DIYbanter - View Single Post - Will RF output (transmitter) be the same wattage as audio output?

Ralph Mowery

In article ,
says...

I can relate to using ceramic sockets, because the standard ones would
likely burn up from such high voltages.
* What are the standard sockets made out of anyhow????

Considering the closeness of the tube socket pins, I could see where
there could be arcing between pins at voltages that are or exceed 1000V.
Plate caps eliminate that problem. However, I would assume that the wire
going to those plate caps would need to have insulation capable of the
voltage, and where they go thru the chassis, would need grommets that
can handle the voltage too. Not to mention the connections below the
chassis such as terminal strips.

I have not worked with any voltages exceeding 1000V (except the HV in
the old tv sets). But since I am on a farm, I know what an electric
fencer can do. If a fence wire gets too close to a tree (for example),
it will snap and shoot a spark a half inch long, or longer. Most of
those fencers are around 5000 V. Those fence wires are all run on
porcelin insultors. (although there are now plastic ones that work as
well).

I have felt them fences far too many times too..... I have been
literally knocked down from them more than once, if I was well
grounded.... NOT FUN.

Fortunately those fencers do not kill a person or animal (or we would
not use them, since livestock are expensive and dead people are not a
good thing). The voltage is high, but the current is low. (and it
pulses).

Anyhow, while I have not done it, I am sure building transmitters (or
anything else) using those high voltages, require special components and
wiring, which in itself requires special knowledge.

I have 2 amplifiers for my ham radios. Both have about 2700 volts on
the plates of the tubes. The current drawn by the tubes is almost one
amp. I have worked on them several times. To do that I make sure the
capacitors have fully discharged by watching the voltmeter on the amps
go near zero. When I take the cover off, vurey carefully, I then short
the capacitors to ground to make sure the volt meter is not giving a
false reading. The voltage and current is not like a fence charger. It
will dump a lot of current into you and often kill. Fence chargers are
more like a static electricity shock, lots of voltage,but little
current. They are made to shock and not to kill.

It does take some special insulated wire for the amps and other high
voltage items. Most common wires are insulated for around 600 volts or
even 300 volts. That 2700 volts will often burn through wire insulated
like that . Only 'good' thing about it,is that it will not jump much of
an air gap. However with RF applied the operaing voltages inside the
amp is somewhat greater and can arc a short distance.

Most of the tubes operate with less than 500 volts on the pins with the
higher voltage going to the cap on the plates. Ceramic is often used
because of the heat on the pins of the tubes. The filiments get hot and
direct transfer heat, and the heat of the plate is radiated to some
extent. Afer all, if an amp is putting out 1000 watts it is using close
to 1500 to 2000 watts to do it. That is almost as much as some of the
smaller 'bathroom' portable electric heaters put out.