Mains interference: Digital TV problems


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The measurement of insertion loss is an implementation of the definition, otherwise it is not insertion loss that is being measured.
You are confused...

...
The intended use is as a design parameter, allowing a loss budget to be completed for a circuit. The technique described does not provide a value which can be used for anything other than comparison to another device, which makes it superfluous. A real insertion loss measurement provides a value that is useful for both the design and the maintenance of equipment.

You claimed 6 dB, roughly 3 dB more than I said. But that clearly is going to cause a measurement which is *lower* than my stated 3.5 dB.
How can you say it is 6 dB if the measurement is going to be slightly greater than 3.5 dB?
You are confused...

So you are claiming that description meant you should use 50 Ohms, even if the device is 135 Ohms and so is the circuit?
Astounding.

That may or may not be 50 Ohms. It is determine by the impedance of the circuit the device is designed to be used in.

I'll grant that *you* probably don't have enough sense to avoid using a 50 Ohm device in a 600 Ohm circuit.
But you are confused!

That is more total confusion on your part.
Of course I am assuming that we are talking about transmission lines. If you mean a piece of wire, that's different. But coax, for example, is a broadband device. It's impedance does not vary over a significant frequency range. It's impedance does not vary with length at *any* frequency.
Your reference to loss tables is another indication of gross confusion on your part. If the characteristic impedance of a cable was a direct indicator of loss, then 75 Ohm cable would necessarily have more loss than 50 Ohm cable. And 600 Ohm cable would be even higher!
Do you actually find that pattern in the loss tables... ;-)

So? It still have the same characteristic impedance.

Do you have a table that shows impedance vs. frequency????

The loss varies by frequency, but the characteristic impedance of the cable is relatively a constant.

Astounding. You are seriously confused about transmission line theory, and given that you can't even understand what defines a coaxial cable, it comes as no surprise.
Cable *loss* increases with length. That is simply the amount of power dissipated per unit of length, and of course it will be twice as much for a cable twice as long. That does not mean the impedance of the cable is different for shorter or longer cables. It just means the losses are parallel.

Yes! Typically the lower the load impedance the higher the output.
Oh, wait... what was that you claimed earlier about maximum power transfer when the impedance is *matched*. How can you relate that to lower impedance causing more power output...
(Not that I'd want to confuse you further, but I am expecting a response to the above that would come from Dilbert's Pointy Haired Boss.)

But you are confusing the impedance of the transmission line cable with the impedance of the load. Two distinct animals, not at all the same...

But that is not an indication that the impedance of the line is different.

But you *don't* know... (apparently anything).

Actually, that is just plain silly.

Oh my. You really are confused. That is purely bullshit on your part.
I don't think there is such a thing as a schematic that suggests exchanging RG59 for RG58...

Read any good book on transmission line theory. Look up things like "stub matching", and "impedance transformation". It will explain what that actually was all about.

You are confused. What has Ohms law got to do with loss related to the characteristic impedance of a transmission line?

No shit, Sherlock! That is because a hybrid can be designed to work with various different circuit impedances; but you *must* measure it at the impedance that it is going to used at, which *must* be the impedance it is designed for (if you want to ensure proper operation).

Exactly. The definition does not specify that we can only have insertion loss at 50 Ohms. That is because we might very well be measuring a 75 Ohm device used in a 75 Ohm circuit.
Your claim that 50 Ohms is a "standard" impedance which must be used is horse pucky.

Okay, you don't. The isolation pads are used to assure voltage measurements are a true indication of the correct power level at a given point, which is done by padding to assure that the impedance is the specified impedance.
Hence if you have a device claimed to be 50 Ohms, it is not valid to connect a signal generator to it and measure the RF voltage across the input, because the voltage will vary with the impedance, which might not actually be 50 Ohms.
If a pad is place between the signal generator and the device, the pad will provide a known impedance. The power level at the device input is determined by the pad, hence a 3 dB pad means there will be half the power measured at the input to the pad. The larger the pad, the more accurate the impedance is guaranteed to be. Typically 3 dB or 6 dB pads are used with most devices. The 10 dB pad specified by the Mil-Std procedure will assure that almost any variation will still result in an accurate reading. In practice, with a 20 dB pad the reading will be accurate (I forget now, but within something like 0.3 dB) even if the output of the pad is either open or a dead short.

So now you admit that the circuit impedance *is* what counts, not some mythical "standard impedance".
I'm sure glad you got over that confusion... ;-)

But I do know that a mismatch will *not* broaden the bandwidth...

Won't work. You are confused.

???? What do you think "tested" means, if not "measured"?

That is exactly my point. It is *not* a "standard impedance", it is the impedance of the system under test that determines the impedances used for test equipment.

Hee hee, I doubt you caught the significance of that...
I see the rest of that article got too deep for you to even attempt a response.
I trimmed the excess. We can assume that points you fail to respond to are stipulated to be as stated. That of course pretty much deletes *everything* you've said so far... :-)
--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska) snipped-for-privacy@apaflo.com
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On Sun, 18 Jun 2006 19:03:34 -0800, snipped-for-privacy@apaflo.com (Floyd L. Davidson) Gave us:

It's flawed logic.
Man has made certain precise toys...
Volt meter to measure volts... Imagine that...
dB meter to measure dB... Imagine that... :-]
Power in... power out... Total number of downstream ports...
Power at each port... An accounting for internal drops...
a little math... VIOLA! Insertion loss!
Doesn't get much simpler, eh!
Instead of thinking about breaking a line to "insert" a device, think of it as being added at the end of a line. One MUST start with the power available at that line end as the reference.
I can't see why he is missing it.
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us:

Nice backpedal.
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