? If you make your own suppressors, you'll spend very little, and
> certainly won't hurt anything.
You can hurt VHF stability Joe. The Measures suppressors I have measured
actually increase VHF Q.
What Rich overlooks is his suppressors with lower Rp are in SERIES with a
long system. In that case, lower series resistance means higher Q in the
system.
What they do accomplish, and it can be an advantage in some cases, is the
nichrome suppressors reduce Q at the operating frequency! They have the
largest Q reduction change near dc, and actually de-Q the circuit less at
VHF than a conventional suppressor.
If you do an internet search, you will see both Rich and I sent suppressors
to N7WS. Rich did not even have his stock suppressor tested, Wes tested a
DUPLICATE of the 80A/B suppressor made from nichrome. The results of that
test showed the nichrome suppressor that was were identical to the
conventional suppressor had the same VHF characteristics, but less Q at HF.
Keep in mind this was not a stock Measures suppressor, but rather one with
considerably more inductance. The stock suppressor actually has higher VHF Q
when measured in the anode system.
If you read my page on tube arcs and gettering, it is quite easy to
understand that after some number of arcs or operation 3-500Z's that are not
pumped down well enough will degass themselves. Rich also DOES include some
useful mods, so all of his mods are not "bad". Some are. Some aren't.
What I object to is the single-minded claim that virtually all arcs and
virtually all failures are caused by parasitics, and the great harm that has
done to basic knowledge in our hobby.
> Also, if parasitics don't exist or are "Voodoo", why are there
> suppressors on just about every amp or tube transmitter??
I'm not and have never said all amps are stable WITHOUT suppressors. Some
amps are are stable without them, some require them.
What I am saying is if you have a tank circuit arc, you had better look for
one of many possible causes. The most likely one, barring defective
components, is how you tune the amplifer. Historically VHF parasitics are
not a likely cause of switch or tube arcs. There are very solid
easy-to-understand technical reasons for this, that can be explained and
proven by measurements.
The most likely source of tube arcs are defects in the tube, as a matter of
fact it is nearly impossible for a healthy tube in an HF amplifier to arc
from a VHF parasitic and work normally at HF at rated power! The most likely
cause of tank arcs are problems at or near the operating frequency, or at
lower frequencies, where reactances are high enough to allow high voltages
to occur.
You'll find virtually all engineers and experienced technical people agree
on this, and only person leads the "conspiricy" campaign.
I relate this parasitic campain closely to my wife and her "creative
medicines". She is constantly telling me how health foods with no value
"cure" her friends. There is no arguing the point, they take a pill and the
illness eventually disappears. She gave me eye pills because I was having
vision problems, and I threw them in the trash. Two weeks later my eye was
fine.
I suspect just laying the nichrome on the amplifier cover, while replacing
the bad parts in the amp, would do the same thing.
73 Tom
------------------------------
To: <amps@contesting.com>
Date: Sun, 9 Mar 2003 17:51:29 -0500
From: "Ed" <edw3nr@nexband.com>
To: "Amps" <amps@contesting.com>
Subject: [Amps] Tuned Input
Message-ID: <00bc01c2e68e$6f6093e0$6401a8c0@edw3nr>
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Message: 6
I want to make sure I am right here. Tune the input for best SWR and maximum
Grid current or ????????? ...........73
Ed W3NR
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------------------------------
To: <amps@contesting.com>
Date: Sun, 9 Mar 2003 23:13:44 +0000
From: "Ian White, G3SEK" <G3SEK@ifwtech.co.uk>
To: amps@contesting.com
Subject: Re: [Amps] AL-80B questions
Message-ID: <2u0riGOoq8a+EAlW@ifwtech.co.uk>
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Reply-To: "Ian White, G3SEK" <g3sek@ifwtech.co.uk>
Message: 7
rlm wrote:
>
>
>>rlm wrote:
>>>
>>>Amplifiers that happen to have tubes with lower than average VHF
>>>amplification tend to be stable.
>>
>>High-gain amplifiers for the VHF bands are perfectly stable too, if they
>>use tubes with short, well-grounded grid (or cathode) connections.
>>
>** HF amplifiers invariably have two resonant circuits connected to the
>anode. VHF amplifiers have one.
>
Not true. VHF/UHF amps all have multiple resonances, both above and
below the operating frequency.
You can't avoid resonances, but you *can* prevent oscillation, by making
sure that feedback at all resonant frequencies is kept very low.
Stability in a VHF amp has very little to do with choosing a tube with
low gain - it's all about preventing feedback. This is just as true
about VHF stability in an HF amp.
