Homebrew Amps: Why not GROUND the B+?

[W9JEF]

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AM broadcast transmitters have featured a grounded B+ since the mid-1980s.

One advantage being, that no blocking capacitor is needed (reducing the inductance).
Plate current flows through the pi-network tank coil, to ground through an RF choke
at 50 ohm output, rather than across the high-Z plate. (B-minus HV fed through cathode.)

Main reason for grounded B+ ham rigs: NO lethal voltage topside,
greatly reducing the safety risk for the experimenter.

Had my homebrew grounded B+ amp (four 811-A's) in operation since 2008. :)

[kb2vxa]

No lethal voltage topside, but would you still put your finger on the top cap of a 4-400A? (;->)

Don't forget the venerable microwave oven with the grounded magnetron being one of two diodes in a half wave voltage doubler, and a current limiting split gapped core transformer.

[koØm]

Nevermind : Matthew 7:6 !

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[kb2vxa]

We won't trample your pearls underfoot, but if you call us dogs or pigs we'll surely turn and tear you to shreds.

[koØm]

Look man, when I read Bumper's message about some pissy 811a's running 1200 volts, I went completely QRO and dashed off a dissertation ala W8JI about amplifier design; I put on my AG6K boots and started stomping on the idea of running REAL B+
under the chassis. I looked at all the words and thought about all the QRO builders and decided not to get into a back and forth with a deletant. I deleted it and made my comment.

No lethal voltage topside, but would you still put your finger on the top cap of a 4-400A? (;->)


Don't forget the venerable microwave oven with the grounded magnetron being one of two diodes in a half wave voltage doubler, and a current limiting split gapped core transformer.

We won't trample your pearls underfoot, but if you call us dogs or pigs we'll surely turn and tear you to shreds.

In the immortal words of Johnnie Cochran, "If the gloves don't fit, you must acquit." Your hand is too big while, the whole glove might fit over Bumper's head. If Bob had the strength, he would have probably weighed in with an Anti-Aircraft Gun.

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[W9JEF]

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I actually have--in "transmit" (HV applied, no excitation)--touched
the 811A plate caps and chassis for shock effect (on the observer).

Another advantage of having no lethal voltage topside:
no enclosure required--much better ventilation--no forced air.

According to the tube table. maximum 811-A plate voltage is 1250.
At full output, they loaf along at 1200 volts (with a brick on the key).

Of course there are always the decadent diehards who
squeal like a pig at the thought of a "perverted" B+.

[kb2vxa]

So why am I being compared to this "Bumper" whomever that is? No matter, my tongue in cheek hamster style gets a bit of getting used to.

The perverted B+ has many design advantages advantages, no sense listing the obvious, like the entertaining squeal of diehards with unshielded mic cables.

[koØm]

So why am I being compared to this "Bumper" whomever that is? No matter, my tongue in cheek hamster style gets a bit of getting used to.

Not you, "Bumper" is the one who started this thread, you know, he's the one who bumps his own Cut and Paste posts back to the top.

The perverted B+ has many design advantages advantages, no sense listing the obvious, like the entertaining squeal of diehards with unshielded mic cables.

If Bumper wants to debate amplifier design I would recommend that he checks out these sites and operators.

http://groups.yahoo.com/group/ham_amplifiers/
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps

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[G7JMZ]

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AM broadcast transmitters have featured a grounded B+ since the mid-1980s.

One advantage being, that no blocking capacitor is needed (reducing the inductance).
Plate current flows through the pi-network tank coil, to ground through an RF choke
at 50 ohm output, rather than across the high-Z plate. (B-minus HV fed through cathode.)

Main reason for grounded B+ ham rigs: NO lethal voltage topside,
greatly reducing the safety risk for the experimenter.

Had my homebrew grounded B+ amp (four 811-A's) in operation since 2008. :)

My interst is piqued, how about a few circuits for those people watching in black and white ?

[W9JEF]

Not you, "Bumper" is the one who started this thread, you know, he's the one who bumps his own Cut and Paste posts back to the top.

Actually it's copy and paste (no caps).
If that's a sin, then may the Pope grant me absolution.
It's the Island software that bumps a thread back to the top
--that or a disgruntled troll.

If Bumper wants to debate amplifier design I would recommend that he checks out these sites and operators.

http://groups.yahoo.com/group/ham_amplifiers/
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps

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What's wrong with posting amplifier design info here?
It is, after all, called the "Homebrew & Mods" Forum.
If you want to debate content, there's another site
where subject matter is much more restricted.