RE: Request for info - integrating 2 K2s to achieve "2nd RX" capability

[JONES, George]

I have acquired a 2nd K2 (via a rally sale) so now have my K2/100 main rig plus a K2 "QRP" rig.
One set-up that I would like to try is using the 2nd rig as an integrated 2nd receiver.
It has "RANT" & I can use separate aerials (antennas) - any advice/cautions would be welcome. I absolutely don't want to destroy anything in either rig !

Note : I have never owned or used a "high-end" rig with this in-built capability

73

George G4TPV
 


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[Geoffrey Mackenzie-Kennedy-2]

George,

If using separate antennas and to protect the front end of your K2's
receiver from RF generated by your K2/100 radiated by its antenna, you might
want to consider adding an external relay at the K2's antenna input
controlled by the EXT AMP KEY line of the K2/100. Although I have not looked
at the timing sequence of this line in the K2/100 it should be such that
anything controlled by it is 'ready and waiting' before RF appears from the
K2/100's Tx output. I am certain that other people on the List would be able
to comment on this. The external relay would be used to disconnect the K2's
antenna from the K2's Rx input and ground the Rx antenna input, and should
be a fast acting type such as a reed relay..

Back- to- back diodes as protection devices should be avoided in a strong
signal environment at any point in a receiver chain unless increased
intermodulation problems are acceptable. The increase in IMD problems that
these diodes cause start well before they are fully switched on by incoming
signals.

73,
Geoff
GM4ESD



On Thursday, April 19, 2007 at 9:40 AM, George G4TPV wrote:

I have acquired a 2nd K2 (via a rally sale) so now have my K2/100 main rig
plus a K2 "QRP" rig.
One set-up that I would like to try is using the 2nd rig as an integrated
2nd receiver.
It has "RANT" & I can use separate aerials (antennas) - any advice/cautions
would be welcome. I absolutely don't want to destroy anything in either rig
!

Note : I have never owned or used a "high-end" rig with this in-built
capability

73

George G4TPV


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[Don Wilhelm-3]

George,

Unless the separate antenna picks up the full power of the transmitting
antenna, you should not encounter any damage.  As was suggested, a relay
driven by the KPA100 Amp keying circuit could break the antenna
connection.  The Amp keying output conducts 15 to 20 ms prior to the
onset of RF output.

Your biggest problem will be in muting the 2nd receiver.  Again the
KPA100 amp keying circuit can be the initiating element.  On the K2
control board, the /MUTE signal from microprocessor (U6) pin 17 drives
the gates of Q6 and Q7.  If you break that signal path and insert a
series resistor (5k to 10k) to protect the microprocessor output, then
  you can mute the K2 from an external source by grounding the gates of
Q6 and Q7 when the other K2 is transmitting.  Use of a series diode in
the path of the external muting signal with the anode connected to the
gates of Q6 and Q7 would provide isolation.

Several builders have tackled similar situations, and a search of the
archives may give you some additional insight, techniques, and
information about the results.

73,
Don W3FPR

JONES, George wrote:
> I have acquired a 2nd K2 (via a rally sale) so now have my K2/100 main rig plus a K2 "QRP" rig.
> One set-up that I would like to try is using the 2nd rig as an integrated 2nd receiver.
> It has "RANT" & I can use separate aerials (antennas) - any advice/cautions would be welcome. I absolutely don't want to destroy anything in either rig !
>
> Note : I have never owned or used a "high-end" rig with this in-built capability
>
> 73
>
> George G4TPV
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