Here's my take on the tube...
The -1000V rating is an absolute max...not part of the RF performance.
Looking at the grid voltage vs plate voltage at 4 kV on the anode and RF swing
down to 1 kV...
* Bias at about -180V for 100 mA of idling current
* Swing up to about +200V for 2A peak plate current at 1 kV
* That's 480V required peak to peak swing of grid voltage
Compare that to an 8877
* Bias at about -5V for 100 mA idling
* Swing up to about +40V for 2A peak plate current at 1 kV
It's a lot easier to drive an amplifier with 45V Peak to Peak swing than 480V of
swing.
If you want to try to use this tube, suggest you use a grid driven design with a
significant step up in impedance. The long leads means it probably needs
parasitic suppression and/or neutralization.
It's not reasonable to try to cathode drive due to the very small voltage gain.
If you want to try a resistively swamped grid design, you might try to use a 4:1
step up ferrite transformer and a 200 Ohm swamping resistor in the grid driven
configuration. That would give the required 480V of swing at a drive level of
146W. Other design with higher step up ratios would make it easier to drive.
Overall, an old fashioned tube...they sometimes look very nice, glowing red
plates, blue from the gas. For similar examples, look up amplifier design in an
old radio book that uses an 304TL, 450TH, or similar low Mu Triode.
jeff, wa1hco
On 12/14/2013 09:04 AM, Jeff Pederson wrote:
Good Day,
Well its been awhile since I posted to this list but read the posts. My
weakness is how to determne if this tube is suitable for use as a ssb amp and
does anyone have a tutorial or link on how to use the constant current
characteristic tube charts? That -1000v grid in the specs makes me think it
wont work or be practical but thats why Im asking.
http://www.ok1rr.com/tubes/Thales/T1000-1.pdf
Happy Holidays
Jeff
KD4LYH
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