Re: Impedence Matching?? Help!

In article <ekcuu4d4jk12ofu812rhqouq221se65vo3@xxxxxxx>,
flipper <flipper@xxxxxxxx> wrote:

On Tue, 21 Apr 2009 17:47:18 -0500, John Byrns <byrnsj@xxxxxxxxxxxxx>
wrote:

In article <ip2ru4t15fqh698b9rtknjg447f1njpquc@xxxxxxx>,
flipper <flipper@xxxxxxxx> wrote:

On Mon, 20 Apr 2009 17:33:02 +0100, Eeyore
<rabbitsfriendsandrelations@xxxxxxxxxxx> wrote:

flipper wrote:

Eeyore <rabbitsfriendsandrelations@xxxxxxxxxxx> wrote:
flipper wrote:
Eeyore <rabbitsfriendsandrelations@xxxxxxxxxxx> wrote:
flipper wrote:
Eeyore <rabbitsfriendsandrelations@xxxxxxxxxxx> wrote:

Do the sums and see how the s/n ratio degrades with maximum
power
transfer.

I don't need to because I'm not dumb enough to pick a "VOLTAGE
transfer" application as a power transfer example.

The OP's question WAS about a voltage transfer question you idiot,
although he
probably didn't realise it due to disinformation in the audio
press.
It seems you
don't either.

The OP's question is not the one being discussed, you idiot.

It is as far as I'm concerned.

Meaning you're too stupid to read what's written and too dishonest to
leave it in a post.

Why are you so argumentative ? Nothing better to do ? All my answers in
this
thread have
been 100% correct. I simply don't get things that wrong.

Haven't been any of them "100% correct" and I get tired of you
snipping out things just so you can argue falsehoods

The question being discussed was, and still is, the one from Byrns:
"What is an example of an application where one is concerned with
"power transfer"?

Yes, and you replied with the example of a "Passive" phone system as a
case where "power transfer" is important.

I gave multiple examples.

Yes, sorry, besides the "passive" telephone system, you also mentioned
"photocell power generation" about which I haven't a clue and so I have
refrained from commenting on it. You also mentioned, "When you have
little or no choice of source impedance like, for starters, air
impedance and you're building an antenna", an area where you obviously
don't have a clue, but don't let that stop you from making vague
implications.

You said "None that I know of especially since it involves wasting
half the power" and I said an antenna was an example.

To which you go brain dead and ask who the hell mentioned antennas.

I did, because it's "an example of an application where one is
concerned with "power transfer"."

OK, what you haven't yet made clear one way or the other is whether the
antenna example is one that "involves wasting half the power"?

You figure it out.

What I have figured out is that you have realized that you don't have a
clue and have made some erroneous statements on the subject that you are
unwilling to correct and now you are squirming in an effort to save face.

Let me give you a real world example, of an application where one is
concerned with "power transfer" to an antenna, and which is related to
audio and tubes. This example goes back to the days when FM
broadcasting was often a source of High Fidelity music used by
audiophiles. Let's consider an antique FM broadcast system from the
early 1960s with which I am personally familiar, an RCA BTF-10D 10 kW FM
transmitter feeding and RCA BTA-8A antenna through about 800 feet of
51.5 Ohm transmission line with an end to end efficiency 89.3%. Between
the transmission line and the antenna was an adjustable "transformer"
which could be adjusted to cancel any reactive impedance in the antenna
and transform the antenna resistance to 51.5 Ohms to perfectly match the
transmission line preventing standing waves on the transmission line.
At the output of the transmitter was a pair of directional couplers, one
to read the forward power, 10 kW, being sent to the antenna by the
transmitter, and the other to read the reverse power, a few watts under
normal conditions, being reflected back towards the transmitter by the
antenna. The reverse power was nominally zero but could increase
significantly in the case of a transmission line or antenna fault, in
which case it was time to call in the riggers to replace the defective
part, or when the antenna became encrusted with ice, in which case the
heating elements built into the antenna would be turned on to melt the
ice and restore normal operation. The transmitter itself used a common
cathode tetrode output stage with an efficiency of 70% in converting B+
supply to RF power.

In this example the transmitter final amplifier takes 14,286 Watts of B+
power and turns it into 4,286 Watts of heat in final amplifier due to
the inefficiency of the tube amplifier, and 10,000 Watts of RF which is
sent towards the antenna. Due to the 89.3% efficiency of the
transmission line 1,071 Watts out of the original 10,000 Watts entering
the transmission are lost as heat in the transmission line on the way to
the antenna, virtually all of the remaining 8,929 Watts are radiated
into the "ether" by the3 antenna. Under normal conditions the antenna
reflects virtually no power back toward the transmitter due the nearly
perfect match between the antenna and transmission line provided by the
"transformer" mounted below the antenna.

The bottom line is that half of the power is not lost due to impedance
matching the antenna. 4,286 Watts are lost as heat in the transmitter
due to the inefficiency of the tube final amplifier, another 1,071 Watts
are lost as heat in the transmission line on the way to the antenna, for
total losses of 5,357 Watts. Even if we take the hypothetical view that
all of the losses are a result of "impedance matching" the antenna,
5,357 Watts are only 37.5% of the DC input power of 14,286 Watts, not
half as predicted.

--
Regards,

John Byrns

Surf my web pages at, http://fmamradios.com/
.

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