Semi-related topic:
Recently, I was hosting a local 2m-SSB net and had my KX3-2M
connected to a 7-element yagi pointed 90-degrees from the
transmitting antenna array (K3+xvtr+150w amp). Spacing is about
40-feet horizontally and 30-feet vertically (Tx ant higher). Its
normal to run the Preamp with the KX3 on 2m and when I transmitted
the signal was strong enough to trigger overload protection in the
KX3 which disables the preamp. Probably 25-dB front-back ratio on
the transmitting antenna and maybe 15-dB rejection off the side of
the Rx antenna (both yagis) so estimated power at the KX3 is +52-dBm
- 40dB = +12 dBm (not including space loss between antennas). +12
dBm into the KX3-2M is pretty marginal for safety of the
preamp. Probably actual level is closer to 0 dBm (because I didn't
include coax loss or space loss). -33 dBm signal from my XG3 will
drive the KX3 to S9+40 (-73 dBm=S9*). *with preamp=ON.
Since antennas are within near-fields, ordinary space loss formula do
not apply. That is the typical situation with the KRX3 used on HF.
1-watt is way too high for safety for my eme preamps. +5 dBm is my
maximum tolerance. >+15 dBm is certainty of blow out. (I disconnect
other antennas when running 1300w on the main array)
73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
dubus...@gmail.com
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