[Elecraft] K3 Sub RX Not Working

[Bernie and Cheryl]

Dave:

I've had a K3s without the subreceiver for years.  When I pushed the 
"Sub" button, "No Sub" appeared in the display just like you described.

A few months ago, I bought the subreceiver and installed it. When I 
first turned the K3s on, the same "No sub" message appeared.  I then 
updated the firmware.  Once I did that, the K3s recognized the 
subreceiver, and all is well now.  It works fine and is a valuable tool 
in DX pileups.

I have four possibilities for your issue:

1) Are you sure the subreceiver is actually installed?  Opening up the 
top of the rig would let you know quickly because the subreceiver comes 
in a metal case that sits on top of the main RF board.  If, when you 
open up the top of your K3, you can see the crystal filters on the RF 
board, then that means you do NOT have a subreceiver, since the 
subreceiver would be on top.  That would explain the "No sub" message.

2) Another possibility is that you haven't updated your firmware like I 
have.  Don't ask me why that made the K3s recognize the presence of the 
subreceiver, but it did.

3) When I was installing the subreceiver, I also had to install a second 
KSYN3 board.  This is the synthesizer used by each receiver.  One KSYN3 
board won't work for both receivers. Additionally, there is an old 
version and a new version of the KSYN3 boards.  Since I had the K3s, my 
radio had the newer version, and I got the newer version of the KSYN3 
board.  I don't know if it is important for the KSYN3 boards used by 
each receiver to match, but that would make sense and it worked for me.

4) There are the TMP cables (little coaxial cables internal the K3s and 
I assume to the K3) that run from the KSYN3 boards to the subreceivers 
and to the radio itself.  Opening the top of the K3 would allow you to 
check to make sure one of these cables hasn't come loose.  One of those 
coming loose would account for the fact that your K3 doesn't recognize 
the presence of the subreceiver.

I hope this is of some help.

73 de Bernie, KF0QS