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On Sat, 13 Mar 2004 13:31:26 -0800, John Larkin
wrote: I don't know of any really fast Schmitts. An HC14 followed by an AC04 should have fast edges. My favorite thing like this is an OnSemi NL37WZ16 with all three sections in parallel. Powered from +6 or so, it puts 5 volts into 50 ohms in something like 750 ps. The old original RCA AC-series parts were sub-ns - crude and rude, they were - but some ACs are now a little slower to reduce ground bounce. Most of the LVDS-to-TTL LVDS line receivers make damned fine comparators with sub-ns output edges. For screaming edges, there's always the step-recovery diode, or a medium-power gaasfet like the CLY2. Thanks, John. I don't see the need for anything super-fast in this instance (I mean - 3 to4 Mhz for God's sake) but was just curious as to what they use in UHF and beyond... 2morrow I'm going to stick Reg's 17.2Mhz BPF in line and see if that kills the 3rd enough to allow the 5th to thrive. -- The BBC: Licensed at public expense to spread lies. |
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On Sat, 13 Mar 2004 13:31:26 -0800, John Larkin
wrote: I don't know of any really fast Schmitts. An HC14 followed by an AC04 should have fast edges. My favorite thing like this is an OnSemi NL37WZ16 with all three sections in parallel. Powered from +6 or so, it puts 5 volts into 50 ohms in something like 750 ps. The old original RCA AC-series parts were sub-ns - crude and rude, they were - but some ACs are now a little slower to reduce ground bounce. Most of the LVDS-to-TTL LVDS line receivers make damned fine comparators with sub-ns output edges. For screaming edges, there's always the step-recovery diode, or a medium-power gaasfet like the CLY2. Thanks, John. I don't see the need for anything super-fast in this instance (I mean - 3 to4 Mhz for God's sake) but was just curious as to what they use in UHF and beyond... 2morrow I'm going to stick Reg's 17.2Mhz BPF in line and see if that kills the 3rd enough to allow the 5th to thrive. -- The BBC: Licensed at public expense to spread lies. |
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On Sat, 13 Mar 2004 16:51:48 +0000, Paul Burridge wrote:
On 13 Mar 2004 07:33:15 -0800, (Tim Shoppa) wrote: Fifth harmonic frequency multipliers do exist, but it's usually much easier to double and triple your way to the final frequency if possible. (You just discovered this, I think!) Yeah, but trying to get the 5th is hardly asking for the moon... The lack of even harmonics is typical of push-pull stages ... if you are messing around with CMOS gates, you might try using a TTL gate (which pulls low much stronger than it pulls high) or an open collector TTL gate, both with smmallish (100-200 ohm) pull-up resistors for doubling. I've a reasonably fast Schmitt I'm going to stick in there in place of the 74HC04 before I resort to anything fancy (same pin-out). Why not do a x3 followed by a x2 to get 17.2 MHz out of 2.866 MHz? Because I don't have a rock lying about for that fundamental! Hopefully some supreme being here will spot a problem with the traces I've now posted... Just a rough guess, since your calling on supreme beings... That input cap... I take it the input source is a reasonable estimate of your square wave... if the time constant of that input RC net isn't right, it'll be a differentiator, and turn your square wave into pulses coincident with the rising and falling edges. Your scope trace suggested otherwise, but IIRC, at that tin=me you were using the filter at the input to the mult., xo things have changed. It doesn't look like you're biased in Class C. All the mults I've seen are Class C biased with the tuned circuit on the collector. And remember, when you're doing this later for some other purpose, in Class C, the transistors Vceo - reverse breakdown - must be at least twice the supply voltage. -- Best Regards, Mike |
On Sat, 13 Mar 2004 20:35:34 +0000, John Woodgate
wrote: I read in sci.electronics.design that Reg Edwards wrote (in et.com) about 'Extracting the 5th Harmonic', on Sat, 13 Mar 2004: Then along came Oliver Heaviside who turned the World upside down by replacing jw with p. I should probably change my name to Phon .oodgate in his honour. (;-) It came out as Poodgate in my use of the transform ... ;-) |
On Sat, 13 Mar 2004 20:35:34 +0000, John Woodgate
