[Elecraft] KRX3 input protection

[Charlie T, K3ICH]

I saw a suggestion somewhere for using a small "grain-of-wheat" bulb across 
the 2nd antenna's lead as you gradually increase transmit power.  If I 
remember correctly, the bulb I used was a 5 V @ 50 mA lamp, typical of those 
used as LCD screen illuminators.

I tried that with a 600 ' Beverage that is at least 75 feet from any 
transmit antenna and was very surprised to see the bulb glowing brightly on 
a couple bands with only 50 watts into the LPDA up at 55'.   The Beverage is 
fed with a 9:1 transformer and is about 8 feet off the ground, running away 
from any active antennas.

Try it, it's quite an eye opener.

73, Charlie k3ICH


----- Original Message ----- 
From: "Arie Kleingeld PA3A" <pa3a at xs4all.nl>
To: <elecraft at mailman.qth.net>
Sent: Friday, January 03, 2014 11:12 AM
Subject: Re: [Elecraft] KRX3 input protection


> Steve,
>
> the subRX of the K3 has its protection (an rf triggered relay if the power 
> coming into the rx is too high).
>
> I've used the K3-KPA500 on a beam and I had a diversity vertical connected 
> to the subrx quite next to it. No problem at all.
> It all depends on the coupling of the antennas. Try and see how you go at 
> your QTH; the subRX is protected.
>
> 73
> Arie PA3A
>
> AD0ES schreef op 3-1-2014 15:23:
>> Hi all,
>>
>> My KRX3 is on the truck and due tuesday.  Quick question:  I will be 
>> running the main receiver on a receive only antenna
>> fed via the KXV3A and the subrx via its bnc aux.  These antennas are 
>> quite close to the xmit antennas.  Should I use
>> any sort of attenuation and/or external TR switch on either of these 
>> receiver inputs?  I eventually will be running a KPA500
>> full power...
>>
>> tia,
>> Steve AD0ES
>
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