It very much illustrate the mismatch. Time values would have been appropriate however.
This is where you fall flat.
That effect is absolutely dependent on the load impedance with respect to the line. Because the load has a frequency dependent impedance, that plot will vary (return pulse magnitude) with frequency. As such, you can see how the system response is load dependent.
The step response test I call for, with the varying load, can characterize the entire system. It's not a difficult test.
Twist is a no-brainer, they can alter that at whim. Color, sometimes the exact color can be a problem. Low smoke zero halogen tray rated UL listed, now that can be a problem....
Do NOT ask for that and flexible and radiation resistant. sigh...I am confident (perhaps erroneously so) that no matter what you require in your wire, I've already been there. (do not burst my bubble.
)Seriously... If you have any questions that you think I might be of help on, do not hesitate to ask me, you are always welcome. I've no desire to steal the work of others.
John
Yes good point, the 50mA is the limit when something breaks but at that point I'm not worrying about THD anymore.
Jan
And, does it matter one jot unless you also take the same approach with the main fuses, and the power company fuse?
And, re - JN -- ditto!
This is where you fall flat.
That effect is absolutely dependent on the load impedance with respect to the line. Because the load has a frequency dependent impedance, that plot will vary (return pulse magnitude) with frequency. As such, you can see how the system response is load dependent.
I am confident (perhaps erroneously so) that no matter what you require in your wire, I've already been there. (do not burst my bubble.
John
JN,
Why make agreeing sound like a disagreement.... We both know that almost all loudspeakers have significant impedance variations and that a simple resistor loading does not show that effect.
As to bursting your bubble. I'll bet you know what a 1/4 wavelength antenna is. Ever put one up 1/2 mile from a 50 KW AM station? Seems to save money some folks want to string wire without conduit! I'll bet you can pick up on those issues. (You know smoking amplifiers, funny noises etc.)
You've missed my point.
For long lines with a non matched frequency dependent load, phase coherence is lost. TDR can show simply the reflection change, but a step function will show much more. It shows the settling time of the system and it's dependence on the load impedance.
Knowing the settling time, you can back into the time shift vs frequency vs load impedance.
For best fidelity at the load, you have to minimize that. Otherwise, temporal coherence is lost.
John
In my workshop, a 10kHz to 200MHz sweep generator (Ro: 50 Ohm) drives a single wire antenna of a varying length with a 1Vrms signal.
At a small fixed distance there are six single wires (0.25m, 0.5m, 1m, 2m, 5.22m, 6.7m) connected in parallel at the input of an analyser which is synchronised to the sweep generator. It’s 1MOhm/20pF input is 50 Ohm terminated. A 50 Ohm broadband diode detector is connected in parallel to it.
The variable in the attached screenshots is the length of the transmitting antenna.
Green numbers show frequency (MHz), white numbers show amplitude (dBV)
Horiz axis is linear 20MHz/div.
First screenshot is the ambient RF noise in my workshop at the basement level.
This noise varies with time and day. It can reach –55dBV on a noisy day.
One floor up and the RF noise goes up by 6 to 9 dB.
I am 5km away (line of sight) from a location with many TV and FM transmitting station antennas and 4km from an air force surveillance radar.
George
Attachments
Apologies -- in amongst the discussion on power fuses I misread your "input" as meaning power in, not signal in.....
Anyone who remembers the very first Outer Limits with the alien sucked in when the DJ turns up the power will recognize the tower directly over my house, within about 100 meters or so. Lots of antennae and different wavelengths to deal with. I think you have it easy George, I'm right in the cone of that antennae, 50kw of radio station and microwave to boot with a bunch of what look like repeaters for radio transmission, a veritable jungle of RF. I don't worry much about cell phone transmission next to my head compared to this RF density!
A friend of mine, who used to build pirate radio transmitters was once asked to look at a problem with someones tv. They were Line of sight to crystal palace transmitter in london which was around 1MW ERP in the analog days and for some reason had the sort of yagi you would use in the boonies. He measured 17V at the TV input.
Use a slow blow fuse for low distortion vs current. But, then protection may not be fast enough to protect sensitive input/hardware. However, fuses are really to prevent fires.
There are faster, low distortion ways.... maybe protection like A-P uses would help you best.
I thought I had blown one of the A-P inputs a month ago when I accidentally put +15vdc on the input... in dc coupled mode. Wouldnt measure distortion. Input must be blown.
After ordering new pair of matched input modules and new protection devices...... going thru thier check list... all seemed OK. I tried it again and it is still working fine. It had just latched up. Now I have a couple rare matched input modules lying around. A-P approach doesnt add distortion and is fast acting.
THx-RNMarsh
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WOW a little front end overload I take it ! Well the signal to noise should have been good. .
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