At about 75' I have a 5kc spread. I was wondering if there was a standard or a characteristic of crystals.

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...

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.

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.

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

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.

4 parts kits mailed out so far this month.

PayPal to alan@antiqueradios.com to contribute.
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a good way to pay forward for all these member contributed free parts kits!

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.

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

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.

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

Oh ok figured it wouldn't be as good as using the xtal oscillator.

I would like to make another one. Are the kits available?

Ed

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

Are these kits available? How would I got about ordering one.

thanks,
ED