wrote: I read in sci.electronics.design that Reg Edwards wrote (in et.com) about 'Extracting the 5th Harmonic', on Sat, 13 Mar 2004: Then along came Oliver Heaviside who turned the World upside down by replacing jw with p. I should probably change my name to Phon .oodgate in his honour. (;-) It came out as Poodgate in my use of the transform ... ;-) |
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On 13 Mar 2004 09:42:37 -0800, (R.Legg) wrote:
budgie wrote in message . .. On Fri, 12 Mar 2004 15:32:23 +0000, Ian Bell wrote: Paul Burridge wrote: In RF circles, the 'normal' way to do this would be a simple Class C amplifier with a collector load tuned to the fifth harmonic. In calls C, conduction only occurs for a small fraction of a cycle which produces a correspondingly higher proportion of higher harmonics than a square wave. I've been waiting for someone to post this. I would only add "The drive level, and the bais point, will vary the amount of fifth (or whichever) you will see." It's as common as noses in RF, as Ian pointed out. Just look at the average two-way radio prior to frequency synthesisers. Crystal freqs were multiplied this way in transmitter chains and for receive injection, although use of fifth wasn't especially common because you normally had enough design control to use the more efficient *2, *3 or *4. 'Tune for smoke' isn't an option for most new products, which have to be manufactured without hands. Agreed, but read Michael Black's post below. It's about awareness of other techniques which help broaden the outlook, rather than starting with a very narrow view of the solution and trying to make that fit the problem. onya Michael. Better to pick a suitable duty cycle (or more likely a conduction time period in a digital circuit), that has an efficient 5th harmonic component, including delays, at low power levels. http://www.wenzel.com/pdffiles/choose.pdf RL |
On 13 Mar 2004 09:42:37 -0800, (R.Legg) wrote:
budgie wrote in message . .. On Fri, 12 Mar 2004 15:32:23 +0000, Ian Bell wrote: Paul Burridge wrote: In RF circles, the 'normal' way to do this would be a simple Class C amplifier with a collector load tuned to the fifth harmonic. In calls C, conduction only occurs for a small fraction of a cycle which produces a correspondingly higher proportion of higher harmonics than a square wave. I've been waiting for someone to post this. I would only add "The drive level, and the bais point, will vary the amount of fifth (or whichever) you will see." It's as common as noses in RF, as Ian pointed out. Just look at the average two-way radio prior to frequency synthesisers. Crystal freqs were multiplied this way in transmitter chains and for receive injection, although use of fifth wasn't especially common because you normally had enough design control to use the more efficient *2, *3 or *4. 'Tune for smoke' isn't an option for most new products, which have to be manufactured without hands. Agreed, but read Michael Black's post below. It's about awareness of other techniques which help broaden the outlook, rather than starting with a very narrow view of the solution and trying to make that fit the problem. onya Michael. Better to pick a suitable duty cycle (or more likely a conduction time period in a digital circuit), that has an efficient 5th harmonic component, including delays, at low power levels. http://www.wenzel.com/pdffiles/choose.pdf RL |
Another way of saying that:
If your only tool is a hammer, all problems look like nails. Jim - -Agreed, but read Michael Black's post below. It's about awareness of other -techniques which help broaden the outlook, rather than starting with a very -narrow view of the solution and trying to make that fit the problem. Jim Weir, VP Eng. RST Eng. WX6RST A&P, CFI, and other good alphabet soup |
Another way of saying that:
If your only tool is a hammer, all problems look like nails. Jim - -Agreed, but read Michael Black's post below. It's about awareness of other -techniques which help broaden the outlook, rather than starting with a very -narrow view of the solution and trying to make that fit the problem. Jim Weir, VP Eng. RST Eng. WX6RST A&P, CFI, and other good alphabet soup |
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Is there some black magic required to get higher order harmonics out
