Any experience with negative impedance?

direct linear conversions do not need a log chart axis.

It is the normal sloppiness of audiophiles. It seems that audio is far more art than science, so normal maths do not apply.

--

-T.

TV uses dBmv and references 0 dBmv as one millivolt at 75 ohms. They don't need power in their calculations, they need voltage. Anyone with at least half a mind can convert, as needed. OTOH, cable & antenna installers don't need to convert, and TVFSM are calibrated in dBmv.

Driver starts shift. Switches to "reverse", to get out of the depot, puts a couple of notches on the controller, and crashes the buffers.

"Oh shit, I forgot it's Tuesday!"

--
"For a successful technology, reality must take precedence  
over public relations, for nature cannot be fooled." 
                                       (Richard Feynman)

Source EMF or terminated?

-- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

According to:

The outer rail is at +420V, and the inner rail at -210V.

Stated to have been chosen to avoid circulating currents in the iron tunnel linings.

--
"For a successful technology, reality must take precedence  
over public relations, for nature cannot be fooled." 
                                       (Richard Feynman)

It's really just a logarithmic way of expressing a ratio.

As are nepers.

--
"For a successful technology, reality must take precedence  
over public relations, for nature cannot be fooled." 
                                       (Richard Feynman)

0dBm references 1 milliwatt, nothing more. 1 milliwatt is 1 milliwatt, whether it is dissipated in 50 ohms, 600 ohms,or a megohm.

You only need to quote the impedance if you are referring it to a voltage.

--
"For a successful technology, reality must take precedence  
over public relations, for nature cannot be fooled." 
                                       (Richard Feynman)

I doubt that such motors are PM ?:-} ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     | 
| Analog Innovations, Inc.                         |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| Phoenix, Arizona  85048    Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

The armatures and fields were in series, so the direction of rotation only depended on their relative polarity, not on their absolute polarity.

A problem which recently afflicted an experimantal tram was caused by the motor-control software being identical at both driving ends. The driver notched up for the first time and the two powered bogies strained to go off in opposite directions.

There is a hidden danger in some modern heavy-current D.C. equipment: some contactors have a permanent-magnet blow-out system for quenching the arc. If the contactor is installed backwards or the current flows in reverse for any reason (such as incorrect polarity), the contactor fails to blows out when breaking a heavy current and the arc propagates back into its terminals and wiring. The older, safer, contactors had the frame magnetised by winding a few turns of the load conductor around it, if the current reversed, so did the blow-out field.

--
~ Adrian Tuddenham ~ 
(Remove the ".invalid"s and add ".co.uk" to reply) 
www.poppyrecords.co.uk

I'm quite surprised to hear that.

I can't imagine why the voltage relative to earth should affect the circulating currents, they would only depend on the current changes in the conductor rails.

--
~ Adrian Tuddenham ~ 
(Remove the ".invalid"s and add ".co.uk" to reply) 
www.poppyrecords.co.uk

I know, I was just having a little fun with Fred >:-}

My A/C contactors have a magnetic blow-out. The contactors look great after 18 years. Wish I could say the same for the heat exchanger... it's Aluminum and developing pin-holes :-( ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     | 
| Analog Innovations, Inc.                         |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| Phoenix, Arizona  85048    Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

Probably not, but it makes a good story ;-)

--
"For a successful technology, reality must take precedence  
over public relations, for nature cannot be fooled." 
                                       (Richard Feynman)

Bels (and dB) are specifically defined as logarithmic ways of expressing a ratio of power, not of anything else.

However:

1) As power measurements are more difficult to make than (for instance) voltage, current or sound pressure, it is permissible to use the easier measurements if they are known to be related to power. Thus it is possible to measure two voltages and compare them in "dB" if they were measured sequentially at the same point in the circuit. You are not really comparing the voltages, only the power they are developing. It is also reasonable to use the dB to compare voltages in two different circuits if they have the same impedance. It is not correct to compare two voltages across different or unspecified impedances in dB.

2) Logarithms may be a convenient way of dealing with large ratios in other measurements, such as voltages in different impedance circuits; but, if "dB" is used, the unit must always be correctly suffixed to show that it is not a true dB, only a convenient application of the logarithmic principle.

3) Decibels cannot be used as an absolute unit, but can be used to compare a power measurement (or power derived fom some other more-measureable unit) with a particular reference power (1 milliwatt in 600 ohms, threshold of hearing etc.). Once again an appropriate suffix is needed, to show what reference unit its being used.

--
~ Adrian Tuddenham ~ 
(Remove the ".invalid"s and add ".co.uk" to reply) 
www.poppyrecords.co.uk

it's into a 75 ohm load.

The meters are have an 'in' and an 'out' port so you can have a terminator on the 'out' port or put a receiver there.

--
?? 100% natural 

--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

Across a 75 Ohm terminator.

"Adrian Tuddenham"

** See half way down this page:

Basically, it is a fool's idea.

FYI:

That 10 ohms of resistance can easily become 15 ohms when the speaker is driven hard - cos copper wire increases in resistance when it get hot.

Cable resistance of 2 to even 4 ohms is not an issue with a 15 ohm woofer.

.... Phil

dBu,

ancient

Yep. Also half powers (used in optics and some optical physics measurements).

?-)

ohms.

voltage.

Oops. Yes, you are correct. That is just what i first learned it as.

?-)