Użytkownik "Ian" napisał w wiadomości
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"Szczepan Bialek" wrote in message
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Hello Ian,
So the earth is necessary in your radio for the static reasons.
In my also:
From: http://en.wikipedia.org/wiki/Warsaw_radio_tower
It seems to me that the same reasons were in Marconi times.
So I repeat my question:
""The necessity or utility of the earth connection has been sometimes
questioned, but in my opinion no practical system of wireless telegraphy
exists
where the instruments are not connected to earth."(Marconi in 1909).
It is still true?
S*
Hello again Szczepan.
The "static to earth" in my HF aerial is merely to get the static to
bypass my receiver. The earth connection is not necessary in order to
receive signals.
Gordon Bussey, in his book "Marconi's Atlantic Leap", discusses aerials
used by Marconi at Poldhu and St John's. He suspects they could well have
been capacitive or inductive (page 68). His book is published by Marconi
Communications.
I'd certainly prefer to use resonant aerials rather than have a mis-match
into a capacitive or inductive aerial. Sometimes the option to use a
resonant aerial is not available for me - such as on 160m.
I have a recollection that Marconi didn't (or couldn't) determine the
wavelength / frequency he was using. This makes it difficult for us to
accurately determine the match or mis-match of his aerials and radios. I
also recall debate in the 1970s as to whether the three dots really had
been received or had been imagined. There was conjecture that the aerials
and frequency used probably used would not propagate across the Atlantic
successfully.
Look at Baird. He demonstrated successful transmissions of moving pictures
via radio. It worked (and I believe it offered colour and 3D) but it soon
became obsolete due to the superior EMI system. Similarly, Marconi
demonstrated the practical use of wireless by keying a spark transmitter.
These days we no longer use spark (and we do a lot more with a radio
signal then key it on and off).
It also has to be remembered that Marconi brought a lot of existing
technology together to form wireless / radio. For example, according to
Wikipedia induction coils date back to Faraday and Ruhmkorff.
So, no, an earth is not necessary to transmit and receive radio signals.
Was Marconi wrong? Let's say that he could (and probably would) have done
better if he understood radio as we understand it to-day.
Kindest regards, Ian.
Hello Ian,
See the topic "Electron gun".
Each antenna liberate EM waves, heat and electrons.
At the end of the mast the voltage is dobled and the "field emmision" works.
The heat is no problem but the escaping of electrons is a problem.
Tesla discovered that the one end of the dipole must be earthed to have the
strong waves.
That should be obvious for you.
"The earth connection is not necessary in order to receive signals."
It is necessery to transmit and to receive.
You have it: "The "static to earth" in my HF aerial is merely to get the
static to bypass
my receiver".
The liberating of electrons by a transmitter and absorbing by a receiver is
a by products of antennas.
The "earth connection" is a remedy.
Best Regards,
S*