[Elecraft] Re: K3 KRX3 - BNC or KAT3?

[Brian Alsop]

A datapoint on whether or not it is likely to generate 1 or 2 watts of 
input to the RX antenna.

A number of contesters had been using ANC-4 noise limiters as preamps 
rather than their intended function.   The RX antenna was ported through 
it and to the receiver.   1/4 watt resistors in the ANC4 input were 
cooked.  Replacing them with 1 watt units solved the problem.   This 
foggy data suggests that 1 watt of power to RX antenna input may be 
unlikely with  something like the below setup.

I was one of these people.  The situation is worse on 160M with several 
receive antennas much closer than 1/4 wave to the transmit antenna-- 
worse case 50'.  Keep in mind 1/4 wave is about 125'.    Running a full 
KW to an inverted L.    

There are ICE units which limit inputs to something under 1/2 volt.  If 
you have receive antennas closer than the above,  you might consider the 
ICE unit.    There are other HB limiters people have created over the years.

If you have an oscilloscope or RF voltmeter, terminate the receive 
antenna with 50 ohms in the shack and measure the voltage.  From that 
you can compute power and see where you stand.

73 de Brian/K3KO

wayne burdick wrote:

> Charles Harpole wrote:
>
>> Can I run power with a good receive antenna connected to
>> rcve only input bnc socket without damage anywhere?
>
>
>
> Yes. We've pumped several watts into the KRX3's aux antenna input 
> without any sign of damage. (But anything above about 1 to 2 watts 
> measured at the sub's AUX input will activate the carrier-operated 
> relay, or COR, which should be avoided because it slows down break-in 
> keying receive recovery.)
>
> As long as the receive antenna is a reasonable distance from the 
> transmit antenna, the COR won't be activated, and you'll be at a safe 
> level. The AUX BNC jack provides somewhat better isolation than the 
> KAT3 connector, so it may be the better choice if you're not sure if 
> the antennas are far enough apart at the intended power level.
>
> 73,
> Wayne
> N6KR
>
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