K3 Sub Receiver and protecting the Sub RX input

[Edward R Cole]

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:
     [hidden email]

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[Elecraft mailing list]

Now this has me wondering about having my 2 meter and 6 meter antennas in close proximity.

 



      From: Edward R Cole <[hidden email]>
 To: [hidden email]
 Sent: Wednesday, January 28, 2015 4:44 PM
 Subject: Re: [Elecraft] K3 Sub Receiver and protecting the Sub RX input
   
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:
    [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]


 
______________________________________________________________
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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Please help support this email list: http://www.qsl.net/donate.html
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