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Old March 30th 08, 12:54 PM posted to rec.radio.amateur.antenna,sci.electronics.design,sci.electronics.basics
Homer J Homer J is offline
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First recorded activity by RadioBanter: Feb 2008
Posts: 11
Default Do receiver antennas need matching or not?

I did not see all the replies nor the original post but in the world of
radio frequency (RF) match yes this would be an ideal situation since
maximum energy transfer occur when Imepdance of the antenna (Zant) =
Imedance of the Receiver Antenna Port (Zrx_port).

All this talk about noise while important to minimum detectable signal more
greatly influenced by the internal Noise Figure (NF) of the receiver (RX).
In my line of work, which is Radar engineering, we use a standard
temperature T = 270 Kelvin to model the noise originating by natural
extgernal sources of which the Sun is the biggest contributor.

The short end answer on HF you will probably not notice a big difference as
long as the antenna is close between a 1/4 to 1/2 wavelength long [e.g.
wavelength = Velocity of Light (C) / Frequency of Operation (Fo)]. However,
if you use one of those collaspable whips found on the portable shortwave
receivers you will. This is because the anyenna impedance is a lot less than
the usual 50 Ohm impedance of the RX antenna port (e.g. Zant Zrx_port ).

You can match very short antennas with antenna tuners to make them transfer
efficently to the RX antenna port but now the nasty parameter of effective
antenna aperature (square feet or meters) reduces it caoture ability (think
of catching a baseball with and without a glove, the probability of catching
the ball is higher with a glove due to it larger capture area).

Well that is enough to put someone to ZZZzzzzzzzzzz. Hi Hi

73, Homer J
on all lower and upper channels Thane-Fer