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Andre Jute[_2_] Andre Jute[_2_] is offline
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You won't believe this if I tell you what the fancy calligraphy says, so I'll just tell you it important to decipher the words. http://www.deviantart.com/moreliketh...39?view_mode=2
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On Wednesday, 31 July 2013 18:41:40 UTC+10, Andre Jute wrote:
You won't believe this if I tell you what the fancy calligraphy says, so I'll just tell you it important to decipher the words. http://www.deviantart.com/moreliketh...39?view_mode=2


Ah, Artists, they cannot be logically figured out. If they can be, its because the figure-outerer is probably a philistine, and so is the artist. Art allows ppl to demand huge possible adoration from those with less imagination.
But I digress....

In about 1988, I entered a bike race of 104km, named The Iron Mike, because it had real hills and most clubsmen hated it. But it was a handicap race and club organisers didn't know my form and gave me a long lead time ahead of the scratchies. Well, off I went, two 52km laps, and at 17km from finish it looked certain I'd win, because scratchies or anyone else could not catch me as they were 5 minutes behind me, and getting tired. But at 17km to go, I had to go over the last cattle grid of 6 in the race, and these are done by "bunny hopping" so you are airborne over the grid for maybe 4 metres. The last grid was on a downhill, so the hop is done at 50kph. Well, I jump up, and when I come down, I connect to saddle with arse just slightly hard, but no harder than I'd done hundreds of times before. But the alloy seat stem snapped right off like a carrot, and seat bounces into scrub. So much for crummy Zeus brand components - I'd broken Zeus cranks as well, and they'd bend a bit too.

In about 0.2 seconds I realise there is a razor sharp jagged bit of metal aimed at my arse, and so I could not sit down for the last 17km, so I figured I better quit, because the seat value was more than the kudos of winning, even if I'd done it standing on the pedals for the last 17kms. I searched for and found the saddle, and got a lift to the finish.

Discretion is the better part of valour they say.

The Canberra Cycling Club still runs the Iron Mike. Mike was a godawful tough ******* who rode in ACT in earlier times, maybe 1960s. He'd delight in riding the route of the 'iron mike' twice a week for training, and of course, to get a race named after you, you have to have died because a concrete truck ran over you or something equally grisly, and Mike died like that.

These days I still ride 220km a week, but the cattle grids have all been removed, and the only grids I have to fiddle with now are in vacuum tubes, thank Unkel Fate.
Patrick Turner.
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220km a week! You're a hard man, Patrick.

Andre Jute
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Andre Jute Aug 4
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220km a week! You're a hard man, Patrick.

Andre Jute

I have averaged between 11,000km and 13,000km per year for the last 3 years..

Last week was 240km, including a 70 km ride last Sunday where I got soaked by rain and temperature stayed below 10C. Remarkably, 3 of the bunch of 6 on the day in the Pedal Power "slow" group were shielas, one Glenys in her mid 60s like me, and Carol who might be close to 60 because her partner is older. He turned for home when the strong headwind became filled with buckets of water and bits of ice. Carol then was left alone to deal with me and I could only just stay ahead of her, with Glenys not far behind. C and G have very fine figures, quite beautiful IMHO. The remaining couple were much slower and they sort of kept together. Weather cleared up and we all stopped for MT after 50km, and I had the intelligent company of the 2 ladies to myself at a table in the sun and a bit out of the wind, and not inside the cafe where mostly fat ppl tucked into brunch consisting of utter junk food I would and could not eat. But coffee was OK and my muffin was quite sufficient.
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"patrick-turner" wrote in message
...

[...]

