On Wed, 25 Oct 2006 18:36:48 +0200, "Henry Kiefer"
wrote:

- LNA design for such a low frequency?

The band noise is the dominant (compared to "white" amplifier) noise
when listening to the band with your transmitter switched off, the
receiver noise performance should be adequate.
How much band noise should I expect?

When listening at the signal e.g. through an SSB receiver, it is quite
easy to know the difference. The equipment noise is more or less
constant "hiss", while the band noise is mainly through numerous
distant lightnings.

Some field strength measurements made in England at 73 kHz during the
summer, using a calibrated meter indicated 25 uV/m in 200 Hz
bandwidth, which would produce about 120 dB more power from a full
sized (2 km) dipole than a single matched resistor at the receiver
input.

Thus, even if the actual antenna efficiency was -100 dB and the LNA
noise figure as bad as 10 dB, the band noise would still be stronger
than the amplifier noise.

While an antenna with -100 dB gain would be usable for receiving, such
antenna would be useless for transmitting.

Paul OH3LWR