of an oscillator? I'm only trying to get 17.2Mhz out of a 3.44Mhz source and am thus far ....[snip].... John L. Reinartz, W1QP, published "A Fundamental-Reinforced Harmonic- Generating Circuit" in the July, 1937, issue of QST. I don't have a copy handy, but a followup article "Putting the Harmonic Generator to Work" in the April, 1938, QST contains this statement: "It will be remembered that in the harmonic-generator circuit the crystal oscillator was operated on the crystal frequency only, and that the following tube was used to generate the even and odd harmonics up to the 11th and 12th. For our present purpose, the 8th harmonic is sufficient; that is, 28 Mc. from an 80-meter crystal...." Hope this helps. --Myron. -- Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448 NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol) |
Is there some black magic required to get higher order harmonics out
of an oscillator? I'm only trying to get 17.2Mhz out of a 3.44Mhz source and am thus far ....[snip].... John L. Reinartz, W1QP, published "A Fundamental-Reinforced Harmonic- Generating Circuit" in the July, 1937, issue of QST. I don't have a copy handy, but a followup article "Putting the Harmonic Generator to Work" in the April, 1938, QST contains this statement: "It will be remembered that in the harmonic-generator circuit the crystal oscillator was operated on the crystal frequency only, and that the following tube was used to generate the even and odd harmonics up to the 11th and 12th. For our present purpose, the 8th harmonic is sufficient; that is, 28 Mc. from an 80-meter crystal...." Hope this helps. --Myron. -- Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448 NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol) |
On Sun, 14 Mar 2004 14:30:28 +1000, Tony wrote:
Even worse than that - relying on simple reasoning (no maths), the 5th will be COMPLETELY suppressed when the input's rising and falling edges are spaced so they correspond in time with the SAME point in the 5th harmonic waveform, Nicely put. Something like Fourier analysis can be an equation that you can apply, or a reality you can visualize. When it becomes "simple reasoning" is when you truly understand it. I suppose that if a being were infinitely intelligent, it wouldn't need any math; everything would be obvious. John |
On Sun, 14 Mar 2004 14:30:28 +1000, Tony wrote:
Even worse than that - relying on simple reasoning (no maths), the 5th will be COMPLETELY suppressed when the input's rising and falling edges are spaced so they correspond in time with the SAME point in the 5th harmonic waveform, Nicely put. Something like Fourier analysis can be an equation that you can apply, or a reality you can visualize. When it becomes "simple reasoning" is when you truly understand it. I suppose that if a being were infinitely intelligent, it wouldn't need any math; everything would be obvious. John |
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On Sat, 13 Mar 2004 22:15:43 -0800, John Larkin
wrote: I suppose that if a being were infinitely intelligent, it wouldn't need any math; everything would be obvious. Yeah, but he wouldn't have much of a social life. -- The BBC: Licensed at public expense to spread lies. |
On Sat, 13 Mar 2004 22:15:43 -0800, John Larkin
wrote: I suppose that if a being were infinitely intelligent, it wouldn't need any math; everything would be obvious. Yeah, but he wouldn't have much of a social life. -- The BBC: Licensed at public expense to spread lies. |
On Sat, 13 Mar 2004 20:23:45 -0500, Active8
wrote: Just a rough guess, since your calling on supreme beings... The post is still vacant as yet... :-) That input cap... I take it the input source is a reasonable estimate of your square wave... if the time constant of that input RC net isn't right, it'll be a differentiator, and turn your square wave into pulses coincident with the rising and falling edges. Your scope trace suggested otherwise, but IIRC, at that tin=me you were using the filter at the input to the mult., xo things have changed. There's been no filtering (other than the selective properties of the tank circuits) whatsoever employed thus far. It doesn't look like you're biased in Class C. All the mults I've seen are Class C biased with the tuned circuit on the collector. And remember, when you're doing this later for some other purpose, in Class C, the transistors Vceo - reverse breakdown - must be at least twice the supply voltage. Yup, perfectly correct. I must admit that going the class C route with the tank tuned to the required harmonic was the way I was 'brought up' as it were. Class C typically generates lots of harmonics as you obviously know. This multiplier seems to be operating in class A, which I admit is odd given its high linearity. But I didn't design the multiplying stage you see here, but the guy who did is an RF expert so I don't argue. :-) But you've just given me an idea: maybe I should increase the value of the 82 ohm base-ground resistor to increase drive signal level and tip the stage into class C. Worth a try? -- The BBC: Licensed at public expense to spread lies. |
