Well, I think that solves the problem. Makes sense, and Droitwich is
certainly a 'very high power transmitter'. But a lot has been mentioned over
the last few days about the technology of high power transmitters. Techniques,
I for one, knew nothing about. Would be very interesting if those in the know
could put together some sort of treatise on these. Or an idea for a lecture at
a future LF Meeting. Just a hint ;-)
I went to take a look at Droitwich a few days ago and noticed something a bit
odd. The Tee top section is not symmetrical. One end seems to have an extra
bit of wire attached to it that the other end does not have. A legacy of the
move from 200 to 198kHz perhaps ?
Andy G4JNT
-----Original Message-----
From: Prof. Arnaldo Coro Antich [SMTP:[email protected]]
Sent: 2002/08/01 12:31
To: [email protected]
Subject: LF: Re: "Downward modulation"
You are certainly talking about DAM...
Dynamic Amplitude Modulation....
a process that is used with very high power
transmitters to save energy.....
When there is no modulation, the carrier
level is moved UP, in order to keep the
signal to noise ratio on the channel at
a better level for the listener ( i.e. no background
noise or co-channel stations... you require
26 dB signal to noise ratio on an AM system
that has between 4 and 5 kiloHertz bandwidth
in order to provide full quieting ...)
AND YES.... there are many high power
AM transmitters nowadays that are facing
very poor operation !!!
73 and DX
Arnie Coro
CO2KK
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