On Fri, 12 Mar 2004 13:56:10 +0000, Paul Burridge
posted this:

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.

Is this a simulated circuit or a "real" one built with "real"
components?

I have at least one suggestion, but I need to know whether to send an
LTspice netlist or a gif.

Jim

Firstly, thanks to everyone who's responded to this question. I've had
plenty of valuable leads to follow up on, for which I am as ever very
grateful.


On Sat, 13 Mar 2004 00:16:28 GMT, James Meyer
wrote:

Is this a simulated circuit or a "real" one built with "real"
components?

It *is* actually a real one in this instance! Although I've simulated
it as well, of course, but that hasn't provided any clues as to what
might be causing the problem with the actual circuit.

I have at least one suggestion, but I need to know whether to send an
LTspice netlist or a gif.

Send 'em both!
--

The BBC: Licensed at public expense to spread lies.

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 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.

On Sun, 14 Mar 2004 12:04:18 -0800, John Larkin
posted this:

On Sun, 14 Mar 2004 19:51:50 GMT, James Meyer
wrote:

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

Because a square wave has to have a particular on to off ratio to get
enough fifth. Because a square wave needs those nasty logic gates. Because
three transistors are simpler.

Jim

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.

On Sun, 14 Mar 2004 12:04:18 -0800, John Larkin
posted this:

On Sun, 14 Mar 2004 19:51:50 GMT, James Meyer
wrote:

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

Because a square wave has to have a particular on to off ratio to get
enough fifth. Because a square wave needs those nasty logic gates. Because
three transistors are simpler.

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, 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 21:27:19 +0000, Paul Burridge
posted this:

On Sun, 14 Mar 2004 19:51:50 GMT, James Meyer
wrote:

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.

3.5 MHz... 3.5 GHz 3.5 uHz... makes no difference. The laws of physics
scale nicely for most electronic circuits. Although some ICs are getting
features small enough that the electrons have to line up single file. 8-)

Jim