I'm soldering on in retirement and working as I please on gear that is
inherently intersting. I'm currently working on an old wien bridge
oscillator, BWD model 141. It used 4 discrete bjts to get 1Hz to 1Mhz, not
bad, but the square wave was bad, and so I gutted it and am using my own
discrete bjts circuit and 12 switched F per decade - much better than the
old dual gang 15k wire wound Compton potentiometer
which seemed worn and unmatched and which gave F which didn't correspond to
the dial calibrations - typical old junk. Range switches are good, but PSU
and all else needed total remake. I did a similar job to a later BWD 160
which has a function generator chip in it. But output Vo was a very 0.5Vac,
and I put in an amp to lift it, and revised output attenuator, and it now is
a very nice bit of gear.

[...]


"I'm soldering on in retirement...", same for me and I'm happy to say
farewell to the SMD tip and reinstall the old 1/4" nail.
I build a wien bridge osc. in the flower power era, today I find those dual
gang wire wound pots are reliable as the osc. is still working. For the
frequency pot Colvern's are used, not Compton's, but I doubt if that makes a
difference.
Getting the BDW141 sine/square converter back to work properly can't be too
difficult. THD specs for the BWD141 look allright (-60dB), so I wonder why
you gutted it if not for a defective dual gang Compton.

Did you find the documentation for the BDW141?
http://goughlui.com/?p=1343bbbbbbb
http://www.kevinchant.com/uploads/7/..._wave_gen..pdf
Unlike the BDW my DIY osc. has a linear dual gang pot which results in an
"unusual" frequency dial, years later a (salvaged) frequency counter module
was added, based on an ICM7216(D), so I could scrap the DIY
paper-on-aluminium f-dial.

For general tests I use a HP3325A nowadays wich has surprising low THD for a
function generator (-65dB singular H), but for distortion testing the wish
for a (very) low THD osc. remains.

An old Elektor publication describes a wien bridge osc. with 2H at -85dB and
3H at -80dB, but before I start building I'm curious what kind of figures
you obtain with your circuit(s)?

Regards,
Gio Re













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patrick-turner patrick-turner is offline
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Default You won't believe this if I tell you...



Gio mentioned.......

"I'm soldering on in retirement...", same for me and I'm happy to say
farewell to the SMD tip and reinstall the old 1/4" nail.
I build a wien bridge osc. in the flower power era, today I find those dual
gang wire wound pots are reliable as the osc. is still working. For the
frequency pot Colvern's are used, not Compton's, but I doubt if that makes a
difference.

These pots seemed to wear out all too easily. Trying to get GOOD log pots isn't easy. I tried a 20k dual Alps Black log pot but the distribution of F along the dial was really bad, stretched out on one section and bunched up in another.

So I put in a dual gang 12 pos switch with carefully calculated and made up resistors to get F based on multiples of 1, 1.25, 1.6, 2.0, 2.5, 3.2, 3.9, 4.7, 5.6, 6.8, 8.2 10.0. The old oscill went from 1Hz to 1MHz in six ranges but there was trace bounce with switched R - partially because my switch is break before make type. Between F the amp goes beserko and then when resettling there's bounce, with a lamp globe as the NFB govener. So, I pulled out the BWD 141 amp and put in my own discrete opamp with 5 bjts and diff input pair using 2SK363 to get high input Z. Bounce remained, so I gave up on a lamp and have installed an MPF102 which has a negative gate voltage increased as V0 rises. This makes the drain to 0V resistance move between about 2 ohms and 600 ohms to the more NFB is applied if V0 rises. I've used it on another oscillator with an opamp, but that only does 2Hz to 200kHz. The MPF102 should work with this new amp to get 1Hz to 1MHz without any bounce because the R value isn't shocked into changing value and then causing LF oscillations until settlement.

I have a single F oscillator to make 1.0kHz, with tuning cap to get +/- 20Hz. I
used a single tiny globe that is 60r cold and about 200r with 2.5Vac across it. I got 8.3Vrms out with NE5534 with +/- 15.6Vdc rails and THD = 0.004%.

Getting the BDW141 sine/square converter back to work properly can't be too
difficult. THD specs for the BWD141 look allright (-60dB), so I wonder why
you gutted it if not for a defective dual gang Compton.

