TX: What does the LOAD, PLATE, & DRIVE knobs actually control?

[billcalley]

Hi All,

I know *how* to tune the finals of a "hybrid" HF transceiver, but I
cannot find schematics of the exact circuits -- or even a good
explanation -- of exactly *what* components are being tuned inside the
transceiver itself. With tube transceivers, what exactly does each
control do? (I.E: the LOAD, PLATE, and DRIVE controls in, lets say, a
Kenwood TS line). Are these controls attached to the output pie
network capacitors and inductor of the PA? (Like a "mini"
transmatch). If so, which control is attached to which component?
And does anyone know of any drawings or diagrams for this?

Thanks for any clarifications!

-Bill

 

[Tom Bruhns]

Hi All,

I know *how* to tune the finals of a "hybrid" HF transceiver, but I
cannot find schematics of the exact circuits -- or even a good
explanation -- of exactly *what* components are being tuned inside the
transceiver itself. With tube transceivers, what exactly does each
control do? (I.E: the LOAD, PLATE, and DRIVE controls in, lets say, a
Kenwood TS line). Are these controls attached to the output pie
network capacitors and inductor of the PA? (Like a "mini"
transmatch). If so, which control is attached to which component?
And does anyone know of any drawings or diagrams for this?

Thanks for any clarifications!

-Bill

Hi Bill,

This is a better question to ask over in rec.radio.amateur.homebrew or
the like. But... The drive control most likely tunes the stages that
supply RF to the power amplifier's grid. The network that couples the
power amplifier's plate circuit to the RF output connector is almost
certainly a PI network, with fixed series inductor selected per band,
but the shunt capacitors at the plate and the output ends are
variables, labeled PLATE and LOAD (or "LOADING").

Do a Google search for "Kenwood TS-520S schematic" and you should turn
up one. You can probably find manuals for others in that line. You
may find it interesting to simulate the PI network in Spice or RFSim99
or some similar program.

Cheers,
Tom

 

[Tim Wescott]

Hi All,

I know *how* to tune the finals of a "hybrid" HF transceiver, but I
cannot find schematics of the exact circuits -- or even a good
explanation -- of exactly *what* components are being tuned inside the
transceiver itself. With tube transceivers, what exactly does each
control do? (I.E: the LOAD, PLATE, and DRIVE controls in, lets say, a
Kenwood TS line). Are these controls attached to the output pie
network capacitors and inductor of the PA? (Like a "mini"
transmatch). If so, which control is attached to which component?
And does anyone know of any drawings or diagrams for this?

Thanks for any clarifications!

-Bill

Plate and load are connected to the final pi network, yes. "Band"
switches the final coil, among other things.

Drive controls the tuning of the final grid circuit (and drive tube
plate). Plate controls the capacitor that's connected (possibly through
a coupling cap) to the final plate, and load controls the capacitor
that's attached to the antenna.

You peak the drive, dip the plate, and adjust load to get the plate
current you want.

My TS-520 came with a schematic -- didn't yours?

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

 

[billcalley]

Hi All,

I know *how* to tune the finals of a "hybrid" HF transceiver, but I
cannot find schematics of the exact circuits -- or even a good
explanation -- of exactly *what* components are being tuned inside the
transceiver itself. With tube transceivers, what exactly does each
control do? (I.E: the LOAD, PLATE, and DRIVE controls in, lets say, a
Kenwood TS line). Are these controls attached to the output pie
network capacitors and inductor of the PA? (Like a "mini"
transmatch). If so, which control is attached to which component?
And does anyone know of any drawings or diagrams for this?

Thanks for any clarifications!

-Bill

Thanks Tim, thanks Tom. Your explanations helps a lot, but the
real TS-520S schems I find on the Web are a little too "real" and
complex for me. (IE: They are not 'instructional' enough, diagram and
clarity-wise, for me to really get a very clear idea as to what
exactly is going on in the PA section).

Best,

-Bill

 

[John Fields]

Thanks Tim, thanks Tom. Your explanations helps a lot, but the
real TS-520S schems I find on the Web are a little too "real" and
complex for me. (IE: They are not 'instructional' enough, diagram and
clarity-wise, for me to really get a very clear idea as to what
exactly is going on in the PA section).

 

[MassiveProng]

It really is in his best interest. Just getting the answer from
someone wouldn't do much good.

 

[SFC]

Hi All,

I know *how* to tune the finals of a "hybrid" HF transceiver, but I
cannot find schematics of the exact circuits -- or even a good
explanation -- of exactly *what* components are being tuned inside the
transceiver itself. With tube transceivers, what exactly does each
control do? (I.E: the LOAD, PLATE, and DRIVE controls in, lets say, a
Kenwood TS line). Are these controls attached to the output pie
network capacitors and inductor of the PA? (Like a "mini"
transmatch). If so, which control is attached to which component?
And does anyone know of any drawings or diagrams for this?

Thanks for any clarifications!

-Bill

Load - antenna coupling/matching
Plate- tunes the network of the tubes anode
Drive- tunes the network of the tubes grid

SFC

 

[billcalley]

Hi All,

I know *how* to tune the finals of a "hybrid" HF transceiver, but I
cannot find schematics of the exact circuits -- or even a good
explanation -- of exactly *what* components are being tuned inside the
transceiver itself. With tube transceivers, what exactly does each
control do? (I.E: the LOAD, PLATE, and DRIVE controls in, lets say, a
Kenwood TS line). Are these controls attached to the output pie
network capacitors and inductor of the PA? (Like a "mini"
transmatch). If so, which control is attached to which component?
And does anyone know of any drawings or diagrams for this?

Thanks for any clarifications!

-Bill

Thanks for the great info guys! The exact concept of where the TX
tuning controls contacted the different parts of the tube circuits is
what confused me (I'm aware of how matching circuits work). I had
also looked through the ARRL Handbook (and the Web) before I asked the
question here, but I did not see a circuit drawing or a satisfying
description of the answer to my question at all, but maybe I just
missed it.

Thanks again,

-Bill

 

[Michael A. Terrell]

Thanks for the great info guys! The exact concept of where the TX
tuning controls contacted the different parts of the tube circuits is
what confused me (I'm aware of how matching circuits work). I had
also looked through the ARRL Handbook (and the Web) before I asked the
question here, but I did not see a circuit drawing or a satisfying
description of the answer to my question at all, but maybe I just
missed it.

Thanks again,

-Bill

There are a lot of transmitter schematics on the BAMA website. Some
complete ham radio manuals, as well.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida