High Frequency Variable Oscillator - Electronic Circuits Projects Diagrams Free

nos_slived · 25th March 2005, 06:40 PM

Hey, I'm attempting to build a high frequency variable oscillator on a range of 18 MHz to 48 MHz(preferably 48, but 42 would work if 48 is too high) using the 4011 quad NAND. I want it to work on the circuit that I'm posting, and I just need the values for C1, R1(pot), and R2(pot). Id like it if only one of the resistors was a Potentiometer, but if it cant cover the entire range, I would use 2. Can anybody help me out?

Sebi · 25th March 2005, 09:11 PM

I mean, this cct can work up to 10..15MHz only. For higher frequencies build one with BJT or FET.

audioguru · 26th March 2005, 12:05 AM

Sebi,
How did you make a 4011 oscillator go so high? With only 27pF and both resistors 1K with a 12V supply mine barely reached 2MHz.
I have heard that a 4049 high current buffer can reach 6MHz without the input resistor.

Do I dare try using a 74HC00 high-speed Cmos IC for 15MHz or do you think it might melt?

nos_slived · 26th March 2005, 01:49 AM

Anybody have a circuit that could reach that range?

Or even if I could hit 1MHz-5MHz, and multiply by 12. Anybody have any ideas?

All I have to do is stay under $10(preferably $5).

audioguru · 26th March 2005, 02:29 AM

The VCO of a 74HC4046 can go up to 17MHz.
http://www.semiconductors.philips.co...046A_CNV_2.pdf

nos_slived · 26th March 2005, 02:39 AM

I need much MUCH higher.

**Nigel Goodwin** · 26th March 2005, 08:58 AM

Quote:

Originally Posted by nos_slived

I need much MUCH higher.

You should probably be looking at LC or crystal oscillators then!, RC are really only suitable for fairly low frequency use.

Sebi · 26th March 2005, 10:06 AM

This cct can work safely on 10MHz, but need 15V supply. Some good pieces work up to 15MHz. I strongly recommend the MC1648 for wideband tuning.

nos_slived · 26th March 2005, 11:46 PM

Once again, I need much higher. I need to hit a controlled range of variable 18-48MHz.

Russlk · 27th March 2005, 05:07 AM

With C3=250Pf, the frequency is 20 mHz. With C3=10pF, the frequency is 45 mHz. A tuning capacitor from an AM radio would probably have that range.

nos_slived · 27th March 2005, 07:20 AM

Thank you, thank you, THANK YOU SO MUCH!

What are V1 and L1?

nos_slived · 27th March 2005, 07:20 AM

Thank you, thank you, THANK YOU SO MUCH!

OOPS: Double post. Could a MOD please delete this post.

Russlk · 28th March 2005, 02:31 AM

V1 is the 5 volt power supply but supply voltage is not critical. L1 is 7 turns #20 enameled wire on a 1/4 inch form (a standard pencil will do). The turns should be close and don't forget that the leads are part of the inductor, so keep them short.

nos_slived · 28th March 2005, 07:20 AM

OK.

Thanks. I have changed the pic a bit. Would this still work? Also, what is the difference between the 2 outputs? Could Q1 be substituted for any other transistor? Why does L1 say 275nH (what does it mean)? Did I mention, "Thank You"?

Russlk · 28th March 2005, 05:52 PM

I had used this circuit as a crystal checker (substitute the crystal for L1, C3 & C4). Out_2 was a 50 ohm drive to my frequency counter. 275 nano-henries is 275*10^-9 henries. Any transistor with Ft greater than 100 mHz should work, eg: 2N3904.

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25th March 2005, 06:40 PM	#1
nos_slived	High Frequency Variable Oscillator Hey, I'm attempting to build a high frequency variable oscillator on a range of 18 MHz to 48 MHz(preferably 48, but 42 would work if 48 is too high) using the 4011 quad NAND. I want it to work on the circuit that I'm posting, and I just need the values for C1, R1(pot), and R2(pot). Id like it if only one of the resistors was a Potentiometer, but if it cant cover the entire range, I would use 2. Can anybody help me out? Attached Thumbnails __________________ http://www.danasoft.com/sig/slived.jpg http://serve.dynasig.net/818.gif

25th March 2005, 09:11 PM	#2
Sebi	I mean, this cct can work up to 10..15MHz only. For higher frequencies build one with BJT or FET.

26th March 2005, 12:05 AM	#3
audioguru	Sebi, How did you make a 4011 oscillator go so high? With only 27pF and both resistors 1K with a 12V supply mine barely reached 2MHz. I have heard that a 4049 high current buffer can reach 6MHz without the input resistor. Do I dare try using a 74HC00 high-speed Cmos IC for 15MHz or do you think it might melt? __________________ Uncle $crooge

26th March 2005, 01:49 AM	#4
nos_slived	Anybody have a circuit that could reach that range? Or even if I could hit 1MHz-5MHz, and multiply by 12. Anybody have any ideas? All I have to do is stay under $10(preferably $5). __________________ http://www.danasoft.com/sig/slived.jpg http://serve.dynasig.net/818.gif

26th March 2005, 02:29 AM	#5
audioguru	The VCO of a 74HC4046 can go up to 17MHz. http://www.semiconductors.philips.co...046A_CNV_2.pdf __________________ Uncle $crooge

26th March 2005, 02:39 AM	#6
nos_slived	I need much MUCH higher. __________________ http://www.danasoft.com/sig/slived.jpg http://serve.dynasig.net/818.gif

26th March 2005, 10:06 AM	#8
Sebi	This cct can work safely on 10MHz, but need 15V supply. Some good pieces work up to 15MHz. I strongly recommend the MC1648 for wideband tuning. Attached Thumbnails

26th March 2005, 11:46 PM	#9
nos_slived	Once again, I need much higher. I need to hit a controlled range of variable 18-48MHz. __________________ http://www.danasoft.com/sig/slived.jpg http://serve.dynasig.net/818.gif

27th March 2005, 05:07 AM	#10
Russlk	With C3=250Pf, the frequency is 20 mHz. With C3=10pF, the frequency is 45 mHz. A tuning capacitor from an AM radio would probably have that range. Attached Thumbnails __________________ see my website: www.geocities.com/russlk

27th March 2005, 07:20 AM	#11
nos_slived	Thank you, thank you, THANK YOU SO MUCH! What are V1 and L1? __________________ http://www.danasoft.com/sig/slived.jpg http://serve.dynasig.net/818.gif

28th March 2005, 02:31 AM	#13
Russlk	V1 is the 5 volt power supply but supply voltage is not critical. L1 is 7 turns #20 enameled wire on a 1/4 inch form (a standard pencil will do). The turns should be close and don't forget that the leads are part of the inductor, so keep them short. __________________ see my website: www.geocities.com/russlk

28th March 2005, 07:20 AM	#14
nos_slived	OK. Thanks. I have changed the pic a bit. Would this still work? Also, what is the difference between the 2 outputs? Could Q1 be substituted for any other transistor? Why does L1 say 275nH (what does it mean)? Did I mention, "Thank You"? Attached Thumbnails __________________ http://www.danasoft.com/sig/slived.jpg http://serve.dynasig.net/818.gif

28th March 2005, 05:52 PM	#15
Russlk	I had used this circuit as a crystal checker (substitute the crystal for L1, C3 & C4). Out_2 was a 50 ohm drive to my frequency counter. 275 nano-henries is 275*10^-9 henries. Any transistor with Ft greater than 100 mHz should work, eg: 2N3904. __________________ see my website: www.geocities.com/russlk