Homebrew Amps: Why not GROUND the B+?

[W9JEF]

.



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 !

.

[W9JEF]

Nevermind : Matthew 7:6 !

.

The Matthew 7:6 comment is taken as good advice.
The original idea was to open a few minds to the advantages
of having no RF choke on the plate (avoiding series resonances
on the higher frequencies) and no plate blocking capacitor
(all the less inductance to induce VHF parasitics).

Throughout this thread, all this ad hominem vitriol.
Excuse me for mistaking this for a technical forum.

The mods will likely close the thread, which at this point
will free me from the futility of attempting a technical discussion
with so much unbridled heckling from the peanut gallery.

Please don't mistake this for whining--the message is wtf.

[ad4mg]

The mods will likely close the thread, which at this point
will free me from the futility of attempting a technical discussion
with so much unbridled heckling from the peanut gallery.

Unlikely. When a man digs a hole in the sand, then climbs into it to continue digging, we merely observe the event with a tinge of mild amusement.

You lost it when you said you were going to mail schematics to Corey for him to scan and post.

And here we sit, tinged with mild amusement...

[W9JEF]

Unlikely. When a man digs a hole in the sand, then climbs into it to continue digging, we merely observe the event with a tinge of mild amusement.

You lost it when you said you were going to mail schematics to Corey for him to scan and post.

And here we sit, tinged with mild amusement...

And the amusement I get when I think about all the nayboobs of negativity
while working low-band DX using an amplifier that they claim will never fly. :rofl:

Can't help wishing the mods would at least keep a technical forum on track.

[N2CHX]

And the amusement I get when I think about all the nayboobs of negativity
while working low-band DX using an amplifier that they claim will never fly. :rofl:

Can't help wishing the mods would at least keep a technical forum on track.

I never said it wouldn't work at all, I merely pointed out the issues of such an amp and I still stand by what I said. I understand how it works and I could draw a schematic of it, but to me it's moot because the problems outweigh any potential benefits. You posted this like it was some great, revolutionary thing that every ham and broadcaster was missing out on and you left me unimpressed.

[N2NH]

Oh second thought...

No.

[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.

.