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 Post subject: Bluetooth, AM Transmitter
PostPosted: Aug Fri 06, 2021 5:20 pm 
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Joined: Mar Thu 02, 2017 1:37 am
Posts: 772
Location: Cedar Rapids, Iowa
I have a difficult time listening to ads and DJ's babbling on about crap that I don't care about, so I decided to add Bluetooth to the Pioneer SX-203 that I use in the garage. I designed and etched a circuit board, built it up, then printed a case for it on the 3D printer.
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It works well and I know I'm going to enjoy it, but what I'd really like to do is build a low power AM transmitter that can be modulated with a Bluetooth module. That way I can play my music on any of my old radios without adding a Bluetooth module to each. I did build a transmitter and it worked, but was very noisy, and I'm not smart enough with that stuff to figure out why. Can someone point me to a relatively simple circuit that I could tinker with?

Thanks,
Rich

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My name is not Craig...look closely. cr = Cedar Rapids, ia - Iowa, geek = geek


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 Post subject: Re: Bluetooth, AM Transmitter
PostPosted: Aug Fri 06, 2021 6:18 pm 
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Joined: Mar Thu 04, 2021 2:18 am
Posts: 511
Location: New Hampshire
Hey Rich,

Nice job on the Bluetooth module, I have tons of cheap Chinese Bluetooth boards that run off 3.7v. They are fun to play around with.
Funny you mention an AM transmitter I was looking into building one myself.

There was a thread a while back in the homebrew section about a Transmitter like this one, https://www.ebay.com/itm/313150374853?h ... SwChpfEX9E

You might get more responses if this thread was in the homebrew section.


Henry


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 Post subject: Re: Bluetooth, AM Transmitter
PostPosted: Aug Fri 06, 2021 8:50 pm 
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Joined: Mar Thu 02, 2017 1:37 am
Posts: 772
Location: Cedar Rapids, Iowa
Thanks Henry! That transmitter you linked looks like it is probably this circuit, with a choice of 3 crystals:

https://scitoys.com/transmitter.html

I tinkered with that and never got satisfactory results. I ordered the kit from Sci-Toys but I'm thinking that the transformer they sent isn't well suited to this purpose.

Where do you get your Bluetooth modules? I got mine from Amazon and they run on 5v.

I was uncertain where to put this thread...homebrew seems like a reasonable suggestion. I assume a mod has to make such moves...can someone help me out?

Thanks,
Rich

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 Post subject: Re: Bluetooth, AM Transmitter
PostPosted: Aug Fri 06, 2021 10:18 pm 
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Joined: Mar Thu 04, 2021 2:18 am
Posts: 511
Location: New Hampshire
criageek wrote:
Thanks Henry! That transmitter you linked looks like it is probably this circuit, with a choice of 3 crystals:

https://scitoys.com/transmitter.html

I tinkered with that and never got satisfactory results. I ordered the kit from Sci-Toys but I'm thinking that the transformer they sent isn't well suited to this purpose.

Where do you get your Bluetooth modules? I got mine from Amazon and they run on 5v.

I was uncertain where to put this thread...homebrew seems like a reasonable suggestion. I assume a mod has to make such moves...can someone help me out?

Thanks,
Rich



Looks like Dave took care of moving it.

One thing I have noticed about the sci-toys websites projects is that there kinda optimistic about their designs. Once I attempted to build a crystal set from them and there was no option for a ground or antenna and were talking a coil, diode, and headphones, simple...

I get my boards from eBay and they look like this- https://www.ebay.com/itm/264403541721?_ ... Ui3SFIwsLG

Once I stuck one in a cheap low-value Hong Kong Transistor radio and used the original VC control as a switch. So I can use it without opening up the case. Looks neat.


I am interested to see what you find out.


Henry


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 Post subject: Re: Bluetooth, AM Transmitter
PostPosted: Aug Fri 06, 2021 10:42 pm 
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Joined: Jan Sat 25, 2020 5:23 am
Posts: 697
Location: Colorado Springs, CO 80917
Here's the homebrew TX thread. Uses fixed frequency oscillator modules driven by an LM386 as the modulator. I have a small supply of oscillators for several different frequencies if you decide to go that route.


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 Post subject: Re: Bluetooth, AM Transmitter
PostPosted: Aug Sat 07, 2021 1:49 am 
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Joined: Mar Thu 02, 2017 1:37 am
Posts: 772
Location: Cedar Rapids, Iowa
Thanks hwhall - did you forget to post the link?

Rich

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 Post subject: Re: Bluetooth, AM Transmitter
PostPosted: Aug Sat 07, 2021 1:56 am 
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Joined: Jan Sat 25, 2020 5:23 am
Posts: 697
Location: Colorado Springs, CO 80917
Looks like I did forget the link!

viewtopic.php?f=12&t=193042


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 Post subject: Re: Bluetooth, AM Transmitter
PostPosted: Aug Sat 07, 2021 2:10 am 
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Joined: Mar Thu 02, 2017 1:37 am
Posts: 772
Location: Cedar Rapids, Iowa
Thanks hwhall!

Rich

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