RF cavities and related devices

[sophiecentaur]

at this point your simply angry.

No - just exasperated that you have been insisting on looking at things your way, which is very often totally wrong.

If you just want to know how much a particular pair of Nike Shoes will cost, then a straight numerical answer suffices but your questions very seldom have a straight possible answer to them because they are so often the wrong questions and not answerable without a lesson.

For instance, how can you suggest using a Klystron to produce a wideband signal that stretches from zero to 700MHz? I thought we had established that even a TV klystron (with specially de-tuned extra cavities) can only manage about 1% bandwidth. I think you would feel the same way as I do when faced with that sort of craziness about something that you actually know about. You claim to know all about the idea of channels so how can you ask about a klystron for DC to Daylight bandwidth? How long would the drift tube of a 1MHz klystron need to be and how big would the cavity be? Don't you realize just how outrageous these ideas are? Ask yourself "Can you buy one?". Why do you think the answer is No.

I suggest you sort out some basics of signals and modulation systems (in detail - not just scanning and saying to yourself "I recognise that - I know it".

If you start another thread about some small part of that topic then you may find someone who is not a quivering wreck will answer you and you may get a reasonable answer. But you have to show some respect for the subject (PF members have fairly thick skins as long as people are polite - which you are) and do not dismiss things as trivial.

 

[artis]

I like your input overall it's just that once you get "exasperated" your input deteriorates like the sound of an AM radio over a receiver with dried up electrolytic caps

I will stop posting and will have to get around frequency modulation and processing for good until I do something, the basics of klystrons would be clear now I also realize that a particular klystron can accept only a small range of frequencies if one hopes to get any decent efficiency out of it, that is fine with me.

The reason I asked about the spectrum is because in AM the carrier frequency is fixed so the klystron being "dumb" only works with that exact carrier frequency to which it is built and has a high Q correct? So why would it care if I modulated a 10Hz sine on that carrier and the next moment decided to modulate a 100Khz Sine on top of the same carrier, in both cases the cavity "works" with the carrier ?

In FM I would understand why a certain klystron can only amplify a specific band because since the information is frequency modulated a wider band (wider range of frequencies) would require the klystron to amplify all those frequencies as well as the "main" one, but I fail to see why the same would be for AM?
Is my logic here so wrong ? Or maybe you misunderstood me and thought I would like to amplify all those frequencies without modulation through the klystron , which I DID NOT intended.

To be honest you never really answered this question just pointed out how I don't know anything (to which I can't entirely object)

 

[sophiecentaur]

The reason I asked about the spectrum is because in AM the carrier frequency is fixed so the klystron being "dumb" only works with that exact carrier frequency to which it is built and has a high Q correct? So why would it care if I modulated a 10Hz sine on that carrier and the next moment decided to modulate a 100Khz Sine on top of the same carrier, in both cases the cavity "works" with the carrier ?

Here's just one answer. If your amplifier has a very narrow (high Q) pass band, centred exactly on the carrier frequency, the modulation sidebands are 'wiped off' the signal and you are left with just the carrier. The 6MHz sound carrier on the multiplex Sound + Vision modulated UHF signal has to get through the klystron (plus the vision sidebands that are on the 'other side' of the carrier. Analogue TV is really not the place to start because the carrier uses Vestigial Sideband Filtering (OMG!) of the Vision signal so that the lower frequency vision components are double sideband modulated and the higher frequency components are single sideband modulated. This is all to get a 'quart into a pint pot' and gives good definition without using the full RF bandwidth that would normally be necessary. (See what I mean?)
Stick with sound Radio AM and FM for the basics. Don't go near old fashioned Analogue TV because it is dying rapidly in favour of Digital signalling when you are (really!) ok with analogue easy modulation methods.

 

[berkeman]

Thread is closed for a bit. The Mentors are discussing how to handle this. Thanks for all who have been trying to help the OP with basic math and the associated intuitive understanding for his/her question.

EDIT / ADD -- Thread will stay closed for now. I'm having a detailed PM discussion with the OP to try to fill in some of the confusing spots, and also to help them find some learning resources at the right level for their background.