[Elecraft] Diversity receive and isolating antennas

[Stewart]

Used my LP-100A to check the isolation between my main antennas and  pennant
receive loops, worked out great. 

Stewart G3RXQ
On Thu, 24 Jun 2010 11:27:52 -0700, Brett Howard wrote:
> This just gave me a great idea...  If any of you have a LP-100A you
> can connect an antenna directly into the back of the unit (where the
> couplers normally connect) and the unit can then be used as a field
> strength meter and it will give values in dBm...  Thats totally how
> I'm going to determine if my separation is going to be good enough...
>
> My hope is to be able to have 3 antennas on the K3 two which are TX/RX
> and one RX only...  The RX only antenna I'm going to run through an
> ICE 196 RF Limiter
> (http://www.iceradioproducts.com/reconly.html#rflimiter).  It starts
> limiting things to .3VRms so that should keep things happy...
>
> ~Brett (N7MG)
>
> On Thu, Jun 24, 2010 at 11:14 AM, Wayne Burdick <n6kr at elecraft.com> wrote:
>> Hi George,
>>
>> If you have an RF voltmeter or milliwatt meter, try terminating the
>> proposed RX antenna in a dummy load, then measure the voltage or power
>> when you transmit. If it's less than about 2.23 Vrms (100 mW, or +20
>> dBm), you'll have no trouble at all.
>>
>> The subreceiver (as well as the RX ANT IN jack) can generally handle
>> far more than this without damage; I pumped several watts in during
>> early testing. But you don't want to take risks in the field, or have
>> the COR (carrier operated relay) switching in and out during keying in
>> CW mode. Antennas can change pattern due to wind, rotation, etc.
>>
>> If the power at the AUX RX input (sub receiver) looks like it may be
>> excessive, you can take additional precautions. You could move the RX
>> antenna farther away, put it in a null of the TX antenna, reduce its
>> gain (length), or use the KEY OUT line to drive an external shunt PIN
>> diode switch.
>>
>> 73,
>> Wayne
>> N6KR
>>
>>
>> On Jun 24, 2010, at 10:04 AM, George A. Thornton wrote:
>>
>>> I am planning to use my dual receive K3 for field day and we want to
>>> try
>>> out diversity receive.
>>>
>>>
>>> This particular setup will be for 20 meters only.  The primary antenna
>>> will be a 20 meter monoband Yagi mounted on a 40-60 ft. tower.
>>>
>>>
>>> We were considering using a Buddipole mounted in vertical position and
>>> tuned for 20 meters voice to serve as a Rx only antenna for the sub.
>>> All transmission will be from the Yagi.  I was planning to hook the
>>> Buddipole into a Rx only connector.
>>>
>>>
>>> We will do the best we can to isolate the two antennas but having not
>>> been to the site before I am not sure what will be possible in the way
>>> of geographic isolation.
>>>
>>>
>>> I want to make sure I won't do any damage to the K3 in case the
>>> isolation is not sufficient.
>>>
>>>
>>> Anyone familiar with this situation able to give me some guidance?
>>>
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