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 CW notch filter 
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Post CW notch filter
Hi there purveyors of wisdom!

My old 747 has got sicker and sicker and has sadly been boxed up and put away to be canabalised at some point, and I've got a new (to me) FT 840

the CW notch filter is not fitted and naturally Yaesu dont make them any more and they cost a fortune on eBay

going old school, I've seen external audio filters that go in the audio output ..... Timewaves and the like. and other much simpler home brew solutions.

are these really going to do a similar job?

thanks!

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Sun Jan 31, 2021 1:12 pm
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 CW notch filter 
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Post Re: CW notch filter
MI0OIM wrote:
Hi there purveyors of wisdom!

My old 747 has got sicker and sicker and has sadly been boxed up and put away to be canabalised at some point, and I've got a new (to me) FT 840

the CW notch filter is not fitted and naturally Yaesu dont make them any more and they cost a fortune on eBay

going old school, I've seen external audio filters that go in the audio output ..... Timewaves and the like. and other much simpler home brew solutions.

are these really going to do a similar job?

thanks!

Notch filters were always inserted within the audio line stages of a transceiver, if in built usually in the lower level pre volume control audio stages.
External ones just do it at the audio output point, but work on exactly the same sweepable narrow bandwidth audio notch principal.
As you say there are many homebrew versions kicking around, I have built a few over the years for either radio use, or as a feedback notch filter for electro acoustic guitars.
The only difference being the frequency range, Q, and where in the audio spectrum they are centred upon.
Most simple notch filters are narrow bandwidth "inverted" sweepable "peak" filters, an example of a sweepable narrow bandwith "peak" filter being the Wah pedal of electric guitar fame.

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Been there and got the T shirt, sadly like the T shirt the memory of it has long since faded, gone rather tatty, and finally been consigned to the bin!


Sun Jan 31, 2021 2:02 pm
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 CW notch filter 
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Keep your eyes open for a Datong FL1, FL2 or FL3

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Sun Jan 31, 2021 4:20 pm
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 CW notch filter 
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great stuff, thanks.

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Sun Jan 31, 2021 5:50 pm
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 CW notch filter 
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Post Re: CW notch filter
have a look here, check out the SCAF filter, it may sute your needs,
https://www.phoenixkitsonline.co.uk/
73 John M0CDL Fists.


Mon Feb 08, 2021 4:23 pm
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