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

Apr 08, 2007 7 Replies
B

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



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T

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

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T

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
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B

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

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J

http://www.arrl.org/catalog/?category=&words=ARRL+Handbook&SearchWords.x=5&SearchWords.y=8
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S

"billcalley" schreef in bericht news: snipped-for-privacy@l77g2000hsb.googlegroups.com...

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

SFC

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B

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

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M

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
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