[Elecraft] K3 Ant 1 and Ant 2 Isolation?

[Guy Olinger K2AV]

Most interactions between feeders and antennas and other antennas and other
antennas' feeders can be managed with physical layout design and effective
attention to common mode current blocking.

To be aware of these interactions, one must cultivate vision of these
circumstances as a soup of *all* conductors.  Just presume every conductor
induces every other conductor, far and away a more accurate assumption than
just considering antenna wires and assuming feedlines are invisible.

Once comfortable with that inconvenient truth about ham sites, one sees
that some combinations of wire and ferrite just aren't worth the trouble.
Too much to figure out, too much to "clean up," particularly for field day
with its time constraints.

Issues between wires are modulated by the wire/rope/support opportunities
at a given site. In my case this last FD, optimally located trees in a far
corner of the property where an RV could be parked, allowed an interesting
specially designed sloped antenna I would never have tried in more crowded
circumstances for considerable cause (long story). This particular long
sloper turned out to be a killer on 40m CW (1119 Q's at 100w). It was
removed from interaction only by the 75 yards back to the nearest station
in our 3A entry.

With the all-conductors-in-play principle firmly in mind for a carefully
planned layout of antennas and conductors, no station ever heard the other.
With a trio of K3's in operation, even with frequent SSB and CW on the same
band, we heard no crud, no crosstalk, no intermod, no transmitted phase
noise, which is a much harder to satisfy requirement than not burning out
front ends. Some considerable portion of the credit for this result goes to
the K3's front-end immunity and clean transmitted signal. BOTH the K3
immunity/clean TX signal AND the interaction-scrubbed antenna layout design
were required to achieve this result.

The question as to whether paying attention to such niceties is a handicap
to a high score will be answered firmly enough by looking for N4C in the 3A
listing in November's FD score reporting -- PVRC NC at Grey Goose Farm. And
yes, the owner did name the farm after the vodka. You should see his man
cave :>)

Making interaction go away with a simple one-size-fits-all rule just does
not happen in less than very large spaces.  But understanding the
electronic physics of interactions and seeing all the conductors in the
solution, one can dance with the physics and the physical layout
possibilities to create some imaginative and excellent site-specific
solutions in the field.

EZNEC and an *all-conductor* model preliminary design is a very good start.

73, Guy K2AV


On Wed, Jul 9, 2014 at 10:15 AM, dave <ho13dave at gmail.com> wrote:

>
> Probably not a good idea.
>
> The interaction between the vertical and the feed to the G5RV will be
> severe. You will have large quantities of RF forced onto the G5RV feeder.
>
> I ran a quick EZNEC model of 2 verticals 2.4" apart. It indicates that at
> 100w you would induce 45w onto the feeder. Even QRP levels would not appear
> to be safe. I'd think you are pretty assured of blowing something up.
>
> It would be an interesting experiment though, if you wanted to try it and
> report back on what burned up . . .
>
> 73 de dave
> ab9ca/4
>
>
>
>
> On 7/9/14 8:32 AM, Rich wrote:
>
>> During FD we were discussing portable antenna options for next year.
>> We were considering a 33' fiberglass pole with a veritical and a G5RV
>> on the same pole.  A 31' piece on wire running vertically down the
>> pole and also a G5RV supported by that same pole.  Then just connect
>> them to the K3 Ant 1 and 2 jacks and away we go, however should we
>> expect to flood the Ant jack which is not in use with RF due to the
>> antennas being so close?
>>
>> Any thoughts?
>>
>> Rich
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