[Elecraft] Re: Question re K3 diversity reception

[wayne burdick]

Jerry Flanders wrote:

> At what approx. RF voltage level sent back into the rx from the second 
> antenna do we need to worry about additional protection like external 
> switching or shorting?

The short answer is: the voltage resulting from input power high enough 
to trigger the COR (probably 0.5 to 2 W in most cases). This will vary 
widely because the impedance of the sub's antenna on the *transmit* 
band may be totally different from its Z on the sub's receive band. At 
very high impedances, strays from the coax and the COR circuitry itself 
come into play. If you use the KAT3's non-TX antenna as the sub's AUX 
source, the small amount of leakage between ANT1 and ANT2 can also 
affect the COR trigger level; this will depend on the load Z and will 
vary from band to band.

> Also, what do I hear when the COR activates? What sound? Is this a 
> reed relay?

You'll hear about the same thing you hear when you switch from CW to 
SSB mode (this throws a relay on the KREF3 module), except it will 
follow the keying. It's not a reed relay, but it is small, and rated 
for very long mechanical life. Still, I recommend not pushing it. If 
you hear it, you should improve the antenna isolation on that band.

> I operate SO2R and occasionally need to measure to verify safe RF 
> level into the second rig and would also like use my 2nd K3 
> (synch-tuned) for diversity rx while tx'ing on 1st K3. An actual RF 
> voltage level I can use as a measurable limit would be a very useful 
> parameter.

What I mentioned above is the best I can give you. If you can keep it 
to 10 Vpp or less, I think you'll be OK, but I'd still advise testing 
things before you operate in a contest.

73,
Wayne
N6KR

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