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 Post subject: 6888 Xmitter L/C
PostPosted: Sep Mon 24, 2007 10:23 pm 
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I noticed that the more "L" and less "C" the stronger the transmitted signal.

On this one I ended up with about five turns (gimmick) of hookup wire of capacitance to max my signal.
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I remember the discussion on this last year, but don't remember the consensus.


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PostPosted: Sep Mon 24, 2007 11:29 pm 
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Yup more L is better(of course there is a limit)... Basically you achieve resonance with less power absorbed by the cap... At least I believe that's the theory of operation...

Tom


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PostPosted: Sep Tue 25, 2007 12:43 am 
Silent Key

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34326
Location: Sandpoint, IDAHO 83864
A higher L/C ratio in any tank circuit will develop more voltage across it than a lower L/C ratio tuned to the same frequency will.

Ever wonder why some sets seem more sensitive as the tuning gets higher in frequency? It is because the L/C ratio becomes better. A lot of the early sets had a potentiometer ganged to the tuning capacitor that was in the cathode circuits of the RF/IF stages to reduce the gain as the tuning went higher for this reason. It usually was called a "compensator" control. The Majestic 90 series is one that comes to my mind.

A lot of people think they can just wind a coil and hope it resonates with whatever capacitor they have laying around. Sometimes you get lucky, but the design of efficient tank circuits is a major study in itself as far as radio is concerned.
Curt

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Curt, N7AH
(Connoisseur of the cold 807) CW forever!


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PostPosted: Sep Tue 25, 2007 3:11 am 
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So then in this line of thought, the same would apply to a homebrew receiver? Does that mean a tank for a regen would benifit from a fine-tune (gear ratio) lower cap and a high matching coil? See. I'm still learning! =0)


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 Post subject:
PostPosted: Sep Tue 25, 2007 12:56 pm 
Silent Key

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34326
Location: Sandpoint, IDAHO 83864
Usually it is correct. However then you run into the problem of not having a wide enough frequency range. If you were building the set for the ham bands where only a few hundred kc were to be covered, it is fine. It gives you good bandspread also.

Please note that the older commercial available plug in coils were wound for specific frequencies with a 140uuF capacitor. Most regenerative sets I have read about in the last couple of years people are using 365uuF variable capacitors.
Curt

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Curt, N7AH
(Connoisseur of the cold 807) CW forever!


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