Johnson–Nyquist noise contribution Antenna noise temperatures?
It depends on the ambient noise &amp; stray signal in each band but I know LNA's are essential for Sat. Rx and GPS Rx as well for VLF global Rx.  The Tx levels, Friis path loss, antennae gains and noise figure and BW of Preamp all are included in C/N ratios and with demodulation gains to S/R ratios. 

So it is not universally true that Johnson-Nyquist Noise is negligible and depends on background interference and Rx threshold &amp; acceptable BER.

\$P_\mathrm{dBm} = 10\ \log_{10}(k_\text{B} T \times 1000) + 10\ \log_{10}(\Delta f)\$

which is more commonly seen approximated for room temperature (T = 300K) as:

\$P_\mathrm{dBm} = -174 + 10\ \mathrm\log_{10} \ (\Delta f)\$ 


for 0dBm= 1mW


e.g. for \$(\Delta f)\$


1 MHz     −114 dBm    Bluetooth channel  ( well below ambient noise)
20 MHz    −101 dBm    WLAN 802.11 channel ( >-80 dBm signal min. typical needed)
80 MHz    −95 dBm     WLAN 802.11ac 80 MHz channel (>-65 dBm often needed )


Even small Capacitors have thermal noise due to V and C and those not using NP0 material are even microphonic.

\$v_{n} = \sqrt{ k_\text{B} T / C }\$


e.g. 1pF 64µV, 1nF 2µV


Then we have \$1/f\$ pink solid-state noise for the spectrum of pink noise in one-dimensional signals and for 2D signals (e.g., images) the power spectrum is \$1/f^2\$.

The most common units of measure for noise is \$dB/\sqrt{Hz}\$.

The understanding of threshold noise depends on many factors including Shannon's Law for SNR vs BER and non-"matched receivers" that match the signal BW and non-ideal discriminators and Ricean Fading loss (phase cancelling reflections) and many other factors.