[K3PZN-List] Subject antennas on RV's

[Curt Milton]

Possibly what you all are alluding to is sometimes called 'mutual coupling.'  Two closely mounted antennas 'experience each other.'  There are two effects -- change in the terminal impedance and distortion of the antenna behavior.  

I didn't get the picture if these verticals are used on different bands or the same one?  

The other question to ask is whether the radios will be okay with one antenna transmitting and the other receiving.  I would very much worry if they are used on the same band -- there is possibility for damage if they are too close, and too close may not be easily to calculate at the extreme.  If these are HF radios used on different bands, the band pass filters in the radio contribute some rejection -- and allows coexistence.  Remember for example when we operated an inverted V below your tribandder at field day.  We didn't have issues because they were on different bands -- and it helped also to have several feet of separation.  
I do think you can operate on different bands using verticals on an RV -- but best to separate them as much as possible.  

As for winter field day -- sounds like cabin fever after 2.5 feet of snow.  And burning some fuel just to stay warm.  I don't know how popular it is in the northern reaches, even here.  A QRP group does FYBO this time of year, but they are based in Arizona.  I don't know, plenty of other activities one can do with radios indoors this time of year.  Outdoors it just might be better to be moving, maybe on some cross-country skis or snow shoes that sitting using a radio.  

CUL 73 Curt
 

    On Thursday, January 28, 2016 7:19 AM, John Stephens <kc3fdl at gmail.com> wrote:
 

 Kerri,

I had the same question a a couple of months back.  So to answer the
question, I contacted Dr. Ed Fong who had recently given a skype
presentation to the CARA club on his Dual Band J-Pole Antennas.  (By the
way, it was VERY interesting and CCARC should do the same!).  He actually
has a patent on his J-Pole design.  His website is
http://edsantennas.weebly.com.

His response was that it isn't the coax you need to be concerned with, it's
the antennas.  They will resonate between themselves.  In order to prevent
the antennas from resonating, 'in theory' (his words) they should be placed
at least 1 wavelength apart from each other.  For example, if you were
setting up 2M antennas they should be placed no closer than 2 meters
apart.  There are some things you can do to mount them closer, like offset
the height, but the physics and math are not trivial. Antenna for differing
bands can be placed closer together, say a couple of feet, without any
significant interference.

Hope this helps.

73 de KC3FDL / John


--------------------------------------------------------
John L. Stephens // KC3FDL
KC3FDL at gmail.com
Latitude: 39.4927 Longitude: -76.8894
MHGL: FM19nm

On Wed, Jan 27, 2016 at 10:50 PM, Kerri Wright <kb3vwk at gmail.com> wrote:

> Is possible to run two vertical antennas at the same time and location
> with out harmful feedback on coaxial line.  If so how defeat that problem?
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