On Sat, 13 Mar 2004 20:23:45 -0500, Active8
wrote: Just a rough guess, since your calling on supreme beings... The post is still vacant as yet... :-) That input cap... I take it the input source is a reasonable estimate of your square wave... if the time constant of that input RC net isn't right, it'll be a differentiator, and turn your square wave into pulses coincident with the rising and falling edges. Your scope trace suggested otherwise, but IIRC, at that tin=me you were using the filter at the input to the mult., xo things have changed. There's been no filtering (other than the selective properties of the tank circuits) whatsoever employed thus far. It doesn't look like you're biased in Class C. All the mults I've seen are Class C biased with the tuned circuit on the collector. And remember, when you're doing this later for some other purpose, in Class C, the transistors Vceo - reverse breakdown - must be at least twice the supply voltage. Yup, perfectly correct. I must admit that going the class C route with the tank tuned to the required harmonic was the way I was 'brought up' as it were. Class C typically generates lots of harmonics as you obviously know. This multiplier seems to be operating in class A, which I admit is odd given its high linearity. But I didn't design the multiplying stage you see here, but the guy who did is an RF expert so I don't argue. :-) But you've just given me an idea: maybe I should increase the value of the 82 ohm base-ground resistor to increase drive signal level and tip the stage into class C. Worth a try? -- The BBC: Licensed at public expense to spread lies. |
Paul Burridge wrote in message . ..
Hi all, Is there some black magic required to get higher order harmonics out of an oscillator? I'm only trying to get 17.2Mhz out of a 3.44Mhz source and am thus far failing spectacularly. I've tried everything I can think of so far to no avail. C2's small size (3.3pF)is attenuating any 5th harmonic current by 6db into Q2's base biasing network, in both posted versions. Biasing the first stage as classC in the second revision is a pretty drastic change from the previous class A revision (100mW). Don't you believe in tiny steps? By the way, when you post a waveform where traces are only identified by node numbers, when the schematic provided is an image only, there's no way we can know where the traces originate, unless you tell us. RL |
Paul Burridge wrote in message . ..
Hi all, Is there some black magic required to get higher order harmonics out of an oscillator? I'm only trying to get 17.2Mhz out of a 3.44Mhz source and am thus far failing spectacularly. I've tried everything I can think of so far to no avail. C2's small size (3.3pF)is attenuating any 5th harmonic current by 6db into Q2's base biasing network, in both posted versions. Biasing the first stage as classC in the second revision is a pretty drastic change from the previous class A revision (100mW). Don't you believe in tiny steps? By the way, when you post a waveform where traces are only identified by node numbers, when the schematic provided is an image only, there's no way we can know where the traces originate, unless you tell us. RL |
On Sat, 13 Mar 2004 11:50:12 +0000, Paul Burridge
posted this: I have at least one suggestion, but I need to know whether to send an LTspice netlist or a gif. Send 'em both! I'm still working on an LTspice version of a varactor multiplier using the base-emitter junction of a class C amp as the varactor. Basically using an "idler" tank or tanks to augment the fifth harmonic. The other idea is to make a doubler and a trippler fed from the fundamental and then feed them into a mixer to get the fifth. If the doubler and trippler are active (class C) stages, you should get as many db out at the higher frequency as you put in at the fundamental. The mixer can have gain too. Three transistors, three tuned circuits, and Bob's yer uncle. Jim |
On Sat, 13 Mar 2004 11:50:12 +0000, Paul Burridge
