[Elecraft] Antenna Separation for Diversity

[dave]

Let me add a bit, if I may. The vertical needs to be broadside and 
centered on the dipole. Draw a line at 90 degrees from the center feed 
point of the dipole and place the vertical on that line.

But if I understand what is meant by the term 'Carolina Windom' this is 
an off-center-fed antenna and will consequently have unequal currents on 
the feeder on some or all bands. This means the feeder will both radiate 
and receive, and will be vertically polarized. Consequently there will 
be coupling between the vert antenna and the feeder of the Windom.

So long as the vert and the Windom are used on different bands it will 
likely work OK, but there will probably be too much coupling to use them 
both on the same band. If a center fed dipole is used with a vertical as 
described above (or another dipole at 90 degrees and centered) they can 
both be on the same band with a few kHz separation. We do that every FD.


73 de dave
ab9ca/4






Brett Howard wrote:
> Huh... Broadside to the vertical provided minimum coupling?  Well I'm going
> to be slapping things together tomorrow and trying them out and trying to
> take a bunch of measurements and logging it all.  Was just wondering if
> anyone else here had a similar setup and might have an answer here.  I'm
> figuring I'll probably be able to pull off about 150 to 200 feet between
> them... Lets hope its enough.  If not I can always make one of them RX only
> and put the ICE Receiver Limiter box on it.
>
> ~Brett (N7MG)
>
> -----Original Message-----
> From: Tom W8JI [mailto:w8ji at w8ji.com] 
> Sent: Thursday, June 24, 2010 6:00 AM
> To: Brett Howard; elecraft
> Subject: Re: [Elecraft] Antenna Separation for Diversity
>
> Brett,
>
> No one can answer that question for you, because both antennas are 
> unpredictable in nearfield performance. Also the layout of the antenna and 
> what is around, under, and between the antennas is very important.
>
> With such a large soup of unknowns, plus there might be other transmitters 
> on site (?), the only way to really know is to try it.
>
> If you had a normal dipole and wanted interaction to a vertical of known 
> efficiency I have all that data. One thing I learned is minimum coupling 
> from a good dipole to a good vertical was with the dipole BROADSIDE to the 
> vertical, not at right angles as I assumed without thinking.
>
> The problem is the Carolina Windom is nothing like a dipole and not nearly 
> as predictable as a dipole for nearfield or close farfield coupling, and 
> that goes on top of the other variables that are bad enough on their own.
>
> Maybe you should go to an antenna forum, like on eHam or QRZ, armed with the
>
> information of the safe signal level the K3 will tolerate. Other than the 
> safe signal level, this is really an antenna theory question and a good 
> answer would be too complex for a radio reflector.
>
> 73 Tom
>
> - Original Message ----- 
> From: "Brett Howard" <brett at livecomputers.com>
> To: "elecraft" <elecraft at mailman.qth.net>
> Sent: Thursday, June 24, 2010 5:14 AM
> Subject: [Elecraft] Antenna Separation for Diversity
>
>
>   
>> So I know I'm going to shoot for as wide as I can get things... But for
>> two main antennas on a k3 one being a Carolina Windom and the other
>> being a 43 foot vertical.
>>
>> How much separation would one expect to be needed in order to prevent
>> the COR's from switching during TX @ 100Watts?
>>
>> ~Brett (N7MG)
>>
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