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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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17th May 2017, 5:22 am | #21 |
Nonode
Join Date: Jun 2013
Location: Surbiton, SW London, UK.
Posts: 2,801
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Re: Cct to improve modulation here, please?
What is more important is that you have an additional audio limiter circuit to prevent the
modulation exceeding 100% on peaks with the average audio level slightly raised to provide an increased s/n ratio. This is easily added. |
17th May 2017, 11:26 am | #22 |
Dekatron
Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
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Re: Cct to improve modulation here, please?
Hmmm, for example using diodes that when forward biased beyond the peak signal level conduct and using associated circuitry , attenuate the overvoltage?
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Al |
17th May 2017, 7:26 pm | #23 | |
Dekatron
Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
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Re: Cct to improve modulation here, please?
Quote:
I'm drawn to several aspects of practical electronics; problem solving, the aesthetic dimension of using and re-purposing materials to fabricate things (which look good, intriguing, or fantastic!), but also to the deeper mysteries, which, ultimately, do include a growing and deepening mathematical understanding. So this is a brilliant and intriguing coincidence around the convergence on 37.6 using three discrete methodologies.
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Al |
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19th May 2017, 9:16 am | #24 |
Dekatron
Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
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Re: Cct to improve modulation here, please?
Quick update: job done!
I easily reconfigured the space to pop in a module I built on a tiny square of copper foil - Mark's transistor Pre-amp. I increased gain to X 10 as modulation needed to be higher on voice. I did in the end convert the RF choke to a tank circuit with 47pF and a tiny trim-cap as well as the series 56pF already in the output transistor, and am also using a wire aerial instead of the loop for the time being. Matching inductance is provided by 1.02 mH in series with the antenna. Quality of the broadcast signal is high, as perceived by listening on 300M medium wave. There is no noticeable noise and the sound is rather fuller when compared to the few stations left on medium wave. Cheers, folks!! Thanks especially to Mark, and to everyone who contributed.
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Al |
22nd May 2017, 2:06 pm | #25 |
Dekatron
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,244
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Re: Cct to improve modulation here, please?
Hi Al,
That's excellent news - glad it's working for you. And sorry for the delay in replying - I was away with limited access to the forum. Cheers, Mark |
22nd May 2017, 2:47 pm | #26 |
Dekatron
Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
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Re: Cct to improve modulation here, please?
Thanks again, Mark, hope you had a good weekend.
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Al |