Pot was fuct, so I replaced is but I didn't like the result. There was no room to install radio tuning gangs which give much less bouncy trace. But vari caps are limited at LF and I want 1Hz.

Did you find the documentation for the BDW141?
http://goughlui.com/?p=1343bbbbbbb
http://www.kevinchant.com/uploads/7/..._wave_gen..pdf

Thanks for the link to BWD141. The schematic there was what I had. I have not removed the schmitt trigger sq.wave amp yet. I want the square wave to make the same 4.5 peak voltage as the sine wave gene. I want LOW output Z from the unit, under 500r max on all ranges, and the attenuator must give the same sine&sq-wave peak voltages on each setting of attenuator. I want the attenuator to give 0dB, -10dB, -20dB and - 30dB, not the -20dB at each setting.
There probably isn't room to install a bjt emitter follower buffer AFTER the attenuator and feeding the output terminal through 47 ohms, 1/8 Watt, with diode protection against stray input.
The 141 seemed to have attrocius DC offset on all outputs, quite intolerable!, so rather than just fix this peice of junk, it better to entirely re-make it. I should end up with a square wave at 1MHz which has its highest F present of about 5MHz, OK for audio where ringing due to square waves needs to be examined.


Unlike the BDW my DIY osc. has a linear dual gang pot which results in an
"unusual" frequency dial, years later a (salvaged) frequency counter module
was added, based on an ICM7216(D), so I could scrap the DIY
paper-on-aluminium f-dial.

One Kikusui Japanese oscillator I modded has a nice radio type dial with vertical pointer on a slide, and a tuning gang. When adjusted right at both ends, the readings along the dial were within 3% and easy to read, and nicely spaced out.


For general tests I use a HP3325A nowadays wich has surprising low THD for a
function generator (-65dB singular H), but for distortion testing the wish
for a (very) low THD osc. remains.

My present low THD 1kHz oscillator makes less than 0.001% at 1Vrms out.
It is the NE5534 oscillator with following active opamp + R&C high slope low pass filter stage.

An old Elektor publication describes a wien bridge osc. with 2H at -85dB and
3H at -80dB, but before I start building I'm curious what kind of figures
you obtain with your circuit(s)?

Good enough figures for me. If you want variable F AND low THD 0.001%, then it gets much more difficult and complex.

But you can make 3 sets of oscillators and following filters, say for 70Hz, 700Hz and 7kHz. The 70Hz is chose because its away from 50Hz and 60Hz mains F, and the harmonics of mains produced by PSU.

Its probably better for a home diyer to make 3 sets of gear than try to have say 2 opamps and switchable R&C values. The fewer switch contacts the better.

One could spend years fiddling around with oscillators, and my time is limited and I have many amp projects to commplete.

I did make a tunable bandpass filter for between 1.4kHz and 11kHz, with Q of 50so its easy to tune to any F in the band using a single pot. It has 3 opamps, a bit complex, but if I want to examine 2,3,4,5,6,7,8,9,10H of 1kHz, then I can easily do it, or I can search for IMD H with say 3kHz + 5kHz. One should find two IMD F, 8kHz, and 2kHz, as sum and difference F. These cannot be H products of either 3kHz or 5kHz.
Usually, if I apply all the necessary zeal required to get THD and noise low and bandwidth wide and Rout low and unconditionally stable then the amp doesn't need much testing, THD will do fine at 1kHz. IMD with standard 4:1 input sig combo, say 1V 70Hz and 0.25V 7kHz will be maybe 3 times THD value at just under clipping with rated load R, and where THD 0.3%.

The high Q filter is online someplace. The BWD schmitt trigger amp is also online if you Google and click 'images' and lots of schematics come up.

In the old Kikusui POS with tubes I fed the sine wave to a pentode amp which has a output R followed by zener diode voltage clamp. Its primitive, but works OK.

