A buddy is trying to get a 1:9 un-un to work on his grid driven tetrode. Terminated in a 450 ohm globar, SWR is 1:1 but only up to aprx 20 mhz. Above 20 mhz, it rapidly all goes to hell....reaching 2
The unun is (my opinion) a waste of time. Just connect your grid input network, usually a pi network for tetrodes, to the grid and design it to do all the impedance transformation. It can be band swi
That 1:9 unun and 450 ohm resistor is obviously for use with a high power linear tetrode amplifier. Passive grid would not work with grid current. Tetrodes requiring a few hundred volts of drive are
Obviously? This is a ham. No telling what a ham will try. I drive a 4-1000 grid with a grid leak bias resistor all the time. Separate screen v. supply Why would a ham want a tube with 15 KW anode dis
Okay, thinking about this some more (rainy day here). Firstly, I apologize for sneering at this idea and those trying it. More information is needed for anyone to help in my opinion. 1. What is the t
Perhaps he just had one on hand? Unfortunately, the electric bill would likely suffer should the user forget to turn it off when finished... (running the filament alone requires 6.3 volts @ 160 amps
The ham might have been asked by a broadcaster to build such amp. I was asked as well about a 30-50KW amp. Helped already in the past with the construction of the 10KW version (2x 3CX3000A7). https:/
Core choice, wire length and winding style all play a part. https://cromwell-intl.com/radio/9-1-unun/ and https://g8jnj.webs.com/Balun%20construction.pdf might help figure out what's happening. Doesn
Study resonance. 73, Jim K9YC _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps
The National NCL-2000, ca 1964-70 used a pair of 8122 tetrodes with an untuned resistive input. The bias was AB1 on SSB and AB2 on CW where grid current was used. Carl That 1:9 unun and 450 ohm resis
What's the impedance of a parallel tuned circuit at frequencies well below resonance? Steve G8GSQ _______________________________________________ Amps mailing list Amps@contesting.com http://lists.c
A much simpler solution would be to use a 50Ohm resistor, no un-un, and more drive power. I don't know what the tube(s) is you are trying to drive, but for example a pair of GU74B's would require abo
Yes, a small grid current through a 50 ohm load will not do much bias shifting and impedance change. 73 Peter, DJ7WW The National NCL-2000, ca 1964-70 used a pair of 8122 tetrodes with an untuned res
Author: Victor Rosenthal 4X6GP <k2vco.vic@gmail.com>
Date: Mon, 25 Oct 2021 22:07:38 +0300
What I did with a 4CX1000A AB1 amplifier was to put a 50 ohm non-inductive resistor from grid to cathode, and feed it through a pi-section lowpass filter (I used 35 MHz as the cutoff). The input capa