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 Post subject: Reproduction KNIGHT AM BROADCASTER
PostPosted: May Fri 03, 2019 7:50 pm 
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Joined: Jun Fri 09, 2017 6:17 am
Posts: 4
I want to build a replica of the Knight kit AM Broadcaster. Can anyone tell me how to make the dual winding inductor in this transmitter? I have searched on line and found a small bit of info. That is maybe #35 wire, maybe 155-160 turns and then the other winding maybe 5 to 10% more wire. (.625 dia or 5/8th inch dia cardboard coil form.) Just too many MAYBES here. Also, #35 wire doesn't seem right. Also I have heard there were two types of this coil made. So can anyone tell me actually how to make one that will work? (I have heard you can buy an oscillator coil from AES with two windings that will work, but I'd prefer to make an original type coil. If all else fails, I'll buy an AES oscillator coil.

Another thing, I understand the one coil is the tank coil, but what is the second winding doing? Is it part of the feedback circuit for oscillation and also for bass boost? If so, is this the coil with more or less turns then the output tank inductor?

Any advice or input would be appreciated.

Lee


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 Post subject: Re: Reproduction KNIGHT AM BROADCASTER
PostPosted: May Sat 04, 2019 5:09 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 13880
We used #28 or 30 wound on I'll guess 5/8" to 1" form(varied by builder) for osc coil used in the 6BM8 transmitter. With 100 turns and overlay of 25% formed the osc coil. That transmitter has many similarities to the Knight Broadcaster. Then Norm introduced his 6888 transmitter causing most of us to forget there was a 6BM8 transmitter. It and Knight Broadcaster suffer from poor modulation plus movement of antenna skews frequency. Transformerless design borders on dangerous.

You want a tip? Forget the Knight and build a 6888, has maybe 25-30% part count and produces much better signal.

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Tom


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 Post subject: Re: Reproduction KNIGHT AM BROADCASTER
PostPosted: May Sat 04, 2019 5:28 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 8267
Location: Beautiful Downtown Burbank CA
The coil from way back then.
Image

The 6888 transmitter is a better choice and 100% frequency stable.


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