On 1/17/23 2:21 AM, Zack Widup wrote:
I have never seen any manufacturer publish s-parameters for tubes.
Pretty much every manufacturer of Traveling Wave Tubes publishes S-parameters - In particular one tends to be interested in the S12 (reverse gain) at the second harmonic of the intended frequency band.
The other thing one tends to be very interested in is the group delay across the band of operation, which is derived from data gathered with a VNA.
I think you're thinking of gridded tubes like tri-, tetr-, and pent-odes.
And the
design techniques are different. The parts and methods used in biasing and
matching tubes are completely different than those used for FET's and
BJT's. The frequency ranges used for most commonly-available tubes do not
require s-parameters. There are very few tube amps around that operate
above 1296 MHz.
I wouldn't be surprised if there are more microwave tube amps today than HF band tube amps. If you want power, tubes are where it's at.
I see no reason to measure a tube on a VNA.
Zack W9SZ
On Mon, Jan 16, 2023 at 8:29 PM Leif M <leif.michaelsson@...> wrote:
I read about first TV sets and their tubes, thats history. And began to
wonder if anyone has measured tubes with VNAs. Do you get meaningfull
results. Connecting something with 200V supply voltage to NanoVna must be
interesting.
That's solved with just a DC block. A bigger issue is not blowing up the VNA with the output power.
(and for the NanoVNA, the fact that the test signal is a square wave)
