Quote:
Originally Posted by patrick-turner
It seems like I am the only ******* left alive on Planet Earth.
Has everyone died?
I have NOT.
Anyway, I have revised my page about the Wien Bridge oscillator with re-done schematics including many new details.
See http://www.turneraudio.com.au/Wien-b...scillator.html
I will estimate its The Most Boring website page ever devised, unless you'd like to make a half decent signal gene.
Of course, I have used a rotary two wafer make-before-break switch that gives 12 F per decade evenly spaced around a dial at enough convenient F to allow plotting most F reponses of any audio gear tested, unless a high Q resonant filter is used, because the adjustablity of a pot of variable C is not present.
For audio amp checking the unit is quite sufficient. Those wanting infinitely varaible F should consider buying a dual gang reverse direction log pot with value 15k. Lord Noze where you'd obtain one, and one that gave you nicely spread out F around 315 degrees of rotation with 1Hz at the max anti clockwise and 10Hz at max clockwise and 3.2Hz at 1/2 rotation.
With a bigger box and slightly more range switch complexity you might incorporate TWO 3 gang AM radio tuning caps with each gang 40 to 440pF thus giving 132pF to 1,320pF which is fine for 100Hz to 1MHz, with fixed R values. The two ranges 1Hz - 10Hz, 10Hz - 100Hz could use a pot with fixed C and values are not difficult to implement. The variable tuning gang as was made in 1950s is hard to beat for a WB oscillator but to get down to 1Hz with max C = 1.320pF the R needs to be 120Meg ohms, an impractical R value. But where you had 6 x 3gang C then C max = 3960pF, and if your lowest range was 2Hz to 20Hz, then R need only be 20Megohms.
The minimum C = 396pF, and R need only be 200r for 2MHz. For stable operation at such a high F you need low value R and C high enough so stray C in devices does not make F adjustment too critical. The j-fet in NFB network for Vo control should work up to 2MHz.
HeeLLLLOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO? anyone there? Ah, they all musta died.
Think I'll go ride a bike, and even being attacked by magpies is just fine.
Patrick Turner. |
Still here Patrick & look in every day or two as I'm sure others do. Today is my 81st so I will go out & do 50 km on the bike. Takes about 2h50m these daze. Twenty years ago could easily do 70 km in that time. But August was good for 550 km anyway.
No Magpies here, they are all in Western Canada. But we got their relatives, Crows, Ravens, Jays & so on. The Redwing Blackbird chase in their nesting season. Almost collided with a flying Wild Turkey a few years ago. That would be a mess, they are kinda large.
This Summer has been mostly manual labour. several trees to cut up, the firewood pile is getting huge. There will be lots of work for the log splitting machine in October.
My electronics this Summer has been construction of a half-wave dipole for FM. The width is obvious. All made with 1/2 inch copper pipe, so the spacing by the formula is about 3 inches to get 300 ohms.
Works OK part way up the tower so now gotta go all the way. Without falling off. Me, that is.
Cheers to all, John