[Amps] Tube swap

[Vic Rosenthal K2VCO]

The AADE meter cannot measure the stray inductance of a resistor. From 
the instruction manual: "Inductors must have a reasonable Q for their
value and negligible distributed capacitance for their value." A 
resistor has very low Q!

It also has trouble with large tubing coils due to the distributed 
capacitance. And it is not good for toroids on cores where the 
permeability varies with frequency.

Given those limitations, the AADE meter can be very useful.

On 1/29/2014 6:01 PM, William Turner wrote:
> Please keep in mind two things:
>
> 1. The AADE meter measures inductance at a very low frequency. At VHF
> the inductance can be considerably different due to distributed
> capacitance between windings. The best tool is an impedance analyzer
> which applies the actual VHF frequency and costs about $10k. I don't
> have one either. It was that or a house.  :-)
>
> 2.  There is no such thing as "non-inductive". Even a short straight
> piece of wire has inductance. If someone tells you a resistor is
> non-inductive, they are prevaricating.
>
> 73, Bill W6WRT
>
>
> ------------ ORIGINAL MESSAGE ------------
>
> On 1/29/2014 5:31 PM, Bryan Swadener wrote:
>> I measured new Ohmite pn OY470KE (47ohm/2W) resistors at 1.6uH
>> inductance.
>> The instrument used was a new factory-assembled and calibrated
>> "Almost All Digital Electronics" L-C Meter (http://www.aade.com/).
>> According
>> to the manufacturer, it compares closely to several high-end L/C/R
>> instruments.  I verified mine, compared to a few other pieces of HP
>> gear that
>> I trust.
>> Before making any measurements, I first nulled the internal inductance
>> with the terminals shorted, using a 1" length of 14ga wire (about 17nH).
>> A NOS Allen-Bradley 47 ohm/2W carbon composition resistor then
>> measured 20nH, and a 3-1/2 turn 14ga parasitic suppressor inductor
>> (Heathkit SB-220) measured 80nH. The OY "resistor" measured 1.58uH.
>> The datasheet for the Ohmite OX/OY resistors
>> (http://www.ohmite.com/cat/res_ox_oy.pdf) says only:
>>
>> "The OX/OY resistors can often replace carbon composition resistors
>> which can be difficult to source."
>>
>> They make NO claim that they are without inductance.  In fact,
>> nowhere in the datasheet is the word "inductance" or "reactance"
>> used, or inferred.
>> eBay seller "bigsmythe74" always seems to have
>> A-B Carbon Composition resistors available for reasonable prices.
>> I have no connection with him other than as a customer.
>> vy 73,
>> Bryan WA7PRC

-- 
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/