[Elecraft] Duplex operation on K3

[Edward R. Cole]

A subject I am also interested in.  The key with the K3 would be 
having the KRX3 subreceiver and using Rx antenna input for receiving 
the satellite downlink.  The subreceiver IF is easily tapped to 
provide signal to a radio like the SDR-IQ.  BUT the question is if 
the hardware connections will allow the subreceiver to operate while 
the K3 transmits.  If the hardware path is possible then I am 
guessing firmware can be done to do this.  Using the 15-KHz K3 DSP 
receiver at the same time as the DSP Tx is probably impossible so I 
am thinking the key is using another receiver on the subRx IF output.

I will be setting my K3 + DEMI L432-28  for uplink and the KX3 + 
KX3-2M for downlink (in the interim).  Of course both will need to be 
tuned in freq. to compensate for Doppler shift.  I believe both 
radios are capable of computer control, but not sure there is any sw 
that can control two separate radios (K3 and KX3 
specifically)?  Otherwise it becomes an exercise in 
right-hand/left-hand (and getting the brain to handle that?).  The 
fortunate thing is uplink tuning is rarely needed on FM Leo sats (a 
shrinking list).  For linear transponder satellites like VO-52, SSB 
requires adjusting both VFO's with a pretty lively Doppler 
effect.  Now try sending CW, as well (how fast can you send with your 
big toe?).

I had both the FT-847 (a superb satellite radio) and the FT-817 (not 
duplex but a suitable radio) operating satellite in simplex.  Both 
are sold and replaced by the K3 (and soon to be KX3).


73, Ed - KL7UW, WD2XSH/45
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