Better is my discrete opamp as a schmitt trigger and it makes a passable looking sq.wave at 470kHz. But the slightest C shunt at output soon rounds the corners of waves as higher F are shunted. For best HF from all test gear making test signals you need to have all outputs rated for 50 ohms output resistance.
Patrick Turner.

Regards,
Gio Re
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"patrick-turner" wrote in message
...

[lot of snips]

These pots seemed to wear out all too easily. Trying to get GOOD log pots
isn't easy. I tried a 20k dual Alps Black log pot but the distribution of F
along the dial was really bad, stretched out on one section and bunched up
in another.


-Like I said, not my experience, for the wearing out part that is.
But true for the "unusual" frequency distribution along the dial, but easily
solved by a frequency counter i.s.o. a dial.

I have a single F oscillator to make 1.0kHz, with tuning cap to get +/-
20Hz. I used a single tiny globe that is 60r cold and about 200r with
2.5Vac across it. I got 8.3Vrms out with NE5534 with +/- 15.6Vdc rails and
THD = 0.004%.


-I had a look at your single F osc. A THD of 0.004%/-88dB looks promising.
However, I'd like to keep F variable.

-While going trough my junk stock I found a 3-gang tuning cap. with about
10-575pF per section. Unfortunatly, but usual I guess, the cap's chassis is
common for all three sections, so, with common connected to the NE5534 +
input the cap's chassis must be mounted insulated from ground. I'll see what
teflon or other insulating standoff's can be found in junk stock, then mount
the cap "floating" in a cookie tin.

-Just measured 25pF parasitic capacity between the tuning cap floating in a
(carrots and peas) tin. The parasitic 25pF is in fact parallel to C2, so I
guess I need an identical cap/trimmer parallel to C1 for compensation.

-BTW, just curious, what does happen, if anything at all, if 2 cap sections
in parallel were used for C2 and at the same time R3||R4 is lowered to half
the value of R1||R2? After all, in that case the basic condition
Xc(C2.R3||R4)= Xc(C1.R1||R2) is still met.
I'm asking because the max. capacity of all 3 sections differ slightly. But
half the capacity of section 1 || 2 is almost equal to the capacity of
section 3. So, in that case the cap has better symmetry.

Pot was fuct, so I replaced is but I didn't like the result. There was no
room to install radio tuning gangs which give much less bouncy trace. But
vari caps are limited at LF and I want 1Hz.


-Don't you get stability and/or THD problems at that low frequency caused by
the limited thermal capacity of the lamp?

Thanks for the link to BWD141. The schematic there was what I had. I have
not removed the schmitt trigger sq.wave amp yet.


-When not in use, the sine-to-square converter is an asymmetrical load to
the sine wave generator output. My gut feeling is THD might improve a little
when the converter is disconnected from the sine wave generator (f.e. at
R12).

The 141 seemed to have attrocius DC offset on all outputs, quite
intolerable!, so rather than just fix this peice of junk, it better to
entirely re-make it. I should end up with a square wave at 1MHz which has
its highest F present of about 5MHz, OK for audio where ringing due to
square waves needs to be examined.


-By design the output has a little positive DC offset (a seldom case where
positive is negative but negative would'nt be positive) via RV3 and R54
caused by the bias across R5. Eversince it's such an old generator did you
check C17/C14?.

An old Elektor publication describes a wien bridge osc. with 2H at -85dB
and 3H at -80dB, but before I start building I'm curious what kind of
figures you obtain with your circuit(s)?


Good enough figures for me. If you want variable F AND low THD 0.001%,
then it gets much more difficult and complex.


One could spend years fiddling around with oscillators, and my time is
limited and I have many amp projects to commplete.


-Exactly the reason I have to be satisfied with building either the "Elektor
oscillator" or the NE5534 based one. So, at the moment for me no
subsequent-to-oscillator filter-gear to get another for tubetronics
unrelevant -15dB on top of a more than perfect -85dB.

Regards,
Gio Re


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