Tube amplifier input circuit

[@W1ZY]

I didn’t know the way to read the MFJ was to interpret X as inductive reactance and varying R as capacitive reactance. Thank you! Question: can it read capacitive reactance as a -j number in “advanced” mode?

[@bparker86]

A nano vna would make your tuning even easier. The abity to see it directly on the smith chart and see if it's + or - johms and not just inductive reactance

[@linearone]

When your MFJ goes into power save mode after sitting idle too long, no need to turn it off and on to read again, just tap the mode button once. Plus, if you have the rechargeable battery bank with the wall wart adapter it won't go into power save.

[@radiomedic111]

As soon as I can get an area set up to do videos, I will be showing step by step how to build Tetrode amps along with how to build some of the necessary items of test equipment and how to get the most out of MOT's on my channel. I will also try to make and show videos to answer questions that viewers may have on how to work with a particular tube or circuit.

[@MM0IMC]

I was looking at some of the input networks for mono bands HF linear amplifiers, i.e. for 40m or 20m. I've seen PI, L or PI L input circuits. What's your thoughts on the various varieties?

[@bellydump-hf7ec]

Would you please consider doing a video on ceramic tube amplifiers for dummies. Just a brief description about applications, part terminology and practical methods of installation, and other relevant information per your experience of course. Thanks in any case for sharing your knowledge via video. Very professional and courteous.

[@KF8OD1]

Thanks for your kind words. I have a website with a lot of construction information. www.qsl.net/kf8od You can email with question. [e-mail] 73, Mike KF8OD

[@bellydump-hf7ec]

@@KF8OD1copy that. Many thanks I have several large valves similar to the one in you use in the video. Along with many smaller ones with pins and many glass vacuum tubes and power supplies, resistors, diodes ,caps, and cabinets with various equipment I salvaged from a decommissioned television broadcast tower. In case your wondering why someone as ignorant as I might be seeking such information .

[@MM0IMC]

Can I ask what the ceramic disc capacitor is connected to on the tube?

[@KF8OD1]

The tube cathode.

[@Wonoketingal]

Nice input 👍👍✅❤️

[@hayesnoe1681]

A trick: watch series at kaldroStream. I've been using it for watching all kinds of movies lately.

[@estebannicolas78]

@Hayes Noe Yup, I have been using flixzone} for years myself :D

[@jamalcarlos9780]

@Hayes Noe yup, been using Flixzone} for years myself :D

[@lindsaymurphy5088]

Hi there, Can you work out the Load and Plate tuning using the same method? regards lindsay

[@KF8OD1]

+Lindsay Murphy Yes, the process is the same. Calculate the plate load impedance, place a resistor of that value between the anode of the tube to ground. Connect the mfj259b to the output of the amp. Use this set up to tap the tank coil and find the tune and load settings. All power is off for this testing.

[@wires2115]

@@KF8OD1 :) u need to tell her how to calculate the plate load as well :) , nice job

[@Kc8qdq]

Nice work let me know how the auto tune works out kc8qdq

[@KF8OD1]

After a little trial and error I think this will work for an input with a 10:1 ratio from the inductor to the caps, but the next step of ganging that to the tune cap would be more complex. Amps that do this have custom gear reductions witch are out of my skill set. I think a discriminator circuit might be the way to go instead. Looked at your QRZ page, what tube is in your big amp? I have worked in the salt mine here in Cleveland, nice place to visit but would not want to be there every day.

[@migueloyarzabal]

schematic the input circuit