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Heath IG-18  IG-5218
Heath IG-18  IG-5218
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Old 22nd February 2012, 12:00 AM   #51
tvrgeek is offline tvrgeek  United States
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Is it possible to get really low numbers when we are dealing with caps and switches? Would one not want to follow the oscillator with narrow bandpass? How about a more modern VCO/AGC?

Need to dust my old one off. I normally use my PC as it is lower distortion, but twitting knobs has its place too. I also have an old HP 409 because nothing beets a bid dial to zero in on a room resonance.
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Old 22nd February 2012, 12:39 AM   #52
jackinnj is offline jackinnj  United States
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Heath IG-18  IG-5218
HP339 uses switches.

For a lot of reasons the VCO/AGC should be addressed -- I am think that the THATCorp "Analog Engine" might be a neat one-chip solution.
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Old 22nd February 2012, 02:28 AM   #53
richiem is offline richiem  United States
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@tvrgeek --- The Tek SG505 uses switches, as does the KH 4402B, etc. At harmonic product levels below (or well below) -120dBu (not even talking noise), you might also ask if wire and solder affect things... and humidity and barometric pressure -- I am serious. Nothing is above a careful look; but some things just take a LOT of time, and time is precious, so a good whack from the intuition genie is worth a lot more than I used to think.

Williams' famous 10kHz oscillator has the huge advantage of being single-frequency. If you're willing to live with that constraint, many things get easier to control.

Anything following the oscillator stage has to be incredibly low in both distortion and noise; I've seen passive LC bandpass circuits that actually made thing much worse, and some that did actually improve the signal, but that was back in the day before I got interested in really low distortions below 1 part per million, so I can't generalize about using either active or passive bandpasses to improve distortion at really low levels.
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Old 30th April 2012, 09:14 AM   #54
mafalda is offline mafalda  France
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Default Where to buy a 90MB

To buy a lampe have a look here :

Osram / Sylvania, Inc. - 90MB - Optoelectronics & Lighting - Lamps - Allied Electronics

around $1,3/unit
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Old 16th September 2013, 08:48 PM   #55
mrsavage is offline mrsavage  United States
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Heath IG-18  IG-5218
Default Redesign the power supply and main PCB's on the IG-18 and IG-5218

Other PCB designs exist, but what about a new one that includes the latest
op-amps and voltage regulators. I would be interested in a group buy for these
new designs.
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Old 16th September 2013, 10:30 PM   #56
richiem is offline richiem  United States
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See what Steve Lafferty has done with putting the very fine HP339A oscillator into the IG-18/5218: Modifications: Heathkit IG-18 Audio Generator

For performance results, see my build here: http://www.moorepage.net/IG-18-3.html

I think you could easily lay out a PCB from his work, or just use perfboard and wire as he did.
Dick Moore
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