Geoffrey Mackenzie-Kennedy wrote:
To avoid any misunderstanding about my use of the term 'strong', the
level of the internal spurious signal at 7 MHz in my K2's receiver was
approximately 10db above the noise floor at the output of the product
detector when viewed with a suitable spectrum analyzer, with the
What's the analyzer bandwidth (resolution)?
receiver connected to a 40m reference dipole at 70ft. The background
noise here on 40m is usually 'below S1' with either dipole or beam,
storm noise excepted. Receiver IF bandwidth was set to 400 Hz ,which is
not, of course, the receiver's noise bandwidth because of the actual
response of the K2's IF filter.
I get -21dB with an analyzer bin width of 10.8Hz, using spectrogram and
an indoor doublet, consisting of about 20m of wire, but with only about
10m horizontal. Note that is 21 dB below the noise in 10.8 Hz, or about
37dB below the noise in 400Hz, and I cannot hear it. I did turn the
AGC off.
Using a 50 ohm dummy load at about 21 degrees C, I get about +28dB in
the same bandwidth. Looking at last month's RadCom article on noise, it
looks like a quiet 7MHz should generate about 35dB over a 25 degree
resistor, which would give -7dB in 10.8Hz even in ideal conditions. My
antenna noise, at 49dB over the resistor, is roughly in the middle of
the range suggested in that article.
Either you are misinterpreting the effective noise bandwidth of the
analyzer, or you have a faulty K2. The birdy, itself, will have very
little bandwidth.
--
David Woolley
"The Elecraft list is a forum for the discussion of topics related to
Elecraft products and more general topics related ham radio"
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