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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Aug Wed 01, 2012 3:57 pm 
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Posts: 9139
Location: Lehighton, PA.
I got mine off of Ebay.

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Larry

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Aug Wed 01, 2012 7:00 pm 
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Joined: Feb Sun 27, 2011 4:23 am
Posts: 543
Hi Rich, I got the MP3 player from Parts Express: http://www.parts-express.com/pe/showdetl.cfm?Partnumber=320-350

Hi Larry, looking good!

-Sam T.


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Aug Thu 02, 2012 6:33 am 
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Location: Omak,WA,usa
Hello Sam,
thanks for the info that would be a cool device to add to my Ge console radio that I'm getting ready to restore :D


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Sep Thu 27, 2012 3:44 am 
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Posts: 543
Built a smaller version, without the mp3 player.

Attachment:
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Attachment:
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DSCN1469.JPG [ 68.63 KiB | Viewed 7151 times ]


This one has a stereo jack for connecting an iPhone, iPod or other music source.
Runs on a 9 volt battery.

Next I plan to build another one with mp3 player, and use a cigar box for an enclosure.
Thanks again to 35Z5!

-Sam T.


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Sep Fri 28, 2012 3:16 pm 
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Ahhh stealth version, could easily hide that one...

Where did you get that little box???


Tom


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Sep Fri 28, 2012 3:59 pm 
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Joined: Feb Sun 27, 2011 4:23 am
Posts: 543
Thanks Tom
I think it was this one: http://www.madvapes.com/3-ml-24mg-19.html

Edit: that one is minus the battery door, try this one instead:
http://www.madvapes.com/30-ml-6mg-18.html

-Sam


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Oct Fri 12, 2012 7:17 pm 
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Joined: Dec Tue 26, 2006 11:46 pm
Posts: 378
Location: Charleston WV
Tom, looks very interesting & I've ordered what I don't have handy to build one. One question and please forgive me if I'm asking something elementary (stoopid)! I've read all the previous posts and remember you or someone posting of smoking the osc. I was also looking at the data sheets for the osc and the 386 chip and read where the osc uses 5V. Your diagram show the osc power coming off the output of the 386 and you mention that using a 9V power source the osc should get approx half or 4.5V. Is this typical of hooking up the power to one of these osc modules? If a lower (ie 5V) source were used, would you hook the 5V directly to pin 14? Thanks - Don


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Oct Fri 12, 2012 7:25 pm 
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Joined: Dec Tue 26, 2006 11:46 pm
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Location: Charleston WV
Never mind! I was having a senior moment! I see now that's the only way it works to get a modulated output. DOH! Again thanks Tom - Don


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Oct Fri 12, 2012 7:53 pm 
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Hi Don, we all have our moments... :lol:

I killed a osc when I tried operation without the DC blocking cap on the antenna output... It was beyond limit, running at close to 12v B+ and the antenna touched ground, dead osc... Using the cap I've run them at over 11v B+(approx 5.5v to osc)without issue but I don't really recommend that much voltage... The osc I've tried have operated at under 2v input and around 9v B+(approx 4.5v to osc) seems to be the sweet spot for the IC combo... At higher voltage the LM386N didn't modulate the osc as cleanly, but that may have been a trait of the batch I was using...


Tom


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Oct Tue 23, 2012 5:52 pm 
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Location: aston, pa, usa
We had kit orders over the summer. Just wondering if anybody is building yet or not? Last one mailed was hergi just before Kutztown.!

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Oct Wed 24, 2012 5:34 pm 
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Location: aston, pa, usa
Heard from hergi he is breadboarding as we speak.

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Oct Sat 27, 2012 6:55 am 
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Location: Texas. USA
I've been thinking of doing a 'portable' one off just a 9V battery but the LED drop for antenna tuning is a problem. However, I found a cute super cheap meter that fits the bill (pun) great: this 99 cent fellah http://www.surplus-electronics-sales.com/index.php?main_page=product_info&cPath=34&products_id=453 They warn there may be minor scratches but I got 3 and all were absolutely pristine with protective plastic still over the face.

It only takes 150mV for full scale so, depending on your unit's final current draw (mine pulls around 13 mA when tuned), the meter across a 6.8 to 10 Ohm resistor in series with the 9V battery works fine and isn't much of a voltage drop. I set mine so 'tuned' was about 2/3 scale and that's only 100 mV.

It's even lighted but that pulls on the order of 30-40 mA so a pushbutton might be a good idea, if you use it.

They're also where I got the cheap $0.75 can OSC and LM386. Hmm, they say only 8 of the 1 MHz OSC left in stock.


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Oct Sat 27, 2012 7:41 am 
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Location: Texas. USA
Well, now I've got a mystery. After futzing with the meter I was going to just listen to it but range is now under 25 feet. That's nothing to do with the meter, in case anyone is wondering. I attributed that to the horrendous noise I always have in this house and it seems worse tonight. Anyway, that's not the mystery. Since it wouldn't reach the opposite end of the house downstairs (transmitter is upstairs) I decided to heck with it and tune my Zenith H845 to the local classical station but as I was looking for it... uh... my AM TRANSMITTER comes in.... ON FM! Why the heck it's coming in around 92.5 MHz I have no idea, but it's there. Not great, mind you, and however it's getting there seems to have pulled AM static along with it but it's marginally listenable, which is more than I can say for at 1 MHz where it's supposed to be. Nothing but static there.

