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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Sep Wed 07, 2016 5:48 pm 
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At about 75' I have a 5kc spread. I was wondering if there was a standard or a characteristic of crystals.


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Sep Wed 07, 2016 9:50 pm 
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I don't remember exact number and I couldn't hear it(I'm done around 7K), but with generator and scope mine produced audio past 15K...


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Sep Tue 13, 2016 4:21 am 
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Mike Toon wrote:
At about 75' I have a 5kc spread. I was wondering if there was a standard or a characteristic of crystals.

Not really, the crystal simply puts out whatever frequency it's designed for. The bandwidth of the RF is mainly dependent on the bandwidth of the audio and the frequency response of the audio components (eg., LM386 etc.). So, if your audio signal tops out at 20kHz, then your RF signal should have about 20kHz bandwidth, unless the LM386 cuts off below that.

The transmitter antenna will also have some effect, but not likely very much. A characteristic of an antenna that's very short compared to the RF wavelength, is that while it can be tuned to the carrier frequency, its bandwidth will be much narrower than an antenna that is comparable in length to the wavelength.


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Oct Thu 27, 2016 11:19 pm 
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Location: Cleona, PA
While searching for parts, I ran across the following at electronicsurplus.com

M-TRON - MTO-T1-S3 - Crystal oscillator. 1.2288MHz. (38) in stock, $0.99 each.
M-TRON - MTO-T1S3-1.536000MHZ - 1.536000MHZ CRY OSC (1) in stock, $2.25 each.
M-TRON - MCO-T1-S3 982.080KHZ - Crystal oscillator. 982.080KHz. (41) in stock, $2.25 each.

This brand was mentioned before in this thread as working the same as ECS. There is a $14 minimum order from this vendor. I have no connection to the vendor and post this here for reference.

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Oct Fri 28, 2016 12:36 pm 
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Interesting, I've seen 1544Khz but never a 982...

I have some older 1980s Dale osc in 537, 828, 921 & 1500Kc but they won't modulate but maybe 15-20% without distortion...

Tom


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Oct Fri 28, 2016 1:32 pm 
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Poking around, found these:
Jameco: 1MHz, full size $1.95; half size $1.19
Alltronics: 1MHz full or half size your choice, $4.00
1.2288MHz $4.00
1.2615MHz $4.00

Same disclaimer, for reference only.

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Dec Mon 05, 2016 5:19 pm 
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4 parts kits mailed out so far this month.

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Dec Fri 16, 2016 6:16 pm 
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PayPal to alan@antiqueradios.com to contribute.
----------------------------------------------------------
a good way to pay forward for all these member contributed free parts kits!

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Feb Mon 06, 2017 4:53 am 
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Location: Florence, SC 29506
Built my third one last week, had the parts. After 18 hours or so, it quit !! Found a bad oscillator. Voltages checked good, so I installed another one. It has been going for almost a week now, so guess I just got a bad one.

Oh yes, my first transmitter from when we first started with these is still operating. I run it 24/7. That's 4 or 5 years.

Ed

Made this one with extra space for additions.

Attachment:
IMG_0559.JPG
IMG_0559.JPG [ 126.36 KiB | Viewed 2708 times ]

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Feb Sat 18, 2017 11:02 pm 
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I haven't read the whole thread, but did anyone actually add a VFO circuit?
Thanks Men. Very interesting, and good work. Much inspirational.

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Feb Sun 19, 2017 1:18 am 
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john8750 wrote:
I haven't read the whole thread, but did anyone actually add a VFO circuit?
Thanks Men. Very interesting, and good work. Much inspirational.
A VFO ain't gonna happen...

The crystal determines freq, unfortunately very limited choices in the BCB band... Besides 1000Kc there are 1228 & 1544, may possibly get lucky and snag something from ebay... but be warned, I have several older different freq that cannot be modulated...

Tom


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Feb Sun 19, 2017 2:19 am 
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35Z5 wrote:
john8750 wrote:
I haven't read the whole thread, but did anyone actually add a VFO circuit?
Thanks Men. Very interesting, and good work. Much inspirational.
A VFO ain't gonna happen...

The crystal determines freq, unfortunately very limited choices in the BCB band... Besides 1000Kc there are 1228 & 1544, may possibly get lucky and snag something from ebay... but be warned, I have several older different freq that cannot be modulated...

Tom



Thanks Tom. Just a fun thought :wink:

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Feb Mon 20, 2017 6:57 am 
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It could be possible to add a VFO maybe if instead of the xtal oscillator a transistor was used with the RF frequency input to the base using the digital AM band frequency generator a forum member made.

Don't know how well that would work though.


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Feb Mon 20, 2017 7:05 am 
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Tube Radio wrote:
It could be possible to add a VFO maybe if instead of the xtal oscillator a transistor was used with the RF frequency input to the base using the digital AM band frequency generator a forum member made.

Don't know how well that would work though.



I saw an add-on, in tube style.
Do you know of a unit with VFO, tube or IC?
Thanks.

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Feb Mon 20, 2017 4:22 pm 
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Tube Radio wrote:
It could be possible to add a VFO maybe if instead of the xtal oscillator a transistor was used with the RF frequency input to the base using the digital AM band frequency generator a forum member made.

Don't know how well that would work though.


You'd basically have a Vectronics 1290K... Uses a somewhat stable 4049 programmable osc to drive a 2N3904 xistor with audio provided by a LM386... I had one(in fact my first broadcaster back in '00), never was really happy with it... A far more simple LM386 Tx blows it away for audio quality...

Here's a link to partial schematic, however doesn't show the osc circuit...

http://www.geocities.ws/raiu_harrison/m ... 1290k.html


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Feb Tue 21, 2017 1:50 am 
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Oh ok figured it wouldn't be as good as using the xtal oscillator.


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Mar Sat 11, 2017 3:27 am 
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I would like to make another one. Are the kits available?

Ed

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Mar Sat 11, 2017 12:07 pm 
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Ed, just need to wait a few weeks until I'm back from vacation. Thanks for your interest in the member provided parts kits. Bill

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Mar Sat 11, 2017 1:22 pm 
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bill hamre wrote:
Ed, just need to wait a few weeks until I'm back from vacation. Thanks for your interest in the member provided parts kits. Bill



Excellent. Thanks !!

Ed

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Mar Sun 26, 2017 12:09 am 
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Location: Celo NC
Are these kits available? How would I got about ordering one.

thanks,
ED


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