I hope that what I *did* say below makes sense to you.
>>The key feature is the total length and inductance of that grounded
>>connection. The length outside the tube is controlled by the layout. The
>>length inside the tube is controlled by the choice of tube. If you also
>>prevent accidental feedback paths, you'll have a stable amplifier.
>>
>** So the g-g internal feedback-C from the anode to the cathode (or grid
>in grounded-screen tetrodes) is nothing that a true amplifier expert
>should be concerned with ?
>
To anyone else reading this: I feel sure you understand why I'm not
willing to let Rich to lead me by the nose with exaggerated questions
like the one above...
>>If you use the correct grounding techniques in a VHF amplifier, it will
>>be stable with both the input and output disconnected.
>>
>** correct gounding has zero inductance ?
...or like that one...
>
>>The gain of tubes does not increase dramatically at lower frequencies
>>like it does with transistors, so if you use "VHF" grounding techniques
>>in an HF amplifier, you'll have a very stable amplifier indeed.
>>
>** VHF grounding also has no L ?
...or that one.
--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek
------------------------------
To: <amps@contesting.com>
Date: Sun, 9 Mar 2003 19:03:50 -0500
From: "Tom Rauch" <w8ji@contesting.com>
To: "mst" <montytaylor@texoma.net>, <amps@contesting.com>
Subject: Re: [Amps] Clipperton Bandswitch wafer
Message-ID: <016001c2e698$88985fa0$1c8001d8@akorn.net>
References:
<!~!UENERkVCMDkAAQACAAAAAAAAAAAAAAAAABgAAAAAAAAArGwDmQQFrEi+OGkRzFMsycKAAAAQ
AAAA9EtA5x8kn0azMGUn1wx0lgEAAAAA@texoma.net>
Content-Type: text/plain;
charset="iso-8859-1"
MIME-Version: 1.0
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Precedence: list
Reply-To: Tom Rauch <w8ji@contesting.com>
Message: 8
> I need a wafer switch for a Dentron Clipperton L. I purchased it about
> a year ago and finally loaded it on 160 to a dummy load the other day
> and "pop, pop, fizz, fizz" that particular wafer started arcing
> immediately. I inspected it and it looks like it had been damaged for
> quite a while.
Monty,
The AL80B bandswitch wafers will fit, and are actually higher voltage
replacements for the Clipperton.
You can get the ceramic sections down to only two sections by using AL80B
wafers.
Use a anti-corona washer on the wafer also, on the terminal that goes to the
doorknobs.
73 Tom
------------------------------
To: <amps@contesting.com>
Date: Sun, 9 Mar 2003 16:00:13 -0800
From: rlm <2@vc.net>
To: "Ed" <edw3nr@nexband.com>, " AMPS" <amps@contesting.com>
Subject: Re: [Amps] Tuned Input
Message-ID: <200303100010.h2A0AmKZ023561@contesting.com>
Content-Type: text/plain; charset="US-ASCII"
MIME-Version: 1.0
Precedence: list
Message: 9
>I want to make sure I am right here. Tune the input for best SWR
** Yes, provided the minimum is under 1.2 to 1. If it's not, the Q of
the tuned input needs to be pumped up,
>and maximum
>Grid current or ????????? ...........73
>
** Tune for max RF out with whatever drive level produces the rated max
anode current. Max out always results in a reasonable amount of
grid-current because if too many electrons are diverted to the grid,
fewer electrons arrive at the anode and output drops.
cheers, Ed
- R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K,
www.vcnet.com/measures.
end
------------------------------
To: <amps@contesting.com>
Date: Sun, 9 Mar 2003 16:00:13 -0800
From: rlm <2@vc.net>
To: "Ian White, G3SEK" <g3sek@ifwtech.co.uk>, " AMPS" <amps@contesting.com>
Subject: Re: [Amps] AL-80B questions
Message-ID: <200303100010.h2A0AmKZ023562@contesting.com>
Content-Type: text/plain; charset="US-ASCII"
MIME-Version: 1.0
Precedence: list
Message: 10
>rlm wrote:
>>
>>
>>>rlm wrote:
>>>>
>>>>Amplifiers that happen to have tubes with lower than average VHF
>>>>amplification tend to be stable.
>>>
>>>High-gain amplifiers for the VHF bands are perfectly stable too, if they
>>>use tubes with short, well-grounded grid (or cathode) connections.
>>>
>>** HF amplifiers invariably have two resonant circuits connected to the
>>anode. VHF amplifiers have one.