I find it hard to believe a 90'th+ something harmonic is getting out but heterodyning with something?

And it would seem our modulated OSC is FM'ing despite being crystal.

It's not just the Zenith either. My 'transistor' clock radio gets it too and I just tried my cellphone, which is digital of course. It comes in at 91.95 MHz.

The classical station is at 91.7 and if I hadn't been going for it I'd have never noticed this.


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Oct Sun 28, 2012 10:53 pm 
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Flipperhome said: "Why the heck it's coming in around 92.5 MHz I have no idea, but it's there."


Hmmmm........ 92.5MHz???? I can't recall a time when I ever came across harmonics that far out.


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Oct Mon 29, 2012 7:14 am 
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Neither have I, which is why I don't believe it. Nor do I believe my 'too weak to receive on AM' signal is 'overloading' the FM tuner.

On the other hand, the radio gets it around 91.95 :shock:

I haven't had time to delve into this mystery but the OSC is a square wave so maybe something ringing?


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Oct Tue 30, 2012 1:45 am 
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Posts: 9139
Location: Lehighton, PA.
I'm running my 2nd one (gifted the 1st) every night now for three months and I love it! Thanks, Tom, for a great design and all those who helped provide the parts to build.

Attachment:
lm386n kit 2-6.jpg
lm386n kit 2-6.jpg [ 26.33 KiB | Viewed 6803 times ]


Larry

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Nov Wed 21, 2012 9:05 pm 
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Joined: Feb Sun 27, 2011 4:23 am
Posts: 543
Here are a couple photos of my latest transmitter build.
The high voltage area is protected with acrylic.

Attachment:
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Attachment:
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DSCN1507.jpg [ 129.17 KiB | Viewed 6703 times ]


I like the idea of using a meter like in 35Z5's separate thread, might have to try that.

-Sam T.


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Nov Wed 21, 2012 9:27 pm 
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Joined: Sep Wed 22, 2010 1:36 am
Posts: 434
Location: Sliver Springs NV.
OK I am kind of at a loss. I wired up one of these. I have a wall wart that is rated for 12 volts at 300Ma.
Unloaded it put out 18.62 volts. I did not plug in the LM366N or the osc. I connected a 390 ohm res between the 220 mf caps and checked voltage before and after the res. I found no voltage drop. First I thought I had miss wired but I have looked it over four times. The last time I followed point by point through the drawing marking them off as I went.
While I was typing I thought maybe a solder bridge and had a look. None found. I then increased the res to 1.5K and the voltage is still not dropping.
So any hints?

On a different subject.
I am not seeing any of Tom's photos and can not pull up any of his links.
I any one else having troubles?
Thanks
Mel W.


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Nov Wed 21, 2012 11:16 pm 
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melw44 wrote:
OK I am kind of at a loss. I wired up one of these. I have a wall wart that is rated for 12 volts at 300Ma.
Unloaded it put out 18.62 volts. I did not plug in the LM366N or the osc. I connected a 390 ohm res between the 220 mf caps and checked voltage before and after the res. I found no voltage drop. First I thought I had miss wired but I have looked it over four times. The last time I followed point by point through the drawing marking them off as I went.
While I was typing I thought maybe a solder bridge and had a look. None found. I then increased the res to 1.5K and the voltage is still not dropping.
So any hints?

On a different subject.
I am not seeing any of Tom's photos and can not pull up any of his links.
I any one else having troubles?
Thanks
Mel W.


Gee they work for me... Something with your browser???

You won't have any voltage drop unless the IC are installed and drawing current... Sometimes it's best to be conservative and install a resistor greater than the recommended and work your way down...

Try this link...

http://amradio.freeiz.com/transmitter/386txps.jpg


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Nov Wed 21, 2012 11:35 pm 
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Location: Texas. USA
Sounds like a DNS problem as I have no problem with any of the pictures or links in this message thread.

On the 'no current' issue, it must be either a wiring error or defective components because the circuit works.

The voltages on your wallwart are typical for that kind as they're nothing more than a rectified and cap filtered transformer. The "12V" is approximately what it puts out at the specified current draw of 300 mA but it will be higher with less, or no, load to make up for losses when fully loaded. That's why I use a 9V 3 terminal regulator on mine because, while you can make the RC drop work if you get all the math right, a regulator eliminates the issue entirely.

Seems to me that changing the 220 to 390 is not enough to drop the voltage down and it may have popped either, or both, the LM386 and brick OSC.

Edit: I found it. I had given a link to that meter earlier in the thread: http://www.surplus-electronics-sales.com/index.php?main_page=product_info&cPath=34&products_id=453 I said, at the time, 99 cents so, now at $1.29, the price has gone up since then.

My original thought was that with only .15 V needed across the meter it would be suitable for use with a 9V battery, whereas an LED drops a comparatively huge amount of the 9V, but when I went to a DC wallwart the whole issue became moot (and the meter would be a PITA to mount).


Last edited by Flipperhome on Oct Sun 27, 2013 4:22 am, edited 1 time in total.

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