K3 RX Antenna Input RF

[Jim Cary]

I seem to be getting too much RF in on my Beverage on 160 when I am  
transmitting, which appears to be causing the K3 RX antenna switching  
relay to chatter along with my dots and dashes.  No problem on 80 when  
using my beverage even though both the TX and RX antennas are the same  
for both bands.  I didn't have this problem with my other rigs, but I  
think that is because they grounded the RX Antenna input when the  
transceiver goes to transmit.  Apparently the K3 does not.

The bottom line I guess is that I need to either ground the RX Antenna  
input, or lift it, when the K3 goes to transmit.  Does anyone have a  
simple circuit that I could use to key a relay off of one of the  
accessory connector pins?

Thanks

Jim
W2SM

[hidden email]


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[.k8dd.-2]

Jim Cary wrote:

> I seem to be getting too much RF in on my Beverage on 160 when I am  
> transmitting, which appears to be causing the K3 RX antenna switching  
> relay to chatter along with my dots and dashes.  No problem on 80 when  
> using my beverage even though both the TX and RX antennas are the same  
> for both bands.  I didn't have this problem with my other rigs, but I  
> think that is because they grounded the RX Antenna input when the  
> transceiver goes to transmit.  Apparently the K3 does not.
>
> The bottom line I guess is that I need to either ground the RX Antenna  
> input, or lift it, when the K3 goes to transmit.  Does anyone have a  
> simple circuit that I could use to key a relay off of one of the  
> accessory connector pins?
>
> Thanks
>
> Jim
> W2SM
>
> [hidden email]

How about putting a couple of 1N34 diodes from the beverage antenna to
ground.  And maybe a night light bulb (not LED) in series with the
beverage feedline.

Beverage ---- bulb _________ RX IN
                     |    |
                    ---- ----
             1N34    \/   /\
                    ---- ----
                     |     |
                     |_____|
                        |
                        |
                      ground

73    Hank    K8DD
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[Bill W4ZV]

Jim Cary wrote

I seem to be getting too much RF in on my Beverage on 160 when I am  
transmitting, which appears to be causing the K3 RX antenna switching  
relay to chatter along with my dots and dashes.  No problem on 80 when  
using my beverage even though both the TX and RX antennas are the same  
for both bands.  I didn't have this problem with my other rigs, but I  
think that is because they grounded the RX Antenna input when the  
transceiver goes to transmit.  Apparently the K3 does not.

The bottom line I guess is that I need to either ground the RX Antenna  
input, or lift it, when the K3 goes to transmit.  Does anyone have a  
simple circuit that I could use to key a relay off of one of the  
accessory connector pins?

What serial number do you have Jim?  If it's before about #300, you may need to install this mod:

http://www.elecraft.com/K3/mods/KXV3_RXA_Board_Installation_Instructions_Rev_B.pdf

"Some operators have very strong pickup of their transmit antenna signal on their dedicated receive antennas. (Beverages, loops etc.) If the the receive antenna is not externally isolated during transmit, this energy could feed back into the K3 via the KXV3 RX antenna in port. Existing transmit isolation in the KXV3 is sufficient for most installations, but in some cases additional isolation is needed. The RXA Mod Kit for the KXV3 significantly improves isolation. (This change has been made to revision B KXV3 main boards.)"

RXA Boards added: Approximately  Feb 20, 2008
Rev B KXV3 Main Board added: March 14, 2008

73,  Bill