posted this: I have at least one suggestion, but I need to know whether to send an LTspice netlist or a gif. Send 'em both! I'm still working on an LTspice version of a varactor multiplier using the base-emitter junction of a class C amp as the varactor. Basically using an "idler" tank or tanks to augment the fifth harmonic. The other idea is to make a doubler and a trippler fed from the fundamental and then feed them into a mixer to get the fifth. If the doubler and trippler are active (class C) stages, you should get as many db out at the higher frequency as you put in at the fundamental. The mixer can have gain too. Three transistors, three tuned circuits, and Bob's yer uncle. Jim |
On Sun, 14 Mar 2004 19:51:50 GMT, James Meyer
wrote: On Sat, 13 Mar 2004 11:50:12 +0000, Paul Burridge posted this: I have at least one suggestion, but I need to know whether to send an LTspice netlist or a gif. Send 'em both! I'm still working on an LTspice version of a varactor multiplier using the base-emitter junction of a class C amp as the varactor. Basically using an "idler" tank or tanks to augment the fifth harmonic. The other idea is to make a doubler and a trippler fed from the fundamental and then feed them into a mixer to get the fifth. If the doubler and trippler are active (class C) stages, you should get as many db out at the higher frequency as you put in at the fundamental. The mixer can have gain too. Three transistors, three tuned circuits, and Bob's yer uncle. Jim Why not just bandpass filter the 5th from the square wave? Too simple? John |
On Sun, 14 Mar 2004 19:51:50 GMT, James Meyer
wrote: On Sat, 13 Mar 2004 11:50:12 +0000, Paul Burridge posted this: I have at least one suggestion, but I need to know whether to send an LTspice netlist or a gif. Send 'em both! I'm still working on an LTspice version of a varactor multiplier using the base-emitter junction of a class C amp as the varactor. Basically using an "idler" tank or tanks to augment the fifth harmonic. The other idea is to make a doubler and a trippler fed from the fundamental and then feed them into a mixer to get the fifth. If the doubler and trippler are active (class C) stages, you should get as many db out at the higher frequency as you put in at the fundamental. The mixer can have gain too. Three transistors, three tuned circuits, and Bob's yer uncle. Jim Why not just bandpass filter the 5th from the square wave? Too simple? John |
On Sun, 14 Mar 2004 13:14:40 +0000, Paul Burridge wrote:
On Sat, 13 Mar 2004 20:23:45 -0500, Active8 wrote: Just a rough guess, since your calling on supreme beings... The post is still vacant as yet... :-) That input cap... I take it the input source is a reasonable estimate of your square wave... if the time constant of that input RC net isn't right, it'll be a differentiator, and turn your square wave into pulses coincident with the rising and falling edges. Your scope trace suggested otherwise, but IIRC, at that tin=me you were using the filter at the input to the mult., xo things have changed. There's been no filtering (other than the selective properties of the tank circuits) whatsoever employed thus far. It doesn't look like you're biased in Class C. All the mults I've seen are Class C biased with the tuned circuit on the collector. And remember, when you're doing this later for some other purpose, in Class C, the transistors Vceo - reverse breakdown - must be at least twice the supply voltage. Yup, perfectly correct. I must admit that going the class C route with the tank tuned to the required harmonic was the way I was 'brought up' as it were. Class C typically generates lots of harmonics as you obviously know. This multiplier seems to be operating in class A, which I admit is odd given its high linearity. But I didn't design the multiplying stage you see here, but the guy who did is an RF expert so I don't argue. :-) But you've just given me an idea: maybe I should increase the value of the 82 ohm base-ground resistor to increase drive signal level and tip the stage into class C. Worth a try? Nah. With a *sine* input, you'd bias it so it only conducts for less than 180 degrees of the fundamental's cycle - keep the trans *out* of conduction for the most part. Now that I think of it, yer using a square wave and should have the stinkin' harmonic already, duh. What was I thinkin'? I still wonder what that input cap is doing to the edges. The trace you posted indicates it *might* be ok if nothing changed. Just for grins, get rid of that input cap and do whatever with the bias to allow you to DC couple the multiplier. That's pretty class C'ish assuming a 0 - 5V square wave. Don't fry your b-e junction. Something's wiping out your 5th, so lets get that input RC outta there. -- Best Regards, Mike |
On Sun, 14 Mar 2004 13:14:40 +0000, Paul Burridge wrote:
