I wonder if the 260 voltmeter circuit could be bootstrapped by lifting the 100M resistor from ground, adding another resistor to ground, and adding a cap from the junction to the636A cathode?
John KK6IL
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On 9/23/2022 5:49 AM, Mikek wrote:
The Boonton 260A manual? has a section on 'Sources of Error' starting on Page 12.
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?I'm surprised that the the tube loading is 90M¦¸ at 50kHz but goes down from there until it is only 60k¦¸ at 50MHz.
? I'm sure with modern electronic components and bootstraping, there is a much better circuit than the 535A tube voltmeter used in the 260A.
?Looking at the 4342A manual they say that the correction factor at 1MHz using the 513A Q standard is 1.04, that tells me that even their voltmeter input resistance is 9,300,000¦¸
?This is back to about the same 14% error measuring a 1400Q coil at 800kHz, i mentioned before.
? Feel free to check my math and logic, my 513A Q standard is 253uh, indicated Q of 235 @1MHz. (effective Q of 251 with 7.9pf distributed capacitance)
?I'm here to learn, I've had a thing for Q and Q measuring for over 30 years, it fascinates me.
??????????????????????????????????? Thank, Mikek
John Kolb