>>
>Not true. VHF/UHF amps all have multiple resonances, both above and
>below the operating frequency.
** Good point, however, for instance, the 3/4-wave resonance of a
1/4-wave line for a 432MHz amplifier is pretty far up there. I have
never built a 144, 432, or 1296MHz amplifier that proved to capricious.
>
>You can't avoid resonances, but you *can* prevent oscillation, by making
>sure that feedback at all resonant frequencies is kept very low.
>
** How do You keep internal tube feedback low ?
>Stability in a VHF amp has very little to do with choosing a tube with
>low gain - it's all about preventing feedback. This is just as true
>about VHF stability in an HF amp.
>
>I hope that what I *did* say below makes sense to you.
** If it made perfect sense, I would have not have asked you the dodged
question.
>
>>>The key feature is the total length and inductance of that grounded
>>>connection. The length outside the tube is controlled by the layout. The
>>>length inside the tube is controlled by the choice of tube. If you also
>>>prevent accidental feedback paths, you'll have a stable amplifier.
>>>
>>** So the g-g internal feedback-C from the anode to the cathode (or grid
>>in grounded-screen tetrodes) is nothing that a true amplifier expert
>>should be concerned with ?
>>
>
>To anyone else reading this: I feel sure you understand why I'm not
>willing to let Rich to lead me by the nose with exaggerated questions
>like the one above...
** So why should internal feed-back capacitance be of no concern ?
>
>>>If you use the correct grounding techniques in a VHF amplifier, it will
>>>be stable with both the input and output disconnected.
>>>
>>** correct gounding has zero inductance ?
>
> ...or like that one...
** Say what ?
>
>>
>>>The gain of tubes does not increase dramatically at lower frequencies
>>>like it does with transistors, so if you use "VHF" grounding techniques
>>>in an HF amplifier, you'll have a very stable amplifier indeed.
>>>
>>** VHF grounding also has no L ?
>
> ...or that one.
>
** ?
- R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K,
www.vcnet.com/measures.
end
------------------------------
To: <amps@contesting.com>
Date: Sun, 9 Mar 2003 16:00:13 -0800
From: rlm <2@vc.net>
To: "Tom Rauch" <w8ji@contesting.com>, " AMPS" <amps@contesting.com>
Subject: Re: [Amps] SB-220 cap arc and the local broadcast station
Message-ID: <200303100010.h2A0AmKZ023564@contesting.com>
Content-Type: text/plain; charset="US-ASCII"
MIME-Version: 1.0
Precedence: list
Message: 11
>> I tried all the cleaning, de-burring type tricks before I
>> bought the late version cap. In my opinion, lack of
>> proper parasitic suppression and an otherwise eager
>> capacitor caused the previous owner (two different
>> brands of) tube failures.
>
>You can not clean and polish a capacitor and restore voltage.
>
** any port in a storm.
- R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K,
www.vcnet.com/measures.
end
------------------------------
To: <amps@contesting.com>
Date: Sun, 9 Mar 2003 16:00:14 -0800
From: rlm <2@vc.net>
To: "Tom Rauch" <w8ji@contesting.com>, " AMPS" <amps@contesting.com>
Subject: Re: [Amps] AL-80B questions
Message-ID: <200303100010.h2A0AnKZ023568@contesting.com>
Content-Type: text/plain; charset="US-ASCII"
MIME-Version: 1.0
Precedence: list
Message: 12
>> Bottom line, the mods fixed the arcing, and I spent less than $3.00.
>> I'd like to ask Tom why these work -- he seems only to say that
>> parasitics don't exist, and the mods don't make sense. If that's the
>> case, why is my amp now working so much better? The filiment mod is
>> very clear to me, same with the step-start mod. Why is this such a big
>> deal? If you make your own suppressors, you'll spend very little, and
>> certainly won't hurt anything.
>
>You can hurt VHF stability Joe. The Measures suppressors I have measured
>actually increase VHF Q.
>
>What Rich overlooks is his suppressors with lower Rp are in SERIES with a
>long system.
** the VHF suppressor is in series with the anode. Since VHF-gain =s
transconductance x VHF-Rp, converting the series R of the suppressor to
the parallel equivalent, Rp, is useful.
>In that case, lower series resistance means higher Q in the
>system.
** True, but high series resistance produces low parallel-equivalent
resistance, which lowers amplification. [Ref. figures 12 and 18 on my
Web site]
- R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K,
www.vcnet.com/measures.
end
------------------------------
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