On Sat, 13 Mar 2004 20:23:45 -0500, Active8 wrote: Just a rough guess, since your calling on supreme beings... The post is still vacant as yet... :-) That input cap... I take it the input source is a reasonable estimate of your square wave... if the time constant of that input RC net isn't right, it'll be a differentiator, and turn your square wave into pulses coincident with the rising and falling edges. Your scope trace suggested otherwise, but IIRC, at that tin=me you were using the filter at the input to the mult., xo things have changed. There's been no filtering (other than the selective properties of the tank circuits) whatsoever employed thus far. It doesn't look like you're biased in Class C. All the mults I've seen are Class C biased with the tuned circuit on the collector. And remember, when you're doing this later for some other purpose, in Class C, the transistors Vceo - reverse breakdown - must be at least twice the supply voltage. Yup, perfectly correct. I must admit that going the class C route with the tank tuned to the required harmonic was the way I was 'brought up' as it were. Class C typically generates lots of harmonics as you obviously know. This multiplier seems to be operating in class A, which I admit is odd given its high linearity. But I didn't design the multiplying stage you see here, but the guy who did is an RF expert so I don't argue. :-) But you've just given me an idea: maybe I should increase the value of the 82 ohm base-ground resistor to increase drive signal level and tip the stage into class C. Worth a try? Nah. With a *sine* input, you'd bias it so it only conducts for less than 180 degrees of the fundamental's cycle - keep the trans *out* of conduction for the most part. Now that I think of it, yer using a square wave and should have the stinkin' harmonic already, duh. What was I thinkin'? I still wonder what that input cap is doing to the edges. The trace you posted indicates it *might* be ok if nothing changed. Just for grins, get rid of that input cap and do whatever with the bias to allow you to DC couple the multiplier. That's pretty class C'ish assuming a 0 - 5V square wave. Don't fry your b-e junction. Something's wiping out your 5th, so lets get that input RC outta there. -- Best Regards, Mike |
On Sun, 14 Mar 2004 19:51:50 GMT, James Meyer
wrote: On Sat, 13 Mar 2004 11:50:12 +0000, Paul Burridge posted this: I have at least one suggestion, but I need to know whether to send an LTspice netlist or a gif. Send 'em both! I'm still working on an LTspice version of a varactor multiplier using the base-emitter junction of a class C amp as the varactor. Basically using an "idler" tank or tanks to augment the fifth harmonic. The other idea is to make a doubler and a trippler fed from the fundamental and then feed them into a mixer to get the fifth. If the doubler and trippler are active (class C) stages, you should get as many db out at the higher frequency as you put in at the fundamental. The mixer can have gain too. Three transistors, three tuned circuits, and Bob's yer uncle. Jim, please remember the fundamental has to be in the order of ~3.5Mhz. -- The BBC: Licensed at public expense to spread lies. |
On Sun, 14 Mar 2004 19:51:50 GMT, James Meyer
wrote: On Sat, 13 Mar 2004 11:50:12 +0000, Paul Burridge posted this: I have at least one suggestion, but I need to know whether to send an LTspice netlist or a gif. Send 'em both! I'm still working on an LTspice version of a varactor multiplier using the base-emitter junction of a class C amp as the varactor. Basically using an "idler" tank or tanks to augment the fifth harmonic. The other idea is to make a doubler and a trippler fed from the fundamental and then feed them into a mixer to get the fifth. If the doubler and trippler are active (class C) stages, you should get as many db out at the higher frequency as you put in at the fundamental. The mixer can have gain too. Three transistors, three tuned circuits, and Bob's yer uncle. Jim, please remember the fundamental has to be in the order of ~3.5Mhz. -- The BBC: Licensed at public expense to spread lies. |
On Sun, 14 Mar 2004 12:04:18 -0800, John Larkin
wrote: Why not just bandpass filter the 5th from the square wave? Too simple? I suggested this a while ago, but no one seemed very keen on that solution for some reason. Pity, as it does seem to Spice very well. A 5/6V TTL level square wave winds up as around .5 of a volt of 5th harmonic, post-filtering. Not bad! -- The BBC: Licensed at public expense to spread lies. |
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