Crystal oscillators... does any exist in 1 MHz sinusoidal output ?

Thread Starter

Externet

Joined Nov 29, 2005
1,823
Hi.
Exploring to make a 1 Watt simple AM voice transmitter on 1 MHz, and never, never seen a canned sinusoidal crystal oscillator. Have you ?

Or, can the square wave be reasonably smoothed with inductors ?

-No, I do not care a bit about U.S. FCC. And have two licenses.-
 

kubeek

Joined Sep 20, 2005
5,772
If think if you measure one end of the crystalconnected to an oscillator you should see a square waveform, and the other end will be more or less sinusoidal.
 

SLK001

Joined Nov 29, 2011
1,548
It is difficult to get a 1 MHz oscillator that isn't eaten up by harmonics. That is why you see the manufacturers just pump the output to contain a TON of harmonics and output a square wave. The reason for this is that the gain of the active device is still very high at harmonics that are way out from 1 MHz. Your best bet would be to either build your own, or filter then amplify the output.
 

AlbertHall

Joined Jun 4, 2014
11,970
It is difficult to get a 1 MHz oscillator that isn't eaten up by harmonics. That is why you see the manufacturers just pump the output to contain a TON of harmonics and output a square wave. The reason for this is that the gain of the active device is still very high at harmonics that are way out from 1 MHz. Your best bet would be to either build your own, or filter then amplify the output.
The ones from the link I posted (post #4) have harmonics at -30dBc
 

ScottWang

Joined Aug 23, 2012
7,186
Or, can the square wave be reasonably smoothed with inductors ?
I had used LC to do that for NE555 before , but the frequency was less than 100Khz, maybe can try it.

As I remembered that the voltage level will be unequal for the positive and negative, so you will need a op amp clamp circuit to shift the voltage level.
 
you will find a 1 Mhz canned xtal osc hard to come by on the surplus market. And if you do it will be close to square wave. Some mafrs
supply a truncated triangular wave which is best input to s smoother BPF. 1. if you want to build a decent AM radio you would be well to look up the PDF of the RETRO 80 radio from Small wonder labs. There is a lot to it. ESP you have to be able to source the modulator Tnsfrmer. 2. if you want to process the output from a high z canned osc. look as go by at the SWL DSW 20+ schematic and use of a high spec Video amp chip to amplify the signal out of the filter. Filter design is up to you. Motorola Appn notes exist. ALT is to go with the scheme used in the Retro 80 and give up on using a canned osc. Again you need to get the xtal for the freq under consideration. The driver chip he used in the retro is still avail from Company Futurlec.com which is based in Australia. Costs a couple of USD I recall. Maybe as little as 1